责任链(过滤器)模式

小鱼儿 2022-07-14 05:28 123阅读 0赞

假设从客户端发送数据给服务端，接着服务端再将数据传输回客户端，同时需要将数据进行一些过滤，这时候就可以考虑过滤器模式。

首先定义Request和Response，里面就封装一个String

public class Request {
    	String requestStr;
    }

public class Response {
    	String responseStr;
    }

定义一个Filter接口

public abstract interface MyFilter {
    	public abstract void doFilter(Request request,Response response,FilterChain fc);
    }

使用进FilterChain行操作

public class FilterChain implements MyFilter{
    	ArrayList<MyFilter> myFilters;
    	int index;
    	public FilterChain() {
    		myFilters = new ArrayList<MyFilter>();
    		index=0;
    	}
    	public void add(MyFilter mf) {
    		myFilters.add(mf);
    	}
    	@Override
    	public void doFilter(Request request, Response response,FilterChain fc) {
    		if(index == fc.myFilters.size()) return;
    		MyFilter mf = myFilters.get(index);
    		index++;
    		mf.doFilter(request,response,fc);
    	}
    }

写2个实现MyFilter的类(具体的拦截类HTMLTagFilter，SensitiveFilter)

public class HTMLTagFilter implements MyFilter{
    
    	@Override
    	public void doFilter(Request request,Response response,FilterChain fc) {
    		request.requestStr=request.requestStr.replaceAll("<", "[").replaceAll(">", "]");
    		request.requestStr += "--HTMLTagFilter";
    		fc.doFilter(request, response, fc);
    		response.responseStr += "--HTMLTagFilter";
    	}
    }

public class SensitiveFilter implements MyFilter{
    
    	@Override
    	public void doFilter(Request request,Response response,FilterChain fc) {
    		request.requestStr=request.requestStr.replaceAll("敏感", "不敏感");
    		request.requestStr += "--SensitiveFilter";
    		fc.doFilter(request, response, fc);
    		response.responseStr +="--SensitiveFilter";
    	}
    }

实现的原理就是，当第一个拦截器拦截完之后，由第一个拦截器去执行下一个拦截器，如此反复，当执行完之后，又会倒序执行拦截器。调用过程main函数：

public class Main {
    	public static void main(String[] args) {
    		String msg = "<a> 你好，敏感，被动，我艹，fuck";
    		Request request = new Request(); 
    		request.requestStr=msg;
    		Response response = new Response();
    		response.responseStr ="responseStr";
    		
    		//MyFilter[] filters ={new HTMLTagFilter(),new SensitiveFilter()};
    		FilterChain fc = new FilterChain();
    		fc.add(new HTMLTagFilter());
    		fc.add(new SensitiveFilter());
    		
    		//MyProcessor myProcessor = new MyProcessor(msg);
    		//String result = myProcessor.process(msg,fc);
    		fc.doFilter(request, response,fc);
    		System.out.println(request.requestStr);
    		System.out.println(response.responseStr);
    	}
    }

执行结果：

[a] 你好，不敏感，被动，我艹，fuck--HTMLTagFilter--SensitiveFilter
    responseStr--SensitiveFilter--HTMLTagFilter