设计模式之责任链模式

     责任链模式（Chain of Responsibility）是Web项目中最经常用到的一个设计模式，比如是Apache Tomcat 的对Encoding的 处理，Struts2 的拦截器， jsp servlet 的Filter 等等，都是基于责任链模式设计的。比如有一个作业任务，先有一个对象对其负责处理，之后又交给其他的一个对象处理，一次传递下去，这是最通俗最简单的责任链模式的应用。

 

 

代码实例：（模拟jsp servlet 的Filter）

 

Filter:处理过滤信息的过滤接口类

package com.lyz.dp.filter;

public interface Filter {
	void doFilter(Request request, Response response, FilterChain chain);
}

 

 

FilterChain:责任链的核心类，执行链式调用 （实现Filter）

 

package com.lyz.dp.filter;

import java.util.ArrayList;
import java.util.List;

public class FilterChain implements Filter {
	List<Filter> filters = new ArrayList<Filter>();
	int index = 0;
	
	public FilterChain addFilter(Filter f) {
		this.filters.add(f);
		return this;
	}
	
	@Override
	public void doFilter(Request request, Response response, FilterChain chain) {
		if(index == filters.size()) return ;
		
		Filter f = filters.get(index);
		index ++;
		f.doFilter(request, response, chain);
	}
}

 

 

HTMLFilter：第一个过滤器 （实现Filter）

package com.lyz.dp.filter;

public class HTMLFilter implements Filter {

	

	@Override
	public void doFilter(Request request, Response response, FilterChain chain) {
		//process the html tag <>
		request.requestStr = request.requestStr.replace('<', '[')
				   .replace('>', ']') + "---HTMLFilter()";
		chain.doFilter(request, response, chain);
		response.responseStr += "---HTMLFilter()";
	}

}

 

 

SesitiveFilter ：第二个过滤器 （实现Filter）

 

package com.lyz.dp.filter;

public class SesitiveFilter implements Filter {

	

	@Override
	public void doFilter(Request request, Response response, FilterChain chain) {
		request.requestStr = request.requestStr.replace("被就业", "就业")
		 .replace("敏感", "") + "---SesitiveFilter()";
		chain.doFilter(request, response, chain);
		response.responseStr += "---SesitiveFilter()";
	
	}
	
	

}

 

　

Request：

 

package com.lyz.dp.filter;

public class Request {
	String requestStr;

	public String getRequestStr() {
		return requestStr;
	}

	public void setRequestStr(String requestStr) {
		this.requestStr = requestStr;
	}
}

 

Response：

 

package com.lyz.dp.filter;

public class Response {
	String responseStr;

	public String getResponseStr() {
		return responseStr;
	}

	public void setResponseStr(String responseStr) {
		this.responseStr = responseStr;
	}
	
}

 

 

测试类：

 

package com.lyz.dp.filter;

public class Main {

	/**
	 * @param args
	 */
	public static void main(String[] args) {
		String msg = "大家好:)，<script>，敏感，被就业";
		Request request = new Request();
		request.setRequestStr(msg);
		Response response = new Response();
		response.setResponseStr("response");
		FilterChain fc = new FilterChain();
		fc.addFilter(new HTMLFilter()).addFilter(new SesitiveFilter());

		fc.doFilter(request, response, fc);
		System.out.println(request.getRequestStr());
		System.out.println(response.getResponseStr());
	}

}

 

 

 

 

执行结果：

大家好:)，[script]，，就业---HTMLFilter()---SesitiveFilter()
response---SesitiveFilter()---HTMLFilter()

----------------------------------------------------------------------------------

执行过程：HTMLFilter()---SesitiveFilter()---SesitiveFilter()---HTMLFilter()

完成链式调用（栈式调用）先进后出。