JSP编译为Java类：
注意可以随便写import的内容；可以写类属性、方法、main函数、内部类；可以使用内部类；
JSP:
<%@ page language="java" import="java.util.*,a.b.*" pageEncoding="UTF-8"%>
<%
String path = request.getContextPath();
String basePath = request.getScheme() + "://" + request.getServerName() + ":" + request.getServerPort() + path + "/";
%>
<!DOCTYPE html>
<html>
<%
int cnt = 0;
%>
<head>
<meta charset="UTF-8">
<title>004index</title>
</head>
<body>
cnt is :<%=++cnt%>
<hr>
<%-- <%= String s = "foo"%>是不行的； --%>
<%=new String[3]%>
<hr>
<%=getCnt()%>
<hr>
<%=new Foo()%>
<%!int cnt = 0;
public static void main(String args) {
System.out.println("a");
}
private int getCnt() {//如果返回void就无法使用表达式输出
return ++cnt;
}
class Foo {
private String a;
public Foo() {
}
public Foo(String a) {
this.a = a;
}
public String getA() {
return a;
}
public String toString() {
return "Foo:" + a;
}
}%>
</body>
</html>
Java:
/*
* Generated by the Jasper component of Apache Tomcat
* Version: Apache Tomcat/7.0.35
* Generated at: 2015-10-12 00:25:50 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 a.b.*; public final class index004_jsp extends org.apache.jasper.runtime.HttpJspBase
implements org.apache.jasper.runtime.JspSourceDependent { int cnt = 0;
public static void main(String args) {
System.out.println("a");
}
private int getCnt() {
return ++cnt;
}
class Foo{
private String a;
public Foo(){}
public Foo(String a){
this.a = a;
}
public String getA(){
return a;
}
public String toString(){
return "Foo:" + a;
}
} 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 javax.el.ExpressionFactory _el_expressionfactory;
private org.apache.tomcat.InstanceManager _jsp_instancemanager; public java.util.Map<java.lang.String,java.lang.Long> getDependants() {
return _jspx_dependants;
} public void _jspInit() {
_el_expressionfactory = _jspxFactory.getJspApplicationContext(getServletConfig().getServletContext()).getExpressionFactory();
_jsp_instancemanager = org.apache.jasper.runtime.InstanceManagerFactory.getInstanceManager(getServletConfig());
} 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; // 注意这个out是JspWriter<java.io.Writer<java.lang.Object;不是Object>Writer>java.io.PrintWriter
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');
out.write('\n'); String path = request.getContextPath();
String basePath = request.getScheme() + "://" + request.getServerName() + ":" + request.getServerPort() + path + "/"; out.write("\r\n");
out.write("<!DOCTYPE html>\r\n");
out.write("<html>\r\n"); int cnt = 0; out.write("\r\n");
out.write("<head>\r\n");
out.write("<meta charset=\"UTF-8\">\r\n");
out.write("<title>b index</title>\r\n");
out.write("</head>\r\n");
out.write("<body>\r\n");
out.write("\tcnt is :");
out.print(++cnt);
out.write("\r\n");
out.write("\t<hr>\r\n");
out.write("\t");
out.write('\r');
out.write('\n');
out.write(' ');
out.print(new String[3]);
out.write("\r\n");
out.write("\t<hr>\r\n");
out.write("\t");
out.print(getCnt());
out.write("\r\n");
out.write("\t<hr>\r\n");
out.write("\t");
out.print(new Foo() );
out.write('\r');
out.write('\n');
out.write(' ');
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 { 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);
}
}
}