Struts2 的OGNL使用简介

<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="@com.mengya.util.Common@myStaticTest()"/>
	  		</li>
	  		<li>
	  			访问静态属性: <s:property value="@com.mengya.util.Common@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.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[com.mengya.bean.User@d2efa1] | [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：