struts2笔记(五)
03 OGNL表达式语言
Object Graph Navigation Language 对象图导航语言
<s:property value=””> 注意： value里的内容称为ognl表达式
User.xxx 只有传入参数，才会构造对象，或者直接在action中new也可以，但是User对象必需具有无参数的构造方法。
{}大括号 在OGNL中可以表示一个集合
OGNL表达式语言访问静态方法，需要在Struts2.xml配置文件如下：
<constant name="struts.ognl.allowStaticMethodAccess" value="true"></constant>
使用一个实例如说明OGNL表达式语言，如下：
Cat类
package com.wjt276.struts2.ognl;
public class Cat {
private Dog friend;
public Dog getFriend() {
return friend;
}
public void setFriend(Dog friend) {
this.friend = friend;
}
public String miaomiao() {
return "miaomiao";
}
}
Dog类
package com. wjt276.struts2.ognl;
public class Dog {
private String name;
public Dog() {}
public Dog(String name) {
super();
this.name = name;
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
@Override
public String toString() {
return "dog: " + name;
}
}
S类
package com. wjt276.struts2.ognl;
public class S {
public static String STR = "STATIC STRING";
public static String s() {
return "static method";}}
User类
package com. wjt276.struts2.ognl;
public class User {
private int age = 8;
public User() {}
public User(int age) {
super();
this.age = age;
}
public int getAge() {
return age;
}
public void setAge(int age) {
this.age = age;
}
@Override
public String toString() {
return "user" + age;
}
}
OgnlAction类
package com. wjt276.struts2.ognl;
public class OgnlAction extends ActionSupport {
private Cat cat;
private Map<String, Dog> dogMap = new HashMap<String, Dog>();
private Set<Dog> dogs = new HashSet<Dog>();
private String password;
private User user;
private String username;
private List<User> users = new ArrayList<User>();
public OgnlAction() {
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"));
}
public String execute() {
return SUCCESS;
}
public Cat getCat() {
return cat;
}
public Map<String, Dog> getDogMap() {
return dogMap;
}
public Set<Dog> getDogs() {
return dogs;
}
public String getPassword() {
return password;
}
public User getUser() {
return user;
}
public String getUsername() {
return username;
}
public List<User> getUsers() {
return users;
}
public String m() {
return "hello";
}
public void setCat(Cat cat) {
this.cat = cat;
}
public void setDogMap(Map<String, Dog> dogMap) {
this.dogMap = dogMap;
}
public void setDogs(Set<Dog> dogs) {
this.dogs = dogs;
}
public void setPassword(String password) {
this.password = password;
}
public void setUser(User user) {
this.user = user;
}
public void setUsername(String username) {
this.username = username;
}
public void setUsers(List<User> users) {
this.users = users;
}
}
Struts2.xml配置文件：
<struts>
<constant name="struts.enable.DynamicMethodInvocation" value="false" />
<constant name="struts.devMode" value="true" />
<!-- 允许ognl访问静态方法 -->
<constant name="struts.ognl.allowStaticMethodAccess" value="true"></constant>
<include file="/com/wjt276/struts2/ognl/ognl.xml"/>
</struts>
Com.wjt276.struts2.ognl.ognl.xml配置文件
<package name="ognl" extends="struts-default">
<action name="ognl" /></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.wjt276.struts2.ognl.S@s()"/></li>
<li>访问静态属性：<s:property value="@com.wjt276.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><%--返回对象的toString()生成的数据--%>
<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><%--头一个 --%>
<li>投影：<s:property value="users.{$#this.age>1}.{age}"/></li><%--最后一个--%>
<li>投影：<s:property value="users.{$#this.age>1}.{age} == null"/></li>
<hr />
<li>[]:<s:property value="[0].username"/></li><%--值堆栈中的对象(Object),从上开始的第0个至堆栈底对象 --%>
</ol>
<s:debug></s:debug>
访问后服务器返回给客户端的结果：
1.访问值栈中的action的普通属性: username = u
2.访问值栈中对象的普通属性(get set方法)：9 | 9 | 9 | wrong:
3.访问值栈中对象的普通属性(get set方法):
4.访问值栈中对象的普通方法：1
5.访问值栈中对象的普通方法：
6.访问值栈中action的普通方法：hello
________________________________________
7.访问静态方法：static method
8.访问静态属性：STATIC STRING
9.访问Math类的静态方法：3
________________________________________
10.访问普通类的构造方法：user8
________________________________________
11.访问List:[user1, user2, user3]
12.访问List中某个元素:user2
13.访问List中元素某个属性的集合:[1, 2, 3]
14.访问List中元素某个属性的集合中的特定值:1 | 1
15.访问Set:[dog: dog1, dog: dog2, dog: dog3]
16.访问Set中某个元素: <!—没有显示是因为在Set中没有排序就不存在的用下标访问了-->
17.访问Map:{dog102=dog: dog102, dog101=dog: dog101, dog100=dog: dog100}
18.访问Map中某个元素:dog: dog101 | dog: dog101 | dog: dog101
19.访问Map中所有的key:[dog102, dog101, dog100]
20.访问Map中所有的value:[dog: dog102, dog: dog101, dog: dog100]
21.访问容器的大小：3 | 3
________________________________________
22.投影(过滤)：user1
23.投影：[2]
24.投影：[3]
25.投影：false
________________________________________
26.[]:u
27.[Debug]
