将Java的List结构通过GSON库转换为JSON的方法示例

发现了google的gson，因为之前对于protocolbuf有一些了解，带着一些好奇心，我开始使用了gson。
GitHub主页：https://github.com/google/gson
经过比较，gson和其他现有java json类库最大的不同时gson需要序列化得实体类不需要使用annotation来标识需要序列化得字段，同时gson又可以通过使用annotation来灵活配置需要序列化的字段。
将List或者Map转换成json非常简单：

public String getJsonData(List<?> list) {
  Gson gson = new Gson();
  String jsonstring = gson.toJson(list);
  return jsonstring;
}

下面我们会有详细的例子。

示例
简单对象转化和带泛型的List转化：

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] 

  }
}

执行结果:

----------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]