Class and field level @JsonView annotation and Object Mapper

Question

I have views and entity class as shown below:

class Views{
   class ViewOne{}
   class ViewTwo{}
}

class Test{

   @JsonView({Views.ViewOne.class})
   public int x;

   @JsonView({Views.ViewTwo.class})
   public int y;

   public int z;

   public int v;
}

My question is that do I need to have @JsonView({Views.ViewOne.class, Views.ViewTwo.class}) at class level so that I have non-annotated fields like z, v in the output response irrespective of View Class passed to Object Mapper?

I did try to look into different resources regarding the use of class level @JsonView annotation but I couldn't find any. Does it have any effect? If yes, pls do explain the same.

Answer 1

Do I need to have @JsonView({Views.ViewOne.class, Views.ViewTwo.class}) at class level so that I have non-annotated fields like z, v in the output response irrespective of view class passed to ObjectMapper?

You won't need that when MapperFeature.DEFAULT_VIEW_INCLUSION is enabled in your ObjectMapper instance. This feature is enabled by default. May have you disabled it somehow?

Here's a quote from the documentation:

Feature that determines whether properties that have no view annotations are included in JSON serialization views (see @JsonView for more details on JSON Views). If enabled, non-annotated properties will be included; when disabled, they will be excluded.

---

Example 1

Let's consider the following Example class:

@Data
public class Example {

    private int a = 1;

    private int b = 2;

    private int c = 3;
}

And let's serialize an instance of Example as a JSON using:

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

It will produce the following JSON:

{"a":1,"b":2,"c":3}

---

Example 2

Now let's take the following views into account:

public class Views {

    public static class Foo {}

    public static class Bar {}
}

And let's the apply the views to the fields of the Example class:

@Data
public class Example {

    @JsonView(Views.Foo.class)
    private int a = 1;

    @JsonView(Views.Bar.class)
    private int b = 2;

    private int c = 3;
}

And let's serialize an instance of Example using the Foo view:

ObjectMapper mapper = new ObjectMapper();
String json = mapper.writerWithView(Views.Foo.class).writeValueAsString(new Example());

It will produce the following JSON:

{"a":1,"c":3}

Now let's disable the default view inclusion an serialize it again:

ObjectMapper mapper = new ObjectMapper();
mapper.disable(MapperFeature.DEFAULT_VIEW_INCLUSION);
String json = mapper.writerWithView(Views.Foo.class).writeValueAsString(new Example());

It will produce the following JSON:

{"a":1}

---

Example 3

Now let's use the following view configuration in the Example class:

@Data
@JsonView(Views.Foo.class)
public static class Example {

    private int a = 1;

    @JsonView(Views.Bar.class)
    private int b = 2;

    private int c = 3;
}

And let's serialize an instance of Example using the Foo view:

ObjectMapper mapper = new ObjectMapper();
String json = mapper.writerWithView(Views.Foo.class).writeValueAsString(new Example());

It will produce the following JSON:

{"a":1,"c":3}

Now let's serialize an instance of Example using the Bar view:

ObjectMapper mapper = new ObjectMapper();
String json = mapper.writerWithView(Views.Bar.class).writeValueAsString(new Example());

It will produce the following JSON:

{"b":2}