Struts2(九)OGNL标签一与Struts2标签

一、什么是OGNL

Object Graph Navigation Language对象图导航语言。

是Struts2默认的表达式语言，开源，功能更强大。和EL表达式有点相似

存取对象的属性，调用对象的方法

访问静态方法，静态属性

访问值栈及Stack Context

支持赋值、运算操作、字段类型转化等。

二、简单例子

导入所需要的struts2的包

web.xml增加struts2过滤器

<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>

实体类

package com.pb.entity;

/*

 * 街道实体类

 */

public class Street {

    private int streetId;            //街道ID

    private String streetName;    //街道名称

    public Street() {

        super();

        // TODO Auto-generated constructor stub

    }

    public Street(int streetId, String streetName) {

        super();

        this.streetId = streetId;

        this.streetName = streetName;

    }

    public int getStreetId() {

        return streetId;

    }

    public String getStreetName() {

        return streetName;

    }

    public void setStreetId(int streetId) {

        this.streetId = streetId;

    }

    public void setStreetName(String streetName) {

        this.streetName = streetName;

    }

}

package com.pb.entity;

/*

 * 房子实体类

 */

public class Hourse {

    private int hourseId;  //房屋ID

    private String hourseName;    //房屋名称

    private Street street;            //房屋所在街道

    public Hourse() {

        super();

        // TODO Auto-generated constructor stub

    }

    public Hourse(int hourseId, String hourseName, Street street) {

        super();

        this.hourseId = hourseId;

        this.hourseName = hourseName;

        this.street = street;

    }

    public int getHourseId() {

        return hourseId;

    }

    public String getHourseName() {

        return hourseName;

    }

    public Street getStreet() {

        return street;

    }

    public void setHourseId(int hourseId) {

        this.hourseId = hourseId;

    }

    public void setHourseName(String hourseName) {

        this.hourseName = hourseName;

    }

    public void setStreet(Street street) {

        this.street = street;

    }

}

HourseAction

package com.pb.web.action;

import com.opensymphony.xwork2.ActionSupport;

import com.pb.entity.Hourse;

import com.pb.entity.Street;

public class HourseAction extends ActionSupport {

        private Hourse hourse;

        @Override

        public String execute() throws Exception {

            //声明街道对象

            Street street =new Street(001,"南新路");

            hourse=new Hourse(11,"一房一厅",street);

            return SUCCESS;

        }

        public Hourse getHourse() {

            return hourse;

        }

        public void setHourse(Hourse hourse) {

            this.hourse = hourse;

        }

}

struts.xml

<?xml version="1.0" encoding="UTF-8" ?>

<!DOCTYPE struts PUBLIC

    "-//Apache Software Foundation//DTD Struts Configuration 2.3//EN"

    "http://struts.apache.org/dtds/struts-2.3.dtd">

<struts>

    <constant name="struts.enable.DynamicMethodInvocation" value="false" />

    <constant name="struts.devMode" value="true" />

    <package name="default" namespace="/" extends="struts-default">

    <action name="hourse" class="com.pb.web.action.HourseAction">

    <result name="success">

    /ognl1.jsp

    </result>

    </action>

    </package>

</struts>

ognl1.jsp

<%@ page language="java" contentType="text/html; charset=UTF-8"

    pageEncoding="UTF-8"%>

<%@ taglib prefix="s" uri="/struts-tags" %>

<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">

<html>

<head>

<meta http-equiv="Content-Type" content="text/html; charset=UTF-8">

<title>OGNL一</title>

</head>

<body>

房屋的名称：<s:property value="hourse.hourseName"/>

房屋的街道名称:<s:property value="hourse.street.streetName"/>

<s:debug/>

</body>

</html>

在地址栏中输入

http://localhost:8080/OGNLDemo1/hourse.action

发生页面跳转，并取出其中的值

三、访问值栈中的值

四、访问List 、Map、Set

struts.xml

    <action name="ognl" class="com.pb.web.action.OgnlAction">

    <result name="success">

    /ognllist.jsp

    </result>

    </action>

ognllistAction

package com.pb.web.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 com.opensymphony.xwork2.ActionSupport;

import com.pb.entity.Street;

public class OgnlAction extends ActionSupport {

    /**

     *

     */

    private static final long serialVersionUID = 1L;

    private List<Street> streetList;

    private Map<String, Street> streetMap;

    private Set <Street> streetSet;

    public List<Street> getStreetList() {

        return streetList;

    }

    public void setStreetList(List<Street> streetList) {

        this.streetList = streetList;

    }

    public Map<String, Street> getStreetMap() {

        return streetMap;

    }

    public void setStreetMap(Map<String, Street> streetMap) {

        this.streetMap = streetMap;

    }

    public Set<Street> getStreetSet() {

        return streetSet;

    }

    public void setStreetSet(Set<Street> streetSet) {

        this.streetSet = streetSet;

    }

    @Override

    public String execute() throws Exception {

        streetList=new ArrayList<Street>();

        streetList.add(new Street(1, "高新南一路"));

        streetList.add(new Street(2, "高新南二路"));

        streetList.add(new Street(3, "高新南三路"));

        streetMap=new HashMap<String,Street>();

        streetMap.put("k1", new Street(4, "高新南四路"));

        streetMap.put("k2", new Street(5, "高新南五路"));

        streetMap.put("k3", new Street(6, "高新南六路"));

        streetSet =new HashSet<Street>();

        streetSet.add(new Street(7, "高新南七路"));

        streetSet.add(new Street(8, "高新南八路"));

        streetSet.add(new Street(9, "高新南九路"));

        return SUCCESS;

    }

}

jsp页页

<%@ page language="java" contentType="text/html; charset=UTF-8"

    pageEncoding="UTF-8"%>

<%@ taglib prefix="s" uri="/struts-tags" %>

<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">

<html>

<head>

<meta http-equiv="Content-Type" content="text/html; charset=UTF-8">

<title>OGNL一</title>

</head>

<body>

<h1>List</h1>

访问List<s:property value="streetList" /><br/>

访问List中第一个元素:<s:property value="streetList[0].streetName" /><br/>

List中的大小:<s:property value="streetList.size()" /><br/>

List是否为空:<s:property value="streetList.isEmpty()" /><br/>

自定义集合List:<s:property value="{1,2,3,4,5}" /><br/>

自定义集合List访问第一个元素:<s:property value="{1,2,3,4,5}[0]" /><br/>

<hr/>

<h1>Map</h1>

访问Map<s:property value="streetMap" /><br/>

访问Map中第一个元素:<s:property value="streetMap['k1'].streetName" />|<s:property value="streetMap.k1.streetName"/><br/>

访问Map 中所有key:<s:property value="streetMap.keys" /><br/>

访问Map 中所有values:<s:property value="streetMap.values" /><br/>

Map中的大小:<s:property value="streetMap.size()" /><br/>

Map是否为空:<s:property value="streetMap.isEmpty()" /><br/>

自定义集合Map:<s:property value="#{'k1':'v1','k2':'v2','k3':'v3'}" /><br/>

自定义集合Mapt访问第一个元素:<s:property value="#{'k1':'v1','k2':'v2','k3':'v3'}['k1']" />|<s:property value="#{'k1':'v1','k2':'v2','k3':'v3'}.k1" />

<br/>

<hr/>

<h1>Set</h1>

访问Set<s:property value="streetSet" /><br/>

访问Set中第一个元素:<s:property value="streetSet.toArray()[0].streetName" />|<s:property value="streetSet.toArray()[0].streetName"/><br/>

Set中的大小:<s:property value="streetSet.size()" /><br/>

Set是否为空:<s:property value="streetSet.isEmpty()" /><br/>

<hr/>

<s:debug/>

</body>

</html>

在页面中输入：http://localhost:8080/OGNLDemo1/ognl.action访问

五、访问静态方法和投影

5.1、访问静态方法和静态属性

package com.pb.demo;

public class Demo {

public final static String STR="STATIC STR";

public static String staticMethod(){

String info="Demo Static Method";

return info;

}

}

在ognl2.jsp 中可以通过如下代码访问该类的静态属性以及静态方法：

<%@taglib uri="/struts-tags" prefix="s"%>

<html>

<head>

<meta http-equiv="Content-Type" content="text/html; charset=UTF-8">

<title>Insert title here</title>

</head>

<body>

<h1>OGNL 对象图导航语言</h1>

调用静态方法：<s:property value="@com.pb.demo.Demo@staticMethod()"/> <br>

调用静态常量：<s:property value="@com.pb.demo.Demo@STR"/>

<s:debug/>

</body>

</html>

struts.xml

//开启静态方法

<constant name="struts.ognl.allowStaticMethodAccess" value="true" />

其中<constant>常量你可以去default.properties 文件中查找并复制使用。

5.2、访问投影

选择就是过滤满足选择条件的集合元素。选择操作的语法是：collection.{X YYY},其中X
是一个选择操作符，后面则是选择用的逻辑表达式，而选择操作符有三种：
?选择满足条件的所有元素
^选择满足条件的第一个元素
$选择满足条件的最后一个元素

package com.pb.entity;

/*

 * 用户名

 */

public class User {

    private Integer age;

    private String name;

    private String pasword;

    public User() {

        super();

        // TODO Auto-generated constructor stub

    }

    public User(String name, String pasword, Integer age) {

        super();

        this.name = name;

        this.pasword = pasword;

        this.age = age;

    }

    public Integer getAge() {

        return age;

    }

    public String getName() {

        return name;

    }

    public String getPasword() {

        return pasword;

    }

    public void setAge(Integer age) {

        this.age = age;

    }

    public void setName(String name) {

        this.name = name;

    }

    public void setPasword(String pasword) {

        this.pasword = pasword;

    }

}

package com.pb.web.action;

import java.util.ArrayList;

import java.util.List;

import com.opensymphony.xwork2.ActionSupport;

import com.pb.entity.User;

public class UserAction extends ActionSupport {

    private User user;

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

    public User getUser() {

        return user;

    }

    public void setUser(User user) {

        this.user = user;

    }

    public List<User> getUsers() {

        return users;

    }

    public void setUsers(List<User> users) {

        this.users = users;

    }

    @Override

    public String execute() throws Exception {

        User u1 = new User();

        u1.setName("zhangsan");

        u1.setPasword("zhangsan");

        u1.setAge(10);

        this.users.add(u1);

        User u2 = new User();

        u2.setName("lisi");

        u2.setPasword("lisi");

        u2.setAge(23);

        this.users.add(u2);

        User u3 = new User();

        u3.setName("wangwu");

        u3.setPasword("wangwu");

        u3.setAge(22);

        this.users.add(u3);

        return SUCCESS;

    }

}

struts.xml

<package name="default" namespace="/" extends="struts-default">

    <action name="login" class="com.pb.web.action.UserAction">

    <result name="success">

    /ognl.jsp

    </result>

    </action>

    </package>

jsp页面

<%@taglib prefix="s" uri="/struts-tags" %>

<!-- 年龄大于18 的所有用户的姓名 -->

集合元素过滤：<s:property value="users.{?#this.age>18}.{name}"/><br/>

<!-- 年龄大于18 的所有用户的第一个用户的姓名 -->

集合元素过滤：<s:property value="users.{^#this.age>18}.{name}"/><br/>

<!-- 年龄大于18 的所有用户的最后一个用户的姓名 -->

集合元素过滤：<s:property value="users.{$#this.age>18}.{name}"/><br/>