jsp本质
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jsp本质：在访问时会被转换为java的类。
1 /* 2 * Generated by the Jasper component of Apache Tomcat 3 * Version: Apache Tomcat/7.0.92 4 * Generated at: 2019-02-25 03:41:55 UTC 5 * Note: The last modified time of this file was set to 6 * the last modified time of the source file after 7 * generation to assist with modification tracking. 8 */ 9 package org.apache.jsp; 10 11 import javax.servlet.*; 12 import javax.servlet.http.*; 13 import javax.servlet.jsp.*; 14 15 public final class page_jsp extends org.apache.jasper.runtime.HttpJspBase 16 implements org.apache.jasper.runtime.JspSourceDependent { 17 18 19 String str="全局变量"; 20 21 22 public void func1(){ 23 System.out.println("全局方法"); 24 } 25 26 27 class C{ 28 private int a; 29 public void f(){ 30 System.out.println("全局类"); 31 } 32 } 33 34 private static final javax.servlet.jsp.JspFactory _jspxFactory = 35 javax.servlet.jsp.JspFactory.getDefaultFactory(); 36 37 private static java.util.Map<java.lang.String,java.lang.Long> _jspx_dependants; 38 39 private volatile javax.el.ExpressionFactory _el_expressionfactory; 40 private volatile org.apache.tomcat.InstanceManager _jsp_instancemanager; 41 42 public java.util.Map<java.lang.String,java.lang.Long> getDependants() { 43 return _jspx_dependants; 44 } 45 46 public javax.el.ExpressionFactory _jsp_getExpressionFactory() { 47 if (_el_expressionfactory == null) { 48 synchronized (this) { 49 if (_el_expressionfactory == null) { 50 _el_expressionfactory = _jspxFactory.getJspApplicationContext(getServletConfig().getServletContext()).getExpressionFactory(); 51 } 52 } 53 } 54 return _el_expressionfactory; 55 } 56 57 public org.apache.tomcat.InstanceManager _jsp_getInstanceManager() { 58 if (_jsp_instancemanager == null) { 59 synchronized (this) { 60 if (_jsp_instancemanager == null) { 61 _jsp_instancemanager = org.apache.jasper.runtime.InstanceManagerFactory.getInstanceManager(getServletConfig()); 62 } 63 } 64 } 65 return _jsp_instancemanager; 66 } 67 68 public void _jspInit() { 69 } 70 71 public void _jspDestroy() { 72 } 73 74 public void _jspService(final javax.servlet.http.HttpServletRequest request, final javax.servlet.http.HttpServletResponse response) 75 throws java.io.IOException, javax.servlet.ServletException { 76 77 final javax.servlet.jsp.PageContext pageContext; 78 javax.servlet.http.HttpSession session = null; 79 final javax.servlet.ServletContext application; 80 final javax.servlet.ServletConfig config; 81 javax.servlet.jsp.JspWriter out = null; 82 final java.lang.Object page = this; 83 javax.servlet.jsp.JspWriter _jspx_out = null; 84 javax.servlet.jsp.PageContext _jspx_page_context = null; 85 86 87 try { 88 response.setContentType("text/html; charset=utf-8"); 89 pageContext = _jspxFactory.getPageContext(this, request, response, 90 null, true, 8192, true); 91 _jspx_page_context = pageContext; 92 application = pageContext.getServletContext(); 93 config = pageContext.getServletConfig(); 94 session = pageContext.getSession(); 95 out = pageContext.getOut(); 96 _jspx_out = out; 97 98 out.write(" "); 99 out.write("<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd"> "); 100 out.write("<html> "); 101 out.write("<head> "); 102 out.write("<meta http-equiv="Content-Type" content="text/html; charset=utf-8"> "); 103 out.write(‘ ‘); 104 out.write(‘ ‘); 105 out.write(‘ ‘); 106 out.write(‘ ‘); 107 out.write(‘ ‘); 108 out.write(‘ ‘); 109 110 int a=1234; 111 String b="java"; 112 out.println(a+b+"局部变量"); 113 114 out.write(" "); 115 out.write("<title>Insert title here</title> "); 116 out.write("</head> "); 117 out.write("<body> "); 118 out.print(b ); 119 out.write(" "); 120 out.write("</body> "); 121 out.write("</html>"); 122 } catch (java.lang.Throwable t) { 123 if (!(t instanceof javax.servlet.jsp.SkipPageException)){ 124 out = _jspx_out; 125 if (out != null && out.getBufferSize() != 0) 126 try { 127 if (response.isCommitted()) { 128 out.flush(); 129 } else { 130 out.clearBuffer(); 131 } 132 } catch (java.io.IOException e) {} 133 if (_jspx_page_context != null) _jspx_page_context.handlePageException(t); 134 else throw new ServletException(t); 135 } 136 } finally { 137 _jspxFactory.releasePageContext(_jspx_page_context); 138 } 139 } 140 }
看
15 public final class page_jsp extends org.apache.jasper.runtime.HttpJspBase
可以知道，将jsp页面转换为了一个类继承自org.apache.jasper.runtime.HttpJspBase
在jsp中定义的全局变量、全局方法、类等都是实际在该类中定义。
看
74 public void _jspService(
知道，静态代码部分实际会在该函数以java的方式输出。jsp中定义的局部变量会被定义在这里。
该函数就是jsp的实际执行函数。
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