javaee el表达式

package com.test.servlet;

import java.io.IOException;
import java.util.ArrayList;
import java.util.List;

import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.http.HttpSession;

import com.test.pojo.Student;

/**
 * Servlet implementation class TestElServlet
 */
@WebServlet("/TestElServlet")
public class TestElServlet extends HttpServlet {
    
    
	private static final long serialVersionUID = 1L;
       
    /**
     * @see HttpServlet#HttpServlet()
     */
    public TestElServlet() {
    
    
        super();
        // TODO Auto-generated constructor stub
    }

	/**
	 * @see HttpServlet#doGet(HttpServletRequest request, HttpServletResponse response)
	 */
	protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
    
    
		// TODO Auto-generated method stub
		//response.getWriter().append("Served at: ").append(request.getContextPath());
	
		request.setAttribute("uname", "daimenglaoshi");
		
		HttpSession session=request.getSession();
		
		session.setAttribute("uname", "daimenglaoshi2");
		
		Student student=new Student();
		student.setSid(1);
		student.setSname("aa");
		student.setMajor("english");
		student.setStu_class("0101");
		
		request.setAttribute("mystudent", student);
		
		List<Student> list=new ArrayList<Student>();
		
		list.add(student);
		
		Student student2=new Student();
		student2.setSid(2);
		student2.setSname("bb");
		student2.setMajor("english");
		student2.setStu_class("0101");
		list.add(student2);
		
		request.setAttribute("mylist", list);
		
		
		request.getRequestDispatcher("index.jsp").forward(request, response);
		
		
	
	}

	/**
	 * @see HttpServlet#doPost(HttpServletRequest request, HttpServletResponse response)
	 */
	protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
    
    
		// TODO Auto-generated method stub
		doGet(request, response);
	}

}

<%@ 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>Insert title here</title>
</head>
<body>

${uname}<br/>
${sessionScope.uname}<br/>
${mystudent.sid}<br/>
${mystudent.sname}<br/>
${mylist[1].sid}<br/>

${param.id}
</body>
</html>

<%@ 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>Insert title here</title>
</head>
<body>
<a href="index.jsp?id=1">传参</a>
</body>
</html>

EL一共11个内置对象，无需创建即可以使用。这11个内置对象中有10个是Map类型的，最后一个是pageContext对象。
pageScope
requestScope
sessionScope
applicationScope
param；
paramValues；
header；
headerValues；
initParam；
cookie；
pageContext；

域内置对象一共有四个：

pageScope：${pageScope.name}等同与pageContext.getAttribute(“name”)；
requestScope：${requestScope.name}等同与request.getAttribute(“name”)；
sessionScoep： ${sessionScope.name}等同与session.getAttribute(“name”)；
applicationScope：${applicationScope.name}等同与application.getAttribute(“name”)；

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