一 JSP页面生命周期图
二 生命周期解释
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
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。