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DefaultBeanExtension.java
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DefaultBeanExtension.java
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/*
* JBoss, Home of Professional Open Source
* Copyright 2010, Red Hat, Inc., and individual contributors
* by the @authors tag. See the copyright.txt in the distribution for a
* full listing of individual contributors.
*
* 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.jboss.weld.extensions.defaultbean;
import java.lang.annotation.Annotation;
import java.util.Collections;
import java.util.HashSet;
import java.util.Iterator;
import java.util.Set;
import javax.enterprise.event.Observes;
import javax.enterprise.inject.Alternative;
import javax.enterprise.inject.Default;
import javax.enterprise.inject.spi.AfterBeanDiscovery;
import javax.enterprise.inject.spi.Bean;
import javax.enterprise.inject.spi.BeanManager;
import javax.enterprise.inject.spi.Extension;
import javax.enterprise.inject.spi.ProcessAnnotatedType;
import javax.enterprise.inject.spi.ProcessBean;
import org.jboss.weld.extensions.bean.BeanBuilder;
import org.jboss.weld.extensions.literal.DefaultLiteral;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
/**
* This extension allows you to register a 'Default Bean' for a given type and
* qualifiers. If no bean with the given type and qualifiers is installed then
* this extensions installs the default bean.
*
* In some ways this is similar to the functionality provided by
* {@link Alternative} however there are some important distinctions
* <ul>
* <li>No XML is required, if an alternative implementation is available it is
* used automatically</li>
* <li>The bean is registered across all modules, not on a per module basis</li>
* </ul>
*
* It is also important to note that beans registered in the
* {@link AfterBeanDiscovery} event may not been see by this extension
*
* @author Stuart Douglas
*
*/
public class DefaultBeanExtension implements Extension
{
Logger log = LoggerFactory.getLogger(DefaultBeanExtension.class);
private final Set<DefaultBeanDefinition> beans = new HashSet<DefaultBeanDefinition>();
private boolean beanDiscoveryOver = false;
/**
* Adds a default bean with the {@link Default} qualifier
*/
public void addDefaultBean(Class<?> type, Bean<?> bean)
{
beans.add(new DefaultBeanDefinition(type, Collections.singleton(DefaultLiteral.INSTANCE), bean));
}
public <X> void processAnnotatedType(@Observes ProcessAnnotatedType<X> event, BeanManager beanManager)
{
if (event.getAnnotatedType().isAnnotationPresent(DefaultBean.class))
{
DefaultBean annotation = event.getAnnotatedType().getAnnotation(DefaultBean.class);
event.veto();
BeanBuilder<X> builder = new BeanBuilder<X>(beanManager);
builder.defineBeanFromAnnotatedType(event.getAnnotatedType());
builder.setTypes((Set) Collections.singleton(annotation.type()));
addDefaultBean(annotation.type(), builder.create());
}
}
/**
* Adds a default bean
*/
public void addDefaultBean(Class<?> type, Set<Annotation> qualifiers, Bean<?> bean)
{
beans.add(new DefaultBeanDefinition(type, Collections.singleton(DefaultLiteral.INSTANCE), bean));
}
public void processBean(@Observes ProcessBean<?> event)
{
if (beanDiscoveryOver)
{
return;
}
Iterator<DefaultBeanDefinition> it = beans.iterator();
while (it.hasNext())
{
DefaultBeanDefinition definition = it.next();
if (definition.matches(event.getBean()))
{
log.info("Preventing install of default bean " + definition.getDefaultBean());
it.remove();
}
}
}
public void afterBeanDiscovery(@Observes AfterBeanDiscovery event)
{
beanDiscoveryOver = true;
for (DefaultBeanDefinition d : beans)
{
log.info("Installing default bean " + d.getDefaultBean());
event.addBean(d.getDefaultBean());
}
beans.clear();
}
}