过滤器为JSP文件生成静态页面

用过滤器为JSP文件生成静态页面，这只是一个简单的实例，客户端浏览器第一次请求JSP页面时，服务器将生成对应的HTML文件，以后访问同一JSP文件，将转为访问生成的HTML文件。
一、过滤器

package com.kenfor.lyb.toHtmlfilter;
import java.io.*;
import java.io.IOException;
import java.text.SimpleDateFormat;
import java.util.Date;
import javax.servlet.Filter;
import javax.servlet.FilterChain;
import javax.servlet.FilterConfig;
import javax.servlet.RequestDispatcher;
import javax.servlet.ServletException;
import javax.servlet.ServletRequest;
import javax.servlet.ServletResponse;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import org.apache.log4j.*;
public class JspFilter implements Filter {
 
 Logger logger = Logger.getLogger(this.getClass());
 
    protected FilterConfig config;
    public void init(FilterConfig config)
        throws ServletException
    {
        // Save the config object
        this.config = config;
    }
 public void destroy() {
 }
 public void doFilter(ServletRequest request, ServletResponse response,
   FilterChain chain) throws IOException, ServletException {
  HttpServletRequest hreq = (HttpServletRequest) request;
  HttpServletResponse hresp = (HttpServletResponse) response;
  String name = hreq.getRequestURL().substring(hreq.getRequestURL().lastIndexOf("/") + 1,
    hreq.getRequestURL().lastIndexOf("."));
   //logger.info("fileName="+name);
  String str_uri = hreq.getRequestURI();
   //logger.info("str_uri="+str_uri);
   String htmpath=hreq.getSession().getServletContext().getRealPath(
    "/")
    + "HTML\\"
    + str_uri.substring(0, str_uri.lastIndexOf("/"))
    //+"/"+time
    + "/" + name + ".html";
    File file = new File(htmpath);
    //logger.info("file="+file);
   String to=hreq.getContextPath() + "/HTML"
     + str_uri.substring(0, str_uri.lastIndexOf("/")) 
     +"/"+ name + ".html";
     //logger.info(to);
  
       
  if (!file.exists()&&hreq.getRequestURL().indexOf(".jsp")> 0) {
       ServletResponse newResponse =new CharResponseWrapper(hresp);    
        chain.doFilter(request, newResponse);
        String text = newResponse.toString();
            if (text != null)
            {
                   PrintWriter pw=new PrintWriter(htmpath);
                   pw.println(text);
                   pw.close();
                   hresp.sendRedirect(to);
            }
    } else {
     
   hresp.sendRedirect(to);
  }
 
 }
 
}

二、响应包装器

package com.kenfor.lyb.toHtmlfilter;
import javax.servlet.*;
import javax.servlet.http.*;
import java.io.*;
/**
 * Simple response wrapper that utilizes a local CharArrayWriter
 * for output
 */
public class CharResponseWrapper
        extends HttpServletResponseWrapper
{
    protected CharArrayWriter charWriter;
    protected PrintWriter writer;
    protected boolean getOutputStreamCalled;
    protected boolean getWriterCalled;
    public CharResponseWrapper(HttpServletResponse response)
    {
        super(response);
        // Create the writer
        charWriter = new CharArrayWriter();
    }
    public ServletOutputStream getOutputStream()
        throws IOException
    {
        // Can't call getOutputStream if getWriter
        // has already been called
        if (getWriterCalled)
        {
            throw new IllegalStateException(
                    "getWriter already called");
        }
        getOutputStreamCalled = true;
        return super.getOutputStream();
    }
    public PrintWriter getWriter()
        throws IOException
    {
        if (writer != null)
        {
            return writer;
        }
        // Can't call getWriter if getOutputStream
        // has already been called
        if (getOutputStreamCalled)
        {
            throw new IllegalStateException(
                    "getOutputStream already called");
        }
        getWriterCalled = true;
        writer = new PrintWriter(charWriter);
        return writer;
    }
    public String toString()
    {
        String s = null;
        // Only return a String if the writer was
        // used.
        if (writer != null)
        {
            s = charWriter.toString();
        }
        return s;
    }
   public char[] toCharArray(){//将响应数据以字符数组返回
         return(charWriter.toCharArray());
   }
  
}

三、web.xml文件

<?xml version="1.0" encoding="ISO-8859-1"?>

<web-app xmlns="http://java.sun.com/xml/ns/j2ee"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://java.sun.com/xml/ns/j2ee http://java.sun.com/xml/ns/j2ee/web-app_2_4.xsd" version="2.4">

<display-name>Welcome to Tomcat</display-name>
<description>
Welcome to Tomcat
</description>

<filter>
  <filter-name>jspfilter</filter-name>
  <filter-class>com.kenfor.lyb.toHtmlfilter.JspFilter</filter-class>
</filter>

<filter-mapping> 
  <filter-name>jspfilter</filter-name>
  <url-pattern>*.jsp</url-pattern>
</filter-mapping>

<servlet> 
  <servlet-name>log4j-init</servlet-name> 
  <servlet-class>example.Log4jInit</servlet-class> 
  <init-param> 
   <param-name>log4j</param-name> 
   <param-value>WEB-INF/log4j.properties</param-value> 
  </init-param> 
 <load-on-startup>1</load-on-startup> 
</servlet> 
</web-app>

测试文件：tohtml.jsp

<%@ page contentType="text/html; charset=gb2312" %>
<%
String name = request.getRequestURL().substring(request.getRequestURL().lastIndexOf("/") + 1,
request.getRequestURL().lastIndexOf("."));
String cox=request.getContextPath();

String str_uri = request.getRequestURI();
out.println(request.getRequestURL()+"<br>");
out.println(name+"<br>");
out.println(str_uri+"<br>");
out.println(cox+"<br>");
out.println(request.getParameter("type")); 
%>

第二次请求tohtml.jsp时，运行图：