Struts2 的OGNL使用简介
程序员文章站
2022-04-18 11:58:09
...
<div align="center">
<ol>
<li>访问值栈中的Action的普通属性：username=<s:property value="username" /> | password=<s:property value="password" /> </li>
<li>Action的user属性值=<s:property value="user"/></li>
<li>访问值栈中的对象的普通属性：Action的user属性的name属性值=<s:property value="user.name" /> | =<s:property value="user['name']" /> </li>
<li>访问值栈中的对象的普通属性：Action->cat->firend->name=<s:property value="cat.firend.name" /> </li>
<hr>
<li>
访问值栈中的对象的普通方法username.length()：<s:property value="username.length()"/>
</li>
<li>
访问值栈中的对象的普通方法cat.miao()：<s:property value="cat.miao()"/>
</li>
<li>
访问Action的普通方法myTest()：<s:property value="myTest()"/>
</li>
<hr>
<li>
访问静态方法: <s:property value="@[email protected]()"/>
</li>
<li>
访问静态属性: <s:property value="@[email protected]"/>
</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.mengya.bean.User()"/>
</li>
<li>
访问普通类的构造方法: <s:property value="new com.mengya.bean.User().setName('mengya')"/>
</li>
<hr>
<li>
访问List：<s:property value="userList" />
</li>
<li>
访问List中的某个元素：<s:property value="userList[1]" />
</li>
<li>
访问List中元素的某个属性的集合：<s:property value="userList.{name}" />
</li>
<li>
访问List中元素的某个属性的集合中的特定值：<s:property value="userList.{name}[1]" /> | <s:property value="userList[1].name" />
</li>
<li>
访问Set：<s:property value="dogSet" />
</li>
<li>
访问Set中的某个元素：<s:property value="dogSet[1]" /><!-- set没有顺序故取不到值 -->
</li>
<li>
访问Map：<s:property value="catMap" />
</li>
<li>
访问Map中某个元素：<s:property value="catMap.cat1" /> | <s:property value="catMap['cat1']" />
</li>
<li>
访问Map中的所有keys：<s:property value="catMap.keys" />
</li>
<li>
访问Map中的所有values：<s:property value="catMap.values" />
</li>
<li>
访问容器的大小：<s:property value="catMap.size()" /> | <s:property value="userList.size()" />
</li>
<hr>
<li>
投影（过滤）user的name为aaa的集合：<s:property value="userList.{?#this.name=='aaa'}" /> | <s:property value="userList.{?#this.name=='aaa'}.{name}" />
<!-- 得到的是一个[[email protected]] | [aaa] 都是集合 --> | <s:property value="userList.{?#this.name=='aaa'}.{name}[0]" />
</li>
<li>
投影（过滤）user的age大于21的第一个元素：<s:property value="userList.{^#this.age>21}" /> | <s:property value="userList.{^#this.age>21}.{name}" />
</li>
<li>
投影（过滤）user的age大于21的第最后一个元素：<s:property value="userList.{$#this.age>21}" /> | <s:property value="userList.{$#this.age>21}.{name}" />
</li>
<li>
投影（过滤）判断：<s:property value="userList.{$#this.age>21}.{name} == null " />
</li>
<hr>
<li>
[0]表示获得的是第一个Action：<s:property value="[0]" /> | <s:property value="[0].username" />
</li>
</ol>
</div>web.xml
<?xml version="1.0" encoding="UTF-8"?> <web-app version="2.4" xmlns="http://java.sun.com/xml/ns/j2ee" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://java.sun.com/xml/ns/j2ee http://java.sun.com/xml/ns/j2ee/web-app_2_4.xsd"> <filter> <filter-name>struts2</filter-name> <filter-class> org.apache.struts2.dispatcher.FilterDispatcher </filter-class> </filter> <filter-mapping> <filter-name>struts2</filter-name> <url-pattern>/*</url-pattern> </filter-mapping> <welcome-file-list> <welcome-file>index.jsp</welcome-file> </welcome-file-list> </web-app>
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>
<!-- 允许访问静态方法 -->
<constant name="struts.ognl.allowStaticMethodAccess" value="true"></constant>
<package name="ognl" extends="struts-default">
<action name="ognl" class="com.mengya.action.OgnlAction">
<result name="success">ognl.jsp</result>
</action>
</package>
</struts>
OgnlAction：
public class OgnlAction extends ActionSupport {
private String username;
private String password;
/**
* 说明：在这里若user对象没有实例化，在页面访问action时给user的属性赋值了，struts2会自动帮我们实例化该user对象
* 前提是User对象提供了无参的构造方法。若页面没有给user的属性赋值则user为null（针对本实例，因为execute方法没有任何操作）
* 在这里若对user对象实例化了，则无论在页面访问action时是否也user的属性赋值，user都不会是null
*/
private User user = null;
// private User user = new User();
private Cat cat = null;
private Common common = null;
private List<User> userList = null;
private Set<Dog> dogSet = null;
public Map<String, Cat> catMap = null;
@Override
public String execute() throws Exception {
// cat = new Cat();
// Dog dog =new Dog();
// dog.setName("Dog");
// cat.setFirend(dog);
userList = new ArrayList<User>();
User u = new User();
u.setName("aaa");
u.setAge(21);
userList.add(u);
u = new User();
u.setName("bb");
u.setAge(22);
userList.add(u);
u = new User();
u.setName("cc");
u.setAge(23);
userList.add(u);
dogSet = new HashSet<Dog>();
Dog d = new Dog();
d.setName("dog1");
dogSet.add(d);
d = new Dog();
d.setName("dog2");
dogSet.add(d);
d = new Dog();
d.setName("dog3");
dogSet.add(d);
catMap = new HashMap<String, Cat>();
catMap.put("cat1", new Cat());
catMap.put("cat2", new Cat());
catMap.put("cat3", new Cat());
return SUCCESS;
}
public String myTest() {
return "myTest方法";
}
public Cat getCat() {
return cat;
}
public String getPassword() {
return password;
}
public User getUser() {
return user;
}
public String getUsername() {
return username;
}
public void setCat(Cat cat) {
this.cat = cat;
}
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 Common getCommon() {
return common;
}
public void setCommon(Common common) {
this.common = common;
}
public List<User> getUserList() {
return userList;
}
public void setUserList(List<User> userList) {
this.userList = userList;
}
public Set<Dog> getDogSet() {
return dogSet;
}
public void setDogSet(Set<Dog> dogSet) {
this.dogSet = dogSet;
}
public Map<String, Cat> getCatMap() {
return catMap;
}
public void setCatMap(Map<String, Cat> catMap) {
this.catMap = catMap;
}
}Action中所引用的Bean：
public class Cat {
private String name;
private Dog firend;
public Dog getFirend() {
return firend;
}
public void setFirend(Dog firend) {
this.firend = firend;
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public String miao(){
return "cat的普遍方法调用";
}
}
public class Dog {
private String name;
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
}
public class User {
private String name;
private int age;
public String getName() {
return name;
}
public String setName(String name) {
this.name = name;
return toString();
}
public int getAge() {
return age;
}
public void setAge(int age) {
this.age = age;
}
}
测试：
推荐阅读