jackson: mapping some fields of json to inner fields of class

Question

I want to map some fields of json to inner fields of a class. e.g

{
 values:[{
 "name":"Abc",
 "age":18,
 "street":"test", 
 "postalcoad":"1231412"
},
 {
  "name":"ccvb",
 "age":20,
 "street":"test2", 
 "postalcoad":"123"
  }
]}

Following i my java class

@JsonIgnoreProperties(ignoreUnknown = true)
public class Customer{
   @JsonProperty("name")
   private string name;

   @JsonProperty("age")
   private int age;

   private Address address;
}

@JsonIgnoreProperties(ignoreUnknown = true)
public class Address{
   @JsonProperty("street")
   private string street;

   @JsonProperty("postalcode")
   private string postalcode;
}


ObjectMapper mapper = new ObjectMapper();
Customer[] c = mapper.readValue(mapper.readTree(json).get("values").toString(), Customer[].class);

It returns me Customer object without Address. Any idea how can i create Address object from this json.

You might be able to gain some insight from this http://stackoverflow.com/q/16570073/13075 — Henrik Aasted Sørensen, Jan 31 '17 at 13:27
In this way i will have to initialise all the fields through constructor. Actually i was avoiding it. There are more than 100 fields and majority of them are using custom Deserializers. — Ahmad.Masood, Jan 31 '17 at 16:09

Vlad Bochenin · Accepted Answer · 2017-01-31T17:18:04.803

One of the options is to use @JsonCreator annotation:

    @JsonCreator
    public Customer(
            @JsonProperty("name") String name,
            @JsonProperty("age")  int age,
            @JsonProperty("street") String street,
            @JsonProperty("postalcode")   String postalcode
    ) {
        this.name = name;
        this.age = age;
        this.address = new Address();
        this.address.street = street;
        this.address.postalcode = postalcode;
    }

Second option is create custom deserializer and bind your class with deserializer using @JsonDeserialize annotation

@JsonDeserialize(using = CustomerDeserializer.class)
public static class Customer{
  ....
}

public class CustomerDeserializer extends StdDeserializer<Customer> {

    public CustomerDeserializer() {
        super(Customer.class);
    }

    @Override
    public Customer deserialize(JsonParser p, DeserializationContext ctxt) throws IOException, JsonProcessingException {
        Customer customer = new Customer();
        JsonNode treeNode = p.readValueAsTree();
        if (treeNode == null) {
            return null;
        }
        customer.setName(treeNode.get("name").asText());
        customer.setAge(treeNode.get("age").asInt());
        Address address = new Address();
        address.setStreet(treeNode.get("street").asText());
        address.setPostalcode(treeNode.get("postalcode").asText());
        customer.setAddress(address);
        return customer;
    }
}

As third option, you can use @JsonAnySetter with some kind of post construct processing:

public interface PostConstruct {
    void postConstruct();
}

public class Customer implements PostConstruct {
    //mapping 

    private Map<String, Object> additionalFields = new HashMap<>();

    @JsonAnySetter
    public void setAdditionalValue(String key, Object value) {
        additionalFields.put(key, value);
    }

    @Override
    public void postConstruct() {
        address = new Address();
        address.setStreet(String.valueOf(additionalFields.get("street")));
        address.setPostalcode(String.valueOf(additionalFields.get("postalcode")));
    }
}


public static class PostConstructDeserializer extends DelegatingDeserializer {
    private final JsonDeserializer<?> deserializer;

    public PostConstructDeserializer(JsonDeserializer<?> deserializer) {
        super(deserializer);
        this.deserializer = deserializer;
    }

    @Override
    protected JsonDeserializer<?> newDelegatingInstance(JsonDeserializer<?> newDelegatee) {
        return deserializer;
    }

    @Override
    public Object deserialize(JsonParser jp, DeserializationContext ctxt) throws IOException {
        Object result = _delegatee.deserialize(jp, ctxt);
        if (result instanceof PostConstruct) {
            ((PostConstruct) result).postConstruct();
        }
        return result;
    }
}


//using of post construct deserializer

    ObjectMapper mapper = new ObjectMapper();
    SimpleModule module = new SimpleModule();
    module.setDeserializerModifier(new BeanDeserializerModifier() {
        @Override
        public JsonDeserializer<?> modifyDeserializer(DeserializationConfig config,
                                                      BeanDescription beanDesc,
                                                      final JsonDeserializer<?> deserializer) {
            return new PostConstructDeserializer(deserializer);
        }
    });
    mapper.registerModule(module);

Is there a way i can use **@JsonDeserialize** over _address_ field in _Customer_ Class. Actually there a lot of fields (Around 100) and they are using custom Deserializers so if i will place a **@JsonDeserialize** over class then i will have to change logic for each field. — Ahmad.Masood, Jan 31 '17 at 16:06
@Ahmad.Masood I don't think so, because you don't have a proper field in `json` for `Address`, so jackson just skip your `address` field in deserialization phase. — Vlad Bochenin, Jan 31 '17 at 17:19
Your answer helped me a lot :) **@JsonAnySetter** did the trick. — Ahmad.Masood, Feb 01 '17 at 10:13

score 1 · Answer 2 · edited May 23 '17 at 12:33

I would create a custom deserializer and inside of it call the default deserializer for Customer and then call the default deseriazlier for Address. Then you add the address to the customer object. This way they both look at the same json but you get two different objects out and you can connect them the way you want.

To call a standard deserializer from a custom deseriazlier see this answer: How do I call the default deserializer from a custom deserializer in Jackson.

jackson: mapping some fields of json to inner fields of class

2 Answers2

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