struts2标签遍历集合过滤：{?1==1}[0]

最近在项目中发现在jsp页面上遍历集合还有这种写法：

 

personlist为List<Person>,遍历时过滤掉name属性为“jack”的元素：

<s:iterator value="personList.{?!name.equals(\"jack\")}"> 
<s:property value="name"/>--- 
<s:property value="password"/> 
</s:iterator>

 persons为Set<Person>,遍历时只取第一个元素：

<s:iterator value="persons.{?1==1}[0]"> 
<s:property value="name"/>--- 
<s:property value="password"/><br/> 
</s:iterator>

 

 Person类为：

public class Person { 
private String name; 
private String password; 

public Person(String name,String password){ 
this.name = name; 
this.password = password; 
} 

public String getName() { 
return name; 
} 
public void setName(String name) { 
this.name = name; 
} 
public String getPassword() { 
return password; 
} 
public void setPassword(String password) { 
this.password = password; 
} 
}

 

 

 

 Action为：

public class TestAction extends ActionSupport { 
private List<Person> personList; 
private Set<Person> persons; 

public List<Person> getPersonList() { 
return personList; 
} 
public void setPersonList(List<Person> personList) { 
this.personList = personList; 
} 
public Set<Person> getPersons() { 
return persons; 
} 
public void setPersons(Set<Person> persons) { 
this.persons = persons; 
} 

@Override 
public String execute() throws Exception { 

personList = new ArrayList<Person>(); 
personList.add(new Person("jack","1111")); 
personList.add(new Person("jack1","2222")); 
personList.add(new Person("jack2","3333")); 
personList.add(new Person("jack3","4444")); 
personList.add(new Person("jack4","5555")); 

persons = new HashSet<Person>(); 
persons.add(new Person("jack","1111")); 
persons.add(new Person("jack1","2222")); 
persons.add(new Person("jack2","3333")); 
persons.add(new Person("jack3","4444")); 
persons.add(new Person("jack4","5555")); 
//下面两行代码是将集合放入栈上下文中
//ActionContext.getContext().put("personList", personList); 
//ActionContext.getContext().put("persons", persons); 
return Action.SUCCESS; 
} 
}