Json转换利器Gson之实例一-简单对象转化和带泛型的List转化

Gson 是 Google 提供的用来在 Java 对象和 JSON 数据之间进行映射的 Java 类库。可以将一个 JSON 字符串转成一个 Java 对象，或者反过来。

 

Gson里最重要的对象有2个Gson 和 GsonBuilder

 

Gson有2个最基本的方法
1) toJson() – 转换java 对象到JSON
2) fromJson() – 转换JSON到java对象

实体类:

public class Student {
    private int id;
    private String name;
    private Date birthDay;

    public int getId() {
        return id;
    }

    public void setId(int id) {
        this.id = id;
    }

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public Date getBirthDay() {
        return birthDay;
    }

    public void setBirthDay(Date birthDay) {
        this.birthDay = birthDay;
    }

    @Override
    public String toString() {
        return "Student [birthDay=" + birthDay + ", id=" + id + ", name="
                + name + "]";
    }

}

测试类:

 

import java.util.ArrayList;
import java.util.Date;
import java.util.List;

import com.google.gson.Gson;
import com.google.gson.reflect.TypeToken;

public class GsonTest1 {

    public static void main(String[] args) {
        Gson gson = new Gson();

        Student student1 = new Student();
        student1.setId(1);
        student1.setName("李坤");
        student1.setBirthDay(new Date());

        // //////////////////////////////////////////////////////////
        System.out.println("----------简单对象之间的转化-------------");
        // 简单的bean转为json
        String s1 = gson.toJson(student1);
        System.out.println("简单Bean转化为Json===" + s1);

        // json转为简单Bean
        Student student = gson.fromJson(s1, Student.class);
        System.out.println("Json转为简单Bean===" + student);
        // 结果:
        // 简单Bean转化为Json==={"id":1,"name":"李坤","birthDay":"Jun 22, 2012 8:27:52 AM"}
        // Json转为简单Bean===Student [birthDay=Fri Jun 22 08:27:52 CST 2012, id=1,
        // name=李坤]
        // //////////////////////////////////////////////////////////

        Student student2 = new Student();
        student2.setId(2);
        student2.setName("曹贵生");
        student2.setBirthDay(new Date());

        Student student3 = new Student();
        student3.setId(3);
        student3.setName("柳波");
        student3.setBirthDay(new Date());

        List<Student> list = new ArrayList<Student>();
        list.add(student1);
        list.add(student2);
        list.add(student3);

        System.out.println("----------带泛型的List之间的转化-------------");
        // 带泛型的list转化为json
        String s2 = gson.toJson(list);
        System.out.println("带泛型的list转化为json==" + s2);

        // json转为带泛型的list
        List<Student> retList = gson.fromJson(s2,
                new TypeToken<List<Student>>() {
                }.getType());
        for (Student stu : retList) {
            System.out.println(stu);
        }

        // 结果:
        // 带泛型的list转化为json== [{"id":1,"name":"李坤","birthDay":"Jun 22, 2012 8:28:52 AM"}, {"id":2,"name":"曹贵生","birthDay":"Jun 22, 2012 8:28:52 AM"}, {"id":3,"name":"柳波","birthDay":"Jun 22, 2012 8:28:52 AM"}]
        // Student [birthDay=Fri Jun 22 08:28:52 CST 2012, id=1, name=李坤]
        // Student [birthDay=Fri Jun 22 08:28:52 CST 2012, id=2, name=曹贵生]
        // Student [birthDay=Fri Jun 22 08:28:52 CST 2012, id=3, name=柳波]

    }
}

 可以看到上面的代码使用了TypeToken，它是gson提供的数据类型转换器，可以支持各种数据集合类型转换。

----------简单对象之间的转化-------------
简单Bean转化为Json==={"id":1,"name":"李坤","birthDay":"Jun 22, 2012 9:10:31 PM"}
Json转为简单Bean===Student [birthDay=Fri Jun 22 21:10:31 CST 2012, id=1, name=李坤]
----------带泛型的List之间的转化-------------
带 泛型的list转化为json==[{"id":1,"name":"李 坤","birthDay":"Jun 22, 2012 9:10:31 PM"},{"id":2,"name":"曹贵 生","birthDay":"Jun 22, 2012 9:10:31 PM"},{"id":3,"name":"柳 波","birthDay":"Jun 22, 2012 9:10:31 PM"}]
Student [birthDay=Fri Jun 22 21:10:31 CST 2012, id=1, name=李坤]
Student [birthDay=Fri Jun 22 21:10:31 CST 2012, id=2, name=曹贵生]
Student [birthDay=Fri Jun 22 21:10:31 CST 2012, id=3, name=柳波]