Struts2中运用OGNL表达式投影（过滤）集合 _Web前端

Struts2中使用OGNL表达式投影（过滤）集合

2010-01-31 20:42

1.集合的投影（过滤）有以下三种方式：
a.“?#”：投影（过滤）所有符合条件的集合，如：users.{?#this.age > 19}；
b.“^#”：投影（过滤）第一个符合条件的元素，如：users.{^#this.age > 19}；
c.“$#”：投影（过滤）最后一个符合条件的元素，如：users.{$#this.age > 19} 。
2.“this”表示集合中的元素；
3.投影（过滤）操作返回的是一个集合，可以使用索引取得集合中指定的元素，如：users.{?#this.age > 19}[0]。

实例：

web.xml:

<?xml version="1.0" encoding="UTF-8"?>
<web-app version="2.5"
xmlns=" http://java.sun.com/xml/ns/javaee "
xmlns:xsi=" http://www.w3.org/2001/XMLSchema-instance "
xsi:schemaLocation=" http://java.sun.com/xml/ns/javaee
http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd ">
<welcome-file-list>
<welcome-file>hello.jsp</welcome-file>
</welcome-file-list>
<filter>
<filter-name>struts2</filter-name>
<filter-class>org.apache.struts2.dispatcher.ng.filter.StrutsPrepareAndExecuteFilter</filter-class>
</filter>
<filter-mapping>
<filter-name>struts2</filter-name>
<url-pattern>/*</url-pattern>
</filter-mapping>
</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 ">

<package name="default" namespace="/" extends="struts-default">
??? <default-action-ref name="index" />
??? <action name="index">
??????? <result type="redirectAction">
??????????? <param name="actionName">HelloWorld</param>
??????????? <param name="namespace">/example</param>
??????? </result>
??? </action>
</package>
-->

<constant name="struts.devMode" value="true" />
<constant name="struts.i18n.encoding" value="GBK" />
<package name="user" namespace="/" extends="struts-default">
??? <action name="user" class="cn.edu.ahau.mgc.struts2.action.UserAction">
??????? <result>/addSuccess.jsp</result>
??? </action>
</package>
</struts>

UserAction.java:

package cn.edu.ahau.mgc.struts2.action;

import java.util.ArrayList;
import java.util.HashMap;
import java.util.HashSet;
import java.util.List;
import java.util.Map;
import java.util.Set;

import cn.edu.ahau.mgc.struts2.model.User;

import com.opensymphony.xwork2.ActionSupport;

public class UserAction extends ActionSupport {

private String userName;

private User user;

private List<User> users = new ArrayList<User>();

private Set<User> usersSet = new HashSet<User>();

private Map<String, User> usersMap = new HashMap<String, User>();

public UserAction() {
??? users.add(new User("1", 19));
??? users.add(new User("2", 20));
??? users.add(new User("3", 21));

??? usersSet.add(new User("1", 19));
??? usersSet.add(new User("2", 20));
??? usersSet.add(new User("3", 21));

??? usersMap.put("u1", new User("1", 19));
??? usersMap.put("u2", new User("2", 20));
??? usersMap.put("u3", new User("3", 21));
}

public String execute() {
??? return SUCCESS;
}

public String getUserName() {
??? return this.userName;
}

public void setUserName(String userName) {
??? this.userName = userName;
}

public User getUser() {
??? return user;
}

public void setUser(User user) {
??? this.user = user;
}

public String test() {
??? return "Action Method";
}

public List<User> getUsers() {
??? return users;
}

public void setUsers(List<User> users) {
??? this.users = users;
}

public Set<User> getUsersSet() {
??? return usersSet;
}

public void setUsersSet(Set<User> usersSet) {
??? this.usersSet = usersSet;
}

public Map<String, User> getUsersMap() {
??? return usersMap;
}

public void setUsersMap(Map<String, User> usersMap) {
??? this.usersMap = usersMap;
}

}

User.java:

package cn.edu.ahau.mgc.struts2.model;

public class User {

private String userName;

private int age;

private User firend;

public User() {
???
}

public User(String userName, int age) {
??? super();
??? this.userName = userName;
??? this.age = age;
}

public User getFirend() {
??? return firend;
}

public void setFirend(User firend) {
??? this.firend = firend;
}

public String getUserName() {
??? return this.userName;
}

public void setUserName(String userName) {
??? this.userName = userName;
}

@Override
public String toString() {
??? return "User(" + this.userName + ", " + this.age + ")";
}

public String hello() {
??? return "Hello World!";
}

public int getAge() {
??? return age;
}

public void setAge(int age) {
??? this.age = age;
}

}

index.jsp:

<%@ page language="java" pageEncoding="GB18030"%>
<%
String path = request.getContextPath();
String basePath = request.getScheme()+"://"+request.getServerName()+":"+request.getServerPort()+path+"/";
%>

<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
<head>
<base href="<%=basePath%>">

<title>ResultParam</title>
<meta http-equiv="pragma" content="no-cache">
<meta http-equiv="cache-control" content="no-cache">
<meta http-equiv="expires" content="0">???
<meta http-equiv="keywords" content="keyword1,keyword2,keyword3">
<meta http-equiv="description" content="This is my page">

</head>

addSuccess.jsp:

<%@ page language="java" pageEncoding="GB18030"%>
<%@ taglib uri="/struts-tags" prefix="s" %>
<%
String path = request.getContextPath();
String basePath = request.getScheme()+"://"+request.getServerName()+":"+request.getServerPort()+path+"/";
%>

<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
<head>
<base href="<%=basePath%>">

<title>Dynamic</title>
<meta http-equiv="pragma" content="no-cache">
<meta http-equiv="cache-control" content="no-cache">
<meta http-equiv="expires" content="0">???
<meta http-equiv="keywords" content="keyword1,keyword2,keyword3">
<meta http-equiv="description" content="This is my page">

</head>

<body>
User Add Success! 
投影（过滤）所有符合条件的集合：users.{?#this.age > 19} --> <s:property value="users.{?#this.age > 19}" /> 
投影（过滤）所有符合条件的集合中指定的元素：users.{?#this.age > 19}[0] --> <s:property value="users.{?#this.age > 19}[0]" /> 
投影（过滤）第一个符合条件的元素：users.{^#this.age > 19} --> <s:property value="users.{^#this.age > 19}" /> 
投影（过滤）最后一个符合条件的元素：users.{$#this.age > 19} --> <s:property value="users.{$#this.age > 19}" /> 
<s:debug></s:debug>
</body>
</html>