Gson

主要介绍Gson用法

<dependency>
    <groupId>com.google.code.gson</groupId>
    <artifactId>gson</artifactId>
    <version>2.8.0</version>
</dependency>

json数据

{
  "msg": "true",
  "result": [
    {
      "attr": "0.0",
      "id": "100.0",
      "product": "0",
      "status": "297.086",
      "updateTime": "20170103"
    },
    {
      "attr": "0.0",
      "id": "100.0",
      "product": "0",
      "status": "162.678"
    }
  ],
  "total": 60,
  "success": true
}

对象

    @Data
    public static class RestResponse2 {
        private Object msg;
        private List<Product> result;
        private Object total;
        private Object success;
    }
    @Data
    public static class Product {
        private String id;
        private String product;
        private String unit;
        private String attr;
        private String status;
        private Date updateTime;
    }

1、复杂类型反序列化

根据key映射对象中的属性，封装对象

RestResponse2 obj = new GsonBuilder().create().fromJson(json, RestResponse2.class);
System.out.println(obj);

结果：

GsonTest.RestResponse2(msg=true, result=[GsonTest.Product(id=100.0, product=0, unit=null, attr=0.0, status=297.086, updateTime=Tue Jan 03 00:00:00 CST 2017), GsonTest.Product(id=100.0, product=0, unit=null, attr=0.0, status=162.678, updateTime=null)], total=60.0, success=true)

数组也会自动反序列化，时间也能解析，常用时间字符串格式能解析，最好指定时间格式化

2、存在时间的序列化与反序列化

    @Test
    public void gsonWithDate() {

        String json = "{\"msg\":\"true\",\"result\":[{\"attr\":\"0.0\",\"id\":\"100.0\",\"product\":\"0\",\"status\":\"297.086\",\"updateTime\":\"20170103091145\"},{\"attr\":\"0.0\",\"id\":\"100.0\",\"product\":\"0\",\"status\":\"162.678\"}],\"total\":60,\"success\":true}";
        Gson gson = new GsonBuilder().setDateFormat("yyyyMMddhhmmss").create();
        RestResponse2 obj = gson.fromJson(json, RestResponse2.class);
        System.out.println(obj);

        //对象转json
        String obj2Json = gson.toJson(obj);
        System.out.println(obj2Json);
    }

结果：时间正常解析

GsonTest.RestResponse2(msg=true, result=[GsonTest.Product(id=100.0, product=0, unit=null, attr=0.0, status=297.086, updateTime=Tue Jan 03 00:00:00 CST 2017), GsonTest.Product(id=100.0, product=0, unit=null, attr=0.0, status=162.678, updateTime=null)], total=60.0, success=true)
{"msg":"true","result":[{"id":"100.0","product":"0","attr":"0.0","status":"297.086","updateTime":"20170103"},{"id":"100.0","product":"0","attr":"0.0","status":"162.678"}],"total":60.0,"success":true}

备注：gson能自动处理一些常用格式时间字符串yyyyMMdd、yyyy-MM-dd、yyyy-MM-dd hh:mm:ss

3、将所有属性定义成Object类型，如果json中还有json数组会转成ArrayList，具体类型LinkedTreeMap

    @Data
    public static class RestResponse {
        private Object msg;
        private Object result;
        private Object total;
        private Object success;
    }

 

    @Test
    public void gsonWithObjectArray() {

        String json = "{\"msg\":\"true\",\"result\":[{\"attr\":\"0.0\",\"id\":\"100.0\",\"product\":\"0\",\"status\":\"297.086\",\"updateTime\":\"20170103\"},{\"attr\":\"0.0\",\"id\":\"100.0\",\"product\":\"0\",\"status\":\"162.678\"}],\"total\":60,\"success\":true}";
        RestResponse obj = new GsonBuilder().create().fromJson(json, RestResponse.class);
        System.out.println(obj);

    }

 内存中预览

或者对象中包含对象，不指定内部对象具体类型，LinkedTreeMap数据类型

    @Test
    public void gsonWithObjInnerObj() {
        String json = "{\"msg\":\"true\",\"result\":{\"attr\":\"0.0\",\"id\":\"100.0\",\"product\":\"0\",\"status\":\"297.086\",\"updateTime\":\"20170103\"},\"total\":60,\"success\":true}";
        RestResponse obj = new GsonBuilder().create().fromJson(json, RestResponse.class);
        System.out.println(obj);
    }

4、如果json串和对象的属性名不一致，可使用别名 如果对象和json 的key不一样，可用注解

json样例：{"biz_data": "test"}

@SerializedName("biz_data")
private BizData bizData;

这样可以反序列化转换到对象，同样是这个注解，序列化成json可得到：{"biz_data": "test"}

5、如果java对象不是规范驼峰命名

    @Data
    public static class RestResponse3 {
        private String Name_OCR;
    }

    @Test
    public void firstCharUp2json() {
        RestResponse3 restResponse3 = new RestResponse3();
        restResponse3.setName_OCR("test_ord");
        String rst = new GsonBuilder().create().toJson(restResponse3);
        System.out.println(rst);
    }

序列化结果 

{"Name_OCR":"test_ord"}