Json字符串转换为Java对象和应用(使用fastjson工具类)

红太狼 2024-04-23 02:30 58阅读 0赞

**记录**：468

**场景**：把Json字符串转换为Java对象。Java对象属性包括String、List、Map等类型。

**版本**：JDK 1.8,Spring Boot 2.6.3,fastjson-2.0.33。

**JSON**：JavaScript Object Notation(JavaScript 对象表示法)。

**JSON语法规则**：数据由名称/值对组成。数据由逗号","分隔。使用斜杆\\来转义字符。大括号\{\}保存对象。中括号\[\]保存数组(或者List类型)，数组可以包含多个对象。

**1.JSON字符串转换为JSONObject**

**1.1JSON字符串**

{
      "cityDescribe": "宁波是港口城市",
      "cityId": 2023062802,
      "cityName": "宁波",
      "updateTime": "2023-07-16 13:15:40"
    }

**1.2转换代码**

public static void f1() {
      String jsonStr = "{\n" +
              "  \"cityDescribe\": \"宁波是港口城市\",\n" +
              "  \"cityId\": 2023062802,\n" +
              "  \"cityName\": \"宁波\",\n" +
              "  \"updateTime\": \"2023-07-16 13:15:40\"\n" +
              "}";
      System.out.println("====================f1====================");
      JSONObject obj = JSON.parseObject(jsonStr);
      System.out.println(obj.get("cityId"));
      System.out.println(obj.get("cityName"));
      System.out.println(obj.get("cityDescribe"));
      System.out.println(obj.get("updateTime"));
    }

**2.JSON字符串转换为CityDto**

**2.1JSON字符串**

{
      "cityDescribe": "宁波是港口城市",
      "cityId": 2023062802,
      "cityName": "宁波",
      "updateTime": "2023-07-16 13:15:40"
    }

**2.2转换代码**

public static void f2() {
      String jsonStr = "{\n" +
              "  \"cityDescribe\": \"宁波是港口城市\",\n" +
              "  \"cityId\": 2023062802,\n" +
              "  \"cityName\": \"宁波\",\n" +
              "  \"updateTime\": \"2023-07-16 13:15:40\"\n" +
              "}";
      System.out.println("====================f2====================");
      CityDto cityDto = JSON.parseObject(jsonStr, CityDto.class);
      System.out.println(cityDto.getCityId());
      System.out.println(cityDto.getCityName());
      System.out.println(cityDto.getCityDescribe());
      System.out.println(cityDto.getUpdateTime());
    }

**2.3实体对象**

@Data
    @Builder
    public class CityDto implements Serializable {
        private Long cityId;
        private String cityName;
        private String cityDescribe;
        private String updateTime;
    }

**3.JSON字符串转换为CityObjectDto,对象属性中是一个对象**

**3.1JSON字符串**

{
    	"cityObj": {
    		"cityName": "宁波",
    		"updateTime": "2023-07-16 13:15:40",
    		"cityId": 2023062802,
    		"cityDescribe": "宁波是港口城市"
    	}
    }

**3.2转换代码**

public static void f3() {
      String jsonStr = "{\n" +
              "  \"cityObj\": {\n" +
              "  \t\"cityName\": \"宁波\",\n" +
              "  \t\"updateTime\": \"2023-07-16 13:15:40\",\n" +
              "  \t\"cityId\": 2023062802,\n" +
              "  \t\"cityDescribe\": \"宁波是港口城市\"\n" +
              "  }\n" +
              "}";
      System.out.println("====================f3====================");
      CityObjectDto cityDto = JSON.parseObject(jsonStr, CityObjectDto.class);
      System.out.println(cityDto.getCityObj().getCityId());
      System.out.println(cityDto.getCityObj().getCityName());
      System.out.println(cityDto.getCityObj().getCityDescribe());
      System.out.println(cityDto.getCityObj().getCityDescribe());
    }

**3.3实体对象**

@Data
    @Builder
    public class CityObjectDto implements Serializable {
        private CityDto cityObj;
    }

**4.JSON字符串转换为Map**

**4.1JSON字符串**

{
      "cityDescribe": "宁波是港口城市",
      "cityId": 2023062802,
      "cityName": "宁波",
      "updateTime": "2023-07-16 13:15:40"
    }

**4.2转换代码**

public static void f4() {
      String jsonStr = "{\n" +
              "  \"cityDescribe\": \"宁波是港口城市\",\n" +
              "  \"cityId\": 2023062802,\n" +
              "  \"cityName\": \"宁波\",\n" +
              "  \"updateTime\": \"2023-07-16 13:15:40\"\n" +
              "}";
      System.out.println("====================f4====================");
      Map mapObj = JSON.parseObject(jsonStr, Map.class);
      System.out.println(mapObj.get("cityId"));
      System.out.println(mapObj.get("cityName"));
      System.out.println(mapObj.get("cityDescribe"));
      System.out.println(mapObj.get("updateTime"));
    }

**5.JSON字符串转换为CityMapDto,对象属性是一个Map类型**

**5.1JSON字符串**

{
      "cityMap": {
      	"cityName": "宁波",
      	"updateTime": "2023-07-16 13:15:40",
      	"cityId": 2023062802,
      	"cityDescribe": "宁波是港口城市"
      }
    }

**5.2转换代码**

public static void f5() {
      String jsonStr = "{\n" +
              "  \"cityMap\": {\n" +
              "  \t\"cityName\": \"宁波\",\n" +
              "  \t\"updateTime\": \"2023-07-16 13:15:40\",\n" +
              "  \t\"cityId\": 2023062802,\n" +
              "  \t\"cityDescribe\": \"宁波是港口城市\"\n" +
              "  }\n" +
              "}";
      System.out.println("====================f5====================");
      CityMapDto cityMapDto = JSON.parseObject(jsonStr, CityMapDto.class);
      System.out.println(cityMapDto.getCityMap().get("cityId"));
      System.out.println(cityMapDto.getCityMap().get("cityName"));
      System.out.println(cityMapDto.getCityMap().get("cityDescribe"));
      System.out.println(cityMapDto.getCityMap().get("updateTime"));
    }

**5.3实体对象**

@Data
    @Builder
    public class CityMapDto implements Serializable {
        private Map<String, Object> cityMap;
    }

**6.JSON字符串转换为List**

**6.1JSON字符串**

[{
    	"cityDescribe": "杭州是互联网城市",
    	"cityId": 2023062801,
    	"cityName": "杭州",
    	"updateTime": "2023-07-16 13:15:40"
    }, {
    	"cityDescribe": "宁波是港口城市",
    	"cityId": 2023062802,
    	"cityName": "宁波",
    	"updateTime": "2023-07-16 13:15:40"
    }]

**6.2转换代码**

public static void f6() {
      String jsonStr = "[{\n" +
              "\t\"cityDescribe\": \"杭州是互联网城市\",\n" +
              "\t\"cityId\": 2023062801,\n" +
              "\t\"cityName\": \"杭州\",\n" +
              "\t\"updateTime\": \"2023-07-16 13:15:40\"\n" +
              "}, {\n" +
              "\t\"cityDescribe\": \"宁波是港口城市\",\n" +
              "\t\"cityId\": 2023062802,\n" +
              "\t\"cityName\": \"宁波\",\n" +
              "\t\"updateTime\": \"2023-07-16 13:15:40\"\n" +
              "}]";
      System.out.println("====================f6====================");
      List<CityDto> cityList = JSON.parseArray(jsonStr, CityDto.class);
      cityList.forEach((cityDto) -> {
                  System.out.println(cityDto.getCityId());
                  System.out.println(cityDto.getCityName());
                  System.out.println(cityDto.getCityDescribe());
                  System.out.println(cityDto.getUpdateTime());
              }
      );
    }

**7.JSON字符串转换为CityListDto,对象属性是一个List类型**

**7.1JSON字符串**

{
    	"cityList": [{
    		"cityDescribe": "杭州是互联网城市",
    		"cityId": 2023062801,
    		"cityName": "杭州",
    		"updateTime": "2023-07-16 13:15:40"
    	}, {
    		"cityDescribe": "宁波是港口城市",
    		"cityId": 2023062802,
    		"cityName": "宁波",
    		"updateTime": "2023-07-16 13:15:40"
    	}]
    }

**7.2转换代码**

public static void f7() {
      String jsonStr = "{\n" +
              "\t\"cityList\": [{\n" +
              "\t\t\"cityDescribe\": \"杭州是互联网城市\",\n" +
              "\t\t\"cityId\": 2023062801,\n" +
              "\t\t\"cityName\": \"杭州\",\n" +
              "\t\t\"updateTime\": \"2023-07-16 13:15:40\"\n" +
              "\t}, {\n" +
              "\t\t\"cityDescribe\": \"宁波是港口城市\",\n" +
              "\t\t\"cityId\": 2023062802,\n" +
              "\t\t\"cityName\": \"宁波\",\n" +
              "\t\t\"updateTime\": \"2023-07-16 13:15:40\"\n" +
              "\t}]\n" +
              "}";
      System.out.println("====================f7====================");
      CityListDto cityListDto = JSON.parseObject(jsonStr, CityListDto.class);
      List<CityDto> cityList = JSON.parseArray(cityListDto.getCityList().toString(), CityDto.class);
      cityList.forEach((cityDto) -> {
                  System.out.println(cityDto.getCityId());
                  System.out.println(cityDto.getCityName());
                  System.out.println(cityDto.getCityDescribe());
                  System.out.println(cityDto.getUpdateTime());
              }
      );
    }

**7.3实体对象**

@Data
    @Builder
    public class CityListDto implements Serializable {
        private List cityList;
    }

**8.复杂的JSON字符串转换为ProvinceDto,在对象中包含对象和List类型**

**8.1JSON字符串**

{
    	"provinceName": "浙江省",
    	"areaNumber": "330000",
    	"data": {
    		"dataFlag": "01",
    		"cityData": {
    			"dataList": [{
    				"cityDescribe": "杭州是互联网城市",
    				"cityId": 2023062801,
    				"cityName": "杭州",
    				"updateTime": "2023-07-16 13:15:40"
    			}, {
    				"cityDescribe": "宁波是港口城市",
    				"cityId": 2023062802,
    				"cityName": "宁波",
    				"updateTime": "2023-07-16 13:15:40"
    			}]
    		}
    	}
    }

**8.2转换代码**

public static void f8() {
      String jsonStr = "{\n" +
              "\t\"provinceName\": \"浙江省\",\n" +
              "\t\"areaNumber\": \"330000\",\n" +
              "\t\"data\": {\n" +
              "\t\t\"dataFlag\": \"01\",\n" +
              "\t\t\"cityData\": {\n" +
              "\t\t\t\"dataList\": [{\n" +
              "\t\t\t\t\"cityDescribe\": \"杭州是互联网城市\",\n" +
              "\t\t\t\t\"cityId\": 2023062801,\n" +
              "\t\t\t\t\"cityName\": \"杭州\",\n" +
              "\t\t\t\t\"updateTime\": \"2023-07-16 13:15:40\"\n" +
              "\t\t\t}, {\n" +
              "\t\t\t\t\"cityDescribe\": \"宁波是港口城市\",\n" +
              "\t\t\t\t\"cityId\": 2023062802,\n" +
              "\t\t\t\t\"cityName\": \"宁波\",\n" +
              "\t\t\t\t\"updateTime\": \"2023-07-16 13:15:40\"\n" +
              "\t\t\t}]\n" +
              "\t\t}\n" +
              "\t}\n" +
              "}";
      System.out.println("====================f8====================");
      //1.解析JSON字符串(嵌套JSON对象逐层解析)
      ProvinceDto provinceDto = JSON.parseObject(jsonStr, ProvinceDto.class);
      DataDto data = JSON.parseObject(provinceDto.getData().toString(), DataDto.class);
      CityDataDto cityData = JSON.parseObject(data.getCityData().toString(), CityDataDto.class);
      List<CityDto> dataList = JSON.parseArray(cityData.getDataList().toString(), CityDto.class);
      //2.解析完成后转换为Java对象
      CityDataDto cityDataResult = CityDataDto.builder()
              .dataList(dataList)
              .build();
      DataDto dataResult = DataDto.builder()
              .dataFlag(data.getDataFlag())
              .cityData(cityDataResult)
              .build();
      ProvinceDto provinceDtoResult = ProvinceDto.builder()
              .provinceName(provinceDto.getProvinceName())
              .areaNumber(provinceDto.getAreaNumber())
              .data(dataResult)
              .build();
      //3.使用Java对象
      System.out.println(provinceDtoResult.getProvinceName());
      System.out.println(provinceDtoResult.getAreaNumber());
      DataDto dataDtoApp = (DataDto) provinceDtoResult.getData();
      System.out.println(dataDtoApp.getDataFlag());
      CityDataDto cityDataDtoApp = (CityDataDto) dataDtoApp.getCityData();
      List<CityDto> dataListApp = (List<CityDto>) cityDataDtoApp.getDataList();
      dataListApp.forEach((cityDto) -> {
                  System.out.println(cityDto.getCityId());
                  System.out.println(cityDto.getCityName());
                  System.out.println(cityDto.getCityDescribe());
                  System.out.println(cityDto.getUpdateTime());
              }
      );
    }

**8.3实体对象**

**8.3.1Java对象ProvinceDto**

(1)示例代码

@Data
    @Builder
    public class ProvinceDto<T> implements Serializable {
      private String provinceName;
      private String areaNumber;
      private T data;
    }

(2)解析代码

ProvinceDto对象对应Json字符串的provinceName、areaNumber、data属性。

**8.3.2Java对象DataDto**

(1)示例代码

@Data
    @Builder
    public class DataDto<T> implements Serializable {
      private String dataFlag;
      private T cityData;
    }

(2)解析代码

DataDto对象对应JSON字符串的data属性的dataFlag、cityData属性。

**8.3.3Java对象CityDataDto**

(1)示例代码

@Data
    @Builder
    public class CityDataDto<T> implements Serializable {
      private T dataList;
    }

(2)解析代码

CityDataDto对象对应JSON字符串的data属性的cityData属性的dataList属性。

**8.3.4Java对象CityDto**

(1)示例代码

@Data
    @Builder
    public class CityDto implements Serializable {
      private Long cityId;
      private String cityName;
      private String cityDescribe;
      private String updateTime;
    }

2)解析代码

CityDto 对象对应JSON字符串的data属性的cityData属性的dataList属性的List中的对象。

以上，感谢。

2023年7月16日