【设计模式】行为型05责任链模式（Chain of responsibility Pattern）

学习地址：http://www.runoob.com/design-pattern/chain-of-responsibility-pattern.html

demo采用了DEBUG级别举例子，理解起来还是比较容易的，略做修改和总结：

责任链模式（Chain of responsibility Pattern

原理：责任链中所有的对象持有下一个状态对象的引用，若自己不满足条件，就交给下一个对象处理

java中应用：filter。。。

类图（晚上画）：

代码：

1、创建抽象类，所有责任链对象继承本类：

package com.pat.chainresp;
/**
 * 责任链模式
 * @author Administrator
 *
 */
public abstract class AbstractLogger {
	public static int INFO=1;
	public static int DEBUG=2;
	public static int ERROR=3;

	protected int level;
	//下一个对象
	protected AbstractLogger nextLogger;
	//
	public void setNextLogger(AbstractLogger  nextLogger ){
		this.nextLogger=nextLogger;
	}
	//责任传递
	public void logMessage(int logLevel,String message) {
		if(this.level==logLevel) {
			write(message);
		}
		if(nextLogger!=null) {
			nextLogger.logMessage(logLevel, message);
		}
	}
	abstract protected void write(String message);

}

2、创建三个级别的子类，分别继承AbstractLogger

info级别：

package com.pat.chainresp;

public class InfoLogger extends AbstractLogger{
	protected int level;
	protected AbstractLogger nextLogger;
	public void setNextLogger(AbstractLogger  nextLogger ){
		this.nextLogger=nextLogger;
	}
	//责任传递
	public void logMessage(int logLevel,String message) {
		if(this.level==logLevel) {
			write(message);
		}
		if(nextLogger!=null) {
			nextLogger.logMessage(logLevel, message);
		}
	}
	@Override
	protected void write(String message) {
		System.out.println("InfoLog>>>"+message);

	}
	public InfoLogger(int level){
		this.level=level;
	}
}

debug级别：

package com.pat.chainresp;

public class DebugLogger extends AbstractLogger{
	protected int level;
	protected AbstractLogger nextLogger;
	public void setNextLogger(AbstractLogger  nextLogger ){
		this.nextLogger=nextLogger;
	}
	//责任传递
	public void logMessage(int logLevel,String message) {
		if(this.level==logLevel) {
			write(message);
		}
		if(nextLogger!=null) {
			nextLogger.logMessage(logLevel, message);
		}
	}
	@Override
	protected void write(String message) {
		System.out.println("DebugLogger>>>"+message);

	}
	public DebugLogger(int level){
		this.level=level;
	}
}

error级别：

package com.pat.chainresp;

public class ErrorLogger extends AbstractLogger{
	protected int level;
	protected AbstractLogger nextLogger;
	public void setNextLogger(AbstractLogger  nextLogger ){
		this.nextLogger=nextLogger;
	}
	//责任传递
	public void logMessage(int logLevel,String message) {
		if(this.level==logLevel) {
			write(message);
		}
		if(nextLogger!=null) {
			nextLogger.logMessage(logLevel, message);
		}
	}
	@Override
	protected void write(String message) {
		System.out.println("ErrorLogger>>>"+message);

	}
	public ErrorLogger(int level){
		this.level=level;
	}
}

3、组装责任链：

//组装责任链链条
	public static AbstractLogger chainOfLevel(){
		//创建三个日志级别的对象
		AbstractLogger info = new InfoLogger(AbstractLogger.INFO);
		AbstractLogger debug= new DebugLogger(AbstractLogger.DEBUG);
		AbstractLogger error= new ErrorLogger(AbstractLogger.ERROR);
		//设置责任链顺序
		error.setNextLogger(debug);
		debug.setNextLogger(info);
		return error;
	} 

4、测试：

package com.pat.chainresp;

public class Test {
	//组装责任链链条
	public static AbstractLogger chainOfLevel(){
		//创建三个日志级别的对象
		AbstractLogger info = new InfoLogger(AbstractLogger.INFO);
		AbstractLogger debug= new DebugLogger(AbstractLogger.DEBUG);
		AbstractLogger error= new ErrorLogger(AbstractLogger.ERROR);
		//设置责任链顺序
		error.setNextLogger(debug);
		debug.setNextLogger(info);
		return error;
	}
	public static void main(String[] args) {
		AbstractLogger chainCtrl = chainOfLevel();
		chainCtrl.logMessage(AbstractLogger.INFO, " 日志级别info消息");
		chainCtrl.logMessage(AbstractLogger.DEBUG, "日志级别debug 消息");
		chainCtrl.logMessage(AbstractLogger.ERROR, "日志级别error 消息");
		/*chainCtrl.logMessage(2, "debug 消息");
		chainCtrl.logMessage(3, "err 消息");*/
	}
}

5、结果：

InfoLog>>> 日志级别info消息
DebugLogger>>>日志级别debug 消息
ErrorLogger>>>日志级别error 消息