GSON详细使用说明

GSON是一个google提供开源类库，可以实现java对象和json字符串的互相转换。Gson（又称Google Gson）是Google公司发布的一个开放源代码的Java库，主要用途为序列化Java对象为JSON字符串，或反序列化JSON字符串成Java对象。

    课下可以看一下json开源组织的网站：

    http://www.json.org/json-zh.html

   

建立java项目，先导入GSON的jar包。为了测试Gson的作用，我们定义两个java类：


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package com.bjsxt.bean;
 
 
public class User {
    private int id;
    private String uname;
    private Address addr;
     
    private int age;
     
     
     
    public int getAge() {
        return age;
    }
    public void setAge(int age) {
        this.age = age;
    }
    public int getId() {
        return id;
    }
    public void setId(int id) {
        this.id = id;
    }
    public String getUname() {
        return uname;
    }
    public void setUname(String uname) {
        this.uname = uname;
    }
    public Address getAddr() {
        return addr;
    }
    public void setAddr(Address addr) {
        this.addr = addr;
    }
    public User(int id, String uname, Address addr) {
        super();
        this.id = id;
        this.uname = uname;
        this.addr = addr;
    }
     
    public User() {
        // TODO Auto-generated constructor stub
    }
}
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package com.bjsxt.bean;
 
public class Address {
    private String country;
    private String city;
    public String getCountry() {
        return country;
    }
    public void setCountry(String country) {
        this.country = country;
    }
    public String getCity() {
        return city;
    }
    public void setCity(String city) {
        this.city = city;
    }
    public Address(String country, String city) {
        super();
        this.country = country;
        this.city = city;
    }
    public Address() {
    }
}


将java对象转成json字符串


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public static void obj2JsonDemo(){
        Address bj = new Address("中国","北京");
        User u = new User(1001, "高淇", bj);
         
        Gson gson = new Gson();
        System.out.println(gson.toJson(u));//{"id":1001,"uname":"高淇","addr":{"country":"中国","city":"北京"}}
    }

结果如下：



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{"id":1001,"uname":"高淇","addr":{"country":"中国","city":"北京"}}


将容器中的对象转成json字符串

 

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public static void list2JsonDemo(){
        Address bj = new Address("中国","北京");
        User u = new User(1001, "高淇", bj);
        Address sh = new Address("中国","上海");
        User u2 = new User(1002, "马士兵", sh);
         
        List list = new ArrayList();
        list.add(u);
        list.add(u2);
         
        Gson gson = new Gson();
        System.out.println(gson.toJson(list));
    }

执行该方法结果如下：



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[
    {"id":1001,"uname":"高淇","addr":{"country":"中国","city":"北京"}},
    {"id":1002,"uname":"马士兵","addr":{"country":"中国","city":"上海"}}
]



JSON字符串转成java对象


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public static void json2Obj(){
        String s1 = "{\"id\":1001,\"uname\":\"高淇\",\"addr\":{\"country\":\"中国\",\"city\":\"北京\"}}";
        Gson gson = new Gson();
        User u = gson.fromJson(s1, User.class);
        System.out.println(u.getUname());
    }



JSON字符串转成容器对象

 

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public static void json2List(){
        String s1 = "[{\"id\":1001,\"uname\":\"高淇\",\"addr\":{\"country\":\"中国\",\"city\":\"北京\"}}," +
                "{\"id\":1002,\"uname\":\"马士兵\",\"addr\":{\"country\":\"中国\",\"city\":\"上海\"}}]";
        Gson gson = new Gson();
        List<User> list = gson.fromJson(s1, new TypeToken<List<User>>(){}.getType());
        System.out.println(list.get(1).getUname());
    }



@Expose注解和@SerializedName注解的使用

 

使用Gson的@Expose注解和@SerializedName ，更加细微控制java对象转成json字符串。

 

@Expose控制是否序列化指定属性

@Expose(serialize=true)

private String uname;

@SerializedName控制java对象属性转成json对象的属性名：

    @SerializedName("年龄")

    private int age;

使用注解定义如下新的java类：

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package com.bjsxt.bean;
 
import com.google.gson.annotations.Expose;
import com.google.gson.annotations.SerializedName;
 
/**
 * 测试使用Gson的@Expose注解和@SerializedName
 * @author dell
 *
 */
public class User2 {
    @Expose(serialize=false)
    private int id;
    @Expose(serialize=true)
    private String uname;
     
     
    @Expose(serialize=true)
    @SerializedName("年龄")
    private int age;
 
    public int getId() {
        return id;
    }
 
    public void setId(int id) {
        this.id = id;
    }
 
    public String getUname() {
        return uname;
    }
 
    public void setUname(String uname) {
        this.uname = uname;
    }
 
 
    public int getAge() {
        return age;
    }
 
    public void setAge(int age) {
        this.age = age;
    }
 
    public User2(int id, String uname, int age) {
        super();
        this.id = id;
        this.uname = uname;
        this.age = age;
    }
     
    public User2() {
        // TODO Auto-generated constructor stub
    }
     
}

测试使用注解转化json字符串：


 

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public static void obj2JsonDemoWithAnnotation(){
    User2 u = new User2(1001, "高淇", 18);
     
    Gson gson = new GsonBuilder().excludeFieldsWithoutExposeAnnotation().create();
    System.out.println(gson.toJson(u));
}

结果：

 

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{"uname":"高淇","年龄":18}

    我们发现，age在json字符串中变成了“年龄”，id由于@Expose(serialize=false)没有在json中生成ID相关的内容。


posted @ 2016-11-15 10:39  hnist_hd  阅读(831)  评论(0)    收藏  举报