Spring Framework example source code file (EmptyTargetSource.java)

This example Spring Framework source code file (EmptyTargetSource.java) is included in the DevDaily.com "Java Source Code Warehouse" project. The intent of this project is to help you "Learn Java by Example" ^TM.

Java - Spring Framework tags/keywords

class, class, emptytargetsource, emptytargetsource, instance, instance, io, object, object, serializable, string, targetsource

The Spring Framework EmptyTargetSource.java source code

/*
 * Copyright 2002-2007 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.ObjectUtils;

/**
 * Canonical <code>TargetSource when there is no target
 * (or just the target class known), and behavior is supplied
 * by interfaces and advisors only.
 *
 * @author Rod Johnson
 * @author Juergen Hoeller
 */
public class EmptyTargetSource implements TargetSource, Serializable {

	/** use serialVersionUID from Spring 1.2 for interoperability */
	private static final long serialVersionUID = 3680494563553489691L;


	//---------------------------------------------------------------------
	// Static factory methods
	//---------------------------------------------------------------------

	/**
	 * The canonical (Singleton) instance of this {@link EmptyTargetSource}.
	 */
	public static final EmptyTargetSource INSTANCE = new EmptyTargetSource(null, true);


	/**
	 * Return an EmptyTargetSource for the given target Class.
	 * @param targetClass the target Class (may be <code>null)
	 * @see #getTargetClass()
	 */
	public static EmptyTargetSource forClass(Class targetClass) {
		return forClass(targetClass, true);
	}

	/**
	 * Return an EmptyTargetSource for the given target Class.
	 * @param targetClass the target Class (may be <code>null)
	 * @param isStatic whether the TargetSource should be marked as static
	 * @see #getTargetClass()
	 */
	public static EmptyTargetSource forClass(Class targetClass, boolean isStatic) {
		return (targetClass == null && isStatic ? INSTANCE : new EmptyTargetSource(targetClass, isStatic));
	}


	//---------------------------------------------------------------------
	// Instance implementation
	//---------------------------------------------------------------------

	private final Class targetClass;

	private final boolean isStatic;


	/**
	 * Create a new instance of the {@link EmptyTargetSource} class.
	 * <p>This constructor is private to enforce the
	 * Singleton pattern / factory method pattern.
	 * @param targetClass the target class to expose (may be <code>null)
	 * @param isStatic whether the TargetSource is marked as static
	 */
	private EmptyTargetSource(Class targetClass, boolean isStatic) {
		this.targetClass = targetClass;
		this.isStatic = isStatic;
	}

	/**
	 * Always returns the specified target Class, or <code>null if none.
	 */
	public Class getTargetClass() {
		return this.targetClass;
	}

	/**
	 * Always returns <code>true.
	 */
	public boolean isStatic() {
		return this.isStatic;
	}

	/**
	 * Always returns <code>null.
	 */
	public Object getTarget() {
		return null;
	}

	/**
	 * Nothing to release.
	 */
	public void releaseTarget(Object target) {
	}


	/**
	 * Returns the canonical instance on deserialization in case
	 * of no target class, thus protecting the Singleton pattern.
	 */
	private Object readResolve() {
		return (this.targetClass == null && this.isStatic ? INSTANCE : this);
	}

	public boolean equals(Object other) {
		if (this == other) {
			return true;
		}
		if (!(other instanceof EmptyTargetSource)) {
			return false;
		}
		EmptyTargetSource otherTs = (EmptyTargetSource) other;
		return (ObjectUtils.nullSafeEquals(this.targetClass, otherTs.targetClass) && this.isStatic == otherTs.isStatic);
	}

	public int hashCode() {
		return EmptyTargetSource.class.hashCode() * 13 + ObjectUtils.nullSafeHashCode(this.targetClass);
	}

	public String toString() {
		return "EmptyTargetSource: " +
				(this.targetClass != null ? "target class [" + this.targetClass.getName() + "]" : "no target class") +
				", " + (this.isStatic ? "static" : "dynamic");
	}

}