com.feilong.lib.digester3.FactoryCreateRule Maven / Gradle / Ivy
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package com.feilong.lib.digester3;
/*
* Licensed to the Apache Software Foundation (ASF) under one
* or more contributor license agreements. See the NOTICE file
* distributed with this work for additional information
* regarding copyright ownership. The ASF licenses this file
* to you 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.
*/
import static java.lang.String.format;
import java.util.Formatter;
import java.util.Stack;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.xml.sax.Attributes;
/**
*
* 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.
*
*
* 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{
/** The Constant log. */
private static final Logger LOGGER = LoggerFactory.getLogger(FactoryCreateRule.class);
// ----------------------------------------------------------- Fields
/** Should exceptions thrown by the factory be ignored? */
private final boolean ignoreCreateExceptions;
/** Stock to manage */
private Stack 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.
*
*
* Exceptions thrown during the object creation process will be propagated.
*
*
* @param className
* Java class name of the object creation factory class
*/
public FactoryCreateRule(String className){
this(className, false);
}
/**
*
* 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.
*
*
* Exceptions thrown during the object creation process will be propagated.
*
*
* @param clazz
* Java class name of the object creation factory class
*/
public FactoryCreateRule(Class> clazz){
this(clazz, false);
}
/**
*
* 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.
*
*
* Exceptions thrown during the object creation process will be propagated.
*
*
* @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);
}
/**
*
* 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.
*
*
* Exceptions thrown during the object creation process will be propagated.
*
*
* @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);
}
/**
*
* Construct a factory create rule using the given, already instantiated, {@link ObjectCreationFactory}.
*
*
* Exceptions thrown during the object creation process will be propagated.
*
*
* @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
/**
* {@inheritDoc}
*/
@Override
public void begin(String namespace,String name,Attributes attributes) throws Exception{
if (ignoreCreateExceptions){
if (exceptionIgnoredStack == null){
exceptionIgnoredStack = new Stack<>();
}
try{
Object instance = getFactory(attributes).createObject(attributes);
if (LOGGER.isDebugEnabled()){
LOGGER.debug(
format(
"[FactoryCreateRule]{%s} New %s",
getDigester().getMatch(),
(instance == null ? "null object" : instance.getClass().getName())));
}
getDigester().push(instance);
exceptionIgnoredStack.push(Boolean.FALSE);
}catch (Exception e){
// log message and error
if (LOGGER.isInfoEnabled()){
LOGGER.info(
format(
"[FactoryCreateRule]{%s} Create exception ignored: %s",
getDigester().getMatch(),
((e.getMessage() == null) ? e.getClass().getName() : e.getMessage())));
if (LOGGER.isDebugEnabled()){
LOGGER.debug("[FactoryCreateRule] Ignored exception:", e);
}
}
exceptionIgnoredStack.push(Boolean.TRUE);
}
}else{
Object instance = getFactory(attributes).createObject(attributes);
if (LOGGER.isDebugEnabled()){
LOGGER.debug(
format(
"[FactoryCreateRule]{%s} New %s",
getDigester().getMatch(),
(instance == null ? "null object" : instance.getClass().getName())));
}
getDigester().push(instance);
}
}
/**
* {@inheritDoc}
*/
@Override
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()
&& exceptionIgnoredStack.pop().booleanValue()){
// creation exception was ignored
// nothing was put onto the stack
if (LOGGER.isTraceEnabled()){
LOGGER.trace(format("[FactoryCreateRule]{%s} No creation so no push so no pop", getDigester().getMatch()));
}
return;
}
Object top = getDigester().pop();
if (LOGGER.isDebugEnabled()){
LOGGER.debug(format("[FactoryCreateRule]{%s} Pop %s", getDigester().getMatch(), top.getClass().getName()));
}
}
/**
* {@inheritDoc}
*/
@Override
public void finish() throws Exception{
if (attributeName != null){
creationFactory = null;
}
}
/**
* {@inheritDoc}
*/
@Override
public String toString(){
Formatter formatter = new Formatter().format("FactoryCreateRule[className=%s, attributeName=%s", className, attributeName);
if (creationFactory != null){
formatter.format(", creationFactory=%s", creationFactory);
}
formatter.format("]");
return (formatter.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
* @return An instance of our associated object creation factory, creating one if necessary
* @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 (LOGGER.isDebugEnabled()){
LOGGER.debug(format("[FactoryCreateRule]{%s} New factory %s", getDigester().getMatch(), realClassName));
}
Class clazz = getDigester().getClassLoader().loadClass(realClassName);
creationFactory = (ObjectCreationFactory) clazz.newInstance();
creationFactory.setDigester(getDigester());
}
return (creationFactory);
}
}