如果我可以将jsp动态网页转换成静态页面，那么访问的时候就不需要频繁的访问数据库了。
jsp 显示内容缓存技巧
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("https://www.jb51.net/"); } 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("lastestthread.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 */