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]