/*
* 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.seam.solder.reflection;
import java.io.Serializable;
import java.lang.annotation.Annotation;
import java.lang.reflect.InvocationHandler;
import java.lang.reflect.InvocationTargetException;
import java.lang.reflect.Proxy;
import java.util.Map;
import java.util.concurrent.ConcurrentHashMap;
import java.util.concurrent.ConcurrentMap;
import javax.enterprise.util.AnnotationLiteral;
/**
* <p>
* Provides dynamic annotation creation. If you know the type of the annotation
* instance to create at development time you should use
* {@link AnnotationLiteral} instead of {@link AnnotationInstanceProvider}.
* </p>
*
* <p>
* {@link AnnotationInstanceProvider} creates a proxy, and will return values as
* provided when the annotation instance was created. An
* {@link AnnotationInstanceProvider} will cache generated proxy classes.
* </p>
*
* @author Stuart Douglas
* @author Pete Muir
*
* @see AnnotationLiteral
*
*/
public class AnnotationInstanceProvider
{
private final ConcurrentMap<Class<?>, Class<?>> cache;
public AnnotationInstanceProvider()
{
cache = new ConcurrentHashMap<Class<?>, Class<?>>();
}
/**
* <p>
* Returns an instance of the given annotation type with attribute values
* specified in the map.
* </p>
*
* <ul>
* <li>
* For {@link Annotation}, array and enum types the values must exactly match
* the declared return type of the attribute or a {@link ClassCastException}
* will result.</li>
*
* <li>
* For character types the the value must be an instance of {@link Character}
* or {@link String}.</li>
*
* <li>
* Numeric types do not have to match exactly, as they are converted using
* {@link Number}.</li>
* </ul>
*
* <p>
* If am member does not have a corresponding entry in the value map then the
* annotations default value will be used.
* </p>
*
* <p>
* If the annotation member does not have a default value then a
* NullMemberException will be thrown
* </p>
*
* @param annotationType the type of the annotation instance to generate
* @param values the attribute values of this annotation
*/
public <T extends Annotation> T get(Class<T> annotationType, Map<String, ?> values)
{
if (annotationType == null)
{
throw new IllegalArgumentException("Must specify an annotation");
}
Class<?> clazz = cache.get(annotationType);
// Not safe against data race, but doesn't matter, we can recompute and
// get the same value
if (clazz == null)
{
// create the proxy class
clazz = Proxy.getProxyClass(annotationType.getClassLoader(), annotationType, Serializable.class);
cache.put(annotationType, clazz);
}
AnnotationInvocationHandler handler = new AnnotationInvocationHandler(values, annotationType);
// create a new instance by obtaining the constructor via relection
try
{
return annotationType.cast(clazz.getConstructor(new Class[] { InvocationHandler.class }).newInstance(new Object[] { handler }));
}
catch (IllegalArgumentException e)
{
throw new IllegalStateException("Error instantiating proxy for annotation. Annotation type: " + annotationType, e);
}
catch (InstantiationException e)
{
throw new IllegalStateException("Error instantiating proxy for annotation. Annotation type: " + annotationType, e);
}
catch (IllegalAccessException e)
{
throw new IllegalStateException("Error instantiating proxy for annotation. Annotation type: " + annotationType, e);
}
catch (InvocationTargetException e)
{
throw new IllegalStateException("Error instantiating proxy for annotation. Annotation type: " + annotationType, e.getCause());
}
catch (SecurityException e)
{
throw new IllegalStateException("Error accessing proxy constructor for annotation. Annotation type: " + annotationType, e);
}
catch (NoSuchMethodException e)
{
throw new IllegalStateException("Error accessing proxy constructor for annotation. Annotation type: " + annotationType, e);
}
}
}