一个实现将动态页面转为静态的方案

 

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

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);
      
[align=left]    abstract public void newLine() throws IOException ;[/align]
[align=left]    abstract public void print(boolean arg0) throws IOException ;[/align]
[align=left]    abstract public void print(char arg0) throws IOException ;[/align]
[align=left]    abstract public void print(int arg0) throws IOException ;[/align]
[align=left]    abstract public void print(long arg0) throws IOException ;[/align]
[align=left]    abstract public void print(float arg0) throws IOException ;[/align]
[align=left]    abstract public void print(double arg0) throws IOException ;[/align]
[align=left]    abstract public void print(char[] arg0) throws IOException ;[/align]
[align=left]    abstract public void print(String arg0) throws IOException ;[/align]
[align=left]    abstract public void print(Object arg0) throws IOException ;[/align]
[align=left]    abstract public void println() throws IOException ;[/align]
[align=left]    abstract public void println(boolean arg0) throws IOException ;[/align]
[align=left]    abstract public void println(char arg0) throws IOException ;[/align]
[align=left]    abstract public void println(int arg0) throws IOException ;[/align]
[align=left]    abstract public void println(long arg0) throws IOException ;[/align]
[align=left]    abstract public void println(float arg0) throws IOException ;[/align]
[align=left]    abstract public void println(double arg0) throws IOException ;[/align]
[align=left]    abstract public void println(char[] arg0) throws IOException ;[/align]
[align=left]    abstract public void println(String arg0) throws IOException ;[/align]
[align=left]    abtract public void println(Object arg0) throws IOException ;[/align]
[align=left]    abstract public void clear() throws IOException ;[/align]
[align=left]    abstract public void clearBuffer() throws IOException ;[/align]
[align=left]    abstract public void flush() throws IOException ;[/align]
[align=left]    abstract public void close() throws IOException ;[/align]
[align=left]    public int getBufferSize() ;[/align]
[align=left]    abstract public int getRemaining() ;[/align]
[align=left]    public boolean isAutoFlush() ;[/align]
}
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

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