责任链模式
责任链模式（Chain of Responsibility Pattern）为请求创建了一个接收者对象的链。
这种模式给予请求的类型，对请求的发送者和接收者进行解耦。这种类型的设计模式属于行为型模式。
在这种模式中，通常每个接收者都包含对另一个接收者的引用。如果一个对象不能处理该请求，那么它会把相同的请求传给下一个接收者，依此类推。
实际案例
类信息概览：
| 类名 | 说明 |
|---|---|
| Main.java | 方法的总入口 |
| LoggerLevel.java | 日志级别 |
| AbstractLogger.java | 抽象 logger |
| Logger.java | logger 接口 |
| ErrorLogger.java | 错误日志 |
| WarnLogger.java | 警告日志 |
| InfoLogger.java | 信息日志 |
定义
- LoggerLevel.java
package com.ryo.design.pattern.note.chainOfResponsibility;
/**
* @author houbinbin
* @version 1.0
* @on 2017/8/12
* @since 1.7
*/
public class LoggerLevel {
/**
* 信息
*/
public static final int INFO = 1;
/**
* 警告
*/
public static final int WARN = 2;
/**
* 错误
*/
public static final int ERROR = 3;
}
- AbstractLogger.java
package com.ryo.design.pattern.note.chainOfResponsibility;
/**
* @author houbinbin
* @version 1.0
* @on 2017/8/12
* @since 1.7
*/
public abstract class AbstractLogger implements Logger {
/**
* 下一个日志打印器
*/
private AbstractLogger nextLogger;
/**
* Logger 本身的日志级别
*/
protected int level;
public AbstractLogger(int level) {
this.level = level;
}
@Override
public void logger(int level, String msg) {
if(this.level <= level) {
write(msg);
}
if(nextLogger != null) {
nextLogger.logger(level, msg);
}
}
public AbstractLogger getNextLogger() {
return nextLogger;
}
public AbstractLogger setNextLogger(AbstractLogger nextLogger) {
this.nextLogger = nextLogger;
return this;
}
protected abstract void write(String message);
}
- Logger.java
package com.ryo.design.pattern.note.chainOfResponsibility;
/**
* @author houbinbin
* @version 1.0
* @on 2017/8/12
* @since 1.7
*/
public interface Logger {
/**
* 打印信息
* @param level 消息级别
* @param msg 消息内容
* @see LoggerLevel 消息级别
*/
void logger(int level, String msg);
}
- ErrorLogger.java
package com.ryo.design.pattern.note.chainOfResponsibility;
/**
* @author houbinbin
* @version 1.0
* @on 2017/8/12
* @since 1.7
*/
public class ErrorLogger extends AbstractLogger {
public ErrorLogger() {
super(LoggerLevel.ERROR);
}
@Override
protected void write(String message) {
System.out.println("[Error] Log: "+message);
}
}
- WarnLogger.java
package com.ryo.design.pattern.note.chainOfResponsibility;
/**
* @author houbinbin
* @version 1.0
* @on 2017/8/12
* @since 1.7
*/
public class WarnLogger extends AbstractLogger {
public WarnLogger() {
super(LoggerLevel.WARN);
}
@Override
protected void write(String message) {
System.out.println("[Warn] Log: "+message);
}
}
- InfoLogger.java
package com.ryo.design.pattern.note.chainOfResponsibility;
/**
* @author houbinbin
* @version 1.0
* @on 2017/8/12
* @since 1.7
*/
public class InfoLogger extends AbstractLogger {
public InfoLogger() {
super(LoggerLevel.INFO);
}
@Override
protected void write(String message) {
System.out.println("[Info] Log: "+message);
}
}
测试
- Main.java
/*
* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS HEADER.
* Copyright (c) 2012-2018. houbinbini Inc.
* design-pattern All rights reserved.
*/
package com.ryo.design.pattern.note.chainOfResponsibility;
/**
* <p> </p>
*
* <pre> Created: 2018/5/20 下午7:15 </pre>
* <pre> Project: design-pattern </pre>
*
* @author houbinbin
* @version 1.0
* @since JDK 1.7
*/
public class Main {
public static void main(String[] args) {
AbstractLogger errorLogger = new ErrorLogger();
AbstractLogger warnLogger = new WarnLogger();
AbstractLogger infoLogger = new InfoLogger();
errorLogger.setNextLogger(warnLogger.setNextLogger(infoLogger));
errorLogger.logger(LoggerLevel.WARN, "warn info test");
}
}
- 测试结果
实现方式
UML & Code
UML
UML 图示如下
Code
代码地址
