欢迎您访问程序员文章站本站旨在为大家提供分享程序员计算机编程知识!
您现在的位置是: 首页

JSP页面生命周期

程序员文章站 2022-04-23 16:55:44
...
一 JSP页面生命周期图

JSP页面生命周期
            
    
    博客分类: java JSP页面生命周期 
 

 
 
二 生命周期解释

JSP页面生命周期
            
    
    博客分类: java JSP页面生命周期 
 
 
三 实战
1、创建JspLifeCycleDemo项目
2、编写index.jsp文件
<%@ page language="java" import="java.util.*" contentType="text/html; charset=UTF-8"%>
<%@ page import="java.text.*" %>
<%
String path = request.getContextPath();
String basePath = request.getScheme()+"://"+request.getServerName()+":"+request.getServerPort()+path+"/";
%>
 
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
  <head>
    <base href="<%=basePath%>">
   
    <title>My JSP 'index.jsp' starting page</title>
        <meta http-equiv="pragma" content="no-cache">
        <meta http-equiv="cache-control" content="no-cache">
        <meta http-equiv="expires" content="0">   
        <meta http-equiv="keywords" content="keyword1,keyword2,keyword3">
        <meta http-equiv="description" content="This is my page">
        <!--
        <link rel="stylesheet" type="text/css" href="styles.css">
        -->
  </head>
 
  <body>
    <h1>JSP生命周期</h1>
    <hr>
    <%
      SimpleDateFormat sdf = new SimpleDateFormat("yyyy年MM月dd日");
      String s = sdf.format(new Date());
    %>
        今天是:<%=s %>
  </body>
</html>
 
四 运行结果

JSP页面生命周期
            
    
    博客分类: java JSP页面生命周期 
 
 
五 运行说明
1、当Tomcat首次启动时,D:\apache-tomcat-7.0.81\work\Catalina\localhost\JspLifeCycleDemo目录为空,因为还没有收到任何请求。
 
2、当JSP页面首次请求时,在D:\apache-tomcat-7.0.81\work\Catalina\localhost\JspLifeCycleDemo\org\apache\jsp目录下会生成对于的Java文件和字节码文件。
其中:_jspInit函数在整个生命周期只运行一次。
_jspService函数每次请求都会运行。
/*
* Generated by the Jasper component of Apache Tomcat
* Version: Apache Tomcat/7.0.81
* Generated at: 2017-09-16 06:54:10 UTC
* Note: The last modified time of this file was set to
*       the last modified time of the source file after
*       generation to assist with modification tracking.
*/
package org.apache.jsp;
import javax.servlet.*;
import javax.servlet.http.*;
import javax.servlet.jsp.*;
import java.util.*;
import java.text.*;
public final class index_jsp extends org.apache.jasper.runtime.HttpJspBase
    implements org.apache.jasper.runtime.JspSourceDependent {
  private static final javax.servlet.jsp.JspFactory _jspxFactory =
          javax.servlet.jsp.JspFactory.getDefaultFactory();
  private static java.util.Map<java.lang.String,java.lang.Long> _jspx_dependants;
  private volatile javax.el.ExpressionFactory _el_expressionfactory;
  private volatile org.apache.tomcat.InstanceManager _jsp_instancemanager;
  public java.util.Map<java.lang.String,java.lang.Long> getDependants() {
    return _jspx_dependants;
  }
  public javax.el.ExpressionFactory _jsp_getExpressionFactory() {
    if (_el_expressionfactory == null) {
      synchronized (this) {
        if (_el_expressionfactory == null) {
          _el_expressionfactory = _jspxFactory.getJspApplicationContext(getServletConfig().getServletContext()).getExpressionFactory();
        }
      }
    }
    return _el_expressionfactory;
  }
  public org.apache.tomcat.InstanceManager _jsp_getInstanceManager() {
    if (_jsp_instancemanager == null) {
      synchronized (this) {
        if (_jsp_instancemanager == null) {
          _jsp_instancemanager = org.apache.jasper.runtime.InstanceManagerFactory.getInstanceManager(getServletConfig());
        }
      }
    }
    return _jsp_instancemanager;
  }
  public void _jspInit() {
  }
  public void _jspDestroy() {
  }
  public void _jspService(final javax.servlet.http.HttpServletRequest request, final javax.servlet.http.HttpServletResponse response)
        throws java.io.IOException, javax.servlet.ServletException {
    final javax.servlet.jsp.PageContext pageContext;
    javax.servlet.http.HttpSession session = null;
    final javax.servlet.ServletContext application;
    final javax.servlet.ServletConfig config;
    javax.servlet.jsp.JspWriter out = null;
    final java.lang.Object page = this;
    javax.servlet.jsp.JspWriter _jspx_out = null;
    javax.servlet.jsp.PageContext _jspx_page_context = null;
    try {
      response.setContentType("text/html; charset=UTF-8");
      pageContext = _jspxFactory.getPageContext(this, request, response,
                  null, true, 8192, true);
      _jspx_page_context = pageContext;
      application = pageContext.getServletContext();
      config = pageContext.getServletConfig();
      session = pageContext.getSession();
      out = pageContext.getOut();
      _jspx_out = out;
      out.write("\r\n");
      out.write("\r\n");
String path = request.getContextPath();
String basePath = request.getScheme()+"://"+request.getServerName()+":"+request.getServerPort()+path+"/";
      out.write("\r\n");
      out.write("\r\n");
      out.write("<!DOCTYPE HTML PUBLIC \"-//W3C//DTD HTML 4.01 Transitional//EN\">\r\n");
      out.write("<html>\r\n");
      out.write("  <head>\r\n");
      out.write("    <base href=\"");
      out.print(basePath);
      out.write("\">\r\n");
      out.write("    \r\n");
      out.write("    <title>My JSP 'index.jsp' starting page</title>\r\n");
      out.write("\t<meta http-equiv=\"pragma\" content=\"no-cache\">\r\n");
      out.write("\t<meta http-equiv=\"cache-control\" content=\"no-cache\">\r\n");
      out.write("\t<meta http-equiv=\"expires\" content=\"0\">    \r\n");
      out.write("\t<meta http-equiv=\"keywords\" content=\"keyword1,keyword2,keyword3\">\r\n");
      out.write("\t<meta http-equiv=\"description\" content=\"This is my page\">\r\n");
      out.write("\t<!--\r\n");
      out.write("\t<link rel=\"stylesheet\" type=\"text/css\" href=\"styles.css\">\r\n");
      out.write("\t-->\r\n");
      out.write("  </head>\r\n");
      out.write("  \r\n");
      out.write("  <body>\r\n");
      out.write("    <h1>JSP生命周期</h1>\r\n");
      out.write("    <hr>\r\n");
      out.write("    ");
      SimpleDateFormat sdf = new SimpleDateFormat("yyyy年MM月dd日");
      String s = sdf.format(new Date());
    
      out.write("\r\n");
      out.write("        今天是:");
      out.print(s );
      out.write("\r\n");
      out.write("  </body>\r\n");
      out.write("</html>\r\n");
    } catch (java.lang.Throwable t) {
      if (!(t instanceof javax.servlet.jsp.SkipPageException)){
        out = _jspx_out;
        if (out != null && out.getBufferSize() != 0)
          try {
            if (response.isCommitted()) {
              out.flush();
            } else {
              out.clearBuffer();
            }
          } catch (java.io.IOException e) {}
        if (_jspx_page_context != null) _jspx_page_context.handlePageException(t);
        else throw new ServletException(t);
      }
    } finally {
      _jspxFactory.releasePageContext(_jspx_page_context);
    }
  }
}
 

 

3、如果JSP页面修改了,JSP引擎会重新编译JSP页面,再重新生成新的字节码文件。
  • JSP页面生命周期
            
    
    博客分类: java JSP页面生命周期 
  • 大小: 164.4 KB
  • JSP页面生命周期
            
    
    博客分类: java JSP页面生命周期 
  • 大小: 192.7 KB
  • JSP页面生命周期
            
    
    博客分类: java JSP页面生命周期 
  • 大小: 24.6 KB