Gson: How to exclude specific fields from Serialization without annotations

Question

I'm trying to learn Gson and I'm struggling with field exclusion. Here are my classes

public class Student {       private Long                id;   private String              firstName        = "Philip";   private String              middleName       = "J.";   private String              initials         = "P.F";   private String              lastName         = "Fry";   private Country             country;   private Country             countryOfBirth; }  public class Country {       private Long                id;   private String              name;   private Object              other; } 

I can use the GsonBuilder and add an ExclusionStrategy for a field name like firstName or country but I can't seem to manage to exclude properties of certain fields like country.name.

Using the method public boolean shouldSkipField(FieldAttributes fa), FieldAttributes doesn't contain enough information to match the field with a filter like country.name.

P.S: I want to avoid annotations since I want to improve on this and use RegEx to filter fields out.

Edit: I'm trying to see if it's possible to emulate the behavior of Struts2 JSON plugin

using Gson

<interceptor-ref name="json">   <param name="enableSMD">true</param>   <param name="excludeProperties">     login.password,     studentList.*\.sin   </param> </interceptor-ref> 

Edit: I reopened the question with the following addition:

I added a second field with the same type to futher clarify this problem. Basically I want to exclude country.name but not countrOfBirth.name. I also don't want to exclude Country as a type. So the types are the same it's the actual place in the object graph that I want to pinpoint and exclude.

Answer 1

Any fields you don't want serialized in general you should use the "transient" modifier, and this also applies to json serializers (at least it does to a few that I have used, including gson).

If you don't want name to show up in the serialized json give it a transient keyword, eg:

private transient String name; 

More details in the Gson documentation

Answer 2

Nishant provided a good solution, but there's an easier way. Simply mark the desired fields with the @Expose annotation, such as:

@Expose private Long id; 

Leave out any fields that you do not want to serialize. Then just create your Gson object this way:

Gson gson = new GsonBuilder().excludeFieldsWithoutExposeAnnotation().create();