动态|静态|页面1.前言为了能深入浅出的理解这个框架的由来，我们首先来了解一下JSP解析器将我们写的JSP代码转换成的JAVA文件的内容。下面是一个JSP文件test.jsp<% page language=java contentType=text/html;charset=GB2312 %><%out.write();%><%= 输出%>经过TOMCAT转换出的JAVA文件test$jsp.java内容如下：package org.apache.jsp;import javax.servlet.*;import javax.servlet.http.*;import javax.servlet.jsp.*;import org.apache.jasper.runtime.*; public class test$jsp extends HttpJspBase {     static {    }    public testOutRedir$jsp( ) {    }     private static boolean _jspx_inited = false;     public final void _jspx_init() throws org.apache.jasper.runtime.JspException {    }     public void _jspService(HttpServletRequest request, HttpServletResponse  response)        throws java.io.IOException, ServletException {         JspFactory _jspxFactory = null;        PageContext pageContext = null;        HttpSession session = null;        ServletContext application = null;        ServletConfig config = null;        JspWriter out = null;        Object page = this;        String  _value = null;        try {             if (_jspx_inited == false) {                synchronized (this) {                    if (_jspx_inited == false) {                        _jspx_init();                        _jspx_inited = true;                    }                }            }            _jspxFactory = JspFactory.getDefaultFactory();            response.setContentType(text/html;charset=GB2312);            pageContext = _jspxFactory.getPageContext(this, request, response,                            , true, 8192, true);             application = pageContext.getServletContext();            config = pageContext.getServletConfig();            session = pageContext.getSession();            out = pageContext.getOut();                //为了节省篇幅，我删除了解释器添加的注释                out.write(\r\n);//上一句是由于<% page language=java  contentType=text/html;charset=GB2312 %>后面的换行产生的                out.write();                out.write(\r\n\r\n\r\n\r\n);                out.print( 输出 );                out.write(\r\n\r\n\r\n\r\n);        } catch (Throwable t) {            if (out != null && out.getBufferSize() != 0)                out.clearBuffer();            if (pageContext != null) pageContext.handlePageException(t);        } finally {            if (_jspxFactory != null) _jspxFactory.releasePageContext(pageContext);        }    }}从上面的代码中可以清晰的看到JSP内建的几个对象（out、request、response、session、pageContext、application、config、page）是怎么产生的，懂servlet的朋友一看就能明白。下面重点理解一下out对象，它被声明为JspWriter类型，JspWriter是一个抽象类，在包javax.servlet.jsp中可以找到它的定义。abstract public class javax.servlet.jsp.JspWriter extends java.io.Writer{       final public static int NO_BUFFER = 0;       final public static int DEFAULT_BUFFER = -1;       final public static int UNBOUNDED_BUFFER = -2;       protected int bufferSize;       protected Boolean autoFlush;       protected javax.servlet.jsp.JspWriter(int arg1, boolean arg2);           abstract public void newLine() throws IOException ;    abstract public void print(boolean arg0) throws IOException ;    abstract public void print(char arg0) throws IOException ;    abstract public void print(int arg0) throws IOException ;    abstract public void print(long arg0) throws IOException ;    abstract public void print(float arg0) throws IOException ;    abstract public void print(double arg0) throws IOException ;    abstract public void print(char[] arg0) throws IOException ;    abstract public void print(String arg0) throws IOException ;    abstract public void print(Object arg0) throws IOException ;    abstract public void println() throws IOException ;    abstract public void println(boolean arg0) throws IOException ;    abstract public void println(char arg0) throws IOException ;    abstract public void println(int arg0) throws IOException ;    abstract public void println(long arg0) throws IOException ;    abstract public void println(float arg0) throws IOException ;    abstract public void println(double arg0) throws IOException ;    abstract public void println(char[] arg0) throws IOException ;    abstract public void println(String arg0) throws IOException ;    abtract public void println(Object arg0) throws IOException ;    abstract public void clear() throws IOException ;    abstract public void clearBuffer() throws IOException ;    abstract public void flush() throws IOException ;    abstract public void close() throws IOException ;    public int getBufferSize() ;    abstract public int getRemaining() ;    public boolean isAutoFlush() ;}我相信当我写到这里你可能已经知道我想怎么做了。是的，来个偷天换日，继承JspWriter类，然后实现其定义的虚函数，然后把out变量替换成你自己实现的类的实例就ok了。2.实现替换假设<% page language=java  contentType=text/html;charset=GB2312 import=jwb.util.HtmlIntoFile,jwb.util.TempSinglet,java.io.File%><%JspWriter out_bak = out;String arg1=argument1;String filePath = /cache/根据参数生成文件名_ + arg1 + .html;//首先判断文件是否已经存在，如果不存在则执行本页面，否则跳转到静态页面就OK了File f = new File(pageContext.getServletContext().getRealPath(filePath));if(f.exists()){ out_bak.clear(); pageContext.forward(filePath); System.out.println(直接转到静态页面); return;}out = new HtmlIntoFile(pageContext.getServletContext().getRealPath(filePath));out.write();%><%= 看吧，这就是输出被重定向到文件的实现，很简单吧^_^%><%out.close();//关闭生成的静态文件out_bak.clear();pageContext.forward(filePath);System.out.println(执行本页面后再转到静态页面);return;%>3.更新问题下面就讨论一下如何更新生成静态文件，其实从上面实现中你可以看到，很简单的就是将生成的静态文件删除即可，至于什么时候删除，要看你的需求了。我能想到的几种情况如下

• 当用来生成页面的数据更新时
• 如果不需要很提供时时的数据可以定时更新
• 永远不更新