Added: websites/staging/olingo/trunk/content/doc/odata4/tutorials/Olingo_Tutorial_AdvancedReadWrite_Batch.html ============================================================================== --- websites/staging/olingo/trunk/content/doc/odata4/tutorials/Olingo_Tutorial_AdvancedReadWrite_Batch.html (added) +++ websites/staging/olingo/trunk/content/doc/odata4/tutorials/Olingo_Tutorial_AdvancedReadWrite_Batch.html Tue Sep 16 12:34:18 2014 @@ -0,0 +1,221 @@ +<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01//EN"> +<html lang="en"> + <head> + <meta http-equiv="content-type" content="text/html; charset=utf-8"> + <meta http-equiv="X-UA-Compatible" content="IE=edge"> + <meta name="viewport" content="width=device-width, initial-scale=1"> + <meta name="description" content="Apache Olingo provides libraries which enable developers to implement OData producers and OData consumers. The available OData Java library implements OData version 2.0. In future on goal is to provide an OData 4.0 compliant library once the OData standard is published at OASIS. The focus within the community is currently on the Java technology but it is up to the community to discuss if other environments find interest."> + <meta name="author" content=""> + <link rel="icon" href="/favicon.ico"> + <title> + Apache Olingo + </title><!-- Bootstrap core CSS --> + <link href="/css/bootstrap.css" rel="stylesheet" type="text/css"><!-- Custom styles for this template --> + <link href="/css/navbar.css" rel="stylesheet" type="text/css"><!-- Just for debugging purposes. 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As a result you get a list with batch parts. Each part separately represents a ChangeSet or a query operation. </li> +<li>Call <code>handler.handleBathPart(batchRequestPart)</code> while looping over the list. The handler delegates the processing of a batch part depending on the type of that batch part. </li> +<li>When all batch parts are completely processed, use the method <code>EntityProvider.writeBatchResponse(final List<BatchResponsePart> batchResponseParts)</code> in order to write all responses in one Batch Response. +The following example shows a possible implementation:</li> +</ul> +<p><strong>Sample Code</strong></p> +<div class="codehilite"><pre><span class="p">@</span><span class="n">Override</span> + <span class="n">public</span> <span class="n">ODataResponse</span> <span class="n">executeBatch</span><span class="p">(</span><span class="n">final</span> <span class="n">BatchHandler</span> <span class="n">handler</span><span class="p">,</span> <span class="n">final</span> <span class="n">String</span> <span class="n">contentType</span><span class="p">,</span> <span class="n">final</span> <span class="n">InputStream</span> <span class="n">content</span><span class="p">)</span> <span class="n">throws</span> <span class="n">ODataException</span> <span class="p">{</span> + <span class="n">ODataResponse</span> <span class="n">batchResponse</span><span class="p">;</span> + <span class="n">List</span><span class="o"><</span><span class="n">BatchResponsePart</span><span class="o">></span> <span class="n">batchResponseParts</span> <span class="p">=</span> <span class="n">new</span> <span class="n">ArrayList</span><span class="o"><</span><span class="n">BatchResponsePart</span><span class="o">></span><span class="p">();</span> + <span class="n">PathInfo</span> <span class="n">pathInfo</span> <span class="p">=</span> <span class="n">getContext</span><span class="p">().</span><span class="n">getPathInfo</span><span class="p">();</span> + <span class="n">EntityProviderBatchProperties</span> <span class="n">batchProperties</span> <span class="p">=</span> <span class="n">EntityProviderBatchProperties</span><span class="p">.</span><span class="n">init</span><span class="p">().</span><span class="n">pathInfo</span><span class="p">(</span><span class="n">pathInfo</span><span class="p">).</span><span class="n">build</span><span class="p">();</span> + <span class="n">List</span><span class="o"><</span><span class="n">BatchRequestPart</span><span class="o">></span> <span class="n">batchRequestParts</span> <span class="p">=</span> <span class="n">EntityProvider</span><span class="p">.</span><span class="n">parseBatchRequest</span><span class="p">(</span><span class="n">contentType</span><span class="p">,</span> <span class="n">content</span><span class="p">,</span> <span class="n">batchProperties</span><span class="p">);</span> + <span class="k">for</span> <span class="p">(</span><span class="n">BatchPart</span> <span class="n">batchPart</span> <span class="p">:</span> <span class="n">batchRequestParts</span><span class="p">)</span> <span class="p">{</span> + <span class="n">BatchResponsePart</span> <span class="n">processedBatchPart</span> <span class="p">=</span> <span class="n">handler</span><span class="p">.</span><span class="n">handleBatchPart</span><span class="p">(</span><span class="n">batchRequestPart</span><span class="p">)</span> + <span class="n">batchResponseParts</span><span class="p">.</span><span class="n">add</span><span class="p">(</span><span class="n">processedBatchPart</span><span class="p">);</span> + <span class="p">}</span> + <span class="n">batchResponse</span> <span class="p">=</span> <span class="n">EntityProvider</span><span class="p">.</span><span class="n">writeBatchResponse</span><span class="p">(</span><span class="n">batchResponseParts</span><span class="p">);</span> + <span class="k">return</span> <span class="n">batchResponse</span><span class="p">;</span> + <span class="p">}</span> +</pre></div> + + +<p><strong>NOTE:</strong> The parameter batchProperties of the method parseBatchRequest contains OData URI informations as PathInfo-object. These informations are necessary for the parsing, that's why the PathInfo-object should not be null.</p> +<h5 id="implement-the-method-executechangeset-of-the-class-odatasingleprocessor">Implement the method executeChangeSet of the class ODataSingleProcessor.</h5> +<p>In order to process a request invoke <code>handler.handleRequest(request)</code>, that delegates a handling of the request to the request handler and provides ODataResponse. +Define a rollback semantics that may be applied when a request within a ChangeSet fails. +The following example shows a possible implementation:</p> +<div class="codehilite"><pre><span class="p">@</span><span class="n">Override</span> + <span class="n">public</span> <span class="n">BatchResponsePart</span> <span class="n">executeChangeSet</span><span class="p">(</span><span class="n">final</span> <span class="n">BatchHandler</span> <span class="n">handler</span><span class="p">,</span> <span class="n">final</span> <span class="n">List</span><span class="o"><</span><span class="n">ODataRequest</span><span class="o">></span> <span class="n">requests</span><span class="p">)</span> <span class="n">throws</span> <span class="n">ODataException</span> <span class="p">{</span> + <span class="n">List</span><span class="o"><</span><span class="n">ODataResponse</span><span class="o">></span> <span class="n">responses</span> <span class="p">=</span> <span class="n">new</span> <span class="n">ArrayList</span><span class="o"><</span><span class="n">ODataResponse</span><span class="o">></span><span class="p">();</span> + <span class="k">for</span> <span class="p">(</span><span class="n">ODataRequest</span> <span class="n">request</span> <span class="p">:</span> <span class="n">requests</span><span class="p">)</span> <span class="p">{</span> + <span class="n">ODataResponse</span> <span class="n">response</span> <span class="p">=</span> <span class="n">handler</span><span class="p">.</span><span class="n">handleRequest</span><span class="p">(</span><span class="n">request</span><span class="p">);</span> + <span class="k">if</span> <span class="p">(</span><span class="n">response</span><span class="p">.</span><span class="n">getStatus</span><span class="p">().</span><span class="n">getStatusCode</span><span class="p">()</span> <span class="o">></span><span class="p">=</span> <span class="n">HttpStatusCodes</span><span class="p">.</span><span class="n">BAD_REQUEST</span><span class="p">.</span><span class="n">getStatusCode</span><span class="p">())</span> <span class="p">{</span> + <span class="o">//</span> <span class="n">Rollback</span> + <span class="n">List</span><span class="o"><</span><span class="n">ODataResponse</span><span class="o">></span> <span class="n">errorResponses</span> <span class="p">=</span> <span class="n">new</span> <span class="n">ArrayList</span><span class="o"><</span><span class="n">ODataResponse</span><span class="o">></span><span class="p">(</span>1<span class="p">);</span> + <span class="n">errorResponses</span><span class="p">.</span><span class="n">add</span><span class="p">(</span><span class="n">response</span><span class="p">);</span> + <span class="k">return</span> <span class="n">BatchResponsePart</span><span class="p">.</span><span class="n">responses</span><span class="p">(</span><span class="n">errorResponses</span><span class="p">).</span><span class="n">changeSet</span><span class="p">(</span><span class="n">false</span><span class="p">).</span><span class="n">build</span><span class="p">();</span> + <span class="p">}</span> + <span class="n">responses</span><span class="p">.</span><span class="n">add</span><span class="p">(</span><span class="n">response</span><span class="p">);</span> + <span class="p">}</span> + <span class="k">return</span> <span class="n">BatchResponsePart</span><span class="p">.</span><span class="n">responses</span><span class="p">(</span><span class="n">responses</span><span class="p">).</span><span class="n">changeSet</span><span class="p">(</span><span class="n">true</span><span class="p">).</span><span class="n">build</span><span class="p">();</span> + <span class="p">}</span> +</pre></div> + + +<p><strong>NOTE:</strong> If a request within a ChangeSet fails, a Batch Response Part contains only the error response and the flag changeSet is set to false.</p> +<h5 id="batch-request-body-example">Batch Request Body Example</h5> +<div class="codehilite"><pre><span class="o">--</span><span class="n">batch_123</span> +<span class="n">Content</span><span class="o">-</span><span class="n">Type</span><span class="p">:</span> <span class="n">multipart</span><span class="o">/</span><span class="n">mixed</span><span class="p">;</span> <span class="n">boundary</span><span class="p">=</span><span class="n">changeset_321</span> + +<span class="o">--</span><span class="n">changeset_321</span> +<span class="n">Content</span><span class="o">-</span><span class="n">Type</span><span class="p">:</span> <span class="n">application</span><span class="o">/</span><span class="n">http</span> +<span class="n">Content</span><span class="o">-</span><span class="n">Transfer</span><span class="o">-</span><span class="n">Encoding</span><span class="p">:</span> <span class="n">binary</span> + +<span class="n">PUT</span> <span class="n">Employees</span><span class="p">(</span><span class="s">'2'</span><span class="p">)</span><span class="o">/</span><span class="n">EmployeeName</span> <span class="n">HTTP</span><span class="o">/</span>1<span class="p">.</span>1 +<span class="n">Content</span><span class="o">-</span><span class="n">Length</span><span class="p">:</span> 100 +<span class="n">DataServiceVersion</span><span class="p">:</span> 1<span class="p">.</span>0 +<span class="n">Content</span><span class="o">-</span><span class="n">Type</span><span class="p">:</span> <span class="n">application</span><span class="o">/</span><span class="n">json</span><span class="p">;</span><span class="n">odata</span><span class="p">=</span><span class="n">verbose</span> +<span class="n">MaxDataServiceVersion</span><span class="p">:</span> 2<span class="p">.</span>0 + +<span class="p">{</span>"<span class="n">EmployeeName</span>"<span class="p">:</span>"<span class="n">Frederic</span> <span class="n">Fall</span> <span class="n">MODIFIED</span>"<span class="p">}</span> + +<span class="o">--</span><span class="n">changeset_321</span><span class="o">--</span> + +<span class="o">--</span><span class="n">batch_123</span> +<span class="n">Content</span><span class="o">-</span><span class="n">Type</span><span class="p">:</span> <span class="n">application</span><span class="o">/</span><span class="n">http</span> +<span class="n">Content</span><span class="o">-</span><span class="n">Transfer</span><span class="o">-</span><span class="n">Encoding</span><span class="p">:</span> <span class="n">binary</span> + +<span class="n">GET</span> <span class="n">Employees</span><span class="p">(</span><span class="s">'2'</span><span class="p">)</span><span class="o">/</span><span class="n">EmployeeName</span>?$<span class="n">format</span><span class="p">=</span><span class="n">json</span> <span class="n">HTTP</span><span class="o">/</span>1<span class="p">.</span>1 +<span class="n">Accept</span><span class="p">:</span> <span class="n">application</span><span class="o">/</span><span class="n">atomsvc</span><span class="o">+</span><span class="n">xml</span><span class="p">;</span><span class="n">q</span><span class="p">=</span>0<span class="p">.</span>8<span class="p">,</span> <span class="n">application</span><span class="o">/</span><span class="n">json</span><span class="p">;</span><span class="n">odata</span><span class="p">=</span><span class="n">verbose</span><span class="p">;</span><span class="n">q</span><span class="p">=</span>0<span class="p">.</span>5<span class="p">,</span> <span class="o">*/*</span><span class="p">;</span><span class="n">q</span><span class="p">=</span>0<span class="p">.</span>1 +<span class="n">MaxDataServiceVersion</span><span class="p">:</span> 2<span class="p">.</span>0 + + +<span class="o">--</span><span class="n">batch_123</span><span class="o">--</span> +</pre></div> + + +<p><strong>NOTE:</strong></p> +<ul> +<li>A Content-Type header of the Batch Request must specify a content type of "multipart/mixed" and a boundary parameter. </li> +<li>Each Batch Part is separated by the boundary string, that must occur at the beginning of a line, following a CRLF. </li> +<li>The boundary of the ChangeSet should be different from that used by the Batch. </li> +</ul> +<h5 id="request-line-of-a-single-request">Request Line of a single request</h5> +<p>The following request lines of a single request (e.g. a retrieve request) will be accepted:</p> +<ul> +<li>GET http://<scheme>/<service_name>/<resource_path> HTTP/1.1 - the request line with an absolute URI </li> +<li>GET <resource_path> HTTP/1.1 - the request line that contains a relative-path reference +Query Options can optionally follow the Resource Path.</li> +</ul> +<p><strong>Note:</strong> An absolute-path reference like /<service_name>/<resource_path> will not be accepted</p> +<h5 id="content-id">Content-ID</h5> +<p>The new entity may be referenced by subsequent requests within the same ChangeSet by referring to the Content-Id value. $<contentIdValue> acts as an alias for the Resource Path of the new entity. +In order to refer the new entity the Request URI must begin with $<contentIdValue>:</p> +<div class="codehilite"><pre><span class="n">POST</span> <span class="n">Customers</span> <span class="n">HTTP</span><span class="o">/</span>1<span class="p">.</span>1 +<span class="n">Content</span><span class="o">-</span><span class="n">ID</span><span class="p">:</span> <span class="n">newCustomer</span> +<span class="p">...</span> +<span class="n">PUT</span> $<span class="n">newCustomer</span><span class="o">/</span><span class="n">Name</span> <span class="n">HTTP</span><span class="o">/</span>1<span class="p">.</span>1 +</pre></div> + + +<p><strong>Note:</strong> Requests in different ChangeSets cannot reference one another, even if they are in the same Batch</p> +<h3 id="references">References</h3> +<p><a href="http://www.odata.org/documentation/odata-v2-documentation/batch-processing/"; title="External Link">http://www.odata.org/documentation/odata-v2-documentation/batch-processing/</a></p><div align="center"> +<p>Copyright © 2013-2014, The Apache Software Foundation<br> + Apache Olingo, Olingo, Apache, the Apache feather, and + the Apache Olingo project logo are trademarks of the Apache Software + Foundation.</p> + <small><a href="/doc/odata2/privacy.html">Privacy</a></small> + </div> + </div><!-- /container --> + <!-- Bootstrap core JavaScript + ================================================== --> + <!-- Placed at the end of the document so the pages load faster --> + 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Added: websites/staging/olingo/trunk/content/doc/odata4/tutorials/Olingo_Tutorial_AdvancedRead_FilterVisitor.html ============================================================================== --- websites/staging/olingo/trunk/content/doc/odata4/tutorials/Olingo_Tutorial_AdvancedRead_FilterVisitor.html (added) +++ websites/staging/olingo/trunk/content/doc/odata4/tutorials/Olingo_Tutorial_AdvancedRead_FilterVisitor.html Tue Sep 16 12:34:18 2014 @@ -0,0 +1,468 @@ +<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01//EN"> +<html lang="en"> + <head> + <meta http-equiv="content-type" content="text/html; charset=utf-8"> + <meta http-equiv="X-UA-Compatible" content="IE=edge"> + <meta name="viewport" content="width=device-width, initial-scale=1"> + <meta name="description" content="Apache Olingo provides libraries which enable developers to implement OData producers and OData consumers. The available OData Java library implements OData version 2.0. In future on goal is to provide an OData 4.0 compliant library once the OData standard is published at OASIS. The focus within the community is currently on the Java technology but it is up to the community to discuss if other environments find interest."> + <meta name="author" content=""> + <link rel="icon" href="/favicon.ico"> + <title> + Apache Olingo + </title><!-- Bootstrap core CSS --> + <link href="/css/bootstrap.css" rel="stylesheet" type="text/css"><!-- Custom styles for this template --> + <link href="/css/navbar.css" rel="stylesheet" type="text/css"><!-- Just for debugging purposes. 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This tutorial will be about consuming and working with the filter tree which an application will get from the OData Java library by implementing a transformation of the filter expression into a JDBC where clause. The example explained here will be kept simple to show the mechanism of the visitor pattern. Security problem which occur when using user input (e.g. the filter string of the URI) inside a where clause will be pointed out but not solved for this tutorial. Knowledge about the visitor pattern is not necessary but helpful. If you want to read further please refer to the further information chapter at the end of this tutorial.</p> +<h3 id="examples">Examples</h3> +<h5 id="simple-example">Simple example</h5> +<p>If a filter expression is parsed by the OData library it will be transformed into a filter tree. A simple tree for the expression âaâ eq âbâ would look like this:</p> +<p><img alt="Picture:Simple Filter Expression" src="/img/FilterExpressionSimple.png" /></p> +<p>To visit a filter tree we have to implement the interface <code>org.apache.olingo.odata2.api.uri.expression.ExpressionVisitor</code>. For this simple example we will only need the following methods:</p> +<ul> +<li><code>visitFilter(â¦)</code></li> +<li><code>visitBinary(â¦)</code> </li> +<li><code>visitLiteral(â¦)</code> </li> +</ul> +<p>These methods will be called if the <code>accept(â¦)</code> method of the filter expression is called. The visitor will always start with the far left of the tree. First visitLiteral is called for 'a' and 'b' before the <code>visitBinary()</code> and finally the <code>visitFilter()</code> is called.</p> +<p>Now lets have a look at the implementation of the <code>visitLiteral()</code>:</p> +<div class="codehilite"><pre><span class="p">@</span><span class="n">Override</span> +<span class="n">public</span> <span class="n">Object</span> <span class="n">visitLiteral</span><span class="p">(</span><span class="n">LiteralExpression</span> <span class="n">literal</span><span class="p">,</span> <span class="n">EdmLiteral</span> <span class="n">edmLiteral</span><span class="p">)</span> <span class="p">{</span> + <span class="k">if</span><span class="p">(</span><span class="n">EdmSimpleTypeKind</span><span class="p">.</span><span class="n">String</span><span class="p">.</span><span class="n">getEdmSimpleTypeInstance</span><span class="p">().</span><span class="n">equals</span><span class="p">(</span><span class="n">edmLiteral</span><span class="p">.</span><span class="n">getType</span><span class="p">()))</span> <span class="p">{</span> + <span class="o">//</span> <span class="n">we</span> <span class="n">have</span> <span class="n">to</span> <span class="n">be</span> <span class="n">carefull</span> <span class="n">with</span> <span class="n">strings</span> <span class="n">due</span> <span class="n">to</span> <span class="n">sql</span> <span class="n">injection</span> + <span class="o">//</span> <span class="n">TODO</span><span class="p">:</span> <span class="n">Prevent</span> <span class="n">sql</span> <span class="n">injection</span> <span class="n">via</span> <span class="n">escaping</span> + <span class="k">return</span> "<span class="s">'" + edmLiteral.getLiteral() + "'</span>"<span class="p">;</span> + <span class="p">}</span> <span class="k">else</span> <span class="p">{</span> + <span class="k">return</span> "<span class="s">'" + edmLiteral.getLiteral() + "'</span>"<span class="p">;</span> + <span class="p">}</span> +<span class="p">}</span> +</pre></div> + + +<p>The signature for this method contains the literal expression as an object as well as the edmLiteral representation. In this case the literal would be "a" without the '. Inside this method we just return the literal. Since this literal is coming from the URL it represents user input. In the case of the type Edm.String we would have to escape the String to make sure no SQL Injection is possible.</p> +<p>Next the method visitBinary is called:</p> +<div class="codehilite"><pre><span class="p">@</span><span class="n">Override</span> + <span class="n">public</span> <span class="n">Object</span> <span class="n">visitBinary</span><span class="p">(</span><span class="n">BinaryExpression</span> <span class="n">binaryExpression</span><span class="p">,</span> <span class="n">BinaryOperator</span> <span class="n">operator</span><span class="p">,</span> <span class="n">Object</span> <span class="n">leftSide</span><span class="p">,</span> <span class="n">Object</span> <span class="n">rightSide</span><span class="p">)</span> <span class="p">{</span> + <span class="o">//</span><span class="n">Transform</span> <span class="n">the</span> <span class="n">OData</span> <span class="n">filter</span> <span class="n">operator</span> <span class="n">into</span> <span class="n">an</span> <span class="n">equivalent</span> <span class="n">sql</span> <span class="n">operator</span> + <span class="n">String</span> <span class="n">sqlOperator</span> <span class="p">=</span> ""<span class="p">;</span> + <span class="k">switch</span> <span class="p">(</span><span class="n">operator</span><span class="p">)</span> <span class="p">{</span> + <span class="k">case</span> <span class="n">EQ</span><span class="p">:</span> + <span class="n">sqlOperator</span> <span class="p">=</span> "<span class="p">=</span>"<span class="p">;</span> + <span class="k">break</span><span class="p">;</span> + <span class="k">case</span> <span class="n">NE</span><span class="p">:</span> + <span class="n">sqlOperator</span> <span class="p">=</span> "<span class="o"><></span>"<span class="p">;</span> + <span class="k">break</span><span class="p">;</span> + <span class="k">case</span> <span class="n">OR</span><span class="p">:</span> + <span class="n">sqlOperator</span> <span class="p">=</span> "<span class="n">OR</span>"<span class="p">;</span> + <span class="k">break</span><span class="p">;</span> + <span class="k">case</span> <span class="n">AND</span><span class="p">:</span> + <span class="n">sqlOperator</span> <span class="p">=</span> "<span class="n">AND</span>"<span class="p">;</span> + <span class="k">break</span><span class="p">;</span> + <span class="k">case</span> <span class="n">GE</span><span class="p">:</span> + <span class="n">sqlOperator</span> <span class="p">=</span> "<span class="o">></span><span class="p">=</span>"<span class="p">;</span> + <span class="k">break</span><span class="p">;</span> + <span class="k">case</span> <span class="n">GT</span><span class="p">:</span> + <span class="n">sqlOperator</span> <span class="p">=</span> "<span class="o">></span>"<span class="p">;</span> + <span class="k">break</span><span class="p">;</span> + <span class="k">case</span> <span class="n">LE</span><span class="p">:</span> + <span class="n">sqlOperator</span> <span class="p">=</span> "<span class="o"><</span><span class="p">=</span>"<span class="p">;</span> + <span class="k">break</span><span class="p">;</span> + <span class="k">case</span> <span class="n">LT</span><span class="p">:</span> + <span class="n">sqlOperator</span> <span class="p">=</span> "<span class="o"><</span>"<span class="p">;</span> + <span class="k">break</span><span class="p">;</span> + <span class="n">default</span><span class="p">:</span> + <span class="o">//</span><span class="n">Other</span> <span class="n">operators</span> <span class="n">are</span> <span class="n">not</span> <span class="n">supported</span> <span class="k">for</span> <span class="n">SQL</span> <span class="n">Statements</span> + <span class="n">throw</span> <span class="n">new</span> <span class="n">UnsupportetOperatorException</span><span class="p">(</span>"<span class="n">Unsupported</span> <span class="n">operator</span><span class="p">:</span> " <span class="o">+</span> <span class="n">operator</span><span class="p">.</span><span class="n">toUriLiteral</span><span class="p">());</span> + <span class="p">}</span> + <span class="o">//</span><span class="k">return</span> <span class="n">the</span> <span class="n">binary</span> <span class="n">statement</span> + <span class="k">return</span> <span class="n">leftSide</span> <span class="o">+</span> " " <span class="o">+</span> <span class="n">sqlOperator</span> <span class="o">+</span> " " <span class="o">+</span> <span class="n">rightSide</span><span class="p">;</span> + <span class="p">}</span> +</pre></div> + + +<p>The signature for this method contains the binaryExpression as an object as well as the left and right Side of this binary expression. In this example the left side would be "a" and the right side would be "b" which we got from the visitLiteral() method. In between we set the operator in its SQL syntax.</p> +<p>Finally the <code>visitFilter()</code> method is called:</p> +<div class="codehilite"><pre> <span class="p">@</span><span class="n">Override</span> + <span class="n">public</span> <span class="n">Object</span> <span class="n">visitFilterExpression</span><span class="p">(</span><span class="n">FilterExpression</span> <span class="n">filterExpression</span><span class="p">,</span> <span class="n">String</span> <span class="n">expressionString</span><span class="p">,</span> <span class="n">Object</span> <span class="n">expression</span><span class="p">)</span> <span class="p">{</span> + <span class="k">return</span> "<span class="n">WHERE</span> " <span class="o">+</span> <span class="n">expression</span><span class="p">;</span> + <span class="p">}</span> +</pre></div> + + +<p>Here we just append the WHERE at the beginning and give the whole thing back to the caller of the <code>accept()</code> method.</p> +<p>A simple test can show how the expression is transformed. As one can see the <code>UriParser</code> can parse a filter expression if necessary. Usually the application will already have the filter expression.</p> +<div class="codehilite"><pre><span class="p">@</span><span class="n">Test</span> +<span class="n">public</span> <span class="n">void</span> <span class="n">printExpression</span><span class="p">()</span> <span class="n">throws</span> <span class="n">Exception</span> <span class="p">{</span> + <span class="n">FilterExpression</span> <span class="n">expression</span> <span class="p">=</span> <span class="n">UriParser</span><span class="p">.</span><span class="n">parseFilter</span><span class="p">(</span><span class="n">null</span><span class="p">,</span> <span class="n">null</span><span class="p">,</span> "<span class="s">'a'</span> <span class="n">eq</span> <span class="s">'b'</span>"<span class="p">);</span> + <span class="n">String</span> <span class="n">whereClause</span> <span class="p">=</span> <span class="p">(</span><span class="n">String</span><span class="p">)</span> <span class="n">expression</span><span class="p">.</span><span class="n">accept</span><span class="p">(</span><span class="n">new</span> <span class="n">JdbcStringVisitor</span><span class="p">());</span> + <span class="n">System</span><span class="p">.</span><span class="n">out</span><span class="p">.</span><span class="n">println</span><span class="p">(</span>"<span class="n">Raw</span><span class="p">:</span> " <span class="o">+</span> <span class="n">rawExpression</span> <span class="o">+</span> " <span class="o">------></span> <span class="n">Whereclause</span><span class="p">:</span> " <span class="o">+</span> <span class="n">whereClause</span><span class="p">);</span> + <span class="n">System</span><span class="p">.</span><span class="n">out</span><span class="p">.</span><span class="n">println</span><span class="p">();</span> + <span class="p">}</span> +</pre></div> + + +<p>The output will be:</p> +<div class="codehilite"><pre><span class="n">Raw</span><span class="p">:</span> <span class="s">'a'</span> <span class="n">eq</span> <span class="s">'b'</span> <span class="o">------></span> <span class="n">Whereclause</span><span class="p">:</span> <span class="s">'a'</span> <span class="p">=</span> <span class="s">'b'</span> +</pre></div> + + +<p>The implementation right now can only transform literals which will not be sufficient if you want to address a property. If an expression contains properties like "EmployeeId" we have to implement the method <code>visitProperty()</code>.</p> +<div class="codehilite"><pre><span class="p">@</span><span class="n">Override</span> +<span class="n">public</span> <span class="n">Object</span> <span class="n">visitProperty</span><span class="p">(</span><span class="n">PropertyExpression</span> <span class="n">propertyExpression</span><span class="p">,</span> <span class="n">String</span> <span class="n">uriLiteral</span><span class="p">,</span> <span class="n">EdmTyped</span> <span class="n">edmProperty</span><span class="p">)</span> <span class="p">{</span> + <span class="k">if</span> <span class="p">(</span><span class="n">edmProperty</span> <span class="o">==</span> <span class="n">null</span><span class="p">)</span> <span class="p">{</span> + <span class="o">//</span><span class="n">If</span> <span class="n">a</span> <span class="n">property</span> <span class="n">is</span> <span class="n">not</span> <span class="n">found</span> <span class="n">it</span> <span class="n">wont</span> <span class="n">be</span> <span class="n">represented</span> <span class="n">in</span> <span class="n">the</span> <span class="n">database</span> <span class="n">thus</span> <span class="n">we</span> <span class="n">have</span> <span class="n">to</span> <span class="n">throw</span> <span class="n">an</span> <span class="n">exception</span> + <span class="n">throw</span> <span class="n">new</span> <span class="n">PropertyNotFoundException</span><span class="p">(</span>"<span class="n">Could</span> <span class="n">not</span> <span class="nb">find</span> <span class="n">Property</span><span class="p">:</span> " <span class="o">+</span> <span class="n">uriLiteral</span><span class="p">);</span> + <span class="p">}</span> <span class="k">else</span> <span class="p">{</span> + <span class="o">//</span><span class="n">It</span> <span class="n">is</span> <span class="n">also</span> <span class="n">possible</span> <span class="n">to</span> <span class="n">use</span> <span class="n">the</span> <span class="n">mapping</span> <span class="n">of</span> <span class="n">the</span> <span class="n">edmProperty</span> <span class="k">if</span> <span class="n">the</span> <span class="n">name</span> <span class="n">differs</span> <span class="n">from</span> <span class="n">the</span> <span class="n">databasename</span> + <span class="k">try</span> <span class="p">{</span> + <span class="k">return</span> <span class="n">edmProperty</span><span class="p">.</span><span class="n">getName</span><span class="p">();</span> + <span class="p">}</span> <span class="k">catch</span> <span class="p">(</span><span class="n">EdmException</span> <span class="n">e</span><span class="p">)</span> <span class="p">{</span> + <span class="n">throw</span> <span class="n">new</span> <span class="n">PropertyNotFoundException</span><span class="p">(</span><span class="n">e</span><span class="p">);</span> + <span class="p">}</span> + <span class="p">}</span> +<span class="p">}</span> +</pre></div> + + +<p>This method has an <code>edmProperty</code> in its signature which is set if the <code>uriLiteral</code> matches a property in the <code>EntityType</code>. Now we could transform an expression like <code>"EmployeeId eq '1'" or "EmployeeId eq '1' and ManagerId eq '2'"</code>. To get a validation if the property exists we have to give an <code>EntityType</code> on which the filter will be applied. In this case we use the <code>EntityType</code> "Employee".</p> +<div class="codehilite"><pre><span class="p">@</span><span class="n">Test</span> +<span class="n">public</span> <span class="n">void</span> <span class="n">printExpressionWithProperty</span><span class="p">()</span> <span class="n">throws</span> <span class="n">Exception</span> <span class="p">{</span> + <span class="o">//</span><span class="n">Use</span> <span class="n">a</span> <span class="n">mocked</span> <span class="n">edmProvider</span> <span class="k">for</span> <span class="n">this</span> <span class="n">tutorial</span> + <span class="n">TestEdmProvider</span> <span class="n">provider</span> <span class="p">=</span> <span class="n">new</span> <span class="n">TestEdmProvider</span><span class="p">();</span> + <span class="n">Edm</span> <span class="n">edm</span> <span class="p">=</span> <span class="n">RuntimeDelegate</span><span class="p">.</span><span class="n">createEdm</span><span class="p">(</span><span class="n">provider</span><span class="p">);</span> + <span class="n">EdmEntityType</span> <span class="n">entityType</span> <span class="p">=</span> <span class="n">edm</span><span class="p">.</span><span class="n">getEntityType</span><span class="p">(</span><span class="n">TestEdmProvider</span><span class="p">.</span><span class="n">NAMESPACE_1</span><span class="p">,</span> <span class="n">TestEdmProvider</span><span class="p">.</span><span class="n">ENTITY_TYPE_1_1</span><span class="p">.</span><span class="n">getName</span><span class="p">());</span> + + <span class="n">String</span> <span class="n">rawExpression</span> <span class="p">=</span> "<span class="n">EmployeeId</span> <span class="n">eq</span> <span class="s">'1'</span>"<span class="p">;</span> + <span class="n">FilterExpression</span> <span class="n">expression</span> <span class="p">=</span> <span class="n">UriParser</span><span class="p">.</span><span class="n">parseFilter</span> <span class="p">(</span><span class="n">null</span><span class="p">,</span> <span class="n">entityType</span><span class="p">,</span> <span class="n">rawExpression</span><span class="p">);</span> + <span class="n">String</span> <span class="n">whereClause</span> <span class="p">=</span> <span class="p">(</span><span class="n">String</span><span class="p">)</span> <span class="n">expression</span><span class="p">.</span><span class="n">accept</span><span class="p">(</span><span class="n">new</span> <span class="n">JdbcSimpleStringVisitor</span><span class="p">());</span> + <span class="n">System</span><span class="p">.</span><span class="n">out</span><span class="p">.</span><span class="n">println</span><span class="p">(</span>"<span class="n">Raw</span><span class="p">:</span> " <span class="o">+</span> <span class="n">rawExpression</span> <span class="o">+</span> " <span class="o">------></span> <span class="n">Whereclause</span><span class="p">:</span> " <span class="o">+</span> <span class="n">whereClause</span><span class="p">);</span> + <span class="n">System</span><span class="p">.</span><span class="n">out</span><span class="p">.</span><span class="n">println</span><span class="p">();</span> +<span class="p">}</span> +</pre></div> + + +<p>The output will be:</p> +<div class="codehilite"><pre><span class="n">Raw</span><span class="o">:</span> <span class="n">EmployeeId</span> <span class="n">eq</span> <span class="s1">'1'</span> <span class="o">------></span> <span class="n">Whereclause</span><span class="o">:</span> <span class="n">WHERE</span> <span class="n">EmployeeId</span> <span class="o">=</span> <span class="s1">'1'</span> +</pre></div> + + +<p>Test in the sources: JdbcSimpleStringVisitorTest.class</p> +<h5 id="advanced-example">Advanced Example</h5> +<p>The implementation shown in the previous chapter can transform simple expressions. But if the expression gets more complex like <code>"'a' eq 'b' or ('c' eq 'd' and 'b' eq 'd')"</code> it won´t produce a correct where clause. The following test shows this.</p> +<div class="codehilite"><pre><span class="p">@</span><span class="n">Test</span> +<span class="n">public</span> <span class="n">void</span> <span class="n">compareSimpleAndAdvancedVisitor</span><span class="p">()</span> <span class="n">throws</span> <span class="n">Exception</span><span class="p">{</span> + <span class="n">String</span> <span class="n">rawExpression</span> <span class="p">=</span> "<span class="s">'a'</span> <span class="n">eq</span> <span class="s">'b'</span> <span class="n">or</span> <span class="p">(</span><span class="s">'c'</span> <span class="n">eq</span> <span class="s">'d'</span> <span class="n">and</span> <span class="s">'b'</span> <span class="n">eq</span> <span class="s">'d'</span><span class="p">)</span>"<span class="p">;</span> + <span class="n">FilterExpression</span> <span class="n">expression</span> <span class="p">=</span> <span class="n">UriParser</span><span class="p">.</span><span class="n">parseFilter</span><span class="p">(</span><span class="n">null</span><span class="p">,</span> <span class="n">null</span><span class="p">,</span> <span class="n">rawExpression</span><span class="p">);</span> + + <span class="n">String</span> <span class="n">whereClauseSimple</span> <span class="p">=</span> <span class="p">(</span><span class="n">String</span><span class="p">)</span> <span class="n">expression</span><span class="p">.</span><span class="n">accept</span><span class="p">(</span><span class="n">new</span> <span class="n">JdbcSimpleStringVisitor</span><span class="p">());</span> + <span class="n">String</span> <span class="n">whereClauseAdvanced</span> <span class="p">=</span> <span class="p">(</span><span class="n">String</span><span class="p">)</span> <span class="n">expression</span><span class="p">.</span><span class="n">accept</span><span class="p">(</span><span class="n">new</span> <span class="n">JdbcAdvancedStringVisitor</span><span class="p">());</span> + <span class="n">System</span><span class="p">.</span><span class="n">out</span><span class="p">.</span><span class="n">println</span><span class="p">(</span>"<span class="n">Simple</span><span class="p">:</span> " <span class="o">+</span> <span class="n">whereClauseSimple</span> <span class="o">+</span> " <span class="o">------></span> <span class="n">Advanced</span><span class="p">:</span> " <span class="o">+</span> <span class="n">whereClauseAdvanced</span><span class="p">);</span> +<span class="p">}</span> +</pre></div> + + +<p>The output will be:</p> +<div class="codehilite"><pre><span class="n">Simple</span><span class="o">:</span> <span class="n">WHERE</span> <span class="s1">'a'</span> <span class="o">=</span> <span class="s1">'b'</span> <span class="n">OR</span> <span class="s1">'c'</span> <span class="o">=</span> <span class="s1">'d'</span> <span class="n">AND</span> <span class="s1">'b'</span> <span class="o">=</span> <span class="s1">'d'</span> <span class="o">------></span> <span class="n">Advanced</span><span class="o">:</span> <span class="n">WHERE</span> <span class="s1">'a'</span> <span class="o">=</span> <span class="s1">'b'</span> <span class="n">OR</span> <span class="o">(</span><span class="s1">'c'</span> <span class="o">=</span> <span class="s1">'d'</span> <span class="n">AND</span> <span class="s1">'b'</span> <span class="o">=</span> <span class="s1">'d'</span><span class="o">)</span> +</pre></div> + + +<p>In the simple implementation the brackets will not be transformed. To fix this the method <code>visitBinary()</code> has to be enhanced.</p> +<div class="codehilite"><pre><span class="p">@</span><span class="n">Override</span> +<span class="n">public</span> <span class="n">Object</span> <span class="n">visitBinary</span><span class="p">(</span><span class="n">BinaryExpression</span> <span class="n">binaryExpression</span><span class="p">,</span> <span class="n">BinaryOperator</span> <span class="n">operator</span><span class="p">,</span> <span class="n">Object</span> <span class="n">leftSide</span><span class="p">,</span> <span class="n">Object</span> <span class="n">rightSide</span><span class="p">)</span> <span class="p">{</span> + <span class="n">String</span> <span class="n">actualLeftSide</span> <span class="p">=</span> <span class="n">leftSide</span><span class="p">.</span><span class="n">toString</span><span class="p">();</span> + <span class="n">String</span> <span class="n">actualRightSide</span> <span class="p">=</span> <span class="n">rightSide</span><span class="p">.</span><span class="n">toString</span><span class="p">();</span> + <span class="k">if</span> <span class="p">(</span><span class="n">leftSide</span> <span class="n">instanceof</span> <span class="n">Expression</span><span class="p">)</span> <span class="p">{</span> + <span class="o">//</span><span class="n">If</span> <span class="n">something</span> <span class="n">is</span> <span class="n">lower</span> <span class="n">in</span> <span class="n">the</span> <span class="n">tree</span> <span class="n">and</span> <span class="n">is</span> <span class="n">of</span> <span class="n">the</span> <span class="n">type</span> <span class="n">AND</span> <span class="n">or</span> <span class="n">OR</span> <span class="n">it</span> <span class="n">needs</span> <span class="n">brackets</span> <span class="n">to</span> <span class="n">show</span> <span class="n">the</span> <span class="n">higher</span> <span class="n">priority</span> + <span class="k">if</span> <span class="p">(</span><span class="n">BinaryOperator</span><span class="p">.</span><span class="n">AND</span><span class="p">.</span><span class="n">equals</span><span class="p">(((</span><span class="n">Expression</span><span class="p">)</span> <span class="n">leftSide</span><span class="p">).</span><span class="n">getOperator</span><span class="p">())</span> <span class="o">||</span> <span class="n">BinaryOperator</span><span class="p">.</span><span class="n">OR</span><span class="p">.</span><span class="n">equals</span><span class="p">(((</span><span class="n">Expression</span><span class="p">)</span> <span class="n">leftSide</span><span class="p">).</span><span class="n">getOperator</span><span class="p">()))</span> <span class="p">{</span> + <span class="n">actualLeftSide</span> <span class="p">=</span> "<span class="p">(</span>" <span class="o">+</span> <span class="n">leftSide</span> <span class="o">+</span> "<span class="p">)</span>"<span class="p">;</span> + <span class="p">}</span> + <span class="p">}</span> + <span class="k">if</span> <span class="p">(</span><span class="n">rightSide</span> <span class="n">instanceof</span> <span class="n">Expression</span><span class="p">)</span> <span class="p">{</span> + <span class="o">//</span><span class="n">If</span> <span class="n">something</span> <span class="n">is</span> <span class="n">lower</span> <span class="n">in</span> <span class="n">the</span> <span class="n">tree</span> <span class="n">and</span> <span class="n">is</span> <span class="n">of</span> <span class="n">the</span> <span class="n">type</span> <span class="n">AND</span> <span class="n">or</span> <span class="n">OR</span> <span class="n">it</span> <span class="n">needs</span> <span class="n">brackets</span> <span class="n">to</span> <span class="n">show</span> <span class="n">the</span> <span class="n">higher</span> <span class="n">priority</span> + <span class="k">if</span> <span class="p">(</span><span class="n">BinaryOperator</span><span class="p">.</span><span class="n">AND</span><span class="p">.</span><span class="n">equals</span><span class="p">(((</span><span class="n">Expression</span><span class="p">)</span> <span class="n">rightSide</span><span class="p">).</span><span class="n">getOperator</span><span class="p">())</span> <span class="o">||</span> <span class="n">BinaryOperator</span><span class="p">.</span><span class="n">OR</span><span class="p">.</span><span class="n">equals</span><span class="p">(((</span><span class="n">Expression</span><span class="p">)</span> <span class="n">rightSide</span><span class="p">).</span><span class="n">getOperator</span><span class="p">()))</span> <span class="p">{</span> + <span class="n">actualRightSide</span> <span class="p">=</span> "<span class="p">(</span>" <span class="o">+</span> <span class="n">rightSide</span> <span class="o">+</span> "<span class="p">)</span>"<span class="p">;</span> + <span class="p">}</span> + <span class="p">}</span> + <span class="o">//</span><span class="n">Transform</span> <span class="n">the</span> <span class="n">OData</span> <span class="n">filter</span> <span class="n">operator</span> <span class="n">into</span> <span class="n">an</span> <span class="n">equivalent</span> <span class="n">sql</span> <span class="n">operator</span> + <span class="n">String</span> <span class="n">sqlOperator</span> <span class="p">=</span> ""<span class="p">;</span> + <span class="k">switch</span> <span class="p">(</span><span class="n">operator</span><span class="p">)</span> <span class="p">{</span> + <span class="k">case</span> <span class="n">EQ</span><span class="p">:</span> + <span class="n">sqlOperator</span> <span class="p">=</span> "<span class="p">=</span>"<span class="p">;</span> + <span class="k">break</span><span class="p">;</span> + <span class="k">case</span> <span class="n">NE</span><span class="p">:</span> + <span class="n">sqlOperator</span> <span class="p">=</span> "<span class="o"><></span>"<span class="p">;</span> + <span class="k">break</span><span class="p">;</span> + <span class="k">case</span> <span class="n">OR</span><span class="p">:</span> + <span class="n">sqlOperator</span> <span class="p">=</span> "<span class="n">OR</span>"<span class="p">;</span> + <span class="k">break</span><span class="p">;</span> + <span class="k">case</span> <span class="n">AND</span><span class="p">:</span> + <span class="n">sqlOperator</span> <span class="p">=</span> "<span class="n">AND</span>"<span class="p">;</span> + <span class="k">break</span><span class="p">;</span> + <span class="k">case</span> <span class="n">GE</span><span class="p">:</span> + <span class="n">sqlOperator</span> <span class="p">=</span> "<span class="o">></span><span class="p">=</span>"<span class="p">;</span> + <span class="k">break</span><span class="p">;</span> + <span class="k">case</span> <span class="n">GT</span><span class="p">:</span> + <span class="n">sqlOperator</span> <span class="p">=</span> "<span class="o">></span>"<span class="p">;</span> + <span class="k">break</span><span class="p">;</span> + <span class="k">case</span> <span class="n">LE</span><span class="p">:</span> + <span class="n">sqlOperator</span> <span class="p">=</span> "<span class="o"><</span><span class="p">=</span>"<span class="p">;</span> + <span class="k">break</span><span class="p">;</span> + <span class="k">case</span> <span class="n">LT</span><span class="p">:</span> + <span class="n">sqlOperator</span> <span class="p">=</span> "<span class="o"><</span>"<span class="p">;</span> + <span class="k">break</span><span class="p">;</span> + <span class="n">default</span><span class="p">:</span> + <span class="o">//</span><span class="n">Other</span> <span class="n">operators</span> <span class="n">are</span> <span class="n">not</span> <span class="n">supported</span> <span class="k">for</span> <span class="n">SQL</span> <span class="n">Statements</span> + <span class="n">throw</span> <span class="n">new</span> <span class="n">UnsupportetOperatorException</span><span class="p">(</span>"<span class="n">Unsupported</span> <span class="n">operator</span><span class="p">:</span> " <span class="o">+</span> <span class="n">operator</span><span class="p">.</span><span class="n">toUriLiteral</span><span class="p">());</span> + <span class="p">}</span> + + <span class="o">//</span><span class="k">return</span> <span class="n">the</span> <span class="n">binary</span> <span class="n">statement</span> + <span class="k">return</span> <span class="n">new</span> <span class="n">Expression</span><span class="p">(</span><span class="n">actualLeftSide</span> <span class="o">+</span> " " <span class="o">+</span> <span class="n">sqlOperator</span> <span class="o">+</span> " " <span class="o">+</span> <span class="n">actualRightSide</span><span class="p">,</span> <span class="n">operator</span><span class="p">);</span> +<span class="p">}</span> +</pre></div> + + +<p>Since simple strings cannot show this complexity a new private class "Expression" was introduced. The signature of all <code>visit()</code> methods accept any kind of object so we can mix in the new class. Now we only have to check if one side of the tree is of type String or Expression.</p> +<p>Test in the sources: JdbcAdvancedStringVisitorTest.class</p> +<h5 id="example-with-prepared-statements">Example with prepared Statements</h5> +<p>Since string concatenation is very vulnerable against SQL Injection a best practice is to use prepared statements. This can be a tough challenge in this case because not only the value of <code>EmployeeId</code> is supplied in the filter expression but the field EmployeeId and the operator as well. Prepared Statements don´t allow statements like <code>"WHERE ? ? ?"</code> thus we have to find a way to prepare the prepared statements in advance which can be very complex as the following example will show: The filter expression <code>"EmployeeId eq '1' and ManagerId eq '2'"</code> is the same as <code>"ManagerId eq '2' and EmployeeId eq '1'"</code> but the prepared statement will always look like <code>"â¦. WHERE EmployeeId = ? and ManagerId = ?"</code>.</p> +<p>This tutorial will not solve this problem. Instead it will show a first idea on how to implement such a prepared statement visitor. Again the Where clause will be created using string concatenation. But this time we will replace literals with a "?". These questionmarks can be set in a prepared statement. The methods <code>visitLiteral</code> and <code>visitProperty</code> will just return their value while the <code>visitBinary</code> will contain the logic.</p> +<p>VisitLiteral:</p> +<div class="codehilite"><pre><span class="p">@</span><span class="n">Override</span> +<span class="n">public</span> <span class="n">Object</span> <span class="n">visitLiteral</span><span class="p">(</span><span class="n">final</span> <span class="n">LiteralExpression</span> <span class="n">literal</span><span class="p">,</span> <span class="n">final</span> <span class="n">EdmLiteral</span> <span class="n">edmLiteral</span><span class="p">)</span> <span class="p">{</span> + <span class="o">//</span><span class="n">Sql</span> <span class="n">Injection</span> <span class="n">is</span> <span class="n">not</span> <span class="n">possible</span> <span class="n">anymore</span> <span class="n">since</span> <span class="n">we</span> <span class="n">are</span> <span class="n">using</span> <span class="n">prepared</span> <span class="n">statements</span><span class="p">.</span> <span class="n">Thus</span> <span class="n">we</span> <span class="n">can</span> <span class="n">just</span> <span class="n">give</span> <span class="n">back</span> <span class="n">the</span> <span class="n">edmLiteral</span> <span class="n">content</span> + <span class="k">return</span> <span class="n">edmLiteral</span><span class="p">.</span><span class="n">getLiteral</span><span class="p">();</span> +<span class="p">}</span> +</pre></div> + + +<p>VisitProperty:</p> +<div class="codehilite"><pre><span class="p">@</span><span class="n">Override</span> +<span class="n">public</span> <span class="n">Object</span> <span class="n">visitProperty</span><span class="p">(</span><span class="n">final</span> <span class="n">PropertyExpression</span> <span class="n">propertyExpression</span><span class="p">,</span> <span class="n">final</span> <span class="n">String</span> <span class="n">uriLiteral</span><span class="p">,</span> <span class="n">final</span> <span class="n">EdmTyped</span> <span class="n">edmProperty</span><span class="p">)</span> <span class="p">{</span> + <span class="k">if</span> <span class="p">(</span><span class="n">edmProperty</span> <span class="o">==</span> <span class="n">null</span><span class="p">)</span> <span class="p">{</span> + <span class="o">//</span><span class="n">If</span> <span class="n">a</span> <span class="n">property</span> <span class="n">is</span> <span class="n">not</span> <span class="n">found</span> <span class="n">it</span> <span class="n">wont</span> <span class="n">be</span> <span class="n">represented</span> <span class="n">in</span> <span class="n">the</span> <span class="n">database</span> <span class="n">thus</span> <span class="n">we</span> <span class="n">have</span> <span class="n">to</span> <span class="n">throw</span> <span class="n">an</span> <span class="n">exception</span> + <span class="n">throw</span> <span class="n">new</span> <span class="n">PropertyNotFoundException</span><span class="p">(</span>"<span class="n">Could</span> <span class="n">not</span> <span class="nb">find</span> <span class="n">Property</span><span class="p">:</span> " <span class="o">+</span> <span class="n">uriLiteral</span><span class="p">);</span> + <span class="p">}</span> <span class="k">else</span> <span class="p">{</span> + <span class="o">//</span><span class="n">To</span> <span class="n">distinguish</span> <span class="n">between</span> <span class="n">literals</span> <span class="n">and</span> <span class="k">properties</span> <span class="n">we</span> <span class="n">give</span> <span class="n">back</span> <span class="n">the</span> <span class="n">whole</span> <span class="n">edmProperty</span> <span class="n">in</span> <span class="n">this</span> <span class="k">case</span> + <span class="k">return</span> <span class="n">edmProperty</span><span class="p">;</span> + <span class="p">}</span> +<span class="p">}</span> +</pre></div> + + +<p>In addition we will use the following class as a container for the where clause and the parameters:</p> +<div class="codehilite"><pre><span class="n">public</span> <span class="n">class</span> <span class="n">Expression</span> <span class="p">{</span> + <span class="n">private</span> <span class="n">String</span> <span class="n">preparedWhere</span><span class="p">;</span> + <span class="n">private</span> <span class="n">List</span><span class="o"><</span><span class="n">Object</span><span class="o">></span> <span class="n">parameters</span><span class="p">;</span> + <span class="n">private</span> <span class="n">BinaryOperator</span> <span class="n">operator</span><span class="p">;</span> + + <span class="n">public</span> <span class="n">Expression</span><span class="p">(</span><span class="n">final</span> <span class="n">BinaryOperator</span> <span class="n">operator</span><span class="p">)</span> <span class="p">{</span> + <span class="n">preparedWhere</span> <span class="p">=</span> ""<span class="p">;</span> + <span class="n">parameters</span> <span class="p">=</span> <span class="n">new</span> <span class="n">ArrayList</span><span class="o"><</span><span class="n">Object</span><span class="o">></span><span class="p">();</span> + <span class="n">this</span><span class="p">.</span><span class="n">operator</span> <span class="p">=</span> <span class="n">operator</span><span class="p">;</span> + <span class="p">}</span> + + <span class="n">public</span> <span class="n">void</span> <span class="n">addParameter</span><span class="p">(</span><span class="n">final</span> <span class="n">Object</span> <span class="n">parameter</span><span class="p">)</span> <span class="p">{</span> + <span class="n">parameters</span><span class="p">.</span><span class="n">add</span><span class="p">(</span><span class="n">parameter</span><span class="p">);</span> + <span class="p">}</span> + + <span class="n">public</span> <span class="n">void</span> <span class="n">setPrepeparedWhere</span><span class="p">(</span><span class="n">final</span> <span class="n">String</span> <span class="n">where</span><span class="p">)</span> <span class="p">{</span> + <span class="n">preparedWhere</span> <span class="p">=</span> <span class="n">where</span><span class="p">;</span> + <span class="p">}</span> + + <span class="n">public</span> <span class="n">List</span><span class="o"><</span><span class="n">Object</span><span class="o">></span> <span class="n">getParameters</span><span class="p">()</span> <span class="p">{</span> + <span class="k">return</span> <span class="n">parameters</span><span class="p">;</span> + <span class="p">}</span> + + <span class="n">public</span> <span class="n">BinaryOperator</span> <span class="n">getOperator</span><span class="p">()</span> <span class="p">{</span> + <span class="k">return</span> <span class="n">operator</span><span class="p">;</span> + <span class="p">}</span> + + <span class="p">@</span><span class="n">Override</span> + <span class="n">public</span> <span class="n">String</span> <span class="n">toString</span><span class="p">()</span> <span class="p">{</span> + <span class="k">return</span> <span class="n">preparedWhere</span><span class="p">;</span> + <span class="p">}</span> +<span class="p">}</span> +</pre></div> + + +<p>Finally the visitBinary method:</p> +<div class="codehilite"><pre><span class="p">@</span><span class="n">Override</span> +<span class="n">public</span> <span class="n">Object</span> <span class="n">visitBinary</span><span class="p">(</span><span class="n">final</span> <span class="n">BinaryExpression</span> <span class="n">binaryExpression</span><span class="p">,</span> <span class="n">final</span> <span class="n">BinaryOperator</span> <span class="n">operator</span><span class="p">,</span> <span class="n">final</span> <span class="n">Object</span> <span class="n">leftSide</span><span class="p">,</span> <span class="n">final</span> <span class="n">Object</span> <span class="n">rightSide</span><span class="p">)</span> <span class="p">{</span> + <span class="o">//</span><span class="n">Transform</span> <span class="n">the</span> <span class="n">OData</span> <span class="n">filter</span> <span class="n">operator</span> <span class="n">into</span> <span class="n">an</span> <span class="n">equivalent</span> <span class="n">sql</span> <span class="n">operator</span> + <span class="n">String</span> <span class="n">sqlOperator</span> <span class="p">=</span> ""<span class="p">;</span> + <span class="k">switch</span> <span class="p">(</span><span class="n">operator</span><span class="p">)</span> <span class="p">{</span> + <span class="k">case</span> <span class="n">EQ</span><span class="p">:</span> + <span class="n">sqlOperator</span> <span class="p">=</span> "<span class="p">=</span>"<span class="p">;</span> + <span class="k">break</span><span class="p">;</span> + <span class="k">case</span> <span class="n">NE</span><span class="p">:</span> + <span class="n">sqlOperator</span> <span class="p">=</span> "<span class="o"><></span>"<span class="p">;</span> + <span class="k">break</span><span class="p">;</span> + <span class="k">case</span> <span class="n">OR</span><span class="p">:</span> + <span class="n">sqlOperator</span> <span class="p">=</span> "<span class="n">OR</span>"<span class="p">;</span> + <span class="k">break</span><span class="p">;</span> + <span class="k">case</span> <span class="n">AND</span><span class="p">:</span> + <span class="n">sqlOperator</span> <span class="p">=</span> "<span class="n">AND</span>"<span class="p">;</span> + <span class="k">break</span><span class="p">;</span> + <span class="k">case</span> <span class="n">GE</span><span class="p">:</span> + <span class="n">sqlOperator</span> <span class="p">=</span> "<span class="o">></span><span class="p">=</span>"<span class="p">;</span> + <span class="k">break</span><span class="p">;</span> + <span class="k">case</span> <span class="n">GT</span><span class="p">:</span> + <span class="n">sqlOperator</span> <span class="p">=</span> "<span class="o">></span>"<span class="p">;</span> + <span class="k">break</span><span class="p">;</span> + <span class="k">case</span> <span class="n">LE</span><span class="p">:</span> + <span class="n">sqlOperator</span> <span class="p">=</span> "<span class="o"><</span><span class="p">=</span>"<span class="p">;</span> + <span class="k">break</span><span class="p">;</span> + <span class="k">case</span> <span class="n">LT</span><span class="p">:</span> + <span class="n">sqlOperator</span> <span class="p">=</span> "<span class="o"><</span>"<span class="p">;</span> + <span class="k">break</span><span class="p">;</span> + <span class="n">default</span><span class="p">:</span> + <span class="o">//</span><span class="n">Other</span> <span class="n">operators</span> <span class="n">are</span> <span class="n">not</span> <span class="n">supported</span> <span class="k">for</span> <span class="n">SQL</span> <span class="n">Statements</span> + <span class="n">throw</span> <span class="n">new</span> <span class="n">UnsupportetOperatorException</span><span class="p">(</span>"<span class="n">Unsupported</span> <span class="n">operator</span><span class="p">:</span> " <span class="o">+</span> <span class="n">operator</span><span class="p">.</span><span class="n">toUriLiteral</span><span class="p">());</span> + <span class="p">}</span> + <span class="o">//</span><span class="n">The</span> <span class="n">idea</span> <span class="n">is</span> <span class="n">to</span> <span class="n">check</span> <span class="k">if</span> <span class="n">the</span> <span class="n">left</span> <span class="n">side</span> <span class="n">is</span> <span class="n">of</span> <span class="n">type</span> <span class="n">property</span><span class="p">.</span> <span class="n">If</span> <span class="n">this</span> <span class="n">is</span> <span class="n">the</span> <span class="k">case</span> <span class="n">we</span> <span class="n">append</span> <span class="n">the</span> <span class="n">property</span> <span class="n">name</span> <span class="n">and</span> <span class="n">the</span> <span class="n">operator</span> <span class="n">to</span> <span class="n">the</span> <span class="n">where</span> <span class="n">clause</span> + <span class="k">if</span> <span class="p">(</span><span class="n">leftSide</span> <span class="n">instanceof</span> <span class="n">EdmTyped</span> <span class="o">&&</span> <span class="n">rightSide</span> <span class="n">instanceof</span> <span class="n">String</span><span class="p">)</span> <span class="p">{</span> + <span class="n">Expression</span> <span class="n">expression</span> <span class="p">=</span> <span class="n">new</span> <span class="n">Expression</span><span class="p">(</span><span class="n">operator</span><span class="p">);</span> + <span class="k">try</span> <span class="p">{</span> + <span class="n">expression</span><span class="p">.</span><span class="n">setPrepeparedWhere</span><span class="p">(((</span><span class="n">EdmTyped</span><span class="p">)</span> <span class="n">leftSide</span><span class="p">).</span><span class="n">getName</span><span class="p">()</span> <span class="o">+</span> " " <span class="o">+</span> <span class="n">sqlOperator</span> <span class="o">+</span> " ?"<span class="p">);</span> + <span class="p">}</span> <span class="k">catch</span> <span class="p">(</span><span class="n">EdmException</span> <span class="n">e</span><span class="p">)</span> <span class="p">{</span> + <span class="n">throw</span> <span class="n">new</span> <span class="n">RuntimeException</span><span class="p">(</span>"<span class="n">EdmException</span> <span class="n">occured</span>"<span class="p">);</span> + <span class="p">}</span> + <span class="n">expression</span><span class="p">.</span><span class="n">addParameter</span><span class="p">(</span><span class="n">rightSide</span><span class="p">);</span> + <span class="k">return</span> <span class="n">expression</span><span class="p">;</span> + <span class="p">}</span> <span class="k">else</span> <span class="k">if</span> <span class="p">(</span><span class="n">leftSide</span> <span class="n">instanceof</span> <span class="n">Expression</span> <span class="o">&&</span> <span class="n">rightSide</span> <span class="n">instanceof</span> <span class="n">Expression</span><span class="p">)</span> <span class="p">{</span> + <span class="n">Expression</span> <span class="n">returnExpression</span> <span class="p">=</span> <span class="n">new</span> <span class="n">Expression</span><span class="p">(</span><span class="n">operator</span><span class="p">);</span> + <span class="n">Expression</span> <span class="n">leftSideExpression</span> <span class="p">=</span> <span class="p">(</span><span class="n">Expression</span><span class="p">)</span> <span class="n">leftSide</span><span class="p">;</span> + <span class="k">if</span> <span class="p">(</span><span class="n">BinaryOperator</span><span class="p">.</span><span class="n">AND</span><span class="p">.</span><span class="n">equals</span> <span class="p">(</span><span class="n">leftSideExpression</span><span class="p">.</span><span class="n">getOperator</span><span class="p">())</span> <span class="o">||</span> <span class="n">BinaryOperator</span><span class="p">.</span><span class="n">OR</span><span class="p">.</span><span class="n">equals</span><span class="p">(</span><span class="n">leftSideExpression</span><span class="p">.</span><span class="n">getOperator</span><span class="p">()))</span> <span class="p">{</span> + <span class="n">leftSideExpression</span><span class="p">.</span><span class="n">setPrepeparedWhere</span><span class="p">(</span>"<span class="p">(</span>" <span class="o">+</span> <span class="n">leftSideExpression</span><span class="p">.</span><span class="n">toString</span><span class="p">()</span> <span class="o">+</span> "<span class="p">)</span>"<span class="p">);</span> + <span class="p">}</span> + <span class="n">Expression</span> <span class="n">rightSideExpression</span> <span class="p">=</span> <span class="p">(</span><span class="n">Expression</span><span class="p">)</span> <span class="n">rightSide</span><span class="p">;</span> + <span class="k">if</span> <span class="p">(</span><span class="n">BinaryOperator</span><span class="p">.</span><span class="n">AND</span><span class="p">.</span><span class="n">equals</span><span class="p">(</span><span class="n">rightSideExpression</span><span class="p">.</span><span class="n">getOperator</span><span class="p">())</span> <span class="o">||</span> <span class="n">BinaryOperator</span><span class="p">.</span><span class="n">OR</span><span class="p">.</span><span class="n">equals</span><span class="p">(</span><span class="n">rightSideExpression</span><span class="p">.</span><span class="n">getOperator</span><span class="p">()))</span> <span class="p">{</span> + <span class="n">rightSideExpression</span><span class="p">.</span><span class="n">setPrepeparedWhere</span><span class="p">(</span>"<span class="p">(</span>" <span class="o">+</span> <span class="n">rightSideExpression</span><span class="p">.</span><span class="n">toString</span><span class="p">()</span> <span class="o">+</span> "<span class="p">)</span>"<span class="p">);</span> + <span class="p">}</span> + <span class="n">returnExpression</span><span class="p">.</span><span class="n">setPrepeparedWhere</span><span class="p">(</span><span class="n">leftSideExpression</span><span class="p">.</span><span class="n">toString</span><span class="p">()</span> <span class="o">+</span> " " <span class="o">+</span> <span class="n">sqlOperator</span> <span class="o">+</span> " " <span class="o">+</span> <span class="n">rightSideExpression</span><span class="p">.</span><span class="n">toString</span><span class="p">());</span> + + <span class="k">for</span> <span class="p">(</span><span class="n">Object</span> <span class="n">parameter</span> <span class="p">:</span> <span class="n">leftSideExpression</span><span class="p">.</span><span class="n">getParameters</span><span class="p">())</span> <span class="p">{</span> + <span class="n">returnExpression</span><span class="p">.</span><span class="n">addParameter</span><span class="p">(</span><span class="n">parameter</span><span class="p">);</span> + <span class="p">}</span> + <span class="k">for</span> <span class="p">(</span><span class="n">Object</span> <span class="n">parameter</span> <span class="p">:</span> <span class="n">rightSideExpression</span><span class="p">.</span><span class="n">getParameters</span><span class="p">())</span> <span class="p">{</span> + <span class="n">returnExpression</span><span class="p">.</span><span class="n">addParameter</span><span class="p">(</span><span class="n">parameter</span><span class="p">);</span> + <span class="p">}</span> + <span class="k">return</span> <span class="n">returnExpression</span><span class="p">;</span> + <span class="p">}</span> <span class="k">else</span> <span class="p">{</span> + <span class="n">throw</span> <span class="n">new</span> <span class="n">RuntimeException</span><span class="p">(</span>"<span class="n">Not</span> <span class="n">right</span> <span class="n">format</span>"<span class="p">);</span> + <span class="p">}</span> +<span class="p">}</span> +</pre></div> + + +<p>This implementation will work if the filter supplies a property on the left side and a literal on the right side. The output of this new implementation could look like this:</p> +<div class="codehilite"><pre><span class="n">Raw</span><span class="o">:</span> <span class="n">EmployeeId</span> <span class="n">eq</span> <span class="s1">'1'</span> <span class="n">or</span> <span class="o">(</span><span class="n">ManagerId</span> <span class="n">eq</span> <span class="s1">'2'</span> <span class="n">and</span> <span class="n">TeamId</span> <span class="n">eq</span> <span class="s1">'3'</span><span class="o">)</span> <span class="o">------></span> <span class="n">Whereclause</span><span class="o">:</span> <span class="n">EmployeeId</span> <span class="o">=</span> <span class="o">?</span> <span class="n">OR</span> <span class="o">(</span><span class="n">ManagerId</span> <span class="o">=</span> <span class="o">?</span> <span class="n">AND</span> <span class="n">TeamId</span> <span class="o">=</span> <span class="o">?)</span> +<span class="mi">1</span> +<span class="mi">2</span> +<span class="mi">3</span> +</pre></div> + + +<p>Test in the sources: JdbcPreparedStatementVisitorTest.class</p> +<h3 id="further-information">Further Information</h3> +<p>Documentation about how to create such a filter expression can be found under <a href="http://www.odata.org"; title="External Link">http://www.odata.org</a> in the OData protocol specification.</p> +<p>Visitor pattern: <a href="http://en.wikipedia.org/wiki/Visitor_pattern"; title="External Link">http://en.wikipedia.org/wiki/Visitor_pattern</a></p><div align="center"> +<p>Copyright © 2013-2014, The Apache Software Foundation<br> + Apache Olingo, Olingo, Apache, the Apache feather, and + the Apache Olingo project logo are trademarks of the Apache Software + Foundation.</p> + <small><a href="/doc/odata2/privacy.html">Privacy</a></small> + </div> + </div><!-- /container --> + <!-- Bootstrap core JavaScript + ================================================== --> + <!-- Placed at the end of the document so the pages load faster --> + <script src="/js/jquery.js" type="text/javascript"> +</script> + <script src="/js/bootstrap.js" type="text/javascript"> + <script src="/js/offcanvas.js" type="text/javascript"> +</script> + <!-- Google Analytics: change UA-XXXXX-X to be your site's ID. --> + <script> + (function(b,o,i,l,e,r){b.GoogleAnalyticsObject=l;b[l]||(b[l]= + function(){(b[l].q=b[l].q||[]).push(arguments)});b[l].l=+new Date; + e=o.createElement(i);r=o.getElementsByTagName(i)[0]; + e.src='//www.google-analytics.com/analytics.js'; + r.parentNode.insertBefore(e,r)}(window,document,'script','ga')); + ga('create','UA-44963757-1');ga('send','pageview'); + </script> + </body> +</html>
