Gson 是 Google 提供的用來在 Java 物件和 JSON 資料之間進行對映的 Java 類庫。可以將一個 JSON 字串轉成一個 Java 物件，或者反過來。

實體類:

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 + "]";
	}

}

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("----------簡單物件之間的轉化-------------");
		// 簡單的bean轉為json
		String s1 = gson.toJson(student1);
		System.out.println("簡單Bean轉化為Json===" + s1);

		// json轉為簡單Bean
		Student student = gson.fromJson(s1, Student.class);
		System.out.println("Json轉為簡單Bean===" + student);
		// 結果:
		// 簡單Bean轉化為Json==={"id":1,"name":"李坤","birthDay":"Jun 22, 2012 8:27:52 AM"}
		// Json轉為簡單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("曹貴生");
		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("----------帶泛型的List之間的轉化-------------");
		// 帶泛型的list轉化為json
		String s2 = gson.toJson(list);
		System.out.println("帶泛型的list轉化為json==" + s2);

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

		// 結果:
		// 帶泛型的list轉化為json==[{"id":1,"name":"李坤","birthDay":"Jun 22, 2012 8:28:52 AM"},{"id":2,"name":"曹貴生","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=曹貴生]
		// Student [birthDay=Fri Jun 22 08:28:52 CST 2012, id=3, name=柳波]

	}
}
 

----------簡單物件之間的轉化-------------
簡單Bean轉化為Json==={"id":1,"name":"李坤","birthDay":"Jun 22, 2012 9:10:31 PM"}
Json轉為簡單Bean===Student [birthDay=Fri Jun 22 21:10:31 CST 2012, id=1, name=李坤]
----------帶泛型的List之間的轉化-------------
帶泛型的list轉化為json==[{"id":1,"name":"李坤","birthDay":"Jun 22, 2012 9:10:31 PM"},{"id":2,"name":"曹貴生","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=曹貴生]
Student [birthDay=Fri Jun 22 21:10:31 CST 2012, id=3, name=柳波]