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：
