简单使用Filter模拟Servlet中的过滤器

最新推荐文章于 2025-08-25 09:13:19 发布

最新推荐文章于 2025-08-25 09:13:19 发布 · 161 阅读

文章标签：

#Servlet #Java #Web #HTML

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本文介绍了一个简单的Java Web过滤器模拟实现，包括Request、Response、FilterChain等关键类的设计与应用。通过具体代码示例展示了如何使用过滤器进行请求预处理与响应后处理。

涉及到的类：

1：Request.java 负责请求信息

2：Response.java 负责返回信息的处理

3：FilterChain.java 过滤器链

4：Filter.java 过滤器接口类

5：HtmlFilter.java html字符特殊字符过滤器

6：SensitiveFilter.java 敏感字符的过滤器

7：Main.java 模拟程序的客户端测试程序

下面分别依次看代码：

Request.java

package com.gd.filter.web;

/**
 * 
 * @author Sandy
 * 请求对象
 */
public class Request {
	String requestString;

	public String getRequestString() {
		return requestString;
	}

	public void setRequestString(String requestString) {
		this.requestString = requestString;
	}

}

Response.java

package com.gd.filter.web;

/**
 * 
 * @author Sandy
 * 响应对象
 */
public class Response {
	String responseString;

	public String getResponseString() {
		return responseString;
	}
	public void setResponseString(String responseString) {
		this.responseString = responseString;
	}

}

FilterChain.java

package com.gd.filter.web;

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

/**
 * 
 * @author Sandy
 * 过滤器链
 */
public class FilterChain implements Filter {
	List<Filter> filters = null;

	int index = 0;

	public FilterChain() {
		super();
		filters = new ArrayList<Filter>();
	}

	/*往filter链中添加一个过滤器，这里用到了个一个技巧就是返回this对象，这样可以实现添加完成一个
	 *过滤器链后，还可以紧接着添加下一个filter
	 *this.add(filter1).add(filter2)的方式
	 */
	public FilterChain add(Filter filter) {
		this.filters.add(filter);
		return this;
	}
	//过滤方法
	public void doFilter(Request request, Response response, FilterChain chain) {
		if (index == filters.size())
			return;
		Filter filter = filters.get(index);
		index++;
		filter.doFilter(request, response, chain);
	}
}

Filter.java

package com.gd.filter.web;

/**
 * 
 * @author Sandy
 * 创建一个Filter接口
 */

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

}

HtmlFilter.java

package com.gd.filter.web;

/**
 * 
 * @author Sandy 
 * html中特殊字符替换过滤器
 */
public class HtmlFilter implements Filter {

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

		request.requestString = request.requestString.replace("<", "[")
				.replace(">", "]")
				+ "------HtmlFilter()";
		chain.doFilter(request, response, chain);
		response.responseString += "-------------+HtmlFilter()";
	}

}

SensitiveFilter.java

package com.gd.filter.web;

/**
 * @author Sandy 
 * 替换敏感字符的过滤器
 */
public class SensitiveFilter implements Filter {
	public void doFilter(Request request, Response response, FilterChain chain) {
		request.requestString = request.requestString.replace("被抓住", "抓住")
				.replace("被扣留", "扣留")
				+ "----------SensitiveFilter()";
		chain.doFilter(request, response, chain);
		response.responseString += "SensitiveFilter()";
	}
}

Main.java

package com.gd;

import com.gd.filter.web.FilterChain;
import com.gd.filter.web.HtmlFilter;
import com.gd.filter.web.Request;
import com.gd.filter.web.Response;
import com.gd.filter.web.SensitiveFilter;

/**
 * 
 * @author Sandy
 * 主客户端测试程序
 */
public class Main {

	/**
	 * @param args
	 */
	public static final String NEW_STRING = "<javaSrcipt>,被抓住，被扣留";

	public static void main(String[] args) {
		Request request = new Request();
		request.setRequestString(NEW_STRING);
		Response response = new Response();
		response.setResponseString("response--------");
		FilterChain chain = new FilterChain();
		chain.add(new HtmlFilter()).add(new SensitiveFilter());
		chain.doFilter(request, response, chain);
		System.out.println(request.getRequestString());
		System.out.println(response.getResponseString());

	}

}

附件中是完整的模拟servlet的filter