GraphQL design

graphql.schema

query GetUser {
  user {
    name
  }
}

type Query {
  user(id: ID!): User
}

type User {
  id: ID!
  name: String
}

Query.java

public class Query {
  private User.Query user;

  private Query(Builder builder) {
    user = builder.user;
  }

  public static Builder builder() {
    return new Builder();
  }

  public static class Builder {
    private User.Query user;

    public Builder user(ID id) {
      this.user = new User.Query(id);
      return this;
    }

    public Query build() {
      return new Query(this);
    }
  }
}

User.java

public class User {
  private final ID id;

  private final String name;

  private User(Builder builder) {
    this.id = builder.id;
    this.name = builder.name;
  }

  public ID getId() {
    return this.id;
  }

  public Optional<String> getName() {
    return Optional.ofNullable(this.name);
  }

  public static Builder builder(ID id) {
    return new Builder(id);
  }

  public static class Builder {
    private final ID id;

    private String name;    

    public Builder(ID id) {
      this.id = id
    }

    public Builder name(String name) {
      this.name = name;
      return this;
    }

    public User build() {
      return new User(this);
    }
  }

  static class Query {
    private final ID id;

    Query(ID id) {
      Preconditions.notNull(id, "id is a required field");
      this.id = id;
    }
  }
}