将Java的List结构通过GSON库转换为JSON的方法示例

2019-11-26 14:09:31

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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]

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