敏感词Filter的实现

首先声明这片文章不是我的原创，我只是为了查遗备缺所以在这里写上。
敏感词的Filter从本质上说是属于一种内容替换Filter。内容替换Filter的工作原理是，在讲Servlet内容输出到Response时，Response将内容缓存起来，在Filter中进行替换，然后再输出到客户端浏览器。由于ServletResponse默认不能严格的缓存输出内容，因此需要自定义一个具备缓存功能的response。扩展javax.servlet.http.HttpServletResponseWrapper类来自定义一个response，该类实现了javax.servlet.http.HttpServletResponse接口的所有方法，根据需要在自己的自定义response中进行覆盖即可。

package com.googlefans.test.filter;

import java.io.CharArrayWriter;
import java.io.PrintWriter;

import javax.servlet.http.HttpServletResponse;
import javax.servlet.http.HttpServletResponseWrapper;

public class HttpCharacterResponseWrapper extends HttpServletResponseWrapper{

	private CharArrayWriter charArrayWriter=new CharArrayWriter();

	public CharArrayWriter getCharArrayWriter() {
		return charArrayWriter;
	}

	public HttpCharacterResponseWrapper(HttpServletResponse response){
		super(response);
	}
	@Override
	public PrintWriter getWriter(){
		return new PrintWriter(charArrayWriter);
	}
}

package com.googlefans.test.filter;

import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.IOException;
import java.io.PrintWriter;
import java.util.Properties;

import javax.servlet.Filter;
import javax.servlet.FilterChain;
import javax.servlet.FilterConfig;
import javax.servlet.ServletException;
import javax.servlet.ServletRequest;
import javax.servlet.ServletResponse;
import javax.servlet.http.HttpServletResponse;

public class OutputReplaceFilter implements Filter{

	private Properties pp=new Properties();
	@Override
	public void destroy() {
		
	}

	@Override
	public void doFilter(ServletRequest req, ServletResponse res,
			FilterChain chain) throws IOException, ServletException {
		HttpCharacterResponseWrapper response=new HttpCharacterResponseWrapper((HttpServletResponse)res);
		chain.doFilter(req,response);
		String output=response.getCharArrayWriter().toString();
		for(Object obj:pp.keySet()){
			String key=(String)obj;
			output.replace(key,pp.getProperty(key));
		}
		PrintWriter out=res.getWriter();
		out.write(output);
		
	}

	@Override
	public void init(FilterConfig config) throws ServletException {
		String file=config.getInitParameter("file");
		String realPath=config.getServletContext().getRealPath(file);
		try {
			pp.load(new FileInputStream(realPath));
		} catch (FileNotFoundException e) {
			e.printStackTrace();
		} catch (IOException e) {
			e.printStackTrace();
		}
	}
	
}

然后是在web.xml中配置

  <filter>
  	<filter-name>outputReplaceFilter</filter-name>
  	<filter-class>com.googlefans.test.filter</filter-class>
  	<init-param>
  		<param-name>file</param-name>
  		<param-value>/XXX</param-value>
  	</init-param>
  </filter>
  <filter-mapping>
  	<filter-name>outputReplaceFilter</filter-name>
  	<url-pattern>/*.do</url-pattern>
  </filter-mapping>

至于敏感词properties的文件内容形式

#敏感词语自动替换配置  
色（和谐）情=**  
情（和谐）色=**  
赌（和谐）博=**