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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] 

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