在json格式的數據里篩選出指定的key值

• 在全國城市數據json格式的文本里篩選出幾個指定的key

• 部分json格式數據如下

    {"sysCatPk": 459,
    "prntSysCatPk": null,
    "prntCd": "9100",
    "prntNmEn": "china",
    "prntNmCn": "中國",
    "cd": "9100.100",
    "nmEn": "beijingshi",
    "nmCn": "北京市",
    "methSysCatPk": 252,
    "methCd": "9100",
    "methNmEn": "china",
    "methNmCn": "中國",
    "desc": "",
    "viewSeq": "",
    "busSeq": "",
    "value": null,
    "level": 1,
    "childSysCatDtozList": [{
    	"sysCatPk": 460,
    	"prntSysCatPk": 459,
    	"prntCd": "9100.100",
    	"prntNmEn": "beijingshi",
    	"prntNmCn": "北京市",
    	"cd": "9100.100.100",
    	"nmEn": "beijingshi",
    	"nmCn": "北京市",
    	"methSysCatPk": 252,
    	"methCd": "9100",
    	"methNmEn": "china",
    	"methNmCn": "中國",
    	"desc": "",
    	"viewSeq": "",
    	"busSeq": "",
    	"value": null,
    	"level": 2,
    	"childSysCatDtozList": [{
    		"sysCatPk": 461,
    		"prntSysCatPk": 460,
    		"prntCd": "9100.100.100",
    		"prntNmEn": "beijingshi",
    		"prntNmCn": "北京市",
    		"cd": "9100.100.100.100",
    		"nmEn": "dongchengqu",
    		"nmCn": "東城區",
    		"methSysCatPk": 252,
    		"methCd": "9100",
    		"methNmEn": "china",
    		"methNmCn": "中國",
    		"desc": "",
    		"viewSeq": "",
    		"busSeq": "",
    		"value": null,
    		"level": 3,
    		"childSysCatDtozList": [],
    		"top": false,
    		"leaf": true
    	},
    	{
    		"sysCatPk": 462,
    		"prntSysCatPk": 460,
    		"prntCd": "9100.100.100",
    		"prntNmEn": "beijingshi",
    		"prntNmCn": "北京市",
    		"cd": "9100.100.100.110",
    		"nmEn": "xichengqu",
    		"nmCn": "西城區",
    		"methSysCatPk": 252,
    		"methCd": "9100",
    		"methNmEn": "china",
    		"methNmCn": "中國",
    		"desc": "",
    		"viewSeq": "",
    		"busSeq": "",
    		"value": null,
    		"level": 3,
    		"childSysCatDtozList": [],
    		"top": false,
    		"leaf": true
    	},
    	{
    		"sysCatPk": 463,
    		"prntSysCatPk": 460,
    		"prntCd": "9100.100.100",
    		"prntNmEn": "beijingshi",
    		"prntNmCn": "北京市",
    		"cd": "9100.100.100.120",
    		"nmEn": "chongwenqu",
    		"nmCn": "崇文區",
    		"methSysCatPk": 252,
    		"methCd": "9100",
    		"methNmEn": "china",
    		"methNmCn": "中國",
    		"desc": "",
    		"viewSeq": "",
    		"busSeq": "",
    		"value": null,
    		"level": 3,
    		"childSysCatDtozList": [],
    		"top": false,
    		"leaf": true
    	}],
    	"top": false,
    	"leaf": false
    }],
    "top": true,
    "leaf": false
  }
  

• 需要的json格式如下，只選取三個字段

    [{"sysCatPk":"459","nmCn":"北京市","childSysCatDtozList":
    		[{"sysCatPk":"460","nmCn":"北京市","childSysCatDtozList":
    			[{"sysCatPk":"461","childSysCatDtozList":[],"nmCn":"東城區"},
    			{"sysCatPk":"462","childSysCatDtozList":[],"nmCn":"西城區"},
    			{"sysCatPk":"463","childSysCatDtozList":[],"nmCn":"崇文區"},
    			{"sysCatPk":"464","childSysCatDtozList":[],"nmCn":"宣武區"},
    			{"sysCatPk":"465","childSysCatDtozList":[],"nmCn":"朝陽區"},
    			{"sysCatPk":"466","childSysCatDtozList":[],"nmCn":"豐台區"},
    			{"sysCatPk":"467","childSysCatDtozList":[],"nmCn":"石景山區"},
    			{"sysCatPk":"468","childSysCatDtozList":[],"nmCn":"海淀區"},
    			{"sysCatPk":"469","childSysCatDtozList":[],"nmCn":"門頭溝區"},
    			{"sysCatPk":"470","childSysCatDtozList":[],"nmCn":"房山區"},
    			{"sysCatPk":"471","childSysCatDtozList":[],"nmCn":"通州區"},
    			{"sysCatPk":"472","childSysCatDtozList":[],"nmCn":"順義區"},
    			{"sysCatPk":"473","childSysCatDtozList":[],"nmCn":"昌平區"},
    			{"sysCatPk":"474","childSysCatDtozList":[],"nmCn":"大興區"},
    			{"sysCatPk":"475","childSysCatDtozList":[],"nmCn":"平谷區"},
    			{"sysCatPk":"476","childSysCatDtozList":[],"nmCn":"懷柔區"},
    			{"sysCatPk":"477","childSysCatDtozList":[],"nmCn":"密雲縣"},
    			{"sysCatPk":"478","childSysCatDtozList":[],"nmCn":"延慶縣"}
    		}]
    }]
  

• 實現方法：

  • 創建一個實體類

  @Data
  public class City {
  		private String sysCatPk;
  		private String nmCn;
   	private List<City> childSysCatDtozList;
  }
  

  • 從文本中讀取json數據

  public class TextRead {
    public static String readFileContent(String fileName) {
       File file = new File(fileName);
       BufferedReader reader = null;
       StringBuffer sbf = new StringBuffer();
       try {
          reader = new BufferedReader(new FileReader(file));
          String tempStr;
          while ((tempStr = reader.readLine()) != null) {
              sbf.append(tempStr);
          }
          reader.close();
          return sbf.toString();
        } catch (IOException e) {
          e.printStackTrace();
        } finally {
          if (reader != null) {
              try {
                  reader.close();
              } catch (IOException e1) {
                  e1.printStackTrace();
              }
          }
      }
      	return sbf.toString();
  	}
  }
  

  • 轉換

   public static void main(String[] asg) throws IOException {
         String str = TextRead.readFileContent("C:\\Users\\mengzhao\\Desktop\\全國城市數據json格式.txt");
         JSONArray array = JSONArray.parseArray(str);
         List<City> cities = array.toJavaList(City.class);
         Object json = JSONArray.toJSON(cities);
         File file = new File("C:\\Users\\mengzhao\\Desktop\\全國城市數據json格式1.txt");
         Writer out = new FileWriter(file);
         out.write(json.toString());
         out.close();
  }