(一)jstl测试el表达式

1.看一下jstl和普通的取值有何区别?
jstl采用的是${}的方式来取值的。

先建一个JstlElServlet:

package com.jxust.jstl;

import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

/**
* 测试El表达式
* @author Administrator
*
*/
public class JstlElServlet extends HttpServlet {

@Override
protected void doGet(HttpServletRequest request, HttpServletResponse response)
   throws ServletException, IOException {
  //普通字符串
  request.setAttribute("hello", "Hello World");

  request.getRequestDispatcher("/jstl_el.jsp").forward(request, response);
}
}
再建一个index.jsp:
<%@ page language="java" import="java.util.*" pageEncoding="GB18030"%>
<%
String path = request.getContextPath();
String basePath = request.getScheme()+"://"+request.getServerName()+":"+request.getServerPort()+path+"/";
%>

<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
  <head>
    <base href="<%=basePath%>">
   
    <title>My JSP 'index.jsp' starting page</title>
<meta http-equiv="pragma" content="no-cache">
<meta http-equiv="cache-control" content="no-cache">
<meta http-equiv="expires" content="0">   
<meta http-equiv="keywords" content="keyword1,keyword2,keyword3">
<meta http-equiv="description" content="This is my page">
<!--
<link rel="stylesheet" type="text/css" href="styles.css">
-->
  </head>
 
  <body>
    <a href="servlet/JstlElServlet">测试EL表达式</a><br>
  </body>
</html>

再建一个jstl_el.jsp:

<%@ page language="java" contentType="text/html; charset=GB18030"
    pageEncoding="GB18030"%>
<!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=GB18030">
<title>Insert title here</title>
</head>
<body>
<h1>测试EL表达式</h1>
<hr>
<li>普通字符串</li><br>
hello(jsp脚本):<%=request.getAttribute("hello") %><br>
hello(el表达式,el表达式使用$和{}):${hello }<br>
</body>
</html>

上面的两个运行结果都是:
  Hello World

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