El 表达式的使用
//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");
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?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
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