org.springframework.aop.TargetSource Maven / Gradle / Ivy
/*
* Copyright 2002-2023 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
*
* https://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;
import org.springframework.lang.Nullable;
/**
* A {@code TargetSource} 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.
*
* If a {@code TargetSource} is "static", it will always return
* the same target, allowing optimizations in the AOP framework. Dynamic
* target sources can support pooling, hot swapping, etc.
*
*
Application developers don't usually need to work with
* {@code TargetSources} directly: this is an AOP framework interface.
*
* @author Rod Johnson
* @author Juergen Hoeller
*/
public interface TargetSource extends TargetClassAware {
/**
* Return the type of targets returned by this {@link TargetSource}.
*
Can return {@code null}, although certain usages of a {@code TargetSource}
* might just work with a predetermined target class.
* @return the type of targets returned by this {@link TargetSource}
*/
@Override
@Nullable
Class getTargetClass();
/**
* Will all calls to {@link #getTarget()} return the same object?
*
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()}.
*
The default implementation returns {@code false}.
* @return {@code true} if the target is immutable
* @see #getTarget
*/
default boolean isStatic() {
return false;
}
/**
* 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,
* or {@code null} if there is no actual target instance
* @throws Exception if the target object can't be resolved
*/
@Nullable
Object getTarget() throws Exception;
/**
* Release the given target object obtained from the
* {@link #getTarget()} method, if any.
*
The default implementation is empty.
* @param target object obtained from a call to {@link #getTarget()}
* @throws Exception if the object can't be released
*/
default void releaseTarget(Object target) throws Exception {
}
}