【JSTL】--测试EL表达式--drp212~

【JSTL】--测试EL表达式--drp212~_第1张图片

 

 

JstlElServlet:

/**
 * 
 */
package com.bjpowrnode.jstl;

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

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

/**
 * @ClassName:JstlElServlet
 * @Description:测试EL表达式
 * @author wm
 * @date 2016年2月14日下午8:45:38
 */
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");
		
		//结构
		Group group =new Group();
		group.setName("动力节点drp 603班");
		
		User user=new User();
		user.setUsername("张三");		
		user.setAge(23);
		user.setGroup( group);		
		request.setAttribute("user", user);
		
		//Map
		Map map=new HashMap();
		map.put("k1", "v1");
		map.put("k2", "v2");
		request.setAttribute("map", map);
		
		//字符串数组
		String[] strArray=new String[]{"a","b","c"}; 
		request.setAttribute("str_array", strArray);
		
		
		//对象数组
		User[] users=new User[10];
		for (int i=0;i<users.length;i++){
			users[i]=new User();
			users[i].setUsername("张三"+i);
		}
		request.setAttribute("users",users);
		
		//List
		List userList=new ArrayList();
		for(int i =0;i<10;i++){
			User usr=new User();
			usr.setUsername("李四" +i);
			userList.add(usr);
		}
		request.setAttribute("userList",userList);
		
		//empty
		request.setAttribute("v2","" );
		request.setAttribute("v3", new ArrayList());
		request.setAttribute("v4", "123456");
		request.setAttribute("v5", null);
		
		request.getRequestDispatcher("/jstl_el.jsp").forward(request, response);;
	}


}

 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:语法:$和{}:${hello}<br>
	hello(el表达式,el内置对象,	pageScope,requestScope,sessionScope,applicationScope	)<br>
	如果不指定范围,它的搜索范围就是pageScope~applicationScope():${requestScope.hello}<br>
	hello(el表达式,从session中取得):${sessionScope.hello}<br>
	
	<p>
	<li>结构,采用。进行导航,或称为存取器</li><br>
	姓名:${user.username}<br>
	年龄:${user.age }<br>
	所属:${user.group.name}<br>
	</p>
	
	<p>
		<li>Map取值</li><br>
		map.k1:${map.k1}<br>
		map.k2:${map.k2}<br>
	</p>
	<p>
	<li>字符串数组:采用[]下标</li><br>
	strArray[1]:${str_array[1] }<br>
	
	<p>
	<li>对象数组:采用[]下标</li>
	users[5].username:${users[5].username }<br>
	
	<p>
	<li>list,采用[] 下标</li>
	userList[6].username:${userList[6].username }<br>
	
	
	<p>
	<li>el表达式对运算符的支持</li>
	1+1= ${1+1 }<br>
	10/5= ${10/5}<br>
	10 div 5=${10 div 5 }<br>
	10%3=${10%3 }<br>
	10 mod 3=${10 mod 3 }<br>
	
	
	<!-- 
		==/eq
		!=/ne
		</lt
		>/gt
		&&/and
		||/or
		!/not
		//div
		%/mod
		
	 -->
	 
	 <p>
	 <li>测试empty</li><br>
	 v1:${empty v1 }<br>
	 v2:${empty v2 }<br>
	 v3:${empty v3 }<br>
	 v4:${empty v4 }<br>
	 v5:${empty v5 }<br>	
</body>
</html>

 web.xml

<?xml version="1.0" encoding="UTF-8"?>
<web-app version="3.0"
    xmlns="http://java.sun.com/xml/ns/javaee"
    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-app_3_0.xsd">
 
	 <servlet>
	 	<servlet-name>JstlElServlet</servlet-name>
	 	<servlet-class>com.bjpowrnode.jstl.JstlElServlet</servlet-class>
	 </servlet>
	<servlet-mapping>
		<servlet-name>JstlElServlet</servlet-name>
		<url-pattern>/servlet/JstlElServlet</url-pattern>
	</servlet-mapping>
		
</web-app>

 Group.java

/**
 * 
 */
package com.bjpowrnode.jstl;

/**
 * @ClassName:Group
 * @Description:TODO
 * @author wm
 * @date 2016年2月15日上午9:41:01
 */
public class Group {
	private String name;

	public String getName() {
		return name;
	}

	public void setName(String name) {
		this.name = name;
	}
	

}

 User.java

/**
 * 
 */
package com.bjpowrnode.jstl;

/**
 * @ClassName:User
 * @Description:TODO
 * @author wm
 * @date 2016年2月15日上午9:42:15
 */
public class User {

	private String username1;
	private  int  age;
	private Group group;
	public String getUsername() {
		return username1;
	}
	public void setUsername(String username1) {
		this.username1 = username1;
	}
	public int getAge() {
		return age;
	}
	public void setAge(int age) {
		this.age = age;
	}
	public Group getGroup() {
		return group;
	}
	public void setGroup(Group group) {
		this.group = group;
	}

}

 

 

感触:学一个东西,要小范围的系统的学,总结一下EL对常用的Map.list.数组的读取,80%学到了就可以了。这样应用级别的入门级别就ok了。

 

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