/*
* Copyright 2002-2011 the original author or authors.
*
* 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.springframework.aop.interceptor;
import java.io.Serializable;
import org.aopalliance.intercept.MethodInterceptor;
import org.aopalliance.intercept.MethodInvocation;
import org.springframework.aop.Advisor;
import org.springframework.aop.support.DefaultPointcutAdvisor;
import org.springframework.core.NamedThreadLocal;
import org.springframework.core.Ordered;
/**
* Interceptor that exposes the current {@link org.aopalliance.intercept.MethodInvocation}
* as a thread-local object. We occasionally need to do this; for example, when a pointcut
* (e.g. an AspectJ expression pointcut) needs to know the full invocation context.
*
* <p>Don't use this interceptor unless this is really necessary. Target objects should
* not normally know about Spring AOP, as this creates a dependency on Spring API.
* Target objects should be plain POJOs as far as possible.
*
* <p>If used, this interceptor will normally be the first in the interceptor chain.
*
* @author Rod Johnson
* @author Juergen Hoeller
*/
public class ExposeInvocationInterceptor implements MethodInterceptor, Ordered, Serializable {
/** Singleton instance of this class */
public static final ExposeInvocationInterceptor INSTANCE = new ExposeInvocationInterceptor();
/**
* Singleton advisor for this class. Use in preference to INSTANCE when using
* Spring AOP, as it prevents the need to create a new Advisor to wrap the instance.
*/
public static final Advisor ADVISOR = new DefaultPointcutAdvisor(INSTANCE) {
@Override
public String toString() {
return ExposeInvocationInterceptor.class.getName() +".ADVISOR";
}
};
private static final ThreadLocal<MethodInvocation> invocation =
new NamedThreadLocal<MethodInvocation>("Current AOP method invocation");
/**
* Return the AOP Alliance MethodInvocation object associated with the current invocation.
* @return the invocation object associated with the current invocation
* @throws IllegalStateException if there is no AOP invocation in progress,
* or if the ExposeInvocationInterceptor was not added to this interceptor chain
*/
public static MethodInvocation currentInvocation() throws IllegalStateException {
MethodInvocation mi = invocation.get();
if (mi == null)
throw new IllegalStateException(
"No MethodInvocation found: Check that an AOP invocation is in progress, and that the " +
"ExposeInvocationInterceptor is upfront in the interceptor chain. Specifically, note that " +
"advices with order HIGHEST_PRECEDENCE will execute before ExposeInvocationInterceptor!");
return mi;
}
/**
* Ensures that only the canonical instance can be created.
*/
private ExposeInvocationInterceptor() {
}
public Object invoke(MethodInvocation mi) throws Throwable {
MethodInvocation oldInvocation = invocation.get();
invocation.set(mi);
try {
return mi.proceed();
}
finally {
invocation.set(oldInvocation);
}
}
public int getOrder() {
return Ordered.HIGHEST_PRECEDENCE + 1;
}
/**
* Required to support serialization. Replaces with canonical instance
* on deserialization, protecting Singleton pattern.
* <p>Alternative to overriding the <code>equals</code> method.
*/
private Object readResolve() {
return INSTANCE;
}
}