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

       
      
       struts2
        
      
       org.apache.struts2.dispatcher.ng.filter.StrutsPrepareAndExecuteFilter
        
       
       
      
       struts2
        
      
       /*
        
     

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

     
         
          
          
          
           
        
             /ognl1.jsp    
            
           
      
     

ognl1.jsp

<%@ page language="java" contentType="text/html; charset=UTF-8"    pageEncoding="UTF-8"%><%@ taglib prefix="s" uri="/struts-tags" %>
     房屋的名称：
     房屋的街道名称:
     
     

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

         
      
           /ognllist.jsp    
          
     

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
     
       streetList;    private Map
      
        streetMap;    private Set 
       
         streetSet;    public List
        
          getStreetList() {        return streetList;    }    public void setStreetList(List
         
           streetList) {        this.streetList = streetList;    }    public Map
          
            getStreetMap() { return streetMap; } public void setStreetMap(Map
           
             streetMap) { this.streetMap = streetMap; } public Set
            
              getStreetSet() { return streetSet; } public void setStreetSet(Set
             
               streetSet) { this.streetSet = streetSet; } @Override public String execute() throws Exception { streetList=new ArrayList
              
               (); 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
               
                (); 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
                
                 (); 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" %>
     
List
访问List
     
访问List中第一个元素:
     
List中的大小:
     
List是否为空:
     
自定义集合List:
     
自定义集合List访问第一个元素:
     
     
Map
访问Map
     
访问Map中第一个元素:
     |
     
访问Map 中所有key:
     
访问Map 中所有values:
     
Map中的大小:
     
Map是否为空:
     
自定义集合Map:
     
自定义集合Mapt访问第一个元素:
     |
      
     
Set
访问Set
     
访问Set中第一个元素:
     |
     
Set中的大小:
     
Set是否为空:
     
     
     

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"%>
     
OGNL 对象图导航语言
调用静态方法：
      
调用静态常量：
     
     

struts.xml

//开启静态方法
     

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
     
       users=new ArrayList
      
       ();    public User getUser() {        return user;    }    public void setUser(User user) {        this.user = user;    }    public List
       
         getUsers() {        return users;    }    public void setUsers(List
        
          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

           
          
       
            /ognl.jsp    
           
           
     

jsp页面

<%@taglib prefix="s" uri="/struts-tags" %>
     集合元素过滤：
     
     集合元素过滤：
     
     集合元素过滤：