Struts2之Ognl-白红宇

Struts2之Ognl

阅读量：5278 次

发布时间：2019-06-14

本文共 5098 字，大约阅读时间需要 16 分钟。

上一篇算是看着学习了下ValueStack、ActionContext,如果还没明白他们之间是怎么回事，没关系，可以先学下Ognl，然后再回头看前面的可能就比较好理解了,我昨天也是一头雾水，现在把Ognl的学习了下，慢慢的有了感觉。

一、概念

OGNL表达式是(Object-Graph Navigation Language)是对象图形化导航语言。OGNL是一个开源的项目，struts2中默认使用OGNL表达式语言来显示数据。与serlvet中的el表达式的作用是一样的。OGNL表达式有下面以下特点：

1.支持对象方法调用，例如：objName.methodName();

2.支持类静态的方法调用和值访问，表达式的格式为

@[类全名（包括包路经）]

@[方法名 | 值名]

例如：

@java.lang.String@format('foo%s','bar')

@tutorial.MyConstant@APP_NAME；

3支持赋值操作和表达式串联，例如：

price=100, discount=0.8, calculatePrice()，这个表达式会返回80；

4.访问OGNL上下文（OGNL context）和ActionContext

5.操作集合对象

二、实践

这里定义了Address、User类

package com.cyw.test;public class Address {    public Address(String city, String street) {        super();        this.city = city;        this.street = street;    }    private String city;    public String getCity() {        return city;    }    public void setCity(String city) {        this.city = city;    }    public String getStreet() {        return street;    }    public void setStreet(String street) {        this.street = street;    }    private String street;}

View Code

package com.cyw.test;import java.util.Date;public class User {    private String name;    private int age;    private Date birthDay;    private Address address;    public User(String name, int age, Date birthDay, Address address) {        super();        this.name = name;        this.age = age;        this.birthDay = birthDay;        this.address = address;    }    public Address getAddress() {        return address;    }    public void setAddress(Address address) {        this.address = address;    }    public Date getBirthDay() {        return birthDay;    }    public void setBirthDay(Date birthDay) {        this.birthDay = birthDay;    }    public String getName() {        return name;    }    public void setName(String name) {        this.name = name;    }    public int getAge() {        return age;    }    public void setAge(int age) {        this.age = age;    }}

View Code

Address address=new Address("深圳市","坂田新天下");        User user=new User("cyw",25,new Date(),address);        //获取javabean的属性值        String name=(String) Ognl.getValue("name", new HashMap(), user)    ;        System.out.println(name);        //获取对象的属性值        String city=(String) Ognl.getValue("address.city", new HashMap(), user)    ;        System.out.println(city);        //修改属性值        name=(String) Ognl.getValue("name='cuiyw'", new HashMap(), user)    ;        System.out.println(name);        Ognl.getValue("setName('cyw')", new HashMap(), user)    ;        //调用对象方法        name=(String) Ognl.getValue("getName()", new HashMap(), user)    ;        System.out.println(name);                //访问静态方法 格式:@包名+类名@静态方法        UUID randomUUID=(UUID)Ognl.getValue("@java.util.UUID@randomUUID()", new HashMap(), user)    ;        System.out.println(randomUUID.toString());        //访问静态变量格式:@包名+类名@静态变量名        double pi=(double)Ognl.getValue("@java.lang.Math@PI", new HashMap(), user);        System.out.println(pi);                //操作索引数组元素        int []array={1,2,3,4};        int first= (int) Ognl.getValue("[0]", new HashMap(), array);        System.out.println(first);                //操作集合        List
     
       userList=new ArrayList
      
       ();        userList.add(user);        name = (String) Ognl.getValue("[0].name", new HashMap(), userList);        System.out.println(name);                //操作Map        Map
       
         map=new HashMap
        
         ();        map.put("key1", "cui");        map.put("key2", "yan");        name = (String) Ognl.getValue("key1", new HashMap(), map);        System.out.println(name);        //创建list        List
         
           list=(List
          
           )Ognl.getValue("{'cui','yan'}", new HashMap(), new Object()); System.out.println(list.get(0)); //创建map map=(Map)Ognl.getValue("#{'name':'cui','name2':'yan'}", new HashMap(), new Object()); System.out.println(map.get("name"));