Dynamic | static | page
1. ForewordIn order to understand the origin of this framework, we first look at the content of the Java file that the JSP parser converts to our JSP code. The following is a JSP file test.jsp <%@ page Language=java contenttype=text/html;charset=gb2312%> <% out.write (); %> <%= Output%> the contents of the Java file Test$jsp.java converted from Tomcat are as follows: package org.apache.jsp; import javax.servlet.*; import javax.servlet.http.*; import javax.servlet.jsp.*; import org.apache.jasper.runtime.*; Public class Test$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 (); // to save space, I removed the annotation added by the interpreter Out . write (\ r \ n); //The last sentence is due to the <%@ page Language=java contenttype=text/html;charset=gb2312%> the following line Out . write (); Out . Write (\r\n\r\n\r\n\r\n); Out . Print (output); 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); } } }From the above code can clearly see the JSP built several objects (out, request, response, session, PageContext, Application, config, page) is how to produce, A friend who knows the servlet can see it. The following is an important understanding of the Out object, which is declared as a jspwriter type, and JspWriter is an abstract class that can be found in the package javax.servlet.jsp.
Abstract
Public
class
Javax.servlet.jsp.JspWriter extends Java.io.Writer{
final public static intNo_buffer = 0;
final public static intDefault_buffer =-1;
final public static intunbounded_buffer =-2;
protected intbuffersize;
protected BooleanAutoFlush;
protectedJavax.servlet.jsp.JspWriter (
intArg1,
BooleanARG2);
Abstract
Public
voidNewLine ()
throwsIOException;
Abstract
Public
voidPrint
BooleanARG0)
throwsIOException;
Abstract
Public
voidPrint
CharARG0)
throwsIOException;
Abstract
Public
voidPrint
intARG0)
throwsIOException;
Abstract
Public
voidPrint
LongARG0)
throwsIOException;
Abstract
Public
voidPrint
floatARG0)
throwsIOException;
Abstract
Public
voidPrint
DoubleARG0)
throwsIOException;
Abstract
Public
voidPrint
Char[] arg0)
throwsIOException;
Abstract
Public
voidPrint (String arg0)
throwsIOException;
Abstract
Public
voidPrint (Object arg0)
throwsIOException;
Abstract
Public
voidprintln ()
throwsIOException;
Abstract
Public
voidprintln
BooleanARG0)
throwsIOException;
Abstract
Public
voidprintln
CharARG0)
throwsIOException;
Abstract
Public
voidprintln
intARG0)
throwsIOException;
Abstract
Public
voidprintln
LongARG0)
throwsIOException;
Abstract
Public
voidprintln
floatARG0)
throwsIOException;
Abstract
Public
voidprintln
DoubleARG0)
throwsIOException;
Abstract
Public
voidprintln
Char[] arg0)
throwsIOException;
Abstract
Public
voidprintln (String arg0)
throwsIOException;
Abtract
Public
voidprintln (Object arg0)
throwsIOException;
Abstract
Public
voidClear ()
throwsIOException;
Abstract
Public
voidClearbuffer ()
throwsIOException;
Abstract
Public
voidFlush ()
throwsIOException;
Abstract
Public
voidClose ()
throwsIOException;
Public
intGetBufferSize ();
Abstract
Public
intGetremaining ();
Public
BooleanIsautoflush ();} I believe that when I write here you may already know what I want to do. Yes, a steal, inherits the JspWriter class, then implements its defined virtual function, and then replaces the out variable with an instance of your own implementation class. OK.
2. Implement ReplacementAssume <%@ 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/generates the filename from the parameter _ + arg1 +. html; //First determine whether the file already exists, if it does not exist then execute this page, otherwise jump to the static page ok file F = new file (Pagecontext.getservletcontext (). Getrealpath (FilePath)); if (f.exists ()) {out_bak.clear (); Pagecontext.forward (FilePath); System.out.println (Go straight to static page); return;} out = new Htmlintofile (Pagecontext.getservletcontext (). Getrealpath (FilePath)); Out. write (); %><%= See, this is the output is redirected to the implementation of the file, very simple ^_^%><%out.close ();//Closes the generated static file out_bak.clear (); Pagecontext.forward (FilePath); System.out.println (run this page and go to static page);return;%>
3. Update issuesHere is a discussion of how to update the generation of static files, in fact, from the above implementation you can see, very simple is to create static files can be deleted, as to when to delete, depends on your needs. I can think of several situations as follows
- When you use to generate data updates for a page
- If you do not need to provide time for the data can be regularly updated
- Never update
