gson java对象与json转换

 

一. Gson 是 Google 提供的用来在 Java 对象和 JSON 数据之间进行映射的 Java 类库。可以将一个 JSON 字符串转成一个 Java 对象，或者反过来。

Gson里最重要的对象有2个Gson 和 GsonBuilder。

Gson有2个最基本的方法

1) toJson() – 转换java 对象到JSON

2) fromJson() – 转换JSON到java对象

二. 几个简单的例子。

 exp1（一个简单对象object和json之间的转换）：

public class MsgInfo2 {
    private String message;
    private String flag;
    public String getMessage() {
        return message;
    }
    public void setMessage(String message) {
        this.message = message;
    }
    public String getFlag() {
        return flag;
    }
    public void setFlag(String flag) {
        this.flag = flag;
    }

}

public class Test1 {

    public static void main(String[] args) {
        MsgInfo2 m2 = new MsgInfo2();
        m2.setFlag("00");
        m2.setMessage("message");
        tojson(m2);

        String json = "{'message':'message1','flag':'00'}";
        toObject(json);
    }

    public static void tojson(MsgInfo2 m) {
        // 将对象编译成json
        Gson gson = new Gson();
        String result = gson.toJson(m);
        System.out.println(result);
        // 输出：{"message":"message","flag":"00"}
    }

    public static void toObject(String m) {
        // 将json编译成对象
        Gson gson = new Gson();
        MsgInfo2 msg = gson.fromJson(m, MsgInfo2.class);
        System.out.println(msg.getFlag());//输出:00
        System.out.println(msg.getMessage());//输出：message1
    }
}

 exp2（一个复杂对象object和json之间的转换）：

json的结构如下：

{
      "org":     {
          "orgId": "orgId",
          "orgName": "orgName"
      },
      "biz":     [
                  {
              "appcode": 55,

              "subscode": "subscode0"
          },
                  {
              "appcode": 66,
              "subscode": "subscode1"
          }
      ]
  }

public class ComOpen {
    private Org org;
    private List<BizObject> biz;
    public Org getOrg() {
        return org;
    }
    public void setOrg(Org org) {
        this.org = org;
    }
    public List<BizObject> getBiz() {
        return biz;
    }
    public void setBiz(List<BizObject> biz) {
        this.biz = biz;
    }
}

public class Org {
    private String orgId;
    private String orgName;
    public String getOrgId() {
        return orgId;
    }
    public void setOrgId(String orgId) {
        this.orgId = orgId;
    }
    public String getOrgName() {
        return orgName;
    }
    public void setOrgName(String orgName) {
        this.orgName = orgName;
    }
}

public class BizObject {
    private int appcode;
    private String subscode;
    public String getSubscode() {
        return subscode;
    }
    public void setSubscode(String subscode) {
        this.subscode = subscode;
    }
    public int getAppcode() {
        return appcode;
    }
    public void setAppcode(int appcode) {
        this.appcode = appcode;
    }
}

/**
 * 测试java对象和json转换
 *
 * @author yangliang
 * @version 1.0
 * @created 2011-10-11 下午03:14:04
 * @history
 * @see
 */
public class Test2 {
    public static void main(String[] args) {
        toJson();
        toObject();
    }
    public static void toJson(){
        ComOpen como = new ComOpen();
        Org org = new Org();
        org.setOrgId("orgId");
        org.setOrgName("orgName");
        como.setOrg(org);
        List<BizObject> biz = new ArrayList<BizObject>();
        BizObject bizObject = new BizObject();
        bizObject.setAppcode(55);
        bizObject.setSubscode("subscode0");
        BizObject bizObject1 = new BizObject();
        bizObject1.setAppcode(66);
        bizObject1.setSubscode("subscode1");
        biz.add(bizObject);
        biz.add(bizObject1);
        como.setBiz(biz);
        Gson gson=new GsonBuilder().create();
        String result = gson.toJson(como);
        System.out.println(result);
        //输出{"org":{"orgId":"orgId","orgName":"orgName"},"biz":接下行
        //[{"appcode":55,"subscode":"subscode0"},{"appcode":66,"subscode":"subscode1"}]}
    }

    public static void toObject(){
        String json = "{'org':{'orgId':'orgId','orgName':'orgName'},'biz':" +
         "[{'appcode':55,'subscode':'subscode0'},{'appcode':66,'subscode':'subscode1'}]}";
        Gson gson=new Gson();
        ComOpen  m3 = gson.fromJson(json, ComOpen.class);
        System.out.println(m3.getBiz().size());//2
        System.out.println("orgId："+m3.getOrg().getOrgId());//orgId：orgId
        System.out.println("appcode："+ m3.getBiz().get(0).getAppcode());//appcode：55
    }
}

 三.其他可参考gson教程和官方帮助文档