El 表达式的施用

El 表达式的使用

在后台设置数据

//普通字符串  
request.setAttribute("hello", "hello world");         
//结构  
Group group = new Group();  
group.setName("中国");          
User user = new User();  
user.setUsername("崔健");  
user.setAge(18);  
user.setGroup(group);         
request.setAttribute("user", user);       
//map  
Map mapValue  = new HashMap();  
mapValue.put("key1", "value1");  
mapValue.put("key2", "value2");  
request.setAttribute("mapvalue", mapValue);       
//字符串数组  
String[] strArray = new String[]{"a", "b", "c"};  
request.setAttribute("strarray", strArray);       
User[] users = new User[10];  
for (int i=0; i<10; i++) {  
    User u = new User();  
    u.setUsername("U_" + i);  
    users[i] = u;  
}  
request.setAttribute("users", users);     
//List集合  
List userList = new ArrayList();  
for (int i=0; i<10; i++) {  
    User uu = new User();  
    uu.setUsername("UU_" + i);  
    userList.add(uu);  
}  
request.setAttribute("userlist", userList);       
//测试empty  
request.setAttribute("value1", null);  
request.setAttribute("value2", "");  
request.setAttribute("value3", new ArrayList());  
request.setAttribute("value4", "123456");  
return mapping.findForward("success");

前台使用EL取出数据

<body><h1>测试EL表达式</h1><br>  
<hr><li>普通字符串</li><br>  
hello(jsp脚本):<%=request.getAttribute("hello") %><br>  
hello(el表达式,el表达式的使用方法$和{}):${hello }<br>  
hello(el表达式,el的隐含对象pageScope,requestScope,sessionScope,applicationScope,<br>   
如果未指定scope,它的搜索顺序为pageScope~applicationScope):${requestScope.hello }<br>  
hello(el表达式,scope=session):${sessionScope.hello }<br>  
<p><li>结构,采用.进行导航，也称存取器</li><br>  
姓名：${user.username }<br>  
年龄：${user.age }<br>  
所属组：${user.group.name }<br>  
<p><li>输出map,采用.进行导航，也称存取器</li><br>  
mapvalue.key1:${mapvalue.key1 }<br>  
mapvalue.key2:${mapvalue.key2 }<br>  
<p><li>输出数组,采用[]和下标</li><br>  
strarray[2]:${strarray[1] }<br>  
<p><li>输出对象数组,采用[]和下标</li><br>  
userarray[3].username:${users[2].username }<br>  
<p><li>输出list,采用[]和下标</li><br>  
userlist[5].username:${userlist[4].username }<br>  
<p><li>el表达式对运算符的支持</li><br>  
1+2=${1+2 }<br>  
10/5=${10/5 }<br>  
10 div 5=${10 div 5 }<br>  
10%3=${10 % 3 }<br>  
10 mod 3=${10 mod 3 }<br>  
<!--  ==/eq  
     !=/ne   
     </lt  
     >/gt  
     <=/le  
     >=/ge  
     &&/and  
     ||/or  
     !/not  
     //div  
     %/mod  -->    
 <li>测试empty</li><br>  
 value1:${empty value1 }<br>  
 value2:${empty value2 }<br>  
 value3:${empty value3 }<br>  
 value4:${empty value4 }<br>  
 value4:${!empty value4 }<br>  
</body>

转自：http://cuisuqiang.iteye.com/blog/736038

El 表达式的施用

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