/*<
* Copyright 2002-2010 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;
/**
* A <code>TargetSource</code> is used to obtain the current "target" of
* an AOP invocation, which will be invoked via reflection if no around
* advice chooses to end the interceptor chain itself.
*
* <p>If a <code>TargetSource</code> is "static", it will always return
* the same target, allowing optimizations in the AOP framework. Dynamic
* target sources can support pooling, hot swapping, etc.
*
* <p>Application developers don't usually need to work with
* <code>TargetSources</code> directly: this is an AOP framework interface.
*
* @author Rod Johnson
*/
public interface TargetSource extends TargetClassAware {
/**
* Return the type of targets returned by this {@link TargetSource}.
* <p>Can return <code>null</code>, although certain usages of a
* <code>TargetSource</code> might just work with a predetermined
* target class.
* @return the type of targets returned by this {@link TargetSource}
*/
Class<?> getTargetClass();
/**
* Will all calls to {@link #getTarget()} return the same object?
* <p>In that case, there will be no need to invoke
* {@link #releaseTarget(Object)}, and the AOP framework can cache
* the return value of {@link #getTarget()}.
* @return <code>true</code> if the target is immutable
* @see #getTarget
*/
boolean isStatic();
/**
* Return a target instance. Invoked immediately before the
* AOP framework calls the "target" of an AOP method invocation.
* @return the target object, which contains the joinpoint
* @throws Exception if the target object can't be resolved
*/
Object getTarget() throws Exception;
/**
* Release the given target object obtained from the
* {@link #getTarget()} method.
* @param target object obtained from a call to {@link #getTarget()}
* @throws Exception if the object can't be released
*/
void releaseTarget(Object target) throws Exception;
}
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