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The Apache Commons Digester package lets you configure an XML to Java
object mapping module which triggers certain actions called rules whenever
a particular pattern of nested XML elements is recognized.
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package org.apache.commons.digester3.annotations;
/*
* 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 org.apache.commons.digester3.annotations.utils.AnnotationUtils.getAnnotationsArrayValue;
import java.lang.annotation.Annotation;
import java.lang.reflect.AnnotatedElement;
import java.lang.reflect.Constructor;
import java.lang.reflect.Field;
import java.lang.reflect.Method;
import java.security.AccessController;
import java.security.PrivilegedAction;
import org.apache.commons.digester3.Rule;
import org.apache.commons.digester3.annotations.reflect.MethodArgument;
import org.apache.commons.digester3.binder.AbstractRulesModule;
/**
* {@link org.apache.commons.digester3.binder.RulesModule} implementation that allows loading rules from
* annotated classes.
*
* @since 3.0
*/
public abstract class FromAnnotationsRuleModule
extends AbstractRulesModule
{
private static final String JAVA_PACKAGE = "java";
private static final AnnotationHandlerFactory DEFAULT_HANDLER_FACTORY = new DefaultAnnotationHandlerFactory();
private AnnotationHandlerFactory annotationHandlerFactory = DEFAULT_HANDLER_FACTORY;
private WithMemoryRulesBinder rulesBinder;
/**
* {@inheritDoc}
*/
@Override
protected final void configure()
{
if ( rulesBinder == null )
{
rulesBinder = new WithMemoryRulesBinder( rulesBinder() );
}
try
{
configureRules();
}
finally
{
rulesBinder = null;
}
}
/**
* Configures a {@link org.apache.commons.digester3.binder.RulesBinder} via the exposed methods.
*/
protected abstract void configureRules();
/**
* Allows users plug a different {@link AnnotationHandlerFactory} to create {@link AnnotationHandler} instances.
*
* @param annotationHandlerFactory A custom {@link AnnotationHandlerFactory} to create
* {@link AnnotationHandler} instances
*/
protected final void useAnnotationHandlerFactory( AnnotationHandlerFactory annotationHandlerFactory )
{
if ( annotationHandlerFactory == null )
{
throw new IllegalArgumentException( "Argument 'annotationHandlerFactory' must be not null" );
}
this.annotationHandlerFactory = annotationHandlerFactory;
}
/**
* Allows users to switch back to the default {@link AnnotationHandlerFactory} implementation.
*/
protected final void useDefaultAnnotationHandlerFactory()
{
useAnnotationHandlerFactory( DEFAULT_HANDLER_FACTORY );
}
/**
* Scan the input Class, looking for Digester rules expressed via annotations, and binds them.
*
* @param type the type has to be analyzed
* @see DigesterRule
*/
protected final void bindRulesFrom( final Class type )
{
if ( type == null || type.getPackage().getName().startsWith( JAVA_PACKAGE )
|| rulesBinder.isAlreadyBound( type ) )
{
return;
}
// TYPE
visitElements( type );
if ( !type.isInterface() )
{
// CONSTRUCTOR
visitElements( new PrivilegedAction[]>()
{
public Constructor[] run()
{
return type.getDeclaredConstructors();
}
} );
// FIELD
visitElements( new PrivilegedAction()
{
public Field[] run()
{
return type.getDeclaredFields();
}
} );
}
// METHOD
visitElements( new PrivilegedAction()
{
public Method[] run()
{
return type.getDeclaredMethods();
}
} );
rulesBinder.markAsBound( type );
bindRulesFrom( type.getSuperclass() );
}
/**
*
*
* @param
* @param action
*/
private void visitElements( PrivilegedAction action )
{
AE[] annotatedElements = null;
if ( System.getSecurityManager() != null )
{
annotatedElements = AccessController.doPrivileged( action );
}
else
{
annotatedElements = action.run();
}
visitElements( annotatedElements );
}
/**
*
*
* @param annotatedElements
*/
private void visitElements( AnnotatedElement... annotatedElements )
{
for ( AnnotatedElement element : annotatedElements )
{
for ( Annotation annotation : element.getAnnotations() )
{
handle( annotation, element );
}
if ( element instanceof Constructor || element instanceof Method )
{
Annotation[][] parameterAnnotations;
Class[] parameterTypes;
if ( element instanceof Constructor )
{
// constructor args
Constructor construcotr = (Constructor) element;
parameterAnnotations = construcotr.getParameterAnnotations();
parameterTypes = construcotr.getParameterTypes();
}
else
{
// method args
Method method = (Method) element;
parameterAnnotations = method.getParameterAnnotations();
parameterTypes = method.getParameterTypes();
}
for ( int i = 0; i < parameterTypes.length; i++ )
{
visitElements( new MethodArgument( i, parameterTypes[i], parameterAnnotations[i] ) );
}
}
}
}
/**
* Handles the current visited element and related annotation, invoking the
* right handler putting the rule provider in the rule set.
*
* @param annotation the current visited annotation.
* @param element the current visited element.
*/
@SuppressWarnings( "unchecked" )
private void handle( A annotation, E element )
{
Class annotationType = annotation.annotationType();
// check if it is one of the @*.List annotation
if ( annotationType.isAnnotationPresent( DigesterRuleList.class ) )
{
Annotation[] annotations = getAnnotationsArrayValue( annotation );
if ( annotations != null && annotations.length > 0 )
{
// if it is an annotations array, process them
for ( Annotation ptr : annotations )
{
handle( ptr, element );
}
}
}
else if ( annotationType.isAnnotationPresent( DigesterRule.class ) )
{
DigesterRule digesterRule = annotationType.getAnnotation( DigesterRule.class );
// the default behavior if the handler is not specified
Class> handlerType =
(Class>) digesterRule.handledBy();
try
{
AnnotationHandler handler =
annotationHandlerFactory.newInstance( handlerType );
// run!
handler.handle( annotation, element, this.rulesBinder );
}
catch ( Exception e )
{
rulesBinder.addError( e );
}
}
}
}