How to hide specific variables in Pojo classes while generating JSON responses

Question

I am trying to hide some fields in a Pojo class while generating Json responses. Assume there are 4 variables in my java class. In the first response, I need all variables to be generated in the json object. For the next response, I only need 3 variables in the json object.

(The hiding part possibly be implemented when object creation and not inside the class implementation.) Is there a way to do this?

Answer 1

This can be achieved with @JsonView feature. This feature allows you to define multiple "views" = set of attributes, for a given class.

Each view is a simple marker class. for convinience, you can put them all inside one wrapper class (it can even be the pojo class itself)

public class PojoViews {
    public static class Response1{}
    public static class Response2{}
    public static class Response3{}
}

The view classes are specified as annotation for every attributre that is to be included in seralization

public class Pojo {

    @JsonView({PojoViews.Response1.class, PojoViews.Response2.class, PojoViews.Response3.class})
    public String attr1;
    @JsonView({PojoViews.Response1.class, PojoViews.Response2.class, PojoViews.Response3.class})
    public int attr2;
    @JsonView({PojoViews.Response1.class, PojoViews.Response2.class})
    public double attr3;
    @JsonView(PojoViews.Response1.class)
    public boolean attr4;
}

at runtime, you can assign a particular view to produce desired set af attributes

ObjectMapper mapper = new ObjectMapper();
Class<?> view = Pojo.Response2.class;  // runtime assignment of view
mapper.writerWithView(view).writeValue(System.out, pojo);