使用过滤器过滤非法文字.doc

过滤非法文字在用户交互过程中，如果在论坛中出现影响网站形象的文字，可能会降低网站信誉，也有的论坛禁止使用某些文字，比如在用户反馈意见时禁止出现一些不文明的字词。实现过程：1 创建页面index.jsp，内容随便输入，为测试使用2 编写MyOutputStream类，它继承ServletOutPutStream类被重写write()方法，使用自己的字节数组输出流实现了数据输出。关键代码如下：import java.io.ByteArrayOutputStream;import java.io.IOException;import javax.servlet.ServletOutputStream;public class MyOutputStream extends ServletOutputStream ByteArrayOutputStream stream;/创建字节数组输出流public MyOutputStream(ByteArrayOutputStream stream)this.stream=stream;/在构造方法初始化输出流Overridepublic void write(int arg0) throws IOException / TODO Auto-generated method stubstream.write(arg0);/使用本类的输出流代替父类的输出方法3 编写ResponseWrapper类，他继承自HttpServletResponseWrapper类，并重写getOutputStream()方法和getWriter()方法返回本类定义的输出流，自定义的toByteArray()方法可以获取这些输出流的数据。关键代码如下：import java.io.ByteArrayOutputStream;import java.io.IOException;import java.io.PrintWriter;import javax.servlet.ServletOutputStream;import javax.servlet.http.HttpServletResponse;import javax.servlet.http.HttpServletResponseWrapper;import com.my.MyOutputStream;public class ResponseWrapper extends HttpServletResponseWrapper private MyOutputStream stream;/声明自定义输出流private ByteArrayOutputStream byteStream;/声明字节输出流private PrintWriter pw;/声明打印输出流public ResponseWrapper(HttpServletResponse response) super(response);/ TODO Auto-generated constructor stubthis.byteStream=new ByteArrayOutputStream();this.stream=new MyOutputStream(this.byteStream);this.pw=new PrintWriter(this.byteStream);Overridepublic ServletOutputStream getOutputStream() throws IOException / TODO Auto-generated method stubreturn this.stream;Overridepublic PrintWriter getWriter() throws IOException / TODO Auto-generated method stubreturn this.pw;public byte toByteArray()return this.byteStream.toByteArray();4 创建LetterFilter过滤器，他是本类的核心类，实现了Filter接口，在doFilter()方法的实现代码中创建自己的应答对象，执行过滤器之后的操作后获取应答对象输出流的内容，然后代替该内容中的非法文字，再通过原有应答对象输出应答数据到浏览器。关键代码如下：import java.io.IOException;import java.io.PrintWriter;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;import com.wrapper.ResponseWrapper;/* * Servlet Filter implementation class LetterFilter */public class LetterFilter implements Filter /* * Default constructor. */ public LetterFilter() / TODO Auto-generated constructor stub /* * see Filter#destroy() */public void destroy() / TODO Auto-generated method stub/* * see Filter#doFilter(ServletRequest, ServletResponse, FilterChain) */public void doFilter(ServletRequest request, ServletResponse response, FilterChain chain) throws IOException, ServletException / TODO Auto-generated method stub/ place your code here/ pass the request along the filter chainHttpServletResponse httpRes=(HttpServletResponse) response;ResponseWrapper responseWrapper=new ResponseWrapper(httpRes);chain.doFilter(request, responseWrapper);/继续执行过滤之后的操作responseWrapper.getWriter().flush();byte bytes=responseWrapper.toByteArray();/获取应答对象的输出数据String content=new String(bytes);/把数据转化为字符串content=content.replace(d, a);/进行替换/System.out.println(content);PrintWriter out=httpRes.getWriter();/获取应答对象的输出流out.print(content);/输出替换后的数据out.close();/* * see Filter#init(FilterConfig) */public void init(FilterConfig fConfig) throws S