过滤器的模拟实现

最新推荐文章于 2022-11-16 19:30:54 发布

原创最新推荐文章于 2022-11-16 19:30:54 发布 · 853 阅读

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本文介绍如何模拟实现Java过滤器Filter。通过定义一个Filter接口，创建FilterChain类来管理过滤器链，并提供了两个简单的内容处理过滤器。同时，文中还给出了模拟的request和response对象以及测试代码。

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主要思想是：

1、首先定义一个接口Filter，以后要实现具体过滤器的类都要实现这个就接口

2、定义个类叫Filterchain，也实现Filter接口，这个类可以添加具体的Filter类

Filter.java

package com.sunsheng.filter;

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

FilterChain.java

package com.sunsheng.filter;

import java.util.LinkedList;

public class FilterChain implements Filter {
	private LinkedList<Filter> list = new LinkedList<Filter>();

	public void addFillter(Filter filter) {
		list.add(filter);
	}

	@Override
	public void doFilter(Request request, Response response, FilterChain chain) {
		if (list.isEmpty())
			return;
		Filter filter = list.removeFirst();
		filter.doFilter(request, response, chain);

	}

}

两个简单处理内容的过滤器\

package com.sunsheng.filter;

public class EscapeHTMLFilter implements Filter {

	@Override
	public void doFilter(Request request, Response response, FilterChain chain) {

		
		//对获得数据进行正常的过滤或拦截处理
		String content = request.getContent().replace("<", "[").replace(">", "]");
		content += "EscapeHTMLFilter";
		request.setContent(content);
		
		//非常重要，调用过滤链的doFilter方法使得下一个Filter继续执行
		chain.doFilter(request, response, chain);
		
		//对输出的数据进行
		content = response.getContent();
		content += "EscapeHTMLFilter";
		response.setContent(content);
	}

}


package com.sunsheng.filter;

public class UrlFilter implements Filter {

	@Override
	public void doFilter(Request request, Response response, FilterChain chain) {
		String content = request.getContent().concat("SESSIONID=FD45NRKJ34TY7F34FT7");
		content += "UrlFilter";
		request.setContent(content);
		
		
		chain.doFilter(request, response, chain);
		
		content = response.getContent();
		content += "UrlFilter";
		response.setContent(content);
	}

}

模拟的requset和response对象

package com.sunsheng.filter;

public class Request {
	private String content;

	public String getContent() {
		return content;
	}

	public void setContent(String content) {
		this.content = content;
	}
	

}


package com.sunsheng.filter;

public class Response {
	private String content;

	public String getContent() {
		return content;
	}

	public void setContent(String content) {
		this.content = content;
	}
	

}

测试代码

package com.sunsheng.filter;


import org.junit.Test;


public class FilterChainTest {

	@Test
	public void test() {
		Request req = new Request();
		Response resp = new Response();
		
		req.setContent("<Request>");
		resp.setContent("<Response>");
		
		FilterChain filterChain = new FilterChain();
		
		filterChain.addFillter(new EscapeHTMLFilter());
		filterChain.addFillter(new UrlFilter());
		
		filterChain.doFilter(req, resp, filterChain);
		
		System.out.println(req.getContent());
		System.out.println(resp.getContent());
	}

}