在json格式的数据里筛选出指定的key值

• 在全国城市数据json格式的文本里筛选出几个指定的key

• 部分json格式数据如下

    {"sysCatPk": 459,
    "prntSysCatPk": null,
    "prntCd": "9100",
    "prntNmEn": "china",
    "prntNmCn": "中国",
    "cd": "9100.100",
    "nmEn": "beijingshi",
    "nmCn": "北京市",
    "methSysCatPk": 252,
    "methCd": "9100",
    "methNmEn": "china",
    "methNmCn": "中国",
    "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": "中国",
    	"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": "东城区",
    		"methSysCatPk": 252,
    		"methCd": "9100",
    		"methNmEn": "china",
    		"methNmCn": "中国",
    		"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": "西城区",
    		"methSysCatPk": 252,
    		"methCd": "9100",
    		"methNmEn": "china",
    		"methNmCn": "中国",
    		"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": "崇文区",
    		"methSysCatPk": 252,
    		"methCd": "9100",
    		"methNmEn": "china",
    		"methNmCn": "中国",
    		"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，只选取三个字段

    [{"sysCatPk":"459","nmCn":"北京市","childSysCatDtozList":
    		[{"sysCatPk":"460","nmCn":"北京市","childSysCatDtozList":
    			[{"sysCatPk":"461","childSysCatDtozList":[],"nmCn":"东城区"},
    			{"sysCatPk":"462","childSysCatDtozList":[],"nmCn":"西城区"},
    			{"sysCatPk":"463","childSysCatDtozList":[],"nmCn":"崇文区"},
    			{"sysCatPk":"464","childSysCatDtozList":[],"nmCn":"宣武区"},
    			{"sysCatPk":"465","childSysCatDtozList":[],"nmCn":"朝阳区"},
    			{"sysCatPk":"466","childSysCatDtozList":[],"nmCn":"丰台区"},
    			{"sysCatPk":"467","childSysCatDtozList":[],"nmCn":"石景山区"},
    			{"sysCatPk":"468","childSysCatDtozList":[],"nmCn":"海淀区"},
    			{"sysCatPk":"469","childSysCatDtozList":[],"nmCn":"门头沟区"},
    			{"sysCatPk":"470","childSysCatDtozList":[],"nmCn":"房山区"},
    			{"sysCatPk":"471","childSysCatDtozList":[],"nmCn":"通州区"},
    			{"sysCatPk":"472","childSysCatDtozList":[],"nmCn":"顺义区"},
    			{"sysCatPk":"473","childSysCatDtozList":[],"nmCn":"昌平区"},
    			{"sysCatPk":"474","childSysCatDtozList":[],"nmCn":"大兴区"},
    			{"sysCatPk":"475","childSysCatDtozList":[],"nmCn":"平谷区"},
    			{"sysCatPk":"476","childSysCatDtozList":[],"nmCn":"怀柔区"},
    			{"sysCatPk":"477","childSysCatDtozList":[],"nmCn":"密云县"},
    			{"sysCatPk":"478","childSysCatDtozList":[],"nmCn":"延庆县"}
    		}]
    }]
  

• 实现方法：

  • 创建一个实体类

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

  • 从文本中读取json数据

  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();
  	}
  }
  

  • 转换

   public static void main(String[] asg) throws IOException {
         String str = TextRead.readFileContent("C:\Users\mengzhao\Desktop\全国城市数据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\全国城市数据json格式1.txt");
         Writer out = new FileWriter(file);
         out.write(json.toString());
         out.close();
  }