Mapping JSON with multiple entries to an array

Question

I have a JSON file with multiple entries that have same attribute names, but different attribute values, such as:

{
  "name" : { "first" : "A", "last" : "B" },
  "gender" : "MALE",
  "married" : false,
  "noOfChildren" : 2
},
{
  "name" : { "first" : "C", "last" : "D" },
  "gender" : "FEMALE",
  "married" : true,
  "noOfChildren" : 1
}

The class that it should be mapped is:

public class Human {

private Name name;
private String gender;
private int age;

<getter, setters etc>

}

EDIT: Service code is :

List<Human> humans = null;
ObjectMapper objectMapper = new ObjectMapper();
        objectMapper.configure(DeserializationFeature.FAIL_ON_UNKNOWN_PROPERTIES, false);

ObjectMapper objectMapper = new ObjectMapper();
objectMapper.configure(DeserializationFeature.FAIL_ON_UNKNOWN_PROPERTIES, false);

try {

    humans= objectMapper.readValue(json, new TypeReference<List<Human>>(){});

} catch (IOException e) {
    e.printStackTrace();
}

JSON is parsed from HTTP entity and with correct format and now I added the annotation ass suggested in the answers.

As you can see, they have some attributes in common, but differ in others, and I would like to map those common fields. Is it possible to map the JSON this way ? I have tried mapping JSON to a collection/list/array of JsonNodes, but I keep getting erros about deserialization, while mapping only one instance of JSON entry works just fine. Is there another way of doing this ?

Dmitry Gorkovets · Accepted Answer · 2017-01-12 09:29:22Z

1

Use

@JsonIgnoreProperties(ignoreUnknown = true)
public class Human {
    private Name name;
    private String gender;
    // getters, settets, default constructor
}

Or if you are using Lombok then it will be

@Data
@NoArgsConstructor
@JsonIgnoreProperties(ignoreUnknown = true)
public class Human {
    private Name name;
    private String gender;
}

answered Jan 12, 2017 at 9:29

Dmitry Gorkovets

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2 Comments

borgmater Over a year ago

I don't want to ignore the whole class, only certain fields. But what about the attributes that aren't consisted in the class, such as noOfChildren or married ?

Dmitry Gorkovets Over a year ago

These attributes will be ignored, only name and gender will be in your object.

Sachin Gupta · Accepted Answer · 2017-01-12 10:23:06Z

1

use

objectMapper.configure(DeserializationFeature.FAIL_ON_UNKNOWN_PROPERTIES, false);

while deserializing json to POJO class.

The JSON you have provide in question will give following error, as it is not a valid one.

Can not deserialize instance of java.util.ArrayList out of START_OBJECT token

Valid Json would be like this:

[
  {
    "name": {
      "first": "A",
      "last": "B"
    },
    "gender": "MALE",
    "married": false,
    "noOfChildren": 2
  },
  {
    "name": {
      "first": "C",
      "last": "D"
    },
    "gender": "FEMALE",
    "married": true,
    "noOfChildren": 1
  }
]

edited Jan 12, 2017 at 10:23

answered Jan 12, 2017 at 9:43

Sachin Gupta

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6 Comments

borgmater Over a year ago

It works for one instance of JSON, but if I have store multiple entries in an array of POJOs, i get something like this : Can not deserialize instance of java.util.ArrayList out of START_OBJECT token

Sachin Gupta Over a year ago

can you show me sample code and json, which you are trying?

Dmitry Gorkovets Over a year ago

@borgmater, difference between curent and my answer is that when we set DeserializationFeature.FAIL_ON_UNKNOWN_PROPERTIES to false for ObjectMapper object then this mapper will ignore unknown properties for any parsed object. In my answer I set to ignore only for class Human, i.e. it will ignore unknown properties for any ObjectMapper which will be used.

Sachin Gupta Over a year ago

please also post exact json. one you have provided in question is not a valid one.

Sachin Gupta Over a year ago

I have updated my answer, I think JSON format was the issue.

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