/* $Id: FactoryCreateRule.java,v 1.21.2.1 2004/07/30 20:11:01 rdonkin Exp $
*
* Copyright 2001-2004 The Apache Software Foundation.
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package org.apache.commons.digester;
import org.xml.sax.Attributes;
import org.apache.commons.collections.ArrayStack;
/**
* <p>Rule implementation that uses an {@link ObjectCreationFactory} to create
* a new object which it pushes onto the object stack. When the element is
* complete, the object will be popped.</p>
*
* <p>This rule is intended in situations where the element's attributes are
* needed before the object can be created. A common senario is for the
* ObjectCreationFactory implementation to use the attributes as parameters
* in a call to either a factory method or to a non-empty constructor.
*/
public class FactoryCreateRule extends Rule {
// ----------------------------------------------------------- Fields
/** Should exceptions thrown by the factory be ignored? */
private boolean ignoreCreateExceptions;
/** Stock to manage */
private ArrayStack exceptionIgnoredStack;
// ----------------------------------------------------------- Constructors
/**
* Construct a factory create rule that will use the specified
* class name to create an {@link ObjectCreationFactory} which will
* then be used to create an object and push it on the stack.
*
* @param digester The associated Digester
* @param className Java class name of the object creation factory class
*
* @deprecated The digester instance is now set in the {@link Digester#addRule} method.
* Use {@link #FactoryCreateRule(String className)} instead.
*/
public FactoryCreateRule(Digester digester, String className) {
this(className);
}
/**
* Construct a factory create rule that will use the specified
* class to create an {@link ObjectCreationFactory} which will
* then be used to create an object and push it on the stack.
*
* @param digester The associated Digester
* @param clazz Java class name of the object creation factory class
*
* @deprecated The digester instance is now set in the {@link Digester#addRule} method.
* Use {@link #FactoryCreateRule(Class clazz)} instead.
*/
public FactoryCreateRule(Digester digester, Class clazz) {
this(clazz);
}
/**
* Construct a factory create rule that will use the specified
* class name (possibly overridden by the specified attribute if present)
* to create an {@link ObjectCreationFactory}, which will then be used
* to instantiate an object instance and push it onto the stack.
*
* @param digester The associated Digester
* @param className Default Java class name of the factory class
* @param attributeName Attribute name which, if present, contains an
* override of the class name of the object creation factory to create.
*
* @deprecated The digester instance is now set in the {@link Digester#addRule} method.
* Use {@link #FactoryCreateRule(String className, String attributeName)} instead.
*/
public FactoryCreateRule(Digester digester,
String className, String attributeName) {
this(className, attributeName);
}
/**
* Construct a factory create rule that will use the specified
* class (possibly overridden by the specified attribute if present)
* to create an {@link ObjectCreationFactory}, which will then be used
* to instantiate an object instance and push it onto the stack.
*
* @param digester The associated Digester
* @param clazz Default Java class name of the factory class
* @param attributeName Attribute name which, if present, contains an
* override of the class name of the object creation factory to create.
*
* @deprecated The digester instance is now set in the {@link Digester#addRule} method.
* Use {@link #FactoryCreateRule(Class clazz, String attributeName)} instead.
*/
public FactoryCreateRule(Digester digester,
Class clazz, String attributeName) {
this(clazz, attributeName);
}
/**
* Construct a factory create rule using the given, already instantiated,
* {@link ObjectCreationFactory}.
*
* @param digester The associated Digester
* @param creationFactory called on to create the object.
*
* @deprecated The digester instance is now set in the {@link Digester#addRule} method.
* Use {@link #FactoryCreateRule(ObjectCreationFactory creationFactory)} instead.
*/
public FactoryCreateRule(Digester digester,
ObjectCreationFactory creationFactory) {
this(creationFactory);
}
/**
* <p>Construct a factory create rule that will use the specified
* class name to create an {@link ObjectCreationFactory} which will
* then be used to create an object and push it on the stack.</p>
*
* <p>Exceptions thrown during the object creation process will be propagated.</p>
*
* @param className Java class name of the object creation factory class
*/
public FactoryCreateRule(String className) {
this(className, false);
}
/**
* <p>Construct a factory create rule that will use the specified
* class to create an {@link ObjectCreationFactory} which will
* then be used to create an object and push it on the stack.</p>
*
* <p>Exceptions thrown during the object creation process will be propagated.</p>
*
* @param clazz Java class name of the object creation factory class
*/
public FactoryCreateRule(Class clazz) {
this(clazz, false);
}
/**
* <p>Construct a factory create rule that will use the specified
* class name (possibly overridden by the specified attribute if present)
* to create an {@link ObjectCreationFactory}, which will then be used
* to instantiate an object instance and push it onto the stack.</p>
*
* <p>Exceptions thrown during the object creation process will be propagated.</p>
*
* @param className Default Java class name of the factory class
* @param attributeName Attribute name which, if present, contains an
* override of the class name of the object creation factory to create.
*/
public FactoryCreateRule(String className, String attributeName) {
this(className, attributeName, false);
}
/**
* <p>Construct a factory create rule that will use the specified
* class (possibly overridden by the specified attribute if present)
* to create an {@link ObjectCreationFactory}, which will then be used
* to instantiate an object instance and push it onto the stack.</p>
*
* <p>Exceptions thrown during the object creation process will be propagated.</p>
*
* @param clazz Default Java class name of the factory class
* @param attributeName Attribute name which, if present, contains an
* override of the class name of the object creation factory to create.
*/
public FactoryCreateRule(Class clazz, String attributeName) {
this(clazz, attributeName, false);
}
/**
* <p>Construct a factory create rule using the given, already instantiated,
* {@link ObjectCreationFactory}.</p>
*
* <p>Exceptions thrown during the object creation process will be propagated.</p>
*
* @param creationFactory called on to create the object.
*/
public FactoryCreateRule(ObjectCreationFactory creationFactory) {
this(creationFactory, false);
}
/**
* Construct a factory create rule that will use the specified
* class name to create an {@link ObjectCreationFactory} which will
* then be used to create an object and push it on the stack.
*
* @param className Java class name of the object creation factory class
* @param ignoreCreateExceptions if true, exceptions thrown by the object
* creation factory
* will be ignored.
*/
public FactoryCreateRule(String className, boolean ignoreCreateExceptions) {
this(className, null, ignoreCreateExceptions);
}
/**
* Construct a factory create rule that will use the specified
* class to create an {@link ObjectCreationFactory} which will
* then be used to create an object and push it on the stack.
*
* @param clazz Java class name of the object creation factory class
* @param ignoreCreateExceptions if true, exceptions thrown by the
* object creation factory
* will be ignored.
*/
public FactoryCreateRule(Class clazz, boolean ignoreCreateExceptions) {
this(clazz, null, ignoreCreateExceptions);
}
/**
* Construct a factory create rule that will use the specified
* class name (possibly overridden by the specified attribute if present)
* to create an {@link ObjectCreationFactory}, which will then be used
* to instantiate an object instance and push it onto the stack.
*
* @param className Default Java class name of the factory class
* @param attributeName Attribute name which, if present, contains an
* override of the class name of the object creation factory to create.
* @param ignoreCreateExceptions if true, exceptions thrown by the object
* creation factory will be ignored.
*/
public FactoryCreateRule(
String className,
String attributeName,
boolean ignoreCreateExceptions) {
this.className = className;
this.attributeName = attributeName;
this.ignoreCreateExceptions = ignoreCreateExceptions;
}
/**
* Construct a factory create rule that will use the specified
* class (possibly overridden by the specified attribute if present)
* to create an {@link ObjectCreationFactory}, which will then be used
* to instantiate an object instance and push it onto the stack.
*
* @param clazz Default Java class name of the factory class
* @param attributeName Attribute name which, if present, contains an
* override of the class name of the object creation factory to create.
* @param ignoreCreateExceptions if true, exceptions thrown by the object
* creation factory will be ignored.
*/
public FactoryCreateRule(
Class clazz,
String attributeName,
boolean ignoreCreateExceptions) {
this(clazz.getName(), attributeName, ignoreCreateExceptions);
}
/**
* Construct a factory create rule using the given, already instantiated,
* {@link ObjectCreationFactory}.
*
* @param creationFactory called on to create the object.
* @param ignoreCreateExceptions if true, exceptions thrown by the object
* creation factory will be ignored.
*/
public FactoryCreateRule(
ObjectCreationFactory creationFactory,
boolean ignoreCreateExceptions) {
this.creationFactory = creationFactory;
this.ignoreCreateExceptions = ignoreCreateExceptions;
}
// ----------------------------------------------------- Instance Variables
/**
* The attribute containing an override class name if it is present.
*/
protected String attributeName = null;
/**
* The Java class name of the ObjectCreationFactory to be created.
* This class must have a no-arguments constructor.
*/
protected String className = null;
/**
* The object creation factory we will use to instantiate objects
* as required based on the attributes specified in the matched XML
* element.
*/
protected ObjectCreationFactory creationFactory = null;
// --------------------------------------------------------- Public Methods
/**
* Process the beginning of this element.
*
* @param attributes The attribute list of this element
*/
public void begin(String namespace, String name, Attributes attributes) throws Exception {
if (ignoreCreateExceptions) {
if (exceptionIgnoredStack == null) {
exceptionIgnoredStack = new ArrayStack();
}
try {
Object instance = getFactory(attributes).createObject(attributes);
if (digester.log.isDebugEnabled()) {
digester.log.debug("[FactoryCreateRule]{" + digester.match +
"} New " + instance.getClass().getName());
}
digester.push(instance);
exceptionIgnoredStack.push(Boolean.FALSE);
} catch (Exception e) {
// log message and error
if (digester.log.isInfoEnabled()) {
digester.log.info("[FactoryCreateRule] Create exception ignored: " +
((e.getMessage() == null) ? e.getClass().getName() : e.getMessage()));
if (digester.log.isDebugEnabled()) {
digester.log.debug("[FactoryCreateRule] Ignored exception:", e);
}
}
exceptionIgnoredStack.push(Boolean.TRUE);
}
} else {
Object instance = getFactory(attributes).createObject(attributes);
if (digester.log.isDebugEnabled()) {
digester.log.debug("[FactoryCreateRule]{" + digester.match +
"} New " + instance.getClass().getName());
}
digester.push(instance);
}
}
/**
* Process the end of this element.
*/
public void end(String namespace, String name) throws Exception {
// check if object was created
// this only happens if an exception was thrown and we're ignoring them
if (
ignoreCreateExceptions &&
exceptionIgnoredStack != null &&
!(exceptionIgnoredStack.empty())) {
if (((Boolean) exceptionIgnoredStack.pop()).booleanValue()) {
// creation exception was ignored
// nothing was put onto the stack
if (digester.log.isTraceEnabled()) {
digester.log.trace("[FactoryCreateRule] No creation so no push so no pop");
}
return;
}
}
Object top = digester.pop();
if (digester.log.isDebugEnabled()) {
digester.log.debug("[FactoryCreateRule]{" + digester.match +
"} Pop " + top.getClass().getName());
}
}
/**
* Clean up after parsing is complete.
*/
public void finish() throws Exception {
if (attributeName != null) {
creationFactory = null;
}
}
/**
* Render a printable version of this Rule.
*/
public String toString() {
StringBuffer sb = new StringBuffer("FactoryCreateRule[");
sb.append("className=");
sb.append(className);
sb.append(", attributeName=");
sb.append(attributeName);
if (creationFactory != null) {
sb.append(", creationFactory=");
sb.append(creationFactory);
}
sb.append("]");
return (sb.toString());
}
// ------------------------------------------------------ Protected Methods
/**
* Return an instance of our associated object creation factory,
* creating one if necessary.
*
* @param attributes Attributes passed to our factory creation element
*
* @exception Exception if any error occurs
*/
protected ObjectCreationFactory getFactory(Attributes attributes)
throws Exception {
if (creationFactory == null) {
String realClassName = className;
if (attributeName != null) {
String value = attributes.getValue(attributeName);
if (value != null) {
realClassName = value;
}
}
if (digester.log.isDebugEnabled()) {
digester.log.debug("[FactoryCreateRule]{" + digester.match +
"} New factory " + realClassName);
}
Class clazz = digester.getClassLoader().loadClass(realClassName);
creationFactory = (ObjectCreationFactory)
clazz.newInstance();
creationFactory.setDigester(digester);
}
return (creationFactory);
}
}