常用设计模式总结--责任链模式

常用设计模式总结--责任链模式

在多线程的编程模型中，责任链模式是一种常用的模式，责任链模式可以将一个任务分解成小的独立的任务单元，让整个任务一目了然。

以一个爬虫爬取某个页面为例，假设url的调度不是有爬虫来管理，而是有专门的urldb模块来实现，那么一个网页的爬取可以分解为以下几个小的子任务。下载网页；解析网页；将当前页面新发现的链接写回urldb。将任务分解成小任务以后，每个小任务的输出就是下一个任务的输入，整个框架就可以清晰明了。辅助于log的信息，在出现问题的时候很容易查找问题出现的地方

废话少说，直接看代码吧

Processor.java

public abstract class Processor {private Processor next;protected int delta;public abstract int doProcess(int base);public void setNext( Processor next ){this.next = next;}public void process(int base){int result = doProcess(base);if( null != next ){next.process(result);}}}

ProcessorChainFactory，负责把小的任务组合起来

package zl.study.designpattern.respchain;public class ProcessorChainFactory {public static Processor assembleChain( Processor ...processor){Processor head = null;Processor pre = null;if( null == processor || 0 >= processor.length){return head;}for(int i = 0; i< processor.length; i ++){Processor current = processor[i];if( i == 0){head =current;}if( null != pre){pre.setNext(current);}pre = current;}return head;}}

示例程序

算了一个算术题

ProcessorAdd.java 加法

package zl.study.designpattern.respchain.test;import zl.study.designpattern.respchain.Processor;public class ProcessorAdd extends Processor{public ProcessorAdd(int delta){this.delta = delta;}@Overridepublic int doProcess(int base) {int result = base + delta;System.out.println(result);return result;}}

ProcessorSub.java 减法

package zl.study.designpattern.respchain.test;import zl.study.designpattern.respchain.Processor;public class ProcessorSub extends Processor{public ProcessorSub( int delta){this.delta = delta;}@Overridepublic int doProcess(int base) {int result = base -delta;System.out.println(result);return result;}}

主程序

package zl.study.designpattern.respchain.test;import zl.study.designpattern.respchain.ProcessorChainFactory;public class RespChainTest {public static void main(String args[]){ProcessorAdd add = new ProcessorAdd(1);ProcessorSub sub = new ProcessorSub(2);ProcessorChainFactory.assembleChain(add,sub);add.process(1);}}