本文详细介绍了Struts2框架中的OGNL表达式的使用方法，包括如何通过OGNL访问对象属性、调用方法及处理集合等内容，并提供了具体的示例代码。
1.先看结构
2.在看流程
struts.xml包含ognl.xml,具体package在ognl.xml中
- struts.xml
<?xml version="1.0" encoding="UTF-8" ?>
<!DOCTYPE struts PUBLIC
"-//Apache Software Foundation//DTD Struts Configuration 2.0//EN"
"http://struts.apache.org/dtds/struts-2.0.dtd">
<struts>
<constant name="struts.enable.DynamicMethodInvocation" value="false" />
<constant name="struts.devMode" value="true" />
<constant name="struts.ognl.allowStaticMethodAccess" value="true"></constant>
<include file="/com/jsly/struts2/ognl/ognl.xml"/>
</struts>
- ognl.xml
<?xml version="1.0" encoding="UTF-8" ?>
<!DOCTYPE struts PUBLIC
"-//Apache Software Foundation//DTD Struts Configuration 2.0//EN"
"http://struts.apache.org/dtds/struts-2.0.dtd">
<struts>
<package name="default" namespace="/" extends="struts-default">
<action name="ognl" class="com.jsly.struts2.ognl.OgnlAction">
<result>
/ognl.jsp
</result>
</action>
<action name="test" class="com.jsly.struts2.ognl.TestAction">
<result type="chain">ognl</result>
</action>
</package>
</struts>
3.还有index.jsp和ognl.jsp
index.jsp负责跳转到ognl.jsp页面
- index.jsp
<?xml version="1.0" encoding="GB18030" ?>
<%@ page language="java" contentType="text/html; charset=GB18030"
pageEncoding="GB18030"%>
<%
String contextPath = request.getContextPath();
%>
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
<head>
<meta http-equiv="Content-Type" content="text/html; charset=GB18030" />
<title>Insert title here</title>
</head>
<body>
访问属性
<a href="<%=contextPath %>/ognl?username=u&password=p&user.age=10">ognl</a>
</body>
</html>
- ognl.jsp（精华，仔细分析）
<?xml version="1.0" encoding="GB18030" ?>
<%@ page language="java" contentType="text/html; charset=GB18030"
pageEncoding="GB18030"%>
<%@ taglib uri="/struts-tags" prefix="s" %>
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
<head>
<meta http-equiv="Content-Type" content="text/html; charset=GB18030" />
<title>OGNL表达式语言学习</title>
</head>
<body>
<ol>
<li>访问值栈中的action的普通属性: username = <s:property value="username"/> </li>
<li>访问值栈中对象的普通属性(get set方法)：<s:property value="user.age"/> | <s:property value="user['age']"/> | <s:property value="user[/"age/"]"/> | wrong: <%--<s:property value="user[age]"/>--%></li>
<li>访问值栈中对象的普通属性(get set方法): <s:property value="cat.friend.name"/></li>
<li>访问值栈中对象的普通方法：<s:property value="password.length()"/></li>
<li>访问值栈中对象的普通方法：<s:property value="cat.miaomiao()" /></li>
<li>访问值栈中action的普通方法：<s:property value="m()" /></li>
<hr />
<li>访问静态方法：<s:property value="@com.bjsxt.struts2.ognl.S@s()"/></li>
<li>访问静态属性：<s:property value="@com.bjsxt.struts2.ognl.S@STR"/></li>
<li>访问Math类的静态方法：<s:property value="@@max(2,3)" /></li>
<hr />
<li>访问普通类的构造方法：<s:property value="new com.bjsxt.struts2.ognl.User(8)"/></li>
<hr />
<li>访问List:<s:property value="users"/></li>
<li>访问List中某个元素:<s:property value="users[1]"/></li>
<li>访问List中元素某个属性的集合:<s:property value="users.{age}"/></li>
<li>访问List中元素某个属性的集合中的特定值:<s:property value="users.{age}[0]"/> | <s:property value="users[0].age"/></li>
<li>访问Set:<s:property value="dogs"/></li>
<li>访问Set中某个元素:<s:property value="dogs[1]"/></li>
<li>访问Map:<s:property value="dogMap"/></li>
<li>访问Map中某个元素:<s:property value="dogMap.dog101"/> | <s:property value="dogMap['dog101']"/> | <s:property value="dogMap[/"dog101/"]"/></li>
<li>访问Map中所有的key:<s:property value="dogMap.keys"/></li>
<li>访问Map中所有的value:<s:property value="dogMap.values"/></li>
<li>访问容器的大小：<s:property value="dogMap.size()"/> | <s:property value="users.size"/> </li>
<hr />
<li>投影(过滤)：<s:property value="users.{?#this.age==1}[0]"/></li>
<li>投影：<s:property value="users.{^#this.age>1}.{age}"/></li>
<li>投影：<s:property value="users.{$#this.age>1}.{age}"/></li>
<li>投影：<s:property value="users.{$#this.age>1}.{age} == null"/></li>
<hr />
<li>[]:<s:property value="[0].username"/></li>
</ol>
<s:debug></s:debug>
</body>
</html>
4.最后Action和java
-
-
- OgnlAction.java
package com.jsly.struts2.ognl;
import java.util.*;
import com.opensymphony.xwork2.ActionSupport;
public class OgnlAction extends ActionSupport{
/**
* 构造函数
*/
public OgnlAction(){
System.out.println("OgnlAction构造函数！");
users.add(new User(1));
users.add(new User(2));
users.add(new User(3));
dogs.add(new Dog("dog1"));
dogs.add(new Dog("dog2"));
dogs.add(new Dog("dog3"));
dogMap.put("dog100", new Dog("dog100"));
dogMap.put("dog101", new Dog("dog101"));
dogMap.put("dog102", new Dog("dog102"));
}
/**
* Override execute
*/
public String execute(){
return SUCCESS;
}
//用户 第二行
private User user; //= new User(); //user.age=10（对象.属性）只有传，才会构造
//username和password 第一行
private String username;
private String password;
//猫 第三行
private Cat cat;
//定义集合属性
private List<User> users = new ArrayList<User>();
private Set<Dog> dogs = new HashSet<Dog>();
private Map<String,Dog> dogMap = new HashMap<String,Dog>();
public String getUsername() {
return username;
}
public void setUsername(String username) {
this.username = username;
}
public String getPassword() {
return password;
}
public void setPassword(String password) {
this.password = password;
}
public User getUser() {
return user;
}
public void setUser(User user) {
this.user = user;
}
public Cat getCat() {
return cat;
}
public void setCat(Cat cat) {
this.cat = cat;
}
public String sayHello(){
return "say hello!" ;
}
public List<User> getUsers() {
return users;
}
public void setUsers(List<User> users) {
this.users = users;
}
public Set<Dog> getDogs() {
return dogs;
}
public void setDogs(Set<Dog> dogs) {
this.dogs = dogs;
}
public Map<String, Dog> getDogMap() {
return dogMap;
}
public void setDogMap(Map<String, Dog> dogMap) {
this.dogMap = dogMap;
}
} - User.java
package com.jsly.struts2.ognl;
public class User {
//年龄
private int age = 8;
public User(){
System.out.println("User构造函数!");
}
public User(int age){
super();
this.age = age;
}
public int getAge() {
return age;
}
public void setAge(int age) {
this.age = age;
}
public String toString(){
return "user.age=" + age;
}
} - Cat.java
package com.jsly.struts2.ognl;
public class Cat {
private Dog friend;
public Cat(){
System.out.println("Cat构造函数！");
}
public Dog getFriend() {
return friend;
}
public void setFriend(Dog friend) {
this.friend = friend;
}
public String miaomiao(){
return "miaomiao";
}
} - Dog.java
package com.jsly.struts2.ognl;
public class Dog {
private String name;
public Dog(){
System.out.println("Dog构造函数！");
}
public Dog(String name){
super();
this.name = name;
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public String toString(){
return "Dog.name=" + name;
}
} - S.java
package com.jsly.struts2.ognl;
public class S {
public static String STR = "STATIC STRING";
public static String s() {
return "static method";
}
} - TestAction.java
package com.jsly.struts2.ognl;
import com.opensymphony.xwork2.ActionSupport;
public class TestAction extends ActionSupport{
public String execute() throws Exception {
return super.execute();
}
}
- OgnlAction.java
-
5.别忘记结果
HELLO，OGNL!
- 访问值栈中的action的普通属性: username = u password = p
- 访问值栈中对象的普通属性(get set方法)+(user.age=10)：10 | 10 | 10 | wrong:
- 访问值栈中对象的普通属性(get set方法)+(cat.friend.name=dog111):
- 访问值栈中对象的普通方法(password.length)：1
- 访问值栈中对象的普通方法(cat.miaomiao()方法)：
- 访问值栈中对象的普通方法(OgnlAction中的普通方法)：say hello!
- 访问静态方法：static method
- 访问静态属性：STATIC STRING
- 访问Math类的静态方法：3
- 访问普通类的构造方法：user.age=8
- 访问List:[user.age=1, user.age=2, user.age=3]
- 访问List中某个元素:user.age=2
- 访问List中元素某个属性的集合:[1, 2, 3]
- 访问List中元素某个属性的集合中的特定值:1 | 1
- 访问Set:[Dog.name=dog3, Dog.name=dog1, Dog.name=dog2]
- 访问Set中某个元素:
- 访问Map:{dog101=Dog.name=dog101, dog100=Dog.name=dog100, dog102=Dog.name=dog102}
- 访问Map中某个元素:Dog.name=dog101 | Dog.name=dog101 | Dog.name=dog101
- 访问Map中所有的key:[dog101, dog100, dog102]
- 访问Map中所有的value:[Dog.name=dog101, Dog.name=dog100, Dog.name=dog102]
- 访问容器的大小：3 | 3
- 投影(过滤)：user.age=1
- 投影：[2]
- 投影：[3]
- 投影：false
- []:u
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