CODEWITHSUNDEEP
javajsonjackson
Grégoire Borel
Grégoire Borel

Reputation: 2038

Get specific value while parsing JSON with Jackson

I have the following JSON:

[  
   {  
      "A":"Lorem Ipsum ",
      "B":"Lorem Ipsum ",
      "C":"Lorem Ipsum ",
      "D":"Lorem Ipsum ",
      "E":"Lorem Ipsum ",
      "F":"Lorem Ipsum ",
      "G":301,
      "H":[  
         {  
            "Lorem Ipsum ":4,
            "Lorem Ipsum ":20,
            "Lorem Ipsum":0
         },
         {  
            "Lorem Ipsum ":5,
            "Lorem Ipsum ":19.2,
            "Lorem Ipsum ":0.8
         },
         {  
            "Lorem Ipsum ":1,
            "Lorem Ipsum ":8,
            "Lorem Ipsum ":4
         },
         {  
            "Lorem Ipsum ":3,
            "Lorem Ipsum ":14.2,
            "Lorem Ipsum ":5.8
         },
         {  
            "Lorem Ipsum ":2,
            "Lorem Ipsum ":20,
            "Lorem Ipsum ":0
         }
      ],
      "I":[  

      ],
      "J":[  

      ],
      "20-01-2014":20,
      "27-01-2014":19.2,
      "30-12-2013":8,
      "13-01-2014":14.2,
      "06-01-2014":20,
      "K":"81.40"
   },
   {  
      "reportKey":"something"
   }
]

I'd like to get the reportKey value and then remove it from the file. But first I need to access it and my code doesn't seem to work:

final ObjectMapper objectMapper = new ObjectMapper();
JsonNode jsonNode = objectMapper.readValue(rawContentParameters, JsonNode.class);

logger.info("ExportController : generatesExportExcel : parameters: {}", jsonNode.get("reportKey").textValue());

but I'm getting a java.lang.NullPointerException. Why?

SOLUTION:

final ObjectMapper objectMapper = new ObjectMapper();
JsonNode rootNode = objectMapper.readValue(rawContentParameters, JsonNode.class);

logger.info("ExportController : generatesExportExcel : parameters: {}", rootNode.get(rootNode.size() - 1).get("reportKey").textValue());

Upvotes: 7

Views: 28449

Answers (3)

Armand
Armand

Reputation: 24393

You are accessing the root JsonNode as if it were an object, but it's wrapped in an array. You need to extract the second object from the array before you can access reportKey:

JsonNode array = objectMapper.readValue(rawContentParameters, JsonNode.class);
JsonNode object = array.get(1);
String reportKey = object.get("reportKey").textValue();
logger.info("ExportController : generatesExportExcel : parameters: {}", reportKey);

Upvotes: 10

forzagreen
forzagreen

Reputation: 2693

You can use JSONObject and JSONArray from org.json library :

//instantiate your json array (e.g. from a string, or a file)
//String s = "[...]";
String s = FileUtils.readFileToString(new File(yourFile));
JSONArray json = new JSONArray(s);

//get the reportKey value:
json.get(1).get("reportKey");

//removing it:
//removing all the node: {"reportKey":"something"}
json.remove(1);
//removing only "reportKey":"something" and keeping {}:
json.get(1).remove("reportKey");

Upvotes: 1

zbig
zbig

Reputation: 3966

First take second element on the list. 

jsonNode.get(1).get("reportKey")

Upvotes: 2

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