/*
* 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.target;
import java.io.Serializable;
import org.springframework.aop.TargetSource;
import org.springframework.util.Assert;
/**
* {@link org.springframework.aop.TargetSource} implementation that
* caches a local target object, but allows the target to be swapped
* while the application is running.
*
* <p>If configuring an object of this class in a Spring IoC container,
* use constructor injection.
*
* <p>This TargetSource is serializable if the target is at the time
* of serialization.
*
* @author Rod Johnson
* @author Juergen Hoeller
*/
public class HotSwappableTargetSource implements TargetSource, Serializable {
/** use serialVersionUID from Spring 1.2 for interoperability */
private static final long serialVersionUID = 7497929212653839187L;
/** The current target object */
private Object target;
/**
* Create a new HotSwappableTargetSource with the given initial target object.
* @param initialTarget the initial target object
*/
public HotSwappableTargetSource(Object initialTarget) {
Assert.notNull(initialTarget, "Target object must not be null");
this.target = initialTarget;
}
/**
* Return the type of the current target object.
* <p>The returned type should usually be constant across all target objects.
*/
public synchronized Class<?> getTargetClass() {
return this.target.getClass();
}
public final boolean isStatic() {
return false;
}
public synchronized Object getTarget() {
return this.target;
}
public void releaseTarget(Object target) {
// nothing to do
}
/**
* Swap the target, returning the old target object.
* @param newTarget the new target object
* @return the old target object
* @throws IllegalArgumentException if the new target is invalid
*/
public synchronized Object swap(Object newTarget) throws IllegalArgumentException {
Assert.notNull(newTarget, "Target object must not be null");
Object old = this.target;
this.target = newTarget;
return old;
}
/**
* Two HotSwappableTargetSources are equal if the current target
* objects are equal.
*/
@Override
public boolean equals(Object other) {
return (this == other || (other instanceof HotSwappableTargetSource &&
this.target.equals(((HotSwappableTargetSource) other).target)));
}
@Override
public int hashCode() {
return HotSwappableTargetSource.class.hashCode();
}
@Override
public String toString() {
return "HotSwappableTargetSource for target: " + this.target;
}
}
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