结识EL
简单介绍下EL的常用形式，继续用程序说明：
package com.keith.el;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import org.apache.struts.action.Action;
import org.apache.struts.action.ActionForm;
import org.apache.struts.action.ActionForward;
import org.apache.struts.action.ActionMapping;
import com.keith.taglibs.Group;
import com.keith.taglibs.User;
public class ElAction extends Action {
@Override
public ActionForward execute(ActionMapping mapping, ActionForm form,
HttpServletRequest request, HttpServletResponse response)
throws Exception {
// 字符串
request.setAttribute("he", "hello EL ");
// 结构
Group group = new Group();
group.setGroupName("KEITH的朋友");
User user = new User();
user.setName("keith");
user.setAge(19);
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);
// 对象数组
User[] user1 = new User[10];
for (int i = 0; i < 10; i++) {
User u = new User();
u.setName("U_" + i);
user1[i] = u;
}
request.setAttribute("user1", user1);
//list
List userList = new ArrayList();
for (int i = 0; i < 10; i++) {
User u_list = new User();
u_list.setName("u_list"+i);
userList.add(u_list);
}
// 测试${empty }
request.setAttribute("value2", "");
request.setAttribute("value3", "abcd");
request.setAttribute("value4", new ArrayList());
request.setAttribute("userList", userList);
return mapping.findForward("elTest");
}
}
用到了User类：
package com.keith.taglibs;
public class User {
private String name;
private int age;
private Group group;
public Group getGroup() {
return group;
}
public void setGroup(Group group) {
this.group = group;
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public int getAge() {
return age;
}
public void setAge(int age) {
this.age = age;
}
}
Group类：
package com.keith.taglibs;
public class Group {
private String groupName;
public String getGroupName() {
return groupName;
}
public void setGroupName(String groupName) {
this.groupName = groupName;
}
}
struts-config.xml:
<action-mappings> <action path="/elTest" type="com.keith.el.ElAction"> <forward name="elTest" path="/elTest.jsp"></forward> </action> <action-mappings>
elTest.jsp页面：由于用到了logic标签所以引入下：
<%@ taglib prefix="logic" uri="http://struts.apache.org/tags-logic"%>
elTest.jsp:
<body>
<h2>
EL表达式TEST
</h2>
<h3>
EL(输出字符串)
</h3>
${he }
<hr>
<h3>
EL(输出结构)
</h3>
<table>
<tr>
<td>
姓名
</td>
<td>
年龄
</td>
<td>
班级
</td>
</tr>
<logic:empty name="user">
<font color="red">user不存在</font>
</logic:empty>
<logic:notEmpty name="user">
<tr>
<td>
${user.name }
</td>
<td>
${user.age }
</td>
<td>
${user.group.groupName }
</td>
</tr>
</logic:notEmpty>
</table>
<hr>
<h3>
EL(输出MAP)
</h3>
mapValue.key1的值是:${mapValue.key1 }
<br />
mapValue.key2的值是:${mapValue.key2 }
<br />
<hr />
<h3>
EL(输出字符串数组)
</h3>
strArray[1]的值:${strArray[1] }
<br />
strArray[2]的值:${strArray[2] }
<br />
<hr />
<h3>
EL(输出对象数组)
</h3>
user1[1].name:${user1[1].name }
<hr />
<h3>
EL(list输出数组)
</h3>
userList[1].name:${userList[1].name }
<hr/>
<h3>EL表达式计算</h3>
1+9=${1+9 }<br/>
1-9=${1-9 }<br/>
1*9=${1*9 }<br/>
1/9=${1/9 }<br/>
<h3>测试EL{empty}</h3>
value1:${empty value1 }<br/>
value2:${empty value2 }<br/>
value3:${empty value3 }<br/>
value4:${empty value4 }<br/>
</body>
很简单............