Want to hide some fields of an object that are being mapped to JSON by Jackson

Question

I have a User class that I want to map to JSON using Jackson.

public class User {
    private String name;
    private int age;
    private int securityCode;

    // getters and setters
}

I map this to a JSON string using -

User user = getUserFromDatabase();

ObjectMapper mapper = new ObjectMapper();   
String json =  mapper.writeValueAsString(user);

I don't want to map the securityCode variable. Is there any way of configuring the mapper so that it ignores this field?

I know I can write custom data mappers or use the Streaming API but I would like to know if it possible to do it through configuration?

Answer 1

You have two options:

1. Jackson works on setters-getters of fields. So, you can just remove getter of field which you want to omit in JSON. ( If you don't need getter at other place.)

2. Or, you can use the @JsonIgnore annotation of Jackson on getter method of that field and you see there in no such key-value pair in resulted JSON.

   @JsonIgnore
   public int getSecurityCode(){
      return securityCode;
   }
   

Answer 2

Adding this here because somebody else may search this again in future, like me. This Answer is an extension to the Accepted Answer

You have two options:

1. Jackson works on setters-getters of fields. So, you can just remove getter of field which you want to omit in JSON. ( If you don't need getter at other place.)

2. Or, you can use the `@JsonIgnore` [annotation of Jackson][1] on getter method of that field and you see there in no such key-value pair in resulted JSON. 

        @JsonIgnore
        public int getSecurityCode(){
           return securityCode;
        }

Actually, newer version of Jackson added READ_ONLY and WRITE_ONLY annotation arguments for JsonProperty. So you could also do something like this.

@JsonProperty(access = Access.WRITE_ONLY)
private String securityCode;

instead of

@JsonIgnore
public int getSecurityCode(){
  return securityCode;
}

Answer 3

you also can gather all properties on an annotation class

@JsonIgnoreProperties( { "applications" })
public MyClass ...

String applications;

Answer 4

If you don't want to put annotations on your Pojos you can also use Genson.

Here is how you can exclude a field with it without any annotations (you can also use annotations if you want, but you have the choice).

Genson genson = new Genson.Builder().exclude("securityCode", User.class).create();
// and then
String json = genson.serialize(user);

Answer 5

Field Level:

public class User {
    private String name;
    private int age;
    @JsonIgnore
    private int securityCode;

    // getters and setters
}

Class Level:

@JsonIgnoreProperties(value = { "securityCode" })
public class User {
    private String name;
    private int age;
    private int securityCode;
}

Answer 6

if you are using GSON you have to mark the field/member declarations as @Expose and use the GsonBuilder().excludeFieldsWithoutExposeAnnotation().create()

Don't forget to mark your sub classes with @Expose otherwise the fields won't show.

Answer 7

I suggest you use this.

   @JsonProperty(access = JsonProperty.Access.WRITE_ONLY)
   private int securityCode;

This allows you to set the value of securityCode(especially if you use lombok @Setter) and also prevent the field from showing up in the GET request.

Answer 8

I had a similar case where I needed some property to be deserialized (JSON to Object) but not serialized (Object to JSON)

First i went for @JsonIgnore - it did prevent serialization of unwanted property, but failed to de-serialize it too. Trying value attribute didn't help either as it requires some condition.

Finally, working @JsonProperty with access attribute worked like a charm.