org.springframework.aop.target.HotSwappableTargetSource.java Source code

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Here is the source code for org.springframework.aop.target.HotSwappableTargetSource.java

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/*
 * Copyright 2002-2018 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.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.
     */
    @Override
    public synchronized Class<?> getTargetClass() {
        return this.target.getClass();
    }

    @Override
    public final boolean isStatic() {
        return false;
    }

    @Override
    public synchronized Object getTarget() {
        return this.target;
    }

    @Override
    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;
    }

}