Parsing JSON Antwort mit Jackson

Question

ich einen Web-Service geschrieben haben, und in der folgenden URL http://192.168.2.34:8081/MyWebService/facility/university

Antwort von diesem Web-Service im JSON-Format gehostet ist:

{ 
    "university": [ 
    { 
     "emailOfPrincipal": "prin1@gmail.com", 
     "labLists": [ 
     { 
      "instrumentLists": [ 
      { 
       "instrumentId": "1", 
       "instrumentName": "Instrument 1" 
      }, 
      { 
       "instrumentId": "2", 
       "instrumentName": "instrument 2" 
      } 
      ], 
      "labId": "11", 
      "labName": "Lab 11" 
     }, 
     { 
      "instrumentLists": [ 
      { 
       "instrumentId": "3", 
       "instrumentName": "instrument 3" 
      }, 
      { 
       "instrumentId": "4", 
       "instrumentName": "instrument 4" 
      } 
      ], 
      "labId": "22", 
      "labName": "Lab 22" 
     } 
     ], 
     "univAddress": "Kolkata", 
     "univId": "111", 
     "univName": "University 111", 
     "univPrincipalName": "Principal 1" 
    }, 
    { 
     "emailOfPrincipal": "prin2@gmail.com", 
     "labLists": [ 
     { 
      "instrumentLists": [ 
      { 
       "instrumentId": "5", 
       "instrumentName": "Instrument 5" 
      }, 
      { 
       "instrumentId": "6", 
       "instrumentName": "Instrument 6" 
      } 
      ], 
      "labId": "33", 
      "labName": "Lab 33" 
     }, 
     { 
      "instrumentLists": [ 
      { 
       "instrumentId": "7", 
       "instrumentName": "Instrument 7" 
      }, 
      { 
       "instrumentId": "8", 
       "instrumentName": "Instrument 8" 
      } 
      ], 
      "labId": "44", 
      "labName": "Lab 44" 
     } 
     ], 
     "univAddress": "Bangalore", 
     "univId": "222", 
     "univName": "University 222", 
     "univPrincipalName": "Principal 2" 
    }, 
    { 
     "emailOfPrincipal": "prin3@gmail.com", 
     "labLists": [ 
     { 
      "instrumentLists": [ 
      { 
       "instrumentId": "9", 
       "instrumentName": "Instrument 9" 
      }, 
      { 
       "instrumentId": "10", 
       "instrumentName": "Instrument 10" 
      } 
      ], 
      "labId": "55", 
      "labName": "Lab 55" 
     }, 
     { 
      "instrumentLists": [ 
      { 
       "instrumentId": "11", 
       "instrumentName": "Instrument 11" 
      }, 
      { 
       "instrumentId": "12", 
       "instrumentName": "Instrument 12" 
      } 
      ], 
      "labId": "66", 
      "labName": "Lab 66" 
     } 
     ], 
     "univAddress": "Hyderabad", 
     "univId": "333", 
     "univName": "University 333", 
     "univPrincipalName": "Principal 3" 
    } 
    ] 
} 

Ich versuche, JSON-Daten zu konvertieren in Java-Objekt mit Jackson-API. Aber einen Fehler bekommen. Meine Java-Objekte sind:

University.java

public class University { 
    private int univId; 
    private String univName; 
    private String univAddress; 
    private String univPrincipalName; 
    private String emailOfPrincipal; 
    private List<Laboratory> labLists = new ArrayList<>(); 

    //... Getter and Setter Methods... 
} 

Laboratory.java

public class Laboratory { 

    private int labId; 
    private String labName; 
    private List<Instruments> instrumentLists = new ArrayList<>(); 
    //... Getter and Setter Methods... 
} 

Instruments.java

public class Instruments { 

    private int instrumentId; 
    private String instrumentName; 
    private String bookingStatus; 
    private Date bookingFrom; 
    private Date bookingTo; 
    private Date requestedTime; 

    //... Getter and Setter Methods... 
} 

Der Kunde geschrieben ist:

public class ParseJSONData { 

    public static void main(String[] args) throws ClientProtocolException, IOException { 
     String URL = "http://192.168.2.34:8081/MyWebService/facility/university"; 
     DefaultHttpClient httpclient = new DefaultHttpClient(); 
     HttpGet httpget = new HttpGet(URL); 
     HttpResponse response = httpclient.execute(httpget); 
     // System.out.println(response); 

     HttpEntity entity = response.getEntity(); 
     String result = EntityUtils.toString(entity); 

     ObjectMapper mapper = new ObjectMapper(); 

     University universities = mapper.readValue(result, University.class); 
     System.out.println(universities.getEmailOfPrincipal()); 
    } 

Der Fehler Ich erhalte sagt

Exception in thread "main" org.codehaus.jackson.map.exc.UnrecognizedPropertyException: Unrecognized field "university" (Class University), not marked as ignorable 
at [Source: java.io.StringReader@100edc0; line: 1, column: 16] (through reference chain: University["university"]) 

Ich kenne meine JSON-Daten Liste der Hochschulen zurückkehrt. Aber wie man diese in der Liste abbildet, ist mir nicht bekannt. Jede Art von Hilfe wird sehr geschätzt.

Answer 1

Sie können übergeordnete Klasse

public class UniversityList { 
    private List<University> university; 
    //... Getter and Setter Methods... 
} 

und uns ist es wie folgt hinzu:

ObjectMapper mapper = new ObjectMapper(); 
UniversityList list = mapper.readValue(json, UniversityList.class)); 
University university = list.getUniversity().get(0) 

Andere Option ist zu erstellen individuelle Deserializer für Ihre University Klasse

Hier Demo:

public static void main(String[] args) throws IOException { 
    ObjectMapper mapper = new ObjectMapper(); 
    SimpleModule module = new SimpleModule(); 
    module.addDeserializer(University.class, new UniversityDeserializer()); 
    mapper.registerModule(module); 
    University university = mapper.readValue(json, University.class); 
} 

public static class UniversityDeserializer extends JsonDeserializer<University> { 
    private ObjectMapper unmodifiedMapper = new ObjectMapper(); 
    @Override 
    public University deserialize(JsonParser p, DeserializationContext ctxt) 
                   throws IOException{ 
     JsonNode node = p.readValueAsTree(); 
     JsonNode array = node.get("university"); 
     if (array != null && array.isArray()){ 
      JsonNode uniNode = array.get(0); 
      return unmodifiedMapper.treeToValue(uniNode, University.class); 
     } 
     return null; 
    } 
}