On Wed, 2003-11-26 at 09:52, robert burrell donkin wrote:
> On 24 Nov 2003, at 23:54, Simon Kitching wrote:
> > I'm *really* in favour of providing expansion in body text as well as
> > attributes.
>
> yep. but i'd favour a sequential approach. remy needs attributes right
> now, so let's do attributes right now :)
>
> > I also personally favour an interface rather than an abstract class.
> > Who
> > knows what implementations people might come up with in the future :
> > retrieve values from LDAP? support emacs macros in variables?.
> > If the "replacement strategy" is an abstract class that brings
> > implementation baggage with it, then it might be more difficult to
> > implement those...
>
> this would be an abstract class that is (from a higher OOP perspective)
> an interface but will be implemented in java as an abstract class. it
> will contain no implementation. most folks will probably subclass the
> base implementation.
>
> > On the other hand, an abstract class *does* allow us to expand the
> > "interface" later by adding operations with default implementations,
> > without breaking code. I personally still feel more comfortable with a
> > pure interface in this case, though.
>
> IMHO being able to maintain backwards compatibility is crucial for a
> good library. unless i can see the need for different inheritance
> hierarchies to implement the interface (which is more common in
> frameworks than library's), experience has taught me that (when
> developing library code) the flexibility that implementing as an
> abstract class gives in java pays dividends in long run.
Attached is a complete implementation of the "variable expansion"
feature. I do also have some unit tests for it, but unfortunately they
are still on my home PC so I will have to send them tomorrow.
This code implements the "multiple sources, configurable var marker"
features I talked about earlier. The implementation came together so
well that I am not sure that there is any point in trying to provide an
alternative "simpler" implementation that just supports one source and
"$" as the marker. If you're happy with this, class MultiVarExpander
could just be renamed to BaseVarExpander or similar.
Preferring abstract classes over interfaces is a new "pattern" to me,
but I am willing to give it a go. Class VarExpander is therefore an
abstract class rather than an interface.
Note that this implementation does almost *no* dynamic memory allocation
at all, and therefore should perform very well. Only one "attributes
wrapper" object exists per Digester instance; it is reused each time
startElement(...) is called. I can't think of any reason why
startElement would be called re-entrantly, so this should be safe.
It also implements expansion of text in body text (adds about 2 extra
lines of code).
Regards,
Simon
>
> - robert
>
>
> ---------------------------------------------------------------------
> To unsubscribe, e-mail: [EMAIL PROTECTED]
> For additional commands, e-mail: [EMAIL PROTECTED]
>
>
Index: src/java/org/apache/commons/digester/Digester.java
===================================================================
RCS file: /home/cvspublic/jakarta-commons/digester/src/java/org/apache/commons/digester/Digester.java,v
retrieving revision 1.86
diff -u -r1.86 Digester.java
--- src/java/org/apache/commons/digester/Digester.java 19 Nov 2003 21:05:19 -0000 1.86
+++ src/java/org/apache/commons/digester/Digester.java 25 Nov 2003 21:57:45 -0000
@@ -360,6 +360,12 @@
protected static final String W3C_XML_SCHEMA =
"http://www.w3.org/2001/XMLSchema";;
+ /** a map which is looked up to find values for variables */
+ private VarExpander varExpander = null;
+
+ /** the attributes wrapper (single instance) */
+ private VarAttributes varAttributes = new VarAttributes();
+
// ------------------------------------------------------------- Properties
@@ -935,6 +941,14 @@
}
+ /**
+ * Defines how variables in xml attributes and body text are expanded.
+ * If null, no expansion is performed (the default behaviour).
+ */
+ public void setVarExpander(VarExpander expander) {
+ varExpander = expander;
+ }
+
// ------------------------------------------------- ContentHandler Methods
@@ -1038,6 +1052,10 @@
List rules = getRules().match(namespaceURI, match);
if ((rules != null) && (rules.size() > 0)) {
String bodyText = this.bodyText.toString();
+ if (varExpander != null) {
+ bodyText = varExpander.expand(bodyText);
+ }
+
for (int i = 0; i < rules.size(); i++) {
try {
Rule rule = (Rule) rules.get(i);
@@ -1283,6 +1301,13 @@
List rules = getRules().match(namespaceURI, match);
if ((rules != null) && (rules.size() > 0)) {
String bodyText = this.bodyText.toString();
+
+ // variable substitution in attributes
+ if (varExpander != null) {
+ varAttributes.init(list, varExpander);
+ list = varAttributes;
+ }
+
for (int i = 0; i < rules.size(); i++) {
try {
Rule rule = (Rule) rules.get(i);
/*
* $Header: $
* $Revision: $
* $Date: $
*
* ====================================================================
*
* The Apache Software License, Version 1.1
*
* Copyright (c) 2001-2003 The Apache Software Foundation. All rights
* reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
*
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
*
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in
* the documentation and/or other materials provided with the
* distribution.
*
* 3. The end-user documentation included with the redistribution,
* if any, must include the following acknowledgement:
* "This product includes software developed by the
* Apache Software Foundation (http://www.apache.org/)."
* Alternately, this acknowledgement may appear in the software itself,
* if and wherever such third-party acknowledgements normally appear.
*
* 4. The names "Apache", "The Jakarta Project", "Commons", and "Apache Software
* Foundation" must not be used to endorse or promote products derived
* from this software without prior written permission. For written
* permission, please contact [EMAIL PROTECTED]
*
* 5. Products derived from this software may not be called "Apache",
* "Apache" nor may "Apache" appear in their names without prior
* written permission of the Apache Software Foundation.
*
* THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESSED OR IMPLIED
* WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
* OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
* DISCLAIMED. IN NO EVENT SHALL THE APACHE SOFTWARE FOUNDATION OR
* ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
* SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
* LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF
* USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
* ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
* OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
* OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
* SUCH DAMAGE.
* ====================================================================
*
* This software consists of voluntary contributions made by many
* individuals on behalf of the Apache Software Foundation. For more
* information on the Apache Software Foundation, please see
* <http://www.apache.org/>.
*
*/
package org.apache.commons.digester;
import java.util.Map;
import java.util.ArrayList;
/**
* <p>Expands variable references from multiple sources.</p>
*
* @author Simon Kitching
* @version $Revision: $ $Date: $
*/
public class MultiVarExpander extends VarExpander {
private int nEntries = 0;
private ArrayList markers = new ArrayList(2);
private ArrayList sources = new ArrayList(2);
public MultiVarExpander() {
}
public void addSource(String marker, Map source) {
++nEntries;
markers.add(marker);
sources.add(source);
}
/*
* Expands any variable declarations using any of the known
* variable marker strings.
*
* @throws IllegalArgumentException if the input param references
* a variable which is not known to the specified source.
*/
public String expand(String param) {
for(int i=0; i<nEntries; ++i) {
param = expand(
param,
(String) markers.get(i),
(Map) sources.get(i));
}
return param;
}
/**
* Replace any occurrences within the string of the form
* "marker{key}" with the value from source[key].
* <p>
* Commonly, the variable marker is "$", in which case variables
* are indicated by ${key} in the string.
* <p>
* Returns the string after performing all substitutions.
* <p>
* If no substitutions were made, the input string object is
* returned (not a copy).
*
* @throws IllegalArgumentException if the input param references
* a variable which is not known to the specified source.
*/
public String expand(String str, String marker, Map source) {
String startMark = marker + "{";
int markLen = startMark.length();
int index = 0;
for(;;)
{
index = str.indexOf(startMark, index);
if (index == -1)
{
return str;
}
int startIndex = index + markLen;
if (startIndex > str.length())
{
throw new IllegalArgumentException(
"var expression starts at end of string");
}
int endIndex = str.indexOf("}", index + markLen);
if (endIndex == -1)
{
throw new IllegalArgumentException(
"var expression starts but does not end");
}
String key = str.substring(index+markLen, endIndex);
Object value = source.get(key);
if (value == null) {
throw new IllegalArgumentException(
"parameter [" + key + "] is not defined.");
}
String varValue = value.toString();
str = str.substring(0, index) + varValue + str.substring(endIndex+1);
index += varValue.length();
}
}
}
/*
* $Header: $
* $Revision: $
* $Date: $
*
* ====================================================================
*
* The Apache Software License, Version 1.1
*
* Copyright (c) 2001-2003 The Apache Software Foundation. All rights
* reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
*
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
*
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in
* the documentation and/or other materials provided with the
* distribution.
*
* 3. The end-user documentation included with the redistribution,
* if any, must include the following acknowledgement:
* "This product includes software developed by the
* Apache Software Foundation (http://www.apache.org/)."
* Alternately, this acknowledgement may appear in the software itself,
* if and wherever such third-party acknowledgements normally appear.
*
* 4. The names "Apache", "The Jakarta Project", "Commons", and "Apache Software
* Foundation" must not be used to endorse or promote products derived
* from this software without prior written permission. For written
* permission, please contact [EMAIL PROTECTED]
*
* 5. Products derived from this software may not be called "Apache",
* "Apache" nor may "Apache" appear in their names without prior
* written permission of the Apache Software Foundation.
*
* THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESSED OR IMPLIED
* WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
* OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
* DISCLAIMED. IN NO EVENT SHALL THE APACHE SOFTWARE FOUNDATION OR
* ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
* SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
* LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF
* USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
* ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
* OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
* OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
* SUCH DAMAGE.
* ====================================================================
*
* This software consists of voluntary contributions made by many
* individuals on behalf of the Apache Software Foundation. For more
* information on the Apache Software Foundation, please see
* <http://www.apache.org/>.
*
*/
package org.apache.commons.digester;
import org.xml.sax.Attributes;
import java.util.Map;
import java.util.ArrayList;
/**
* <p>Wrapper for an org.xml.sax.Attributes object which expands any
* "variables" referenced in the attribute value via ${foo} or similar.
* This is only done something actually asks for the attribute value,
* thereby imposing no performance penalty if the attribute is not used.</p>
*
* @author Simon Kitching
* @version $Revision: $ $Date: $
*/
public class VarAttributes implements Attributes {
// list of mapped attributes.
private ArrayList values = new ArrayList(10);
private Attributes attrs;
private VarExpander expander;
// ------------------- Public Methods
/**
* Specify which attributes class this object is a proxy for.
*/
public void init(Attributes attrs, VarExpander expander) {
this.attrs = attrs;
this.expander = expander;
// I hope this doesn't release the memory for this array; for
// efficiency, this should just mark the array as being size 0.
values.clear();
}
public String getValue(int index) {
if (index >= values.size()) {
// Expand the values array with null elements, so the later
// call to set(index, s) works ok.
//
// Unfortunately, there is no easy way to set the size of
// an arraylist; we must repeatedly add null elements to it..
values.ensureCapacity(index+1);
for(int i = values.size(); i<= index; ++i) {
values.add(null);
}
}
String s = (String) values.get(index);
if (s == null) {
// we have never been asked for this value before.
// get the real attribute value and perform substitution
// on it.
s = attrs.getValue(index);
if (s != null) {
s = expander.expand(s);
values.set(index, s);
}
}
return s;
}
public String getValue(String qname) {
int index = attrs.getIndex(qname);
if (index == -1) {
return null;
}
return getValue(index);
}
public String getValue(String uri, String localname) {
int index = attrs.getIndex(uri, localname);
if (index == -1) {
return null;
}
return getValue(index);
}
// plain proxy methods follow : nothing interesting :-)
public int getIndex(String qname) {
return attrs.getIndex(qname);
}
public int getIndex(String uri, String localpart) {
return attrs.getIndex(uri, localpart);
}
public int getLength() {
return attrs.getLength();
}
public String getLocalName(int index) {
return attrs.getLocalName(index);
}
public String getQName(int index) {
return attrs.getQName(index);
}
public String getType(int index) {
return attrs.getType(index);
}
public String getType(String qname) {
return attrs.getType(qname);
}
public String getType(String uri, String localname) {
return attrs.getType(uri, localname);
}
public String getURI(int index) {
return attrs.getURI(index);
}
}
/*
* $Header: $
* $Revision: $
* $Date: $
*
* ====================================================================
*
* The Apache Software License, Version 1.1
*
* Copyright (c) 2001-2003 The Apache Software Foundation. All rights
* reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
*
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
*
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in
* the documentation and/or other materials provided with the
* distribution.
*
* 3. The end-user documentation included with the redistribution,
* if any, must include the following acknowledgement:
* "This product includes software developed by the
* Apache Software Foundation (http://www.apache.org/)."
* Alternately, this acknowledgement may appear in the software itself,
* if and wherever such third-party acknowledgements normally appear.
*
* 4. The names "Apache", "The Jakarta Project", "Commons", and "Apache Software
* Foundation" must not be used to endorse or promote products derived
* from this software without prior written permission. For written
* permission, please contact [EMAIL PROTECTED]
*
* 5. Products derived from this software may not be called "Apache",
* "Apache" nor may "Apache" appear in their names without prior
* written permission of the Apache Software Foundation.
*
* THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESSED OR IMPLIED
* WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
* OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
* DISCLAIMED. IN NO EVENT SHALL THE APACHE SOFTWARE FOUNDATION OR
* ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
* SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
* LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF
* USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
* ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
* OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
* OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
* SUCH DAMAGE.
* ====================================================================
*
* This software consists of voluntary contributions made by many
* individuals on behalf of the Apache Software Foundation. For more
* information on the Apache Software Foundation, please see
* <http://www.apache.org/>.
*
*/
/**
* <p>An Interface describing a class capable of expanding strings which
* may contain variable references. The exact syntax of the "reference",
* and the mechanism for determining the corresponding value to be used
* is up to the concrete implementation.</p>
*
* @author Simon Kitching
* @version $Revision: $ $Date: $
*/
package org.apache.commons.digester;
public abstract class VarExpander {
/**
* Return the input string with any variables replaced by their
* corresponding value. If there are no variables in the string,
* then the input parameter is returned unaltered.
*/
abstract public String expand(String param);
}
---------------------------------------------------------------------
To unsubscribe, e-mail: [EMAIL PROTECTED]
For additional commands, e-mail: [EMAIL PROTECTED]
