前段时间做自己社区的论坛，在jive的基础上做一个页面显示所有论坛的帖子,可以称之为总版，模仿Forum类的接口做个SuperForum并且实现Cachable，不过因为这个页面刷新量比较大，虽然被Cache了，我还是想办法进行页面的缓存，感觉用jsp产生的html静态内容当缓存,页面访问速度应该有所提高.首先想到的一种办法,是采用java.net的URLConnection把服务器上的jsp抓过来做缓存,不过我觉得这样做太见外了,自己服务器上的东西,为何要用HTTP去访问.于是想另外一个办法，把jsp的out对象的输出控制到自己希望的地方.比如输出到静态文件,又或者保存成全局的字符串变量.这样的话,浏览就不需要执行jsp,只是浏览该html了.仅仅在数据有更新的时候进行一次update操作,把jsp重新输出为html.我觉得，浏览事件比数据插入或更新发生的次数多的时候.不妨试试这个办法来提高页面访问速度.整件事情有点像把jsp当作模板,生成静态的html页面.
将如下代码写入web-xml <filter> <filter-name>FileCaptureFilter</filter-name> <filter-class>com.junjing.filter.FileCaptureFilter</filter-class> </filter> <filter-mapping> <filter-name>FileCaptureFilter</filter-name> <url-pattern>/latest.jsp</url-pattern> </filter-mapping>latest.jsp是我要cache的页面java源码代码如下
/** * START File FileCaptureFilter.java */package com.junjing.filter;import javax.servlet.*;import javax.servlet.http.*;import java.io.*;public class FileCaptureFilter implements Filter{private String protDirPath;public void init(FilterConfig filterConfig) throws ServletException { protDirPath = filterConfig.getServletContext().getRealPath("/"); } public void doFilter(ServletRequest request,ServletResponse response,FilterChain chain) throws IOException, ServletException { String fileName = protDirPath + "forum/lastest.html"; PrintWriter out = response.getWriter(); FileCaptureResponseWrapper responseWrapper = new FileCaptureResponseWrapper((HttpServletResponse)response); chain.doFilter(request, responseWrapper); // fill responseWrapper up String html = responseWrapper.toString();//得到的html页面结果字符串 //responseWrapper.writeFile(fileName); // dump the contents 写成html文件，也可以保存在内存 //responseWrapper.writeResponse( out ); // back to browser //responseWrapper.sendRedirect("lastThread.jsp");} public void destroy() {}}/** * END File FileCaptureFilter.java */ /** * START File FileCaptureResponseWrapper.java */package com.junjing.filter;import javax.servlet.*;import javax.servlet.http.*;import java.io.*;public class FileCaptureResponseWrapper extends HttpServletResponseWrapper{ private CharArrayWriter output; public String toString() { return output.toString(); } public FileCaptureResponseWrapper(HttpServletResponse response) { super(response); output = new CharArrayWriter(); } public PrintWriter getWriter() { return new PrintWriter(output); } public void writeFile(String fileName) throws IOException { FileWriter fw = new FileWriter(fileName); fw.write( output.toCharArray() ); fw.close(); } public void writeResponse(PrintWriter out) { out.print( output.toCharArray() ); }}/** * END File FileCaptureResponseWrapper.java */附件源代码 不过采用resin服务器的话，以上代码会失效。因为resin没有实现getWriter方法，而是采用getOutputStream取而代之，所以必须修改些代码来迎合resin运行环境：/** * START File FileCaptureResponseWrapper.java */package com.junjing.filter;import javax.servlet.*;import javax.servlet.http.*;import java.io.*;public class FileCaptureResponseWrapper extends HttpServletResponseWrapper{ private CharArrayWriter output; public String toString() { return output.toString(); } public FileCaptureResponseWrapper(HttpServletResponse response) { super(response); output = new CharArrayWriter(); } public PrintWriter getWriter() { return new PrintWriter(output); } public void writeFile(String fileName) throws IOException { FileWriter fw = new FileWriter(fileName); fw.write( output.toString()); fw.close(); } public ServletOutputStream getOutputStream() throws java.io.IOException { return new ServletOutputStream() { public void write(int b) throws IOException { output.write(b); } public void write(byte b[]) throws IOException { output.write(new String(b,"GBK")); } public void write(byte b[], int off, int len) throws IOException { output.write(new String(b, off, len)); } };} public void writeResponse(PrintWriter out) { out.print(output.toCharArray()); }}/** * END File FileCaptureResponseWrapper.java */
