diff --git a/lib/active_model/serializer/adapter/json_api.rb b/lib/active_model/serializer/adapter/json_api.rb
index e00a46eac..69a07e54d 100644
--- a/lib/active_model/serializer/adapter/json_api.rb
+++ b/lib/active_model/serializer/adapter/json_api.rb
@@ -6,9 +6,8 @@ class JsonApi < Base
         autoload :PaginationLinks
         autoload :FragmentCache
         autoload :Link
-        autoload :Association
-        autoload :ResourceIdentifier
         autoload :Deserialization
+        require 'active_model/serializer/adapter/json_api/api_objects'
 
         # TODO: if we like this abstraction and other API objects to it,
         # then extract to its own file and require it.
@@ -99,7 +98,7 @@ def resource_objects_for(serializers)
         end
 
         def process_resource(serializer, primary)
-          resource_identifier = JsonApi::ResourceIdentifier.new(serializer).as_json
+          resource_identifier = ApiObjects::ResourceIdentifier.new(serializer).as_json
           return false unless @resource_identifiers.add?(resource_identifier)
 
           resource_object = resource_object_for(serializer)
@@ -135,7 +134,7 @@ def attributes_for(serializer, fields)
 
         def resource_object_for(serializer)
           resource_object = cache_check(serializer) do
-            resource_object = JsonApi::ResourceIdentifier.new(serializer).as_json
+            resource_object = ApiObjects::ResourceIdentifier.new(serializer).as_json
 
             requested_fields = fieldset && fieldset.fields_for(resource_object[:type])
             attributes = attributes_for(serializer, requested_fields)
@@ -156,12 +155,13 @@ def resource_object_for(serializer)
         def relationships_for(serializer, requested_associations)
           include_tree = IncludeTree.from_include_args(requested_associations)
           serializer.associations(include_tree).each_with_object({}) do |association, hash|
-            hash[association.key] = JsonApi::Association.new(serializer,
-                                                             association.serializer,
-                                                             association.options,
-                                                             association.links,
-                                                             association.meta)
-                                    .as_json
+            hash[association.key] = ApiObjects::Relationship.new(
+              serializer,
+              association.serializer,
+              association.options,
+              association.links,
+              association.meta
+            ).as_json
           end
         end
 
diff --git a/lib/active_model/serializer/adapter/json_api/api_objects.rb b/lib/active_model/serializer/adapter/json_api/api_objects.rb
new file mode 100644
index 000000000..bad3173c3
--- /dev/null
+++ b/lib/active_model/serializer/adapter/json_api/api_objects.rb
@@ -0,0 +1,13 @@
+module ActiveModel
+  class Serializer
+    module Adapter
+      class JsonApi
+        module ApiObjects
+          extend ActiveSupport::Autoload
+          autoload :Relationship
+          autoload :ResourceIdentifier
+        end
+      end
+    end
+  end
+end
diff --git a/lib/active_model/serializer/adapter/json_api/api_objects/relationship.rb b/lib/active_model/serializer/adapter/json_api/api_objects/relationship.rb
new file mode 100644
index 000000000..d1ebc1b96
--- /dev/null
+++ b/lib/active_model/serializer/adapter/json_api/api_objects/relationship.rb
@@ -0,0 +1,52 @@
+module ActiveModel
+  class Serializer
+    module Adapter
+      class JsonApi
+        module ApiObjects
+          class Relationship
+            def initialize(parent_serializer, serializer, options = {}, links = {}, meta = nil)
+              @object = parent_serializer.object
+              @scope = parent_serializer.scope
+
+              @options = options
+              @data = data_for(serializer, options)
+              @links = links.each_with_object({}) do |(key, value), hash|
+                hash[key] = Link.new(parent_serializer, value).as_json
+              end
+              @meta = meta.respond_to?(:call) ? parent_serializer.instance_eval(&meta) : meta
+            end
+
+            def as_json
+              hash = {}
+              hash[:data] = data if options[:include_data]
+              links = self.links
+              hash[:links] = links if links.any?
+              meta = self.meta
+              hash[:meta] = meta if meta
+
+              hash
+            end
+
+            protected
+
+            attr_reader :object, :scope, :data, :options, :links, :meta
+
+            private
+
+            def data_for(serializer, options)
+              if serializer.respond_to?(:each)
+                serializer.map { |s| ResourceIdentifier.new(s).as_json }
+              else
+                if options[:virtual_value]
+                  options[:virtual_value]
+                elsif serializer && serializer.object
+                  ResourceIdentifier.new(serializer).as_json
+                end
+              end
+            end
+          end
+        end
+      end
+    end
+  end
+end
diff --git a/lib/active_model/serializer/adapter/json_api/api_objects/resource_identifier.rb b/lib/active_model/serializer/adapter/json_api/api_objects/resource_identifier.rb
new file mode 100644
index 000000000..058f06031
--- /dev/null
+++ b/lib/active_model/serializer/adapter/json_api/api_objects/resource_identifier.rb
@@ -0,0 +1,39 @@
+module ActiveModel
+  class Serializer
+    module Adapter
+      class JsonApi
+        module ApiObjects
+          class ResourceIdentifier
+            def initialize(serializer)
+              @id = id_for(serializer)
+              @type = type_for(serializer)
+            end
+
+            def as_json
+              { id: id, type: type }
+            end
+
+            protected
+
+            attr_reader :id, :type
+
+            private
+
+            def type_for(serializer)
+              return serializer._type if serializer._type
+              if ActiveModelSerializers.config.jsonapi_resource_type == :singular
+                serializer.object.class.model_name.singular
+              else
+                serializer.object.class.model_name.plural
+              end
+            end
+
+            def id_for(serializer)
+              serializer.read_attribute_for_serialization(:id).to_s
+            end
+          end
+        end
+      end
+    end
+  end
+end
diff --git a/lib/active_model/serializer/adapter/json_api/association.rb b/lib/active_model/serializer/adapter/json_api/association.rb
deleted file mode 100644
index b6cfc70dd..000000000
--- a/lib/active_model/serializer/adapter/json_api/association.rb
+++ /dev/null
@@ -1,48 +0,0 @@
-module ActiveModel
-  class Serializer
-    module Adapter
-      class JsonApi
-        class Association
-          def initialize(parent_serializer, serializer, options, links, meta)
-            @object = parent_serializer.object
-            @scope = parent_serializer.scope
-
-            @options = options
-            @data = data_for(serializer, options)
-            @links = links
-                     .map { |key, value| { key => Link.new(parent_serializer, value).as_json } }
-                     .reduce({}, :merge)
-            @meta = meta.respond_to?(:call) ? parent_serializer.instance_eval(&meta) : meta
-          end
-
-          def as_json
-            hash = {}
-            hash[:data] = @data if @options[:include_data]
-            hash[:links] = @links if @links.any?
-            hash[:meta] = @meta if @meta
-
-            hash
-          end
-
-          protected
-
-          attr_reader :object, :scope
-
-          private
-
-          def data_for(serializer, options)
-            if serializer.respond_to?(:each)
-              serializer.map { |s| ResourceIdentifier.new(s).as_json }
-            else
-              if options[:virtual_value]
-                options[:virtual_value]
-              elsif serializer && serializer.object
-                ResourceIdentifier.new(serializer).as_json
-              end
-            end
-          end
-        end
-      end
-    end
-  end
-end
diff --git a/lib/active_model/serializer/adapter/json_api/resource_identifier.rb b/lib/active_model/serializer/adapter/json_api/resource_identifier.rb
deleted file mode 100644
index 99bff2981..000000000
--- a/lib/active_model/serializer/adapter/json_api/resource_identifier.rb
+++ /dev/null
@@ -1,41 +0,0 @@
-module ActiveModel
-  class Serializer
-    module Adapter
-      class JsonApi
-        class ResourceIdentifier
-          def initialize(serializer)
-            @id = id_for(serializer)
-            @type = type_for(serializer)
-          end
-
-          def as_json
-            { id: @id.to_s, type: @type }
-          end
-
-          protected
-
-          attr_reader :object, :scope
-
-          private
-
-          def type_for(serializer)
-            return serializer._type if serializer._type
-            if ActiveModelSerializers.config.jsonapi_resource_type == :singular
-              serializer.object.class.model_name.singular
-            else
-              serializer.object.class.model_name.plural
-            end
-          end
-
-          def id_for(serializer)
-            if serializer.respond_to?(:id)
-              serializer.id
-            else
-              serializer.object.id
-            end
-          end
-        end
-      end
-    end
-  end
-end
diff --git a/test/adapter/json_api/api_objects/relationship_test.rb b/test/adapter/json_api/api_objects/relationship_test.rb
new file mode 100644
index 000000000..5564400ea
--- /dev/null
+++ b/test/adapter/json_api/api_objects/relationship_test.rb
@@ -0,0 +1,168 @@
+require 'test_helper'
+
+module ActiveModel
+  class Serializer
+    module Adapter
+      class JsonApi
+        module ApiObjects
+          class RelationshipTest < ActiveSupport::TestCase
+            def setup
+              @blog = Blog.new(id: 1)
+              @author = Author.new(id: 1, name: 'Steve K.', blog: @blog)
+              @serializer = BlogSerializer.new(@blog)
+              ActionController::Base.cache_store.clear
+            end
+
+            def test_relationship_with_data
+              expected = {
+                data: {
+                  id: '1',
+                  type: 'blogs'
+                }
+              }
+              test_relationship(expected, options: { include_data: true })
+            end
+
+            def test_relationship_with_nil_model
+              @serializer = BlogSerializer.new(nil)
+              expected = { data: nil }
+              test_relationship(expected, options: { include_data: true })
+            end
+
+            def test_relationship_with_nil_serializer
+              @serializer = nil
+              expected = { data: nil }
+              test_relationship(expected, options: { include_data: true })
+            end
+
+            def test_relationship_with_data_array
+              posts = [Post.new(id: 1), Post.new(id: 2)]
+              @serializer = ActiveModel::Serializer::ArraySerializer.new(posts)
+              @author.posts = posts
+              @author.blog = nil
+              expected = {
+                data: [
+                  {
+                    id: '1',
+                    type: 'posts'
+                  },
+                  {
+                    id: '2',
+                    type: 'posts'
+                  }
+                ]
+              }
+              test_relationship(expected, options: { include_data: true })
+            end
+
+            def test_relationship_data_not_included
+              test_relationship({}, options: { include_data: false })
+            end
+
+            def test_relationship_simple_link
+              links = { self: 'a link' }
+              test_relationship({ links: { self: 'a link' } }, links: links)
+            end
+
+            def test_relationship_many_links
+              links = {
+                self: 'a link',
+                related: 'another link'
+              }
+              expected = {
+                links: {
+                  self: 'a link',
+                  related: 'another link'
+                }
+              }
+              test_relationship(expected, links: links)
+            end
+
+            def test_relationship_block_link
+              links = { self: proc { "#{object.id}" } }
+              expected = { links: { self: "#{@blog.id}" } }
+              test_relationship(expected, links: links)
+            end
+
+            def test_relationship_block_link_with_meta
+              links = {
+                self: proc do
+                  href "#{object.id}"
+                  meta(id: object.id)
+                end
+              }
+              expected = {
+                links: {
+                  self: {
+                    href: "#{@blog.id}",
+                    meta: { id: @blog.id }
+                  }
+                }
+              }
+              test_relationship(expected, links: links)
+            end
+
+            def test_relationship_simple_meta
+              meta = { id: '1' }
+              expected = { meta: meta }
+              test_relationship(expected, meta: meta)
+            end
+
+            def test_relationship_block_meta
+              meta =  proc do
+                { id: object.id }
+              end
+              expected = {
+                meta: {
+                  id: @blog.id
+                }
+              }
+              test_relationship(expected, meta: meta)
+            end
+
+            def test_relationship_with_everything
+              links = {
+                self: 'a link',
+                related: proc do
+                  href "#{object.id}"
+                  meta object.id
+                end
+
+              }
+              meta = proc do
+                { id: object.id }
+              end
+              expected = {
+                data: {
+                  id: '1',
+                  type: 'blogs'
+                },
+                links: {
+                  self: 'a link',
+                  related: {
+                    href: '1', meta: 1
+                  }
+                },
+                meta: {
+                  id: @blog.id
+                }
+              }
+              test_relationship(expected, meta: meta, options: { include_data: true }, links: links)
+            end
+
+            private
+
+            def test_relationship(expected, params = {})
+              options = params.fetch(:options, {})
+              links = params.fetch(:links, {})
+              meta = params[:meta]
+              parent_serializer = AuthorSerializer.new(@author)
+              relationship = Relationship.new(parent_serializer, @serializer, options, links, meta)
+              assert_equal(expected, relationship.as_json)
+            end
+          end
+        end
+      end
+    end
+  end
+end
diff --git a/test/adapter/json_api/api_objects/resource_identifier_test.rb b/test/adapter/json_api/api_objects/resource_identifier_test.rb
new file mode 100644
index 000000000..a40f07071
--- /dev/null
+++ b/test/adapter/json_api/api_objects/resource_identifier_test.rb
@@ -0,0 +1,88 @@
+require 'test_helper'
+
+module ActiveModel
+  class Serializer
+    module Adapter
+      class JsonApi
+        module ApiObjects
+          class ResourceIdentifierTest < ActiveSupport::TestCase
+            class WithDefinedTypeSerializer < Serializer
+              type 'with_defined_type'
+            end
+
+            class WithDefinedIdSerializer < Serializer
+              def id
+                'special_id'
+              end
+            end
+
+            class FragmentedSerializer < Serializer; end
+
+            def setup
+              @model = Author.new(id: 1, name: 'Steve K.')
+              ActionController::Base.cache_store.clear
+            end
+
+            def test_defined_type
+              test_type(WithDefinedTypeSerializer, 'with_defined_type')
+            end
+
+            def test_singular_type
+              test_type_inflection(AuthorSerializer, 'author', :singular)
+            end
+
+            def test_plural_type
+              test_type_inflection(AuthorSerializer, 'authors', :plural)
+            end
+
+            def test_id_defined_on_object
+              test_id(AuthorSerializer, @model.id.to_s)
+            end
+
+            def test_id_defined_on_serializer
+              test_id(WithDefinedIdSerializer, 'special_id')
+            end
+
+            def test_id_defined_on_fragmented
+              FragmentedSerializer.fragmented(WithDefinedIdSerializer.new(@author))
+              test_id(FragmentedSerializer, 'special_id')
+            end
+
+            private
+
+            def test_type_inflection(serializer_class, expected_type, inflection)
+              original_inflection = ActiveModelSerializers.config.jsonapi_resource_type
+              ActiveModelSerializers.config.jsonapi_resource_type = inflection
+              test_type(serializer_class, expected_type)
+              ActiveModelSerializers.config.jsonapi_resource_type = original_inflection
+            end
+
+            def test_type(serializer_class, expected_type)
+              serializer = serializer_class.new(@model)
+              resource_identifier = ResourceIdentifier.new(serializer)
+              expected = {
+                id: @model.id.to_s,
+                type: expected_type
+              }
+
+              assert_equal(expected, resource_identifier.as_json)
+            end
+
+            def test_id(serializer_class, id)
+              serializer = serializer_class.new(@model)
+              resource_identifier = ResourceIdentifier.new(serializer)
+              inflection = ActiveModelSerializers.config.jsonapi_resource_type
+              type = @model.class.model_name.send(inflection)
+              expected = {
+                id: id,
+                type: type
+              }
+
+              assert_equal(expected, resource_identifier.as_json)
+            end
+          end
+        end
+      end
+    end
+  end
+end