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-<html>
-<head>
-<title>Package Documentation for org.apache.struts.taglib.logic Package</title>
-</head>
-<body bgcolor="white">
-
- <p>
- The "struts-bean" tag library contains tags that are useful in
managing conditional
- generation of output text, looping over object collections for
repetitive generation
- of output text, and application flow management
- </p>
- <a name="doc.Description"></a>
-
- <p>
-
-<div align="center"> <a href="#doc.Introduction">[Introduction]</a> <a
href="#doc.Functionality">[Logic
- Functionality]</a> <a href="#doc.Properties">[Logic Properties]</a> <a
href="#doc.Examples">[Logic
- Examples]</a> </div>
- <p></p>
-
- <hr />
-<a name="doc.Intro"></a>
-<h3>Introduction<a name="doc.Introduction"></a></h3>
-
- <p>
- The Logic library supplies tags that are useful for manipulating
presentation logic
- without the use of scriptlets.
- </p>
-
-
-<a name="doc.Functionality"></a>
-<h3>Logic Tag Functionality<a name="doc.Functionality"></a></h3>
-<p> The functionality of the logic tags can be divided into four groups:</p>
-<p><b>Value Comparisions -</b> The purpose of these tags is to print out the body
- of the tag if the comparision evaluates to <i>true. </i></p>
-<ul>
- <li><b><a href="/struts-logic.html#equal">equal,</a> <a
href="/struts-logic.html#notEqual">notEqual</a></b>
- </li>
- <li><b><a href="/struts-logic.html#greaterEqual">greaterEqual</a>, <a
href="/struts-logic.html#lessEqual">lessEqual</a></b></li>
- <li><b><a href="/struts-logic.html#greaterThan">greaterThan</a>,<a
href="/struts-logic.html#lessThan">
- lessThan</a></b></li>
-</ul>
-<p><b>Substring Matching -</b> The purpose of these tags is to match substrings
- inside of other Strings</p>
-<ul>
- <li><b><a href="/struts-logic.html#match">match</a>, <a
href="/struts-logic.html#notMatch">notMatch</a></b></li>
-</ul>
-<p><b>Presentation Location -</b> The purpose of these tags is to change the
location
- of the presentation page</p>
-<ul>
- <li><a href="/struts-logic.html#forward"><b>forward</b></a></li>
- <li><a href="/struts-logic.html#redirect"><b>redirect</b></a></li>
-</ul>
-<p><b>Collection Utilities -</b>The purpose of these tags is to handle
Collections</p>
-<ul>
- <li><a href="/struts-logic.html#iterate"><b>iterate</b></a> </li>
-</ul>
-<h3>Logic Tag Properties<a name="doc.Properties"></a></h3>
-<p>Each of the four groups of logic tags have a common set of attributes associated
- with them. :</p>
-<blockquote>
- <p><b>Value Comparisions</b> (equal, notEqual, greaterEqual, lessEqual,
greaterThan,
- lessThan, present, notPresent)</p>
- <p>Each of the value comparision tags takes a <i>value</i> and compares it to
- the value of a comparision attribute. If the value given can be successfully
- converted to a <i>float</i> or <i>double</i>, then a number comparision is
- performed on the value given and the value of the comparision attribute.
Otherwise
- a String comparision is performed. You have to specify one of the comparision
- attributes: <i>cookie</i>, <i>header</i>, <i>parameter</i>, <i>property</i>
- or <i>name. </i>For each of the examples, the tag
"<i>someComparisionTag"</i>can
- be replaced by any of the value comparision tags.</p>
- <ul>
- <li>value - the value to which this tag is going to compare, used in
conjunction
- with one of the comparision attributes: <i>cookie</i>, <i>header</i>,
<i>parameter</i>,
- <i>and property</i> and/or <i>name. </i></li>
- <li>cookie - the name of the cookie to compare to <i>value</i>
- <ul>
- <li>example:
- <pre><logic:<i>someComparisionTag</i> value="someUserName"
cookie="userName">
- User Logged In
-</logic:<i>someComparisionTag</i>>
-</pre>
- </li>
- </ul>
- </li>
- <li>header - the name of the HTTP header to compare to <i>value</i>
- <ul>
- <li>example:
- <pre><logic:<i>someComparisionTag</i> value="en_US"
header="Accept-Language">
- Welcome English-speaking User*
-</logic:<i>someComparisionTag</i>>
-*Note: See the section in the user's guide on <a
href="../../../../../../building_view.html#i18n">Internationalized Messages</a> to do
things like this better
- </pre>
- </li>
- </ul>
- </li>
- <li>name - the variable to be compared to <i>value</i> is the JSP bean
specified
- by this attribute, if property is not specified, or the value of the
specified
- property of this bean, if property is specified.
- <ul>
- <li>example:
- <pre><%
- String testString = "pantalones";
- pageContext.setAttribute("testString", testString,
PageContext.PAGE_SCOPE);
-%>
-<jsp:useBean id="testString" scope="page"
type="java.lang.String" />
-
-
-<logic:<i>someComparisionTag</i> name="testString"
value="pantalones">
- Usted tiene pantalones!
-</logic:<i>someComparision</i>></pre>
- </li>
- </ul>
- </li>
- <li>parameter - the name of the request parameter to compare to <i>value</i>
- <ul>
- <li>example:
- <pre><logic:<i>someComparisionTag</i> value=""
parameter="username">
- Error: a username must be specified
-</logic:<i>someComparisionTag</i>></pre>
- </li>
- </ul>
- </li>
- <li>property - the variable to be compared with <i>value</i> is the property
- (of the bean specified by the name attribute) specified by this attribute.
- The property reference can be simple, nested, and/or indexed. <i>property</i>
- is used in conjunction with <i>name</i> to specify a property in the bean
- specified by <i>name</i>. For the type of syntax used for property, see
- the users guide on the Bean Tags.</li>
- <li>scope - the bean scope within which to search for the bean named by the
- name property, or "any scope" if not specified. Possible values are
"page",
- "request", "session", "application", or
"any
- scope" </li>
- </ul>
- <p><b>Substring Matching</b> (match, notMatch)</p>
- <p>The substring matching tags take all the same arguments as the value
comparision
- tags. You compare the String specified by <i>value</i> to any of the
comparision
- values you give it, specified by <i>cookie</i>, <i>header</i>,
<i>parameter</i>,
- <i>property</i> or <i>name.</i> Note that in the examples, <i>matchTag</i>
- corresponds either the <i>match </i>or <i>notMatch</i> tag. Matching tags
- also have an additional <i>location</i> attribute added:</p>
- <ul>
- <li>location - has two possible values, "start" and "end".
- If "start", the substring is attempted to be matched at the
beginning
- of the String, if "end", then the substring is attempted to be
- matched to the end of the String
- <ul>
- <li>example:
- <pre><logic:<i>matchTag</i> parameter="action"
value="processLogin">
- Processing Login....
-</logic:<i>matchTag</i>>
-
-
-Basically, in this short example, a request parameter "action"
-was compared to see if it was equal to the String value "processLogin".
-In this case, <i>matchTag</i> would have to be <logic:match>.</pre>
- </li>
- </ul>
- </li>
- </ul>
- <p><b>Presentation Location</b> (forward, redirect)</p>
- <p>The <i>redirect</i> tag is resposible for sending a re-direct to the client's
- browser, complete with URL-rewriting if it's supported by the container. It
- has one argument:</p>
- <ul>
- <li>href - The context-relative path to forward to</li>
- </ul>
- <p>The <i>forward</i> tag is responsible for either redirecting or forwarding
- to a specified global action forward. To define a global ActionForward, see
- The <a href="../../../../../../building_controller.html#config">Action Mappings
- Configuration File</a>. You can specify whether the forward re-directs or
- forwards when executed in the config file. The forward tag has one
attribute:</p>
- <ul>
- <li>name - The logical name of the ActionForward to use</li>
- </ul>
- <p><b>Collection Utilities</b> (iterate)</p>
- <p>The <i>iterate</i> tag is responsible for executing it's body content once
- for every element inside of the specified Collection. There is one required
- attribute:</p>
- <ul>
- <li>id - The name of a page scope JSP bean that will contain the current
element
- of the collection on each iteration</li>
- </ul>
- <p>The other attributes allow for more flexibility on which Collection to iterate
- and how to do it:</p>
- <ul>
- <li>collection - a runtime expression that evaluates to a Collection to be
- iterated
- <ul>
- <li>example:
- <pre><%
- java.util.Vector vector = new java.util.Vector();
- vector.add(new Integer(12));
- vector.add(new Integer(5))
- %></pre>
- </li>
- </ul>
- </li>
- </ul>
- <blockquote>
- <blockquote>
- <pre><bean:iterate id="myCollectionElement"
collection="<% vector %>">
-<i> Do something with myCollectionElement</i>
-</bean:iterate></pre>
- </blockquote>
- </blockquote>
- <ul>
- <li>length - The maximum number of entries (from the underlying collection)
- to be iterated through on this page. This can be either an integer that
- directly expresses the desired value, or the name of a JSP bean (in any
- scope) of type java.lang.Integer that defines the desired value. If not
- present, there will be no limit on the number of iterations performed</li>
- <li>name - The name of the JSP bean containing the collection to be iterated
- (if property is not specified), or the JSP bean whose property getter returns
- the collection to be iterated (if property is specified).
- <ul>
- <li>example:
- <pre><%<br> java.util.ArrayList list = new
java.util.ArrayList();<br> list.add("First");<br>
list.add("Second");<br> list.add("Third");<br>
list.add("Fourth");<br> list.add("Fifth");<br>
pageContext.setAttribute("list", list, PageContext.PAGE_SCOPE);<br> %>
-
-<logic:iterate id="myCollectionElement" name="list">
- <i>Do something with myCollectionElement</i>
-</logic:iterate></pre>
- </li>
- </ul>
- </li>
- <li>offset - The zero-relative index of the starting point at which entries
- from the underlying collection will be iterated through. This can be either
- an integer that directly expresses the desired value, or the name of a JSP
- bean (in any scope) of type java.lang.Integer that defines the desired value.
- If not present, zero is assumed (meaning that the collection will be iterated
- from the beginning. </li>
- <li>property - Name of the property, of the JSP bean specified by name, whose
- getter returns the collection to be iterated. See the user's guide for the
- bean tag library for the syntax of the property attribute</li>
- <li>scope - The bean scope within which to search for the bean named by the
- name property, or "any scope" if not specified. Possible values are
"page",
- "request", "session", "application", or
"any
- scope" </li>
- <li>type - Fully qualified Java class name of the element to be exposed through
- the JSP bean named from the id attribute. If not present, no type conversions
- will be performed. NOTE: The actual elements of the collection must be
assignment-compatible
- with this class, or a request time ClassCastException will occur.
- <ul>
- <li>example:
- <pre><%<br> java.util.ArrayList list = new
java.util.ArrayList();<br> list.add("First");<br>
list.add("Second");<br> list.add("Third");<br>
list.add("Fourth");<br> list.add("Fifth");<br>
pageContext.setAttribute("list", list, PageContext.PAGE_SCOPE);<br> %>
-
-<logic:iterate id="myCollectionElement" name="list"
type="java.lang.String">
- <i>Do something with myCollectionElement</i>
-</logic:iterate></pre>
- </li>
- </ul>
- </li>
- </ul>
-</blockquote>
-<p> </p>
-<h3>Logic Examples</h3>
-<blockquote>
- <p><b>Value Comparisions</b></p>
- <blockquote>
- <p><u></u><u></u><u>Logic Equivalence Tags (equal, notEqual, greaterEqual,
- lessEqual, lessThan, greaterThan)</u></p>
- <blockquote>
- <p>You can compare these tags to the "==", "!="
,">=",
- "<=", "<", and ">"logic operators
- in most languages. Their usage is fairly straightforward for numbers.
- For an example, we'll create a small "Guess That Number" game
- that uses request parameters from a form input to play. The number will
- be hardcoded as "7", because this is just an example. Note that
- this is actually putting application logic inside of jsp pages, and isn't
- the recommended development method for Struts. It's just an easy way to
- show how these tags are used:</p>
- <p>The first step is to develop the form that will call on the processing
- jsp page. This form will use the "GET" method so that you can
- see the request parameter in the URL. The POST method can also be used
- with no problem or changes.</p>
- <p>[numberGuess.jsp]</p>
- <pre><form action="numberProcess.jsp" method="GET">
- Please Enter a Number From 1-10: <input type="text"
name="number" /><br />
-
- <center>
- <input type="submit" name="Guess Number" />
-
- </center>
-</form>
-
-</pre>
- The next step is to create the processing page. It uses the struts-logic
- taglib. For information on how to set this tag library up in your application
- to use, see <a
href="../../../../../../building_controller.html#dd_config">The
- Web Application Deployment Descriptor</a><br>
- <br>
- <p>[numberProcess.jsp]</p>
- <pre><%@ page language="java" %><br><%@ taglib
uri="/WEB-INF/struts-logic.tld" prefix="logic" %></pre>
- <pre><!-- Is the number guess right? -->
-<logic:equal parameter="number" value="7">
- You guessed right! You win a high speed blender!
-</logic:equal></pre>
- <pre><!-- If the number guessed was wrong -->
-<logic:notEqual parameter="number" value="7">
- <!-- Less Than -->
- <logic:lessThan parameter="number" value="7">
- A little higher...
- </logic:lessThan>
- <!-- Greater Than -->
- <logic:greaterThan parameter="number" value="7">
- A little lower...
- </logic:greaterThan>
-</logic:notEqual></pre>
- <pre>
-
-</pre>
- <p>Basically, the numberProcess.jsp page uses the equal tag to check if
- the guess is 7, and if so, prints out a congratulatory message. If the
- number isn't equal, specified by the use of the <logic:notEqual>
- tag, it uses the greaterThan and lessThan tags to check if the number
- is higher or lower than 7, and prints out a hint. As said before, this
- is a horribly designed small application, with no validity checks on the
- number input, but shows the basic usage of the logic equal tags</p>
- <p>For String comparisions, the equal tags use the
java.lang.String.compareTo()
- method. See the javadocs on the compareTo() method for more information,
- located <a
href="http://www.javasoft.com/products/jdk/1.2/docs/api/java/lang/String.html#compareTo(java.lang.Object)">here</a>.</p>
- </blockquote>
- <p><u>Match and Present Tags (match, notMatch, present, notPresent)</u></p>
- <blockquote>
- <p>You use the match tags in conjunction with the present tags in order
- to do substring matches. For an example using this we'll use headers,
- specifically the "Referer" header. The HTTP referer header gives
- the URL of the document that refers to the requested URL. We'll use this
- to check if the user is coming from a link specified by a <a
href="http://www.google.com">Google</a>
- search, and offer a personalized greeting, frightening users that find
- our site through the search engine with our amazing intimate knowledge
- of their browsing habits:</p>
- <p>[sneaky.jsp]</p>
- <pre><%@ page language="java" %>
-<%@ taglib uri="/WEB-INF/struts-logic.tld" prefix="logic"
%>
-
-
-<!-- Check to see if the "Referer" header is present -->
-<logic:present header="Referer">
- <logic:match header="Referer" value="google.com">
- I see you found our site through Google... interesting.
- </logic:match>
- <logic:notMatch header="Referer" value="google.com">
- Welcome to the site, we're secretly logging what site you came from,
- because we're shady...
- </logic:notMatch>
-</logic:present>
-
-<!-- If the header is not present -->
-<logic:notPresent header="Referer">
- Hi, welcome to our site. Please fill out our <a
href="nonExistantForm.jsp">Form</a> and
- tell us where you're coming from.
-</logic:notPresent></pre>
- <p>Note: Another interesting usage of these tags and headers would be to
- use the "User-Agent" header to display browser-specific
javascript.</p>
- </blockquote>
- </blockquote>
- <p><b>Collection Utilities (iterate)</b></p>
- <blockquote>
- <p>For an example of using the <logic:iterate> tag, we'll use one of
- the previous examples given, in it's entirety. This example uses the
<bean:write>
- tag from the Bean Tag Library, see the User's Guide on the bean tag library
- for more information on it's usage:</p>
- <p>[iterate.jsp]</p>
- <pre><%@ page language="java" %><br><%@ taglib
uri="/WEB-INF/struts-bean.tld" prefix="bean" %><br><%@
taglib uri="/WEB-INF/struts-logic.tld" prefix="logic" %></pre>
- </blockquote>
-</blockquote>
-<pre> <%
- java.util.ArrayList list = new java.util.ArrayList();
- list.add("First");
- list.add("Second");
- list.add("Third");
- list.add("Fourth");
- list.add("Fifth");
- pageContext.setAttribute("list", list,
PageContext.PAGE_SCOPE);
- %>
-
- <logic:iterate id="myCollectionElement"
name="list">
- Element Value: <bean:write
name="myCollectionElement" /><br />
- </logic:iterate></pre>
-<blockquote>
- <blockquote> </blockquote>
-</blockquote>
-</body>
-</html>
-
-
-
-
\ No newline at end of file
+<html>
+<head>
+<title>Package Documentation for org.apache.struts.taglib.logic Package</title>
+</head>
+<body bgcolor="white">
+
+ <p>
+ The "struts-logic" tag library contains tags that are useful in managing
conditional
+ generation of output text, looping over object collections for repetitive
generation
+ of output text, and application flow management
+ </p>
+ <a name="doc.Description"></a>
+
+ <p>
+
+<div align="center"> <a href="#doc.Introduction">[Introduction]</a> <a
href="#doc.Functionality">[Logic
+ Functionality]</a> <a href="#doc.Properties">[Logic Properties]</a> <a
href="#doc.Examples">[Logic
+ Examples]</a> </div>
+ <p></p>
+
+ <hr />
+<a name="doc.Intro"></a>
+<h3>Introduction<a name="doc.Introduction"></a></h3>
+
+ <p>
+ The Logic library supplies tags that are useful for manipulating presentation
logic
+ without the use of scriptlets.
+ </p>
+
+
+<a name="doc.Functionality"></a>
+<h3>Logic Tag Functionality<a name="doc.Functionality"></a></h3>
+<p> The functionality of the logic tags can be divided into four groups:</p>
+<p><b>Value Comparisions -</b> The purpose of these tags is to print out the body
+ of the tag if the comparision evaluates to <i>true. </i></p>
+<ul>
+ <li><b><a href="/struts-logic.html#equal">equal,</a> <a
href="/struts-logic.html#notEqual">notEqual</a></b>
+ </li>
+ <li><b><a href="/struts-logic.html#greaterEqual">greaterEqual</a>, <a
href="/struts-logic.html#lessEqual">lessEqual</a></b></li>
+ <li><b><a href="/struts-logic.html#greaterThan">greaterThan</a>,<a
href="/struts-logic.html#lessThan">
+ lessThan</a></b></li>
+</ul>
+<p><b>Substring Matching -</b> The purpose of these tags is to match substrings
+ inside of other Strings</p>
+<ul>
+ <li><b><a href="/struts-logic.html#match">match</a>, <a
href="/struts-logic.html#notMatch">notMatch</a></b></li>
+</ul>
+<p><b>Presentation Location -</b> The purpose of these tags is to change the
location
+ of the presentation page</p>
+<ul>
+ <li><a href="/struts-logic.html#forward"><b>forward</b></a></li>
+ <li><a href="/struts-logic.html#redirect"><b>redirect</b></a></li>
+</ul>
+<p><b>Collection Utilities -</b>The purpose of these tags is to handle
Collections</p>
+<ul>
+ <li><a href="/struts-logic.html#iterate"><b>iterate</b></a> </li>
+</ul>
+<h3>Logic Tag Properties<a name="doc.Properties"></a></h3>
+<p>Each of the four groups of logic tags have a common set of attributes associated
+ with them. :</p>
+<blockquote>
+ <p><b>Value Comparisions</b> (equal, notEqual, greaterEqual, lessEqual,
greaterThan,
+ lessThan, present, notPresent)</p>
+ <p>Each of the value comparision tags takes a <i>value</i> and compares it to
+ the value of a comparision attribute. If the value given can be successfully
+ converted to a <i>float</i> or <i>double</i>, then a number comparision is
+ performed on the value given and the value of the comparision attribute.
Otherwise
+ a String comparision is performed. You have to specify one of the comparision
+ attributes: <i>cookie</i>, <i>header</i>, <i>parameter</i>, <i>property</i>
+ or <i>name. </i>For each of the examples, the tag
"<i>someComparisionTag"</i>can
+ be replaced by any of the value comparision tags.</p>
+ <ul>
+ <li>value - the value to which this tag is going to compare, used in conjunction
+ with one of the comparision attributes: <i>cookie</i>, <i>header</i>,
<i>parameter</i>,
+ <i>and property</i> and/or <i>name. </i></li>
+ <li>cookie - the name of the cookie to compare to <i>value</i>
+ <ul>
+ <li>example:
+<pre><logic:<i>someComparisionTag</i> value="someUserName"
cookie="userName">
+ User Logged In
+</logic:<i>someComparisionTag</i>>
+</pre>
+ </li>
+ </ul>
+ </li>
+ <li>header - the name of the HTTP header to compare to <i>value</i>
+ <ul>
+ <li>example:
+<pre><logic:<i>someComparisionTag</i> value="en_US"
header="Accept-Language">
+ Welcome English-speaking User*
+</logic:<i>someComparisionTag</i>>
+</pre></li>
+<li><p>*Note: See the section in the user's guide on <a
href="../../../../../../building_view.html#i18n">Internationalized Messages</a> to do
things like this better.</p></li>
+ </ul>
+ </li>
+ <li>name - the variable to be compared to <i>value</i> is the JSP bean specified
+ by this attribute, if property is not specified, or the value of the specified
+ property of this bean, if property is specified.
+ <ul>
+ <li>example:
+<pre><%
+ String testString = "pantalones";
+ pageContext.setAttribute("testString", testString,
PageContext.PAGE_SCOPE);
+%>
+<jsp:useBean id="testString" scope="page"
type="java.lang.String" />
+<logic:<i>someComparisionTag</i> name="testString"
value="pantalones">
+ Usted tiene pantalones!
+</logic:<i>someComparision</i>>
+</pre>
+ </li>
+ </ul>
+ </li>
+ <li>parameter - the name of the request parameter to compare to <i>value</i>
+ <ul>
+ <li>example:
+<pre><logic:<i>someComparisionTag</i> value=""
parameter="username">
+ Error: a username must be specified
+</logic:<i>someComparisionTag</i>>
+</pre>
+ </li>
+ </ul>
+ </li>
+ <li>property - the variable to be compared with <i>value</i> is the property
+ (of the bean specified by the name attribute) specified by this attribute.
+ The property reference can be simple, nested, and/or indexed. <i>property</i>
+ is used in conjunction with <i>name</i> to specify a property in the bean
+ specified by <i>name</i>. For the type of syntax used for property, see
+ the users guide on the Bean Tags.</li>
+ <li>scope - the bean scope within which to search for the bean named by the
+ name property, or "any scope" if not specified. Possible values are
"page",
+ "request", "session", "application", or
"any
+ scope" </li>
+ </ul>
+ <p><b>Substring Matching</b> (match, notMatch)</p>
+ <p>The substring matching tags take all the same arguments as the value
comparision
+ tags. You compare the String specified by <i>value</i> to any of the comparision
+ values you give it, specified by <i>cookie</i>, <i>header</i>, <i>parameter</i>,
+ <i>property</i> or <i>name.</i> Note that in the examples, <i>matchTag</i>
+ corresponds either the <i>match </i>or <i>notMatch</i> tag. Matching tags
+ also have an additional <i>location</i> attribute added:</p>
+ <ul>
+ <li>location - has two possible values, "start" and "end".
+ If "start", the substring is attempted to be matched at the
beginning
+ of the String, if "end", then the substring is attempted to be
+ matched to the end of the String
+ <ul>
+ <li>example:
+<pre><logic:<i>matchTag</i> parameter="action"
value="processLogin">
+ Processing Login....
+</logic:<i>matchTag</i>>
+
+Basically, in this short example, a request parameter "action"
+was compared to see if it was equal to the String value "processLogin".
+In this case, <i>matchTag</i> would have to be <logic:match>.
+</pre>
+ </li>
+ </ul>
+ </li>
+ </ul>
+ <p><b>Presentation Location</b> (forward, redirect)</p>
+ <p>The <i>redirect</i> tag is resposible for sending a re-direct to the client's
+ browser, complete with URL-rewriting if it's supported by the container. It
+ has one argument:</p>
+ <ul>
+ <li>href - The context-relative path to forward to</li>
+ </ul>
+ <p>The <i>forward</i> tag is responsible for either redirecting or forwarding
+ to a specified global action forward. To define a global ActionForward, see
+ The <a href="../../../../../../building_controller.html#config">Action Mappings
+ Configuration File</a>. You can specify whether the forward re-directs or
+ forwards when executed in the config file. The forward tag has one
attribute:</p>
+ <ul>
+ <li>name - The logical name of the ActionForward to use</li>
+ </ul>
+ <p><b>Collection Utilities</b> (iterate)</p>
+ <p>The <i>iterate</i> tag is responsible for executing it's body content once
+ for every element inside of the specified Collection. There is one required
+ attribute:</p>
+ <ul>
+ <li>id - The name of a page scope JSP bean that will contain the current element
+ of the collection on each iteration</li>
+ </ul>
+ <p>The other attributes allow for more flexibility on which Collection to iterate
+ and how to do it:</p>
+ <ul>
+ <li>collection - a runtime expression that evaluates to a Collection to be
+ iterated
+ <ul>
+ <li>example:
+<pre><%
+ java.util.Vector vector = new java.util.Vector();
+ vector.add(new Integer(12));
+ vector.add(new Integer(5))
+ %>
+</pre>
+ </li>
+ </ul>
+ </li>
+ </ul>
+ <blockquote>
+ <blockquote>
+<pre><bean:iterate id="myCollectionElement" collection="<%
vector %>">
+<i> Do something with myCollectionElement</i>
+</bean:iterate>
+</pre>
+ </blockquote>
+ </blockquote>
+ <ul>
+ <li>length - The maximum number of entries (from the underlying collection)
+ to be iterated through on this page. This can be either an integer that
+ directly expresses the desired value, or the name of a JSP bean (in any
+ scope) of type java.lang.Integer that defines the desired value. If not
+ present, there will be no limit on the number of iterations performed</li>
+ <li>name - The name of the JSP bean containing the collection to be iterated
+ (if property is not specified), or the JSP bean whose property getter returns
+ the collection to be iterated (if property is specified).
+ <ul>
+ <li>example:
+<pre><%<br>
+ java.util.ArrayList list = new java.util.ArrayList();
+ list.add("First");
+ list.add("Second");
+ list.add("Third");
+ list.add("Fourth");
+ list.add("Fifth");
+ pageContext.setAttribute("list", list, PageContext.PAGE_SCOPE);
+%>
+
+<logic:iterate id="myCollectionElement" name="list">
+ <i>Do something with myCollectionElement</i>
+</logic:iterate></pre>
+ </li>
+ </ul>
+ </li>
+ <li>offset - The zero-relative index of the starting point at which entries
+ from the underlying collection will be iterated through. This can be either
+ an integer that directly expresses the desired value, or the name of a JSP
+ bean (in any scope) of type java.lang.Integer that defines the desired value.
+ If not present, zero is assumed (meaning that the collection will be iterated
+ from the beginning. </li>
+ <li>property - Name of the property, of the JSP bean specified by name, whose
+ getter returns the collection to be iterated. See the user's guide for the
+ bean tag library for the syntax of the property attribute</li>
+ <li>scope - The bean scope within which to search for the bean named by the
+ name property, or "any scope" if not specified. Possible values are
"page",
+ "request", "session", "application", or
"any
+ scope" </li>
+ <li>type - Fully qualified Java class name of the element to be exposed through
+ the JSP bean named from the id attribute. If not present, no type conversions
+ will be performed. NOTE: The actual elements of the collection must be
assignment-compatible
+ with this class, or a request time ClassCastException will occur.
+ <ul>
+ <li>example:
+<pre><% java.util.ArrayList list = new java.util.ArrayList();
+list.add("First");
+list.add("Second");
+list.add("Third");
+list.add("Fourth");
+list.add("Fifth");
+ pageContext.setAttribute("list", list, PageContext.PAGE_SCOPE);
+ %>
+
+<logic:iterate id="myCollectionElement" name="list"
type="java.lang.String">
+ <i>Do something with myCollectionElement</i>
+</logic:iterate></pre>
+ </li>
+ </ul>
+ </li>
+ </ul>
+</blockquote>
+<h3>Logic Examples</h3>
+<blockquote>
+ <p><b>Value Comparisions</b></p>
+ <blockquote>
+ <p><u></u><u></u><u>Logic Equivalence Tags (equal, notEqual, greaterEqual,
+ lessEqual, lessThan, greaterThan)</u></p>
+ <blockquote>
+ <p>You can compare these tags to the "==", "!="
,">=",
+ "<=", "<", and ">"logic operators
+ in most languages. Their usage is fairly straightforward for numbers.
+ For an example, we'll create a small "Guess That Number" game
+ that uses request parameters from a form input to play. The number will
+ be hardcoded as "7", because this is just an example. Note that
+ this is actually putting application logic inside of jsp pages, and isn't
+ the recommended development method for Struts. It's just an easy way to
+ show how these tags are used:</p>
+ <p>The first step is to develop the form that will call on the processing
+ jsp page. This form will use the "GET" method so that you can
+ see the request parameter in the URL. The POST method can also be used
+ with no problem or changes.</p>
+ <p>[numberGuess.jsp]</p>
+<pre><form action="numberProcess.jsp" method="GET">
+Please Enter a Number From 1-10: <input type="text"
name="number" /><br />
+ <center>
+ <input type="submit" name="Guess Number" />
+ </center>
+</form>
+</pre>
+ The next step is to create the processing page. It uses the struts-logic
+ taglib. For information on how to set this tag library up in your application
+ to use, see <a href="../../../../../../building_controller.html#dd_config">The
+ Web Application Deployment Descriptor</a>
+
+ <p>[numberProcess.jsp]</p>
+<pre><%@ page language="java" %>
+<%@ taglib uri="/WEB-INF/struts-logic.tld" prefix="logic"
%>
+</pre>
+<pre><!-- Is the number guess right? -->
+<logic:equal parameter="number" value="7">
+ You guessed right! You win a high speed blender!
+</logic:equal>
+</pre>
+<pre><!-- If the number guessed was wrong -->
+<logic:notEqual parameter="number" value="7">
+ <!-- Less Than -->
+ <logic:lessThan parameter="number" value="7">
+ A little higher...
+ </logic:lessThan>
+ <!-- Greater Than -->
+ <logic:greaterThan parameter="number" value="7">
+ A little lower...
+ </logic:greaterThan>
+</logic:notEqual>
+</pre>
+ <p>Basically, the numberProcess.jsp page uses the equal tag to check if
+ the guess is 7, and if so, prints out a congratulatory message. If the
+ number isn't equal, specified by the use of the <logic:notEqual>
+ tag, it uses the greaterThan and lessThan tags to check if the number
+ is higher or lower than 7, and prints out a hint. As said before, this
+ is a horribly designed small application, with no validity checks on the
+ number input, but shows the basic usage of the logic equal tags</p>
+ <p>For String comparisions, the equal tags use the
java.lang.String.compareTo()
+ method. See the javadocs on the compareTo() method for more information,
+ located <a
href="http://www.javasoft.com/products/jdk/1.2/docs/api/java/lang/String.html#compareTo(java.lang.Object)">here</a>.</p>
+ </blockquote>
+ <p><u>Match and Present Tags (match, notMatch, present, notPresent)</u></p>
+ <blockquote>
+ <p>You use the match tags in conjunction with the present tags in order
+ to do substring matches. For an example using this we'll use headers,
+ specifically the "Referer" header. The HTTP referer header gives
+ the URL of the document that refers to the requested URL. We'll use this
+ to check if the user is coming from a link specified by a <a
href="http://www.google.com">Google</a>
+ search, and offer a personalized greeting, frightening users that find
+ our site through the search engine with our amazing intimate knowledge
+ of their browsing habits:</p>
+ <p>[sneaky.jsp]</p>
+ <pre><%@ page language="java" %>
+<%@ taglib uri="/WEB-INF/struts-logic.tld" prefix="logic"
%>
+
+
+<!-- Check to see if the "Referer" header is present -->
+<logic:present header="Referer">
+ <logic:match header="Referer" value="google.com">
+ I see you found our site through Google... interesting.
+ </logic:match>
+ <logic:notMatch header="Referer" value="google.com">
+ Welcome to the site, we're secretly logging what site you came from,
+ because we're shady...
+ </logic:notMatch>
+</logic:present>
+
+<!-- If the header is not present -->
+<logic:notPresent header="Referer">
+ Hi, welcome to our site. Please fill out our
+ <a href="nonExistantForm.jsp">Form</a> and
+ tell us where you're coming from.
+</logic:notPresent></pre>
+ <p>Note: Another interesting usage of these tags and headers would be to
+ use the "User-Agent" header to display browser-specific
javascript.</p>
+ </blockquote>
+ </blockquote>
+ <p><b>Collection Utilities (iterate)</b></p>
+ <blockquote>
+ <p>For an example of using the <logic:iterate> tag, we'll use one of
+ the previous examples given, in it's entirety. This example uses the
<bean:write>
+ tag from the Bean Tag Library, see the User's Guide on the bean tag library
+ for more information on it's usage:</p>
+ <p>[iterate.jsp]</p>
+<pre><%@ page language="java" %>
+<%@ taglib uri="/WEB-INF/struts-bean.tld" prefix="bean" %>
+<%@ taglib uri="/WEB-INF/struts-logic.tld" prefix="logic"
%>
+</pre>
+<pre><%
+java.util.ArrayList list = new java.util.ArrayList();
+ list.add("First");
+ list.add("Second");
+ list.add("Third");
+ list.add("Fourth");
+ list.add("Fifth");
+ pageContext.setAttribute("list", list, PageContext.PAGE_SCOPE);
+%>
+
+<logic:iterate id="myCollectionElement" name="list">
+ Element Value: <bean:write name="myCollectionElement" /><br
/>
+</logic:iterate></pre>
+</blockquote>
+</blockquote>
+</body>
+</html>
