如何使用Jackson从Json文件中获取未命名的属性？

Question

I have a JSON feed which I am trying to parse:

{
    "test": [
        "5",
        {
            "data": "someData",
            "number": "9"
        },
        {
            "data": "someData",
            "number": "9"
        }
    ]
}

I am using Jackson to parse the JSON file for me and using annotations:

  private ArrayList<Test> test = new ArrayList<Test>();
  /**
   * @param test the test to set
   */
  public void setTest(ArrayList<Test> test) {
    this.test = test;
  }

And my Test class:

 class Test{
   private String data= "";
   private String number= "";

  /**
   * @return the data
   */
  public String getData() {
     return data;
  }

  /**
   * @param data  the data to set
   */
  public void setData(String data) {
     this.data= data;
  }

  /**
   * @return the number
   */
  public String getNumber() {
     return number;
  }
  /**
   * @param number the number to set
   */
  public void setNumber(String number) {
     this.number= number;
  }

}

If I remove the 5 from my JSON , it works fine. However the 5 will be in the feed so I need a way to parse it. I'm completely new to jackson and annotations in general and after spending most of the day trying to figure this out without any luck, I need some help!

How can I ignore the "5" if its not named, I've tried creating a container class which holds a String and the ArrayList and passed that as a paramater to the setTest method but that didnt work either.

Answer 1

Your Java Test class represents the object, {"data": "someData", "number": "9"} , in the array. You will need to define another Java class to map your Test JSON object, something like

class TopLevel {
    private int count;
    List<Test> testList = new ArrayList<Test>();

    // ...
    //setters and getters
}

Answer 2

You can write custom deserializer for this list:

class TestListDeserializer extends JsonDeserializer<List<Test>> {
    @Override
    public List<Test> deserialize(JsonParser jp, DeserializationContext ctxt) throws IOException,
            JsonProcessingException {
        List<Test> result = new ArrayList<Test>();
        while (jp.nextToken() != JsonToken.END_ARRAY) {
            if (jp.getCurrentToken() == JsonToken.START_OBJECT) {
                result.add(jp.readValueAs(Test.class));
            }
        }
        return result;
    }
}

Now, you have to annotated test property:

@JsonDeserialize(using = TestListDeserializer.class)
private List<Test> test;

Answer 3

You can do it this way

String jsonStr ="{\"test\": [\"5\",{ \"data\": \"someData\", \"number\": \"9\"}, 
                                   { \"data\": \"someData\",\"number\": \"10\"}]}";
JSONObject jsonObject =new JSONObject(jsonStr);
String jsonArr = jsonObject.get("test").toString();
JSONArray jsonArray = new JSONArray(jsonArr);
for(int i =1 ;i<jsonArray.length();i++){
    JSONObject object = new JSONObject(jsonArray.get(i).toString());
    System.out.println(object.get("data")); // use setter instead
    System.out.println(object.get("number"));  // use setter instead

}