java 过滤非法字符_javaweb开发之Filter实现过滤非法文字

一、概述

在论坛或者网站中，我们会发现一些用户发表一些不文明或者非法的文字。这样可能导致论坛的不文明和谐，甚至还可能带来一些法律上的纠纷。我们可以使用过滤器来帮助我们过滤掉这些不文明的文字。

二、思路

统一维护非法文字，为了提高程序运行效率，可以将其缓存到内存中。当用户提交请求后，利用过滤器对指定程序(如发表言论)请求的内容进行过滤。发现有非法字符后替换成合法字符(如“*”)。

三、具体实现​

keyword.properties

?12 讨哥=** 荡漾=xx

这里我们使用properties文件保存非法字符。

key是非法文字，value是要被替换后的文字。

ContentFilter.java​

package cn.heimar.filter.contentfilter.util; import

java.io.IOException; 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.HttpServletRequest; import

javax.servlet.http.HttpServletResponse; public class ContentFilter

implements Filter { @Override public void init(FilterConfig config)

throws ServletException { // TODO Auto-generated method stub }

@Override public void doFilter(ServletRequest req, ServletResponse

resp, FilterChain chain) throws IOException, ServletException {

HttpServletRequest request = (HttpServletRequest) req;

HttpServletResponse response = (HttpServletResponse) resp;

//思路：得到提交数据，替换，重新设置进去 //使用包装对象来包裹原请求对象

//如果是第一次请求，则加载关键字,缓存到ServletContext

ContentReplaceHttpServletRequestWapper wapper=new

ContentReplaceHttpServletRequestWapper(request);

chain.doFilter(wapper, resp); } @Override public void destroy() {

// TODO Auto-generated method stub } }​

ContentReplaceHttpServletRequestWapper.java

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package cn.heimar.filter.contentfilter.util; import

java.io.IOException; import java.io.UnsupportedEncodingException;

import java.util.Properties; import

javax.servlet.http.HttpServletRequest; import

javax.servlet.http.HttpServletRequestWrapper; public class

ContentReplaceHttpServletRequestWapper extends

HttpServletRequestWrapper { private static Properties keywords;

static { keywords = new Properties(); try {

keywords.load(ContentReplaceHttpServletRequestWapper.class

.getClassLoader().getResourceAsStream("keyword.properties")); }

catch (IOException e) { e.printStackTrace(); } } public

ContentReplaceHttpServletRequestWapper(HttpServletRequest request)

{ super(request); } @Override public String getParameter(String

name) { //content和name是要过滤的请求参数名称 if ("content".equals(name)

"title".equals(name)) { String old = super.getParameter(name);

old = doFilter(old); return old; } return super.getParameter(name);

} private String doFilter(String old) { for (Object temp :

keywords.keySet()) { try { String key = new String(((String)

temp).getBytes("ISO-8859-1"),"UTF-8"); old = old.replaceAll(key,

keywords.getProperty((String)temp)); } catch

(UnsupportedEncodingException e) { e.printStackTrace(); } } return

old; } }