如何在Java中获取深度嵌套的JSON对象

Question

I have a JSON string where i want to get the value of one field which is nested in multiple objects. How can I get that field in a nice and performant way? Here's the code I tried so far. It's working, but it's quite lengthy code. I'm looking for a better solution.

Json Response

{  
   "status":"success",
   "response":{  
      "setId":1,
      "response":{  
         "match":{  
            "matches":{  
               "matchesSchema":{  
                  "rules":[  
                     {  
                        "ruleId":"Abs"
                     }
                  ]
               }
            }
         }
      }
   }

lengthy code :

JsonParser jp=new JsonParser();
Object obj = jp.parse(JSONString); 
JSONObject jsonObject =(JSONObject) (obj);
JSONObject get1 = jsonObject.getJSONObject("response");
JSONObject get2 = get1 .getJSONObject("response");
JSONObject get3 = get2 .getJSONObject("match");
JSONObject get4 = get3 .getJSONObject("matches");
JSONObject get5 = get4 .getJSONObject("matchesSchema");
JSONObject get6 = get5 .getJSONObject("rules");
JSONArray result = get6 .getJSONArray("rules");
JSONObject result1 = result.getJSONObject(0);
String lat = result1 .getString("rule");

The result is ruleId = Abs

is there a good alternative for fetching the ruleId from the nested json object (something like response.response.match.matches.matchesSchema.rules.ruleId )

Answer 1

You can use Jackson's JsonNode with JsonPath to get ruleId as follows:

ObjectMapper mapper = new ObjectMapper();
JsonNode jsonObj = mapper.readTree(JSONString);
String lat = jsonObj.at("/response/response/match/matches/matchesSchema/rules/0/ruleId").asText()

It's also null -safe and returns a MissingNode object on a null node that returns an empty string when you do a .asText()

Answer 2

It's super easy with JsonPath .

String ruleId = JsonPath.read(jsonString, "$.response.response.match.matches.matchesSchema.rules[0].ruleId");

Or if you read the path multiple times, it's better to pre-compile JsonPath expression

JsonPath ruleIdPath = JsonPath.compile("$.response.response.match.matches.matchesSchema.rules[0].ruleId");
String ruleId = ruleIdPath.read(json);