JSP基本原理实战

以你之姓@ 2021-07-24 20:11 368阅读 0赞

**一 创建jspPrinciple项目**

**二 项目结构如下**

D:\Program\Tomcat8\webapps\jspPrinciple>tree /f
    卷 Program 的文件夹 PATH 列表
    卷序列号为 2E2F-D762
    D:.
    │  first.jsp
    │  test.jsp
    │
    └─WEB-INF
            web.xml

**三 代码**

1 first.jsp

<%@ page contentType="text/html; charset=GBK" language="java" errorPage="" %>
 <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN"
 "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
 <html xmlns="http://www.w3.org/1999/xhtml">
 <head>
 <title>欢迎</title>
 <meta name="website" content="http://www.crazyit.org" />
 </head>
 <body>
 欢迎学习Java Web知识，现在时间是:
 <%out.println(new java.util.Date());%>
 </body>
 </html>

2 test.jsp

<%@ page contentType="text/html; charset=GBK" language="java" errorPage="" %>
 <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN"
 "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
 <html xmlns="http://www.w3.org/1999/xhtml">
 <head>
 <title> 第二个JSP页面 </title>
 <meta name="website" content="http://www.crazyit.org" />
 </head>
 <body>
 
 <%for(int i = 0 ; i < 7; i++)
 {
 out.println("");
 %>
 疯狂Java训练营(Wild Java Camp)
 
 <%}%>
 </body>
 </html>

**四 测试**

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L2NoZW5ncWl1bWluZw_size_16_color_FFFFFF_t_70][]

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L2NoZW5ncWl1bWluZw_size_16_color_FFFFFF_t_70 1][]

**五 说明**

JSP的实质还是Servlet，例如上面的test.jsp经过编译后，对应的Servlet文件位于下面目录：

D:\\Program\\Tomcat8\\work\\Catalina\\localhost\\jspPrinciple\\org\\apache\\jsp

对应Java文件和class文件分别是test\_jsp.java和test\_jsp.class

test\_jsp.java的源码如下，实质上就是一个Servlet。

/*
 * Generated by the Jasper component of Apache Tomcat
 * Version: Apache Tomcat/8.5.43
 * Generated at: 2019-09-02 12:05:21 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 test_jsp extends org.apache.jasper.runtime.HttpJspBase
 implements org.apache.jasper.runtime.JspSourceDependent,
 org.apache.jasper.runtime.JspSourceImports {
 
 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 static final java.util.Set<java.lang.String> _jspx_imports_packages;
 
 private static final java.util.Set<java.lang.String> _jspx_imports_classes;
 
 static {
 _jspx_imports_packages = new java.util.HashSet<>();
 _jspx_imports_packages.add("javax.servlet");
 _jspx_imports_packages.add("javax.servlet.http");
 _jspx_imports_packages.add("javax.servlet.jsp");
 _jspx_imports_classes = null;
 }
 
 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 java.util.Set<java.lang.String> getPackageImports() {
 return _jspx_imports_packages;
 }
 
 public java.util.Set<java.lang.String> getClassImports() {
 return _jspx_imports_classes;
 }
 
 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 java.lang.String _jspx_method = request.getMethod();
 if (!"GET".equals(_jspx_method) && !"POST".equals(_jspx_method) && !"HEAD".equals(_jspx_method) && !javax.servlet.DispatcherType.ERROR.equals(request.getDispatcherType())) {
 response.sendError(HttpServletResponse.SC_METHOD_NOT_ALLOWED, "JSPs only permit GET POST or HEAD");
 return;
 }
 
 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=GBK");
 pageContext = _jspxFactory.getPageContext(this, request, response,
 "", 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");
 out.write("\r\n");
 out.write("<!DOCTYPE html PUBLIC \"-//W3C//DTD XHTML 1.0 Transitional//EN\"\r\n");
 out.write("\t\"http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd\">\r\n");
 out.write("<html xmlns=\"http://www.w3.org/1999/xhtml\">\r\n");
 out.write("<head>\r\n");
 out.write("\t<title> 第二个JSP页面 </title>\r\n");
 out.write("\t<meta name=\"website\" content=\"http://www.crazyit.org\" />\r\n");
 out.write("</head>\r\n");
 out.write("<body>\r\n");
 out.write("\r\n");
 for(int i = 0 ; i < 7; i++)
 {
 out.println("");
 
 out.write("\r\n");
 out.write("疯狂Java训练营(Wild Java Camp)\r\n");
 out.write(" \r\n");
 }
 out.write("\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);
 }
 }
 }

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