標籤：let tde catch cat w3c ase head response code
jsp其實就是servlet，當訪問這個頁面時，伺服器會先把jsp頁面編譯為一個xxx_jsp.class和xxx_jsp.java，存在work中
使用eclipse的同學可以在你的eclipse的workspace的workspace\.metadata\.plugins\org.eclipse.wst.server.core\tmp0\work下找到
舉例：一個最簡單hello頁面
訪問後可得到2個檔案
<%@ page language="java" contentType="text/html; charset=UTF-8" pageEncoding="UTF-8"%><!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd"><html><head><meta http-equiv="Content-Type" content="text/html; charset=UTF-8"><title>title hello</title></head><body>hello</body></html>
他的java檔案是這樣的
/* * Generated by the Jasper component of Apache Tomcat * Version: Apache Tomcat/7.0.70 * Generated at: 2016-10-21 03:13:57 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.*;public final class hello_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("<!DOCTYPE html PUBLIC \"-//W3C//DTD HTML 4.01 Transitional//EN\" \"http://www.w3.org/TR/html4/loose.dtd\">\r\n"); out.write("<html>\r\n"); out.write("<head>\r\n"); out.write("<meta http-equiv=\"Content-Type\" content=\"text/html; charset=UTF-8\">\r\n"); out.write("<title>title hello</title>\r\n"); out.write("</head>\r\n"); out.write("<body>\r\n"); out.write("hello\r\n"); out.write("</body>\r\n"); out.write("</html>"); } 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); } }}
這是不是很像剛學servlet的時寫得servlet代碼，只是他繼承的是HttpJspBase
而這個看起來陌生的HttpJspBase實則就是個servlet，讓我們看看他的源碼
/*** Eclipse Class Decompiler plugin, copyright (c) 2012 Chao Chen ([email protected]) ***/package org.apache.jasper.runtime;import java.io.IOException;import javax.servlet.ServletConfig;import javax.servlet.ServletException;import javax.servlet.http.HttpServlet;import javax.servlet.http.HttpServletRequest;import javax.servlet.http.HttpServletResponse;import javax.servlet.jsp.HttpJspPage;import org.apache.jasper.compiler.Localizer;public abstract class HttpJspBase extends HttpServlet implements HttpJspPage { private static final long serialVersionUID = 1L; public final void init(ServletConfig config) throws ServletException { super.init(config); jspInit(); _jspInit(); } public String getServletInfo() { return Localizer.getMessage("jsp.engine.info"); } public final void destroy() { jspDestroy(); _jspDestroy(); } public final void service(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { _jspService(request, response); } public void jspInit() { } public void _jspInit() { } public void jspDestroy() { } protected void _jspDestroy() { } public abstract void _jspService(HttpServletRequest paramHttpServletRequest, HttpServletResponse paramHttpServletResponse) throws ServletException, IOException;}
所以說jsp頁面就是個servlet
servlet和jsp學習指南（四）jsp頁面
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