[@] JSP的运行原理.docVIP

Jsp运行原理 JSP的运行原理如下图所示： 当客户端向一个JSP页面发出请求时，Web Container将JSP转化成Servlet的源代码(只在第一次请求时)，然后编译转化后的Servlet并加载到内存中执行，执行的结果Response到客户端。JSP只在第一次执行的时候会转化为Servlet，以后每次执行Web容器都是直接执行编译后的Servlet,所以JSP和Servlet只是在第一次执行的时候不一样，JSP慢一点，以后的执行都是相同的。下面看看JSP文件在各个阶段的内容。 源文件：success.jsp %@ page contentType=text/html;charset=gb2312% html head title登录成功/title /head body h2${sessionScope.userid}您好，欢迎登录网上书店！/h2 /body /html 与Servlet的运行原理不同的是，JSP需要先转换成Java文件。success.jsp文件被转换成的Java文件的内容如下（位于Tomcat安装目录下的work\Catalina\localhost\ch2\org\apache\jsp文件夹中，ch2是我的应用的名字）： package org.apache.jsp; import javax.servlet.*; import javax.servlet.http.*; import javax.servlet.jsp.*; public final class success_jsp extends org.apache.jasper.runtime.HttpJspBase implements org.apache.jasper.runtime.JspSourceDependent { private static java.util.Vector _jspx_dependants; public java.util.List getDependants() { return _jspx_dependants; } public void (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; JspWriter _jspx_out = null; PageContext _jspx_page_context = null; try { _jspxFactory = JspFactory.getDefaultFactory(); response.setContentType(text/html;charset=gb2312); 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(html\r\n); out.write( head\r\n); out.write( title登录成功/title\r\n); out.write( /head\r\n); out.write( body\r\