From 5b973fdf7a5a32ffbae9c44bb3dcc1be8b88a34d Mon Sep 17 00:00:00 2001
From: Sander Van Dooren <sander.vandooren@gmail.com>
Date: Thu, 22 Nov 2018 11:18:09 +0100
Subject: [PATCH 01/12] Support construct queries.

---
 driver/sparql/Connection.php                  | 31 +++++++++++++++++++
 modules/rdf_export/src/RdfSerializer.php      |  2 +-
 .../Driver/sparql/ConnectionInterface.php     | 22 +++++++++++++
 3 files changed, 54 insertions(+), 1 deletion(-)

diff --git a/driver/sparql/Connection.php b/driver/sparql/Connection.php
index b83b93e3..627a1ee5 100644
--- a/driver/sparql/Connection.php
+++ b/driver/sparql/Connection.php
@@ -8,6 +8,7 @@
 use Drupal\rdf_entity\Database\Driver\sparql\ConnectionInterface;
 use Drupal\rdf_entity\Database\Driver\sparql\StatementStub;
 use Drupal\rdf_entity\Exception\SparqlQueryException;
+use EasyRdf\Graph;
 use EasyRdf\Http\Exception as EasyRdfException;
 use EasyRdf\Sparql\Client;
 use EasyRdf\Sparql\Result;
@@ -89,6 +90,36 @@ public function __construct(Client $easy_rdf_client, array $connection_options)
    * {@inheritdoc}
    */
   public function query(string $query, array $args = [], array $options = []): Result {
+    return $this->doQuery($query, $args, $options);
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function constructQuery(string $query, array $args = [], array $options = []): Graph {
+    return $this->doQuery($query, $args, $options);
+  }
+
+  /**
+   * Execute the query against the endpoint.
+   *
+   * @param string $query
+   *   The string query to execute.
+   * @param array $args
+   *   An array of arguments for the query.
+   * @param array $options
+   *   An associative array of options to control how the query is run.
+   *
+   * @return \EasyRdf\Sparql\Result | \EasyRdf\Graph
+   *   The query result.
+   *
+   * @throws \InvalidArgumentException
+   *   If $args value is passed but arguments replacement is not yet
+   *   supported. To be removed in #55.
+   *
+   * @see https://github.com/ec-europa/rdf_entity/issues/55
+   */
+  public function doQuery(string $query, array $args = [], array $options = []) {
     // @todo Remove this in #55.
     // @see https://github.com/ec-europa/rdf_entity/issues/55
     if ($args) {
diff --git a/modules/rdf_export/src/RdfSerializer.php b/modules/rdf_export/src/RdfSerializer.php
index b80ac345..14e9ba7a 100644
--- a/modules/rdf_export/src/RdfSerializer.php
+++ b/modules/rdf_export/src/RdfSerializer.php
@@ -49,7 +49,7 @@ public function serializeEntity(RdfInterface $entity, string $format = 'turtle')
 SPARQL;
 
     /** @var \EasyRdf\Graph $graph */
-    $graph = $this->sparqlEndpoint->query($query);
+    $graph = $this->sparqlEndpoint->constructQuery($query);
     return $graph->serialise($format);
   }
 
diff --git a/src/Database/Driver/sparql/ConnectionInterface.php b/src/Database/Driver/sparql/ConnectionInterface.php
index 5d447020..1bfdd194 100644
--- a/src/Database/Driver/sparql/ConnectionInterface.php
+++ b/src/Database/Driver/sparql/ConnectionInterface.php
@@ -5,6 +5,7 @@
 namespace Drupal\rdf_entity\Database\Driver\sparql;
 
 use Drupal\Core\Database\Log;
+use EasyRdf\Graph;
 use EasyRdf\Sparql\Client;
 use EasyRdf\Sparql\Result;
 
@@ -34,6 +35,27 @@ interface ConnectionInterface {
    */
   public function query(string $query, array $args = [], array $options = []): Result;
 
+  /**
+   * Executes the actual query against the Sparql endpoint.
+   *
+   * @param string $query
+   *   The string query to execute.
+   * @param array $args
+   *   An array of arguments for the query.
+   * @param array $options
+   *   An associative array of options to control how the query is run.
+   *
+   * @return \EasyRdf\Sparql\Result
+   *   The query result.
+   *
+   * @throws \InvalidArgumentException
+   *   If $args value is passed but arguments replacement is not yet
+   *   supported. To be removed in #55.
+   *
+   * @see https://github.com/ec-europa/rdf_entity/issues/55
+   */
+  public function constructQuery(string $query, array $args = [], array $options = []): Graph;
+
   /**
    * Execute the actual update query against the Sparql endpoint.
    *

From 254908a215d532b45c3ec0e30c08526294baacb4 Mon Sep 17 00:00:00 2001
From: Sander Van Dooren <sander.vandooren@gmail.com>
Date: Thu, 22 Nov 2018 11:45:59 +0100
Subject: [PATCH 02/12] Coding standards fixes.

---
 driver/sparql/Connection.php | 4 +++-
 rdf_entity.module            | 2 +-
 2 files changed, 4 insertions(+), 2 deletions(-)

diff --git a/driver/sparql/Connection.php b/driver/sparql/Connection.php
index 627a1ee5..e3da290f 100644
--- a/driver/sparql/Connection.php
+++ b/driver/sparql/Connection.php
@@ -110,12 +110,14 @@ public function constructQuery(string $query, array $args = [], array $options =
    * @param array $options
    *   An associative array of options to control how the query is run.
    *
-   * @return \EasyRdf\Sparql\Result | \EasyRdf\Graph
+   * @return \EasyRdf\Sparql\Result|\EasyRdf\Graph
    *   The query result.
    *
    * @throws \InvalidArgumentException
    *   If $args value is passed but arguments replacement is not yet
    *   supported. To be removed in #55.
+   * @throws SparqlQueryException
+   *   Exception during query execution, e.g. timeout.
    *
    * @see https://github.com/ec-europa/rdf_entity/issues/55
    */
diff --git a/rdf_entity.module b/rdf_entity.module
index 59989c15..19fb0438 100755
--- a/rdf_entity.module
+++ b/rdf_entity.module
@@ -351,7 +351,7 @@ function rdf_entity_type_mapping_submit(array &$form, FormStateInterface $form_s
     /** @var \Drupal\rdf_entity\RdfEntityTypeInterface $entity */
     $bundle_entity = $form_state->getFormObject()->getEntity();
     $mapping = RdfEntityMapping::create([
-      'entity_type_id' => $bundle_entity->getEntityType()->getBundleOf() ,
+      'entity_type_id' => $bundle_entity->getEntityType()->getBundleOf(),
       'bundle' => $form_state->getFormObject()->getEntity()->id(),
     ]);
   }

From 2cbc272eae35c850f8b3910de70a085e25f6dfd0 Mon Sep 17 00:00:00 2001
From: Sander Van Dooren <sander.vandooren@gmail.com>
Date: Mon, 26 Nov 2018 13:53:57 +0100
Subject: [PATCH 03/12] Turn doQuery into a protected method, as this should
 not be external.

---
 driver/sparql/Connection.php | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/driver/sparql/Connection.php b/driver/sparql/Connection.php
index e3da290f..e0964911 100644
--- a/driver/sparql/Connection.php
+++ b/driver/sparql/Connection.php
@@ -121,7 +121,7 @@ public function constructQuery(string $query, array $args = [], array $options =
    *
    * @see https://github.com/ec-europa/rdf_entity/issues/55
    */
-  public function doQuery(string $query, array $args = [], array $options = []) {
+  protected function doQuery(string $query, array $args = [], array $options = []) {
     // @todo Remove this in #55.
     // @see https://github.com/ec-europa/rdf_entity/issues/55
     if ($args) {

From 8d9172c81d0924eb58e8c86d61447747b47b3898 Mon Sep 17 00:00:00 2001
From: Sander Van Dooren <sander.vandooren@gmail.com>
Date: Mon, 26 Nov 2018 14:07:30 +0100
Subject: [PATCH 04/12] Improve interface documentation.

---
 src/Database/Driver/sparql/ConnectionInterface.php | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/src/Database/Driver/sparql/ConnectionInterface.php b/src/Database/Driver/sparql/ConnectionInterface.php
index 1bfdd194..0d36053d 100644
--- a/src/Database/Driver/sparql/ConnectionInterface.php
+++ b/src/Database/Driver/sparql/ConnectionInterface.php
@@ -15,7 +15,7 @@
 interface ConnectionInterface {
 
   /**
-   * Executes the actual query against the Sparql endpoint.
+   * Execute a select/insert/update query, returning a query result.
    *
    * @param string $query
    *   The string query to execute.
@@ -36,7 +36,7 @@ interface ConnectionInterface {
   public function query(string $query, array $args = [], array $options = []): Result;
 
   /**
-   * Executes the actual query against the Sparql endpoint.
+   * Execute a construct query, returning a graph of triples.
    *
    * @param string $query
    *   The string query to execute.

From 6c9b0d5450432aedf386b9ee4f13d357000a9970 Mon Sep 17 00:00:00 2001
From: Sander Van Dooren <sander.vandooren@gmail.com>
Date: Mon, 26 Nov 2018 14:36:41 +0100
Subject: [PATCH 05/12] Fix docblock with correct return type.

---
 src/Database/Driver/sparql/ConnectionInterface.php | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/src/Database/Driver/sparql/ConnectionInterface.php b/src/Database/Driver/sparql/ConnectionInterface.php
index 0d36053d..0d667657 100644
--- a/src/Database/Driver/sparql/ConnectionInterface.php
+++ b/src/Database/Driver/sparql/ConnectionInterface.php
@@ -45,8 +45,8 @@ public function query(string $query, array $args = [], array $options = []): Res
    * @param array $options
    *   An associative array of options to control how the query is run.
    *
-   * @return \EasyRdf\Sparql\Result
-   *   The query result.
+   * @return \EasyRdf\Graph
+   *   The set of triples.
    *
    * @throws \InvalidArgumentException
    *   If $args value is passed but arguments replacement is not yet

From 0bb2e65f04402d2cb83b4b3b209655bee0b2cbc9 Mon Sep 17 00:00:00 2001
From: Sander Van Dooren <sander.vandooren@gmail.com>
Date: Fri, 30 Nov 2018 10:02:04 +0100
Subject: [PATCH 06/12] Add content negotiation to rdf_export.

---
 modules/rdf_export/rdf_export.services.yml    | 29 ++++++++++
 modules/rdf_export/src/Encoder/RdfEncoder.php | 57 +++++++++++++++++++
 .../src/EventSubscriber/RdfSubscriber.php     | 37 ++++++++++++
 .../src/Normalizer/NormalizerBase.php         | 20 +++++++
 .../src/Normalizer/RdfEntityNormalizer.php    | 39 +++++++++++++
 .../Driver/sparql/ConnectionInterface.php     |  4 +-
 6 files changed, 184 insertions(+), 2 deletions(-)
 create mode 100644 modules/rdf_export/src/Encoder/RdfEncoder.php
 create mode 100644 modules/rdf_export/src/EventSubscriber/RdfSubscriber.php
 create mode 100644 modules/rdf_export/src/Normalizer/NormalizerBase.php
 create mode 100644 modules/rdf_export/src/Normalizer/RdfEntityNormalizer.php

diff --git a/modules/rdf_export/rdf_export.services.yml b/modules/rdf_export/rdf_export.services.yml
index 857b025f..fcf86f69 100644
--- a/modules/rdf_export/rdf_export.services.yml
+++ b/modules/rdf_export/rdf_export.services.yml
@@ -7,3 +7,32 @@ services:
   rdf_export.serializer:
     class: Drupal\rdf_export\RdfSerializer
     arguments: ['@sparql_endpoint']
+  rdf_export.encoder.jsonld:
+    class: Drupal\rdf_export\Encoder\RdfEncoder
+    tags:
+      - { name: encoder, format: jsonld }
+  rdf_export.encoder.rdfxml:
+    class: Drupal\rdf_export\Encoder\RdfEncoder
+    tags:
+      - { name: encoder, format: rdfxml }
+  rdf_export.encoder.ntriples:
+    class: Drupal\rdf_export\Encoder\RdfEncoder
+    tags:
+      - { name: encoder, format: ntriples }
+  rdf_export.encoder.turtle:
+    class: Drupal\rdf_export\Encoder\RdfEncoder
+    tags:
+      - { name: encoder, format: turtle }
+  rdf_export.encoder.n3:
+    class: Drupal\rdf_export\Encoder\RdfEncoder
+    tags:
+      - { name: encoder, format: n3 }
+  rdf_export.rdfsubscriber:
+    class: Drupal\rdf_export\EventSubscriber\RdfSubscriber
+    tags:
+      - { name: event_subscriber }
+  serializer.normalizer.entity.rdf:
+    class: Drupal\rdf_export\Normalizer\RdfEntityNormalizer
+    arguments: ['@rdf_export.serializer']
+    tags:
+      - { name: normalizer, priority: 10 }
\ No newline at end of file
diff --git a/modules/rdf_export/src/Encoder/RdfEncoder.php b/modules/rdf_export/src/Encoder/RdfEncoder.php
new file mode 100644
index 00000000..42f0a110
--- /dev/null
+++ b/modules/rdf_export/src/Encoder/RdfEncoder.php
@@ -0,0 +1,57 @@
+<?php
+
+namespace Drupal\rdf_export\Encoder;
+
+use EasyRdf\Format;
+use Symfony\Component\Serializer\Encoder\EncoderInterface;
+
+/**
+ * Adds RDF encoder support for the Serialization API.
+ */
+class RdfEncoder implements EncoderInterface {
+
+  /**
+   * The formats that this encoder supports.
+   *
+   * @var array
+   */
+  protected static $supportedFormats = [
+    'jsonld',
+    'rdfxml',
+    'ntriples',
+    'turtle',
+    'n3',
+  ];
+
+  /**
+   * {@inheritdoc}
+   */
+  public function supportsEncoding($format) {
+    return in_array($format, static::supportedFormats());
+  }
+
+  /**
+   * {@inheritdoc}
+   *
+   * Uses HTML-safe strings, with several characters escaped.
+   */
+  public function encode($data, $format, array $context = []) {
+    if (isset($data['_rdf_entity'])) {
+      return $data['_rdf_entity'];
+    }
+    return NULL;
+  }
+
+  /**
+   * Build a list of supported formats.
+   *
+   * @return \EasyRdf\Format[]
+   *   List of supported formats.
+   */
+  public static function supportedFormats(): array {
+    $formats = Format::getFormats();
+    /** @var \EasyRdf\Format[] $supported_formats */
+    return array_intersect($formats, static::$supportedFormats);
+  }
+
+}
diff --git a/modules/rdf_export/src/EventSubscriber/RdfSubscriber.php b/modules/rdf_export/src/EventSubscriber/RdfSubscriber.php
new file mode 100644
index 00000000..21afc188
--- /dev/null
+++ b/modules/rdf_export/src/EventSubscriber/RdfSubscriber.php
@@ -0,0 +1,37 @@
+<?php
+
+namespace Drupal\rdf_export\EventSubscriber;
+
+use Drupal\rdf_export\Encoder\RdfEncoder;
+use Symfony\Component\HttpKernel\KernelEvents;
+use Symfony\Component\HttpKernel\Event\GetResponseEvent;
+use Symfony\Component\EventDispatcher\EventSubscriberInterface;
+
+/**
+ * Event subscriber for adding RDF content types to the request.
+ */
+class RdfSubscriber implements EventSubscriberInterface {
+
+  /**
+   * Register content type formats on the request object.
+   *
+   * @param \Symfony\Component\HttpKernel\Event\GetResponseEvent $event
+   *   The Event to process.
+   */
+  public function onKernelRequest(GetResponseEvent $event) {
+    /** @var \EasyRdf\Format $format */
+    foreach (RdfEncoder::supportedFormats() as $format) {
+      $mime = array_keys($format->getMimeTypes());
+      $event->getRequest()->setFormat($format->getName(), $mime);
+    }
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public static function getSubscribedEvents() {
+    $events[KernelEvents::REQUEST][] = ['onKernelRequest'];
+    return $events;
+  }
+
+}
diff --git a/modules/rdf_export/src/Normalizer/NormalizerBase.php b/modules/rdf_export/src/Normalizer/NormalizerBase.php
new file mode 100644
index 00000000..bcbdd819
--- /dev/null
+++ b/modules/rdf_export/src/Normalizer/NormalizerBase.php
@@ -0,0 +1,20 @@
+<?php
+
+namespace Drupal\rdf_export\Normalizer;
+
+use Drupal\rdf_export\Encoder\RdfEncoder;
+use Drupal\serialization\Normalizer\NormalizerBase as SerializationNormalizerBase;
+
+/**
+ * Base class for Normalizers.
+ */
+abstract class NormalizerBase extends SerializationNormalizerBase {
+
+  /**
+   * {@inheritdoc}
+   */
+  protected function checkFormat($format = NULL) {
+    return in_array($format, RdfEncoder::supportedFormats());
+  }
+
+}
diff --git a/modules/rdf_export/src/Normalizer/RdfEntityNormalizer.php b/modules/rdf_export/src/Normalizer/RdfEntityNormalizer.php
new file mode 100644
index 00000000..edd8820c
--- /dev/null
+++ b/modules/rdf_export/src/Normalizer/RdfEntityNormalizer.php
@@ -0,0 +1,39 @@
+<?php
+
+namespace Drupal\rdf_export\Normalizer;
+
+use Drupal\rdf_export\RdfSerializer;
+use Drupal\serialization\Normalizer\FieldableEntityNormalizerTrait;
+
+/**
+ * Converts the Drupal entity object structure to a HAL array structure.
+ */
+class RdfEntityNormalizer extends NormalizerBase {
+
+  use FieldableEntityNormalizerTrait;
+
+  /**
+   * The interface or class that this Normalizer supports.
+   *
+   * @var string
+   */
+  protected $supportedInterfaceOrClass = 'Drupal\rdf_entity\RdfInterface';
+
+  /**
+   * RdfEntityNormalizer constructor.
+   *
+   * @param \Drupal\rdf_export\RdfSerializer $rdfSerializer
+   *   RDF Serializer service.
+   */
+  public function __construct(RdfSerializer $rdfSerializer) {
+    $this->rdfSerializer = $rdfSerializer;
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function normalize($entity, $format = NULL, array $context = []) {
+    return ['_rdf_entity' => $this->rdfSerializer->serializeEntity($entity, $format)];
+  }
+
+}
diff --git a/src/Database/Driver/sparql/ConnectionInterface.php b/src/Database/Driver/sparql/ConnectionInterface.php
index 1bfdd194..bcce0436 100644
--- a/src/Database/Driver/sparql/ConnectionInterface.php
+++ b/src/Database/Driver/sparql/ConnectionInterface.php
@@ -45,8 +45,8 @@ public function query(string $query, array $args = [], array $options = []): Res
    * @param array $options
    *   An associative array of options to control how the query is run.
    *
-   * @return \EasyRdf\Sparql\Result
-   *   The query result.
+   * @return \EasyRdf\Graph
+   *   The set of triples.
    *
    * @throws \InvalidArgumentException
    *   If $args value is passed but arguments replacement is not yet

From d343bb4f3c35e9eec2e2e026917d6ca3d12a6c0a Mon Sep 17 00:00:00 2001
From: Sander Van Dooren <sander.vandooren@gmail.com>
Date: Mon, 3 Dec 2018 09:23:26 +0100
Subject: [PATCH 07/12] Newline :(

---
 modules/rdf_export/rdf_export.services.yml | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/modules/rdf_export/rdf_export.services.yml b/modules/rdf_export/rdf_export.services.yml
index fcf86f69..4324e215 100644
--- a/modules/rdf_export/rdf_export.services.yml
+++ b/modules/rdf_export/rdf_export.services.yml
@@ -35,4 +35,4 @@ services:
     class: Drupal\rdf_export\Normalizer\RdfEntityNormalizer
     arguments: ['@rdf_export.serializer']
     tags:
-      - { name: normalizer, priority: 10 }
\ No newline at end of file
+      - { name: normalizer, priority: 10 }

From 71713d7dc619694a88e6d58eb25b080abb8ef656 Mon Sep 17 00:00:00 2001
From: Claudiu Cristea <clau.cristea@gmail.com>
Date: Mon, 3 Dec 2018 17:12:06 +0200
Subject: [PATCH 08/12] Now, rdf_export depends on serialization module.

---
 modules/rdf_export/rdf_export.info.yml | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/modules/rdf_export/rdf_export.info.yml b/modules/rdf_export/rdf_export.info.yml
index e0637b4a..14b66c6e 100644
--- a/modules/rdf_export/rdf_export.info.yml
+++ b/modules/rdf_export/rdf_export.info.yml
@@ -6,4 +6,5 @@ core: 8.x
 
 # These modules are required by the tests, must be available at bootstrap time
 dependencies:
-  - rdf_entity
+  - rdf_entity:rdf_entity
+  - drupal:serialization

From 1059e01100fdbf96730fb094addce197551c8447 Mon Sep 17 00:00:00 2001
From: Claudiu Cristea <clau.cristea@gmail.com>
Date: Tue, 4 Dec 2018 10:21:35 +0200
Subject: [PATCH 09/12] Make it easier to add new formats.

---
 modules/rdf_export/rdf_export.services.yml    | 13 ++++---
 modules/rdf_export/src/Encoder/RdfEncoder.php | 36 ++++++++-----------
 .../src/EventSubscriber/RdfSubscriber.php     |  2 +-
 .../src/Normalizer/NormalizerBase.php         |  2 +-
 .../rdf_export/src/RdfEncoderCompilerPass.php | 33 +++++++++++++++++
 .../rdf_export/src/RdfEncoderInterface.php    | 22 ++++++++++++
 .../src/RdfExportServiceProvider.php          | 24 +++++++++++++
 7 files changed, 103 insertions(+), 29 deletions(-)
 create mode 100644 modules/rdf_export/src/RdfEncoderCompilerPass.php
 create mode 100644 modules/rdf_export/src/RdfEncoderInterface.php
 create mode 100644 modules/rdf_export/src/RdfExportServiceProvider.php

diff --git a/modules/rdf_export/rdf_export.services.yml b/modules/rdf_export/rdf_export.services.yml
index 4324e215..f1ee2e5c 100644
--- a/modules/rdf_export/rdf_export.services.yml
+++ b/modules/rdf_export/rdf_export.services.yml
@@ -7,24 +7,27 @@ services:
   rdf_export.serializer:
     class: Drupal\rdf_export\RdfSerializer
     arguments: ['@sparql_endpoint']
-  rdf_export.encoder.jsonld:
+  rdf_export.encoder_base:
+    abstract: true
     class: Drupal\rdf_export\Encoder\RdfEncoder
+  rdf_export.encoder.jsonld:
+    parent: rdf_export.encoder_base
     tags:
       - { name: encoder, format: jsonld }
   rdf_export.encoder.rdfxml:
-    class: Drupal\rdf_export\Encoder\RdfEncoder
+    parent: rdf_export.encoder_base
     tags:
       - { name: encoder, format: rdfxml }
   rdf_export.encoder.ntriples:
-    class: Drupal\rdf_export\Encoder\RdfEncoder
+    parent: rdf_export.encoder_base
     tags:
       - { name: encoder, format: ntriples }
   rdf_export.encoder.turtle:
-    class: Drupal\rdf_export\Encoder\RdfEncoder
+    parent: rdf_export.encoder_base
     tags:
       - { name: encoder, format: turtle }
   rdf_export.encoder.n3:
-    class: Drupal\rdf_export\Encoder\RdfEncoder
+    parent: rdf_export.encoder_base
     tags:
       - { name: encoder, format: n3 }
   rdf_export.rdfsubscriber:
diff --git a/modules/rdf_export/src/Encoder/RdfEncoder.php b/modules/rdf_export/src/Encoder/RdfEncoder.php
index 42f0a110..4cdac675 100644
--- a/modules/rdf_export/src/Encoder/RdfEncoder.php
+++ b/modules/rdf_export/src/Encoder/RdfEncoder.php
@@ -2,38 +2,30 @@
 
 namespace Drupal\rdf_export\Encoder;
 
+use Drupal\rdf_export\RdfEncoderInterface;
 use EasyRdf\Format;
-use Symfony\Component\Serializer\Encoder\EncoderInterface;
 
 /**
  * Adds RDF encoder support for the Serialization API.
  */
-class RdfEncoder implements EncoderInterface {
+class RdfEncoder implements RdfEncoderInterface {
 
   /**
-   * The formats that this encoder supports.
+   * Static cache for supported formats.
    *
-   * @var array
+   * @var \EasyRdf\Serialiser[]
    */
-  protected static $supportedFormats = [
-    'jsonld',
-    'rdfxml',
-    'ntriples',
-    'turtle',
-    'n3',
-  ];
+  protected static $supportedFormats;
 
   /**
    * {@inheritdoc}
    */
   public function supportsEncoding($format) {
-    return in_array($format, static::supportedFormats());
+    return !empty(static::getSupportedFormats()[$format]);
   }
 
   /**
    * {@inheritdoc}
-   *
-   * Uses HTML-safe strings, with several characters escaped.
    */
   public function encode($data, $format, array $context = []) {
     if (isset($data['_rdf_entity'])) {
@@ -43,15 +35,15 @@ public function encode($data, $format, array $context = []) {
   }
 
   /**
-   * Build a list of supported formats.
-   *
-   * @return \EasyRdf\Format[]
-   *   List of supported formats.
+   * {@inheritdoc}
    */
-  public static function supportedFormats(): array {
-    $formats = Format::getFormats();
-    /** @var \EasyRdf\Format[] $supported_formats */
-    return array_intersect($formats, static::$supportedFormats);
+  public static function getSupportedFormats(): array {
+    if (!isset(static::$supportedFormats)) {
+      $container_registered_formats = \Drupal::getContainer()->getParameter('rdf_export.encoders');
+      $rdf_serializers = Format::getFormats();
+      static::$supportedFormats = array_intersect_key($rdf_serializers, $container_registered_formats);
+    }
+    return static::$supportedFormats;
   }
 
 }
diff --git a/modules/rdf_export/src/EventSubscriber/RdfSubscriber.php b/modules/rdf_export/src/EventSubscriber/RdfSubscriber.php
index 21afc188..b69e72c0 100644
--- a/modules/rdf_export/src/EventSubscriber/RdfSubscriber.php
+++ b/modules/rdf_export/src/EventSubscriber/RdfSubscriber.php
@@ -20,7 +20,7 @@ class RdfSubscriber implements EventSubscriberInterface {
    */
   public function onKernelRequest(GetResponseEvent $event) {
     /** @var \EasyRdf\Format $format */
-    foreach (RdfEncoder::supportedFormats() as $format) {
+    foreach (RdfEncoder::getSupportedFormats() as $format) {
       $mime = array_keys($format->getMimeTypes());
       $event->getRequest()->setFormat($format->getName(), $mime);
     }
diff --git a/modules/rdf_export/src/Normalizer/NormalizerBase.php b/modules/rdf_export/src/Normalizer/NormalizerBase.php
index bcbdd819..c40c1cc2 100644
--- a/modules/rdf_export/src/Normalizer/NormalizerBase.php
+++ b/modules/rdf_export/src/Normalizer/NormalizerBase.php
@@ -14,7 +14,7 @@ abstract class NormalizerBase extends SerializationNormalizerBase {
    * {@inheritdoc}
    */
   protected function checkFormat($format = NULL) {
-    return in_array($format, RdfEncoder::supportedFormats());
+    return !empty(RdfEncoder::getSupportedFormats()[$format]);
   }
 
 }
diff --git a/modules/rdf_export/src/RdfEncoderCompilerPass.php b/modules/rdf_export/src/RdfEncoderCompilerPass.php
new file mode 100644
index 00000000..7fa2ac51
--- /dev/null
+++ b/modules/rdf_export/src/RdfEncoderCompilerPass.php
@@ -0,0 +1,33 @@
+<?php
+
+declare(strict_types = 1);
+
+namespace Drupal\rdf_export;
+
+use EasyRdf\Format;
+use Symfony\Component\DependencyInjection\Compiler\CompilerPassInterface;
+use Symfony\Component\DependencyInjection\ContainerBuilder;
+
+/**
+ * Collects all RDF encoders and stores them into a service container parameter.
+ */
+class RdfEncoderCompilerPass implements CompilerPassInterface {
+
+  /**
+   * {@inheritdoc}
+   */
+  public function process(ContainerBuilder $container): void {
+    $rdf_formats = array_keys(Format::getFormats());
+    $encoders = [];
+    foreach ($container->findTaggedServiceIds('encoder') as $id => $attributes) {
+      $class = $container->getDefinition($id)->getClass();
+      $interfaces = class_implements($class);
+      $format = $attributes[0]['format'];
+      if (isset($interfaces[RdfEncoderInterface::class]) && in_array($format, $rdf_formats)) {
+        $encoders[$format] = $format;
+      }
+      $container->setParameter('rdf_export.encoders', $encoders);
+    }
+  }
+
+}
diff --git a/modules/rdf_export/src/RdfEncoderInterface.php b/modules/rdf_export/src/RdfEncoderInterface.php
new file mode 100644
index 00000000..dee45271
--- /dev/null
+++ b/modules/rdf_export/src/RdfEncoderInterface.php
@@ -0,0 +1,22 @@
+<?php
+
+declare(strict_types = 1);
+
+namespace Drupal\rdf_export;
+
+use Symfony\Component\Serializer\Encoder\EncoderInterface;
+
+/**
+ * Provides an interface to RDF encoders.
+ */
+interface RdfEncoderInterface extends EncoderInterface {
+
+  /**
+   * Builds a list of supported formats.
+   *
+   * @return \EasyRdf\Serialiser[]
+   *   List of supported formats.
+   */
+  public static function getSupportedFormats(): array;
+
+}
diff --git a/modules/rdf_export/src/RdfExportServiceProvider.php b/modules/rdf_export/src/RdfExportServiceProvider.php
new file mode 100644
index 00000000..bfd652b9
--- /dev/null
+++ b/modules/rdf_export/src/RdfExportServiceProvider.php
@@ -0,0 +1,24 @@
+<?php
+
+declare(strict_types = 1);
+
+namespace Drupal\rdf_export;
+
+use Drupal\Core\DependencyInjection\ContainerBuilder;
+use Drupal\Core\DependencyInjection\ServiceProviderInterface;
+use Symfony\Component\DependencyInjection\Compiler\PassConfig;
+
+/**
+ * RDF Export dependency injection container.
+ */
+class RdfExportServiceProvider implements ServiceProviderInterface {
+
+  /**
+   * {@inheritdoc}
+   */
+  public function register(ContainerBuilder $container) {
+    // Run this compiler pass after the child definitions were resolved.
+    $container->addCompilerPass(new RdfEncoderCompilerPass(), PassConfig::TYPE_OPTIMIZE, -10);
+  }
+
+}

From 719c500500d1e28d9d10c7f7520b6876315f780a Mon Sep 17 00:00:00 2001
From: Claudiu Cristea <clau.cristea@gmail.com>
Date: Tue, 4 Dec 2018 10:55:53 +0200
Subject: [PATCH 10/12] Fix remaining QA remarks.

---
 modules/rdf_export/src/Encoder/RdfEncoder.php       | 13 ++++++++-----
 .../src/Normalizer/RdfEntityNormalizer.php          |  3 ++-
 2 files changed, 10 insertions(+), 6 deletions(-)

diff --git a/modules/rdf_export/src/Encoder/RdfEncoder.php b/modules/rdf_export/src/Encoder/RdfEncoder.php
index 4cdac675..7367f777 100644
--- a/modules/rdf_export/src/Encoder/RdfEncoder.php
+++ b/modules/rdf_export/src/Encoder/RdfEncoder.php
@@ -1,9 +1,12 @@
 <?php
 
+declare(strict_types = 1);
+
 namespace Drupal\rdf_export\Encoder;
 
 use Drupal\rdf_export\RdfEncoderInterface;
 use EasyRdf\Format;
+use Symfony\Component\Serializer\Exception\UnexpectedValueException;
 
 /**
  * Adds RDF encoder support for the Serialization API.
@@ -20,18 +23,18 @@ class RdfEncoder implements RdfEncoderInterface {
   /**
    * {@inheritdoc}
    */
-  public function supportsEncoding($format) {
+  public function supportsEncoding($format): bool {
     return !empty(static::getSupportedFormats()[$format]);
   }
 
   /**
    * {@inheritdoc}
    */
-  public function encode($data, $format, array $context = []) {
-    if (isset($data['_rdf_entity'])) {
-      return $data['_rdf_entity'];
+  public function encode($data, $format, array $context = []): string {
+    if (!isset($data['_rdf_entity'])) {
+      throw new UnexpectedValueException("Data to be encoded is missing the '_rdf_entity' key.");
     }
-    return NULL;
+    return $data['_rdf_entity'];
   }
 
   /**
diff --git a/modules/rdf_export/src/Normalizer/RdfEntityNormalizer.php b/modules/rdf_export/src/Normalizer/RdfEntityNormalizer.php
index edd8820c..bd99d885 100644
--- a/modules/rdf_export/src/Normalizer/RdfEntityNormalizer.php
+++ b/modules/rdf_export/src/Normalizer/RdfEntityNormalizer.php
@@ -2,6 +2,7 @@
 
 namespace Drupal\rdf_export\Normalizer;
 
+use Drupal\rdf_entity\RdfInterface;
 use Drupal\rdf_export\RdfSerializer;
 use Drupal\serialization\Normalizer\FieldableEntityNormalizerTrait;
 
@@ -17,7 +18,7 @@ class RdfEntityNormalizer extends NormalizerBase {
    *
    * @var string
    */
-  protected $supportedInterfaceOrClass = 'Drupal\rdf_entity\RdfInterface';
+  protected $supportedInterfaceOrClass = RdfInterface::class;
 
   /**
    * RdfEntityNormalizer constructor.

From d8cf0b58d41658ddfc4db36ac906b631415f0140 Mon Sep 17 00:00:00 2001
From: Claudiu Cristea <clau.cristea@gmail.com>
Date: Tue, 4 Dec 2018 16:15:54 +0200
Subject: [PATCH 11/12] Add testing for rdf_export.

---
 .../src/Normalizer/RdfEntityNormalizer.php    |  6 +-
 .../tests/fixtures/content-negotiation/jsonld |  1 +
 .../tests/fixtures/content-negotiation/n3     |  6 ++
 .../fixtures/content-negotiation/ntriples     |  3 +
 .../tests/fixtures/content-negotiation/rdfxml | 11 +++
 .../tests/fixtures/content-negotiation/turtle |  6 ++
 .../rdf_entity.mapping.rdf_entity.fruit.yml   | 26 +++++
 .../install/rdf_entity.rdfentity.fruit.yml    |  7 ++
 .../rest.resource.entity.rdf_entity.yml       | 21 ++++
 .../rdf_export_test/rdf_export_test.info.yml  |  8 ++
 .../tests/src/Functional/RdfExportTest.php    | 98 +++++++++++++++++++
 11 files changed, 190 insertions(+), 3 deletions(-)
 create mode 100644 modules/rdf_export/tests/fixtures/content-negotiation/jsonld
 create mode 100644 modules/rdf_export/tests/fixtures/content-negotiation/n3
 create mode 100644 modules/rdf_export/tests/fixtures/content-negotiation/ntriples
 create mode 100644 modules/rdf_export/tests/fixtures/content-negotiation/rdfxml
 create mode 100644 modules/rdf_export/tests/fixtures/content-negotiation/turtle
 create mode 100644 modules/rdf_export/tests/modules/rdf_export_test/config/install/rdf_entity.mapping.rdf_entity.fruit.yml
 create mode 100644 modules/rdf_export/tests/modules/rdf_export_test/config/install/rdf_entity.rdfentity.fruit.yml
 create mode 100644 modules/rdf_export/tests/modules/rdf_export_test/config/install/rest.resource.entity.rdf_entity.yml
 create mode 100644 modules/rdf_export/tests/modules/rdf_export_test/rdf_export_test.info.yml
 create mode 100644 modules/rdf_export/tests/src/Functional/RdfExportTest.php

diff --git a/modules/rdf_export/src/Normalizer/RdfEntityNormalizer.php b/modules/rdf_export/src/Normalizer/RdfEntityNormalizer.php
index bd99d885..4fb0e794 100644
--- a/modules/rdf_export/src/Normalizer/RdfEntityNormalizer.php
+++ b/modules/rdf_export/src/Normalizer/RdfEntityNormalizer.php
@@ -23,11 +23,11 @@ class RdfEntityNormalizer extends NormalizerBase {
   /**
    * RdfEntityNormalizer constructor.
    *
-   * @param \Drupal\rdf_export\RdfSerializer $rdfSerializer
+   * @param \Drupal\rdf_export\RdfSerializer $rdf_serializer
    *   RDF Serializer service.
    */
-  public function __construct(RdfSerializer $rdfSerializer) {
-    $this->rdfSerializer = $rdfSerializer;
+  public function __construct(RdfSerializer $rdf_serializer) {
+    $this->rdfSerializer = $rdf_serializer;
   }
 
   /**
diff --git a/modules/rdf_export/tests/fixtures/content-negotiation/jsonld b/modules/rdf_export/tests/fixtures/content-negotiation/jsonld
new file mode 100644
index 00000000..66d30160
--- /dev/null
+++ b/modules/rdf_export/tests/fixtures/content-negotiation/jsonld
@@ -0,0 +1 @@
+[{"@id":"http://example.com/apple","@type":["http://example.com/type/fruit"],"http://example.com/fruit/uid":[{"@value":0}],"http://example.com/fruit/label":[{"@value":"Apple","@language":"en"}]},{"@id":"http://example.com/type/fruit"}]
diff --git a/modules/rdf_export/tests/fixtures/content-negotiation/n3 b/modules/rdf_export/tests/fixtures/content-negotiation/n3
new file mode 100644
index 00000000..59a3c762
--- /dev/null
+++ b/modules/rdf_export/tests/fixtures/content-negotiation/n3
@@ -0,0 +1,6 @@
+@prefix ns0: <http://example.com/fruit/> .
+
+<http://example.com/apple>
+  a <http://example.com/type/fruit> ;
+  ns0:uid 0 ;
+  ns0:label "Apple"@en .
diff --git a/modules/rdf_export/tests/fixtures/content-negotiation/ntriples b/modules/rdf_export/tests/fixtures/content-negotiation/ntriples
new file mode 100644
index 00000000..2fab24a3
--- /dev/null
+++ b/modules/rdf_export/tests/fixtures/content-negotiation/ntriples
@@ -0,0 +1,3 @@
+<http://example.com/apple> <http://www.w3.org/1999/02/22-rdf-syntax-ns#type> <http://example.com/type/fruit> .
+<http://example.com/apple> <http://example.com/fruit/uid> "0"^^<http://www.w3.org/2001/XMLSchema#integer> .
+<http://example.com/apple> <http://example.com/fruit/label> "Apple"@en .
diff --git a/modules/rdf_export/tests/fixtures/content-negotiation/rdfxml b/modules/rdf_export/tests/fixtures/content-negotiation/rdfxml
new file mode 100644
index 00000000..8ec38e39
--- /dev/null
+++ b/modules/rdf_export/tests/fixtures/content-negotiation/rdfxml
@@ -0,0 +1,11 @@
+<?xml version="1.0" encoding="utf-8" ?>
+<rdf:RDF xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#"
+         xmlns:ns0="http://example.com/fruit/">
+
+  <rdf:Description rdf:about="http://example.com/apple">
+    <rdf:type rdf:resource="http://example.com/type/fruit"/>
+    <ns0:uid rdf:datatype="http://www.w3.org/2001/XMLSchema#integer">0</ns0:uid>
+    <ns0:label xml:lang="en">Apple</ns0:label>
+  </rdf:Description>
+
+</rdf:RDF>
diff --git a/modules/rdf_export/tests/fixtures/content-negotiation/turtle b/modules/rdf_export/tests/fixtures/content-negotiation/turtle
new file mode 100644
index 00000000..59a3c762
--- /dev/null
+++ b/modules/rdf_export/tests/fixtures/content-negotiation/turtle
@@ -0,0 +1,6 @@
+@prefix ns0: <http://example.com/fruit/> .
+
+<http://example.com/apple>
+  a <http://example.com/type/fruit> ;
+  ns0:uid 0 ;
+  ns0:label "Apple"@en .
diff --git a/modules/rdf_export/tests/modules/rdf_export_test/config/install/rdf_entity.mapping.rdf_entity.fruit.yml b/modules/rdf_export/tests/modules/rdf_export_test/config/install/rdf_entity.mapping.rdf_entity.fruit.yml
new file mode 100644
index 00000000..687f052b
--- /dev/null
+++ b/modules/rdf_export/tests/modules/rdf_export_test/config/install/rdf_entity.mapping.rdf_entity.fruit.yml
@@ -0,0 +1,26 @@
+langcode: en
+status: true
+dependencies:
+  config:
+    - rdf_entity.graph.default
+    - rdf_entity.rdfentity.fruit
+third_party_settings: {  }
+id: rdf_entity.fruit
+entity_type_id: rdf_entity
+bundle: fruit
+rdf_type: 'http://example.com/type/fruit'
+base_fields_mapping:
+  rid:
+    target_id:
+      predicate: 'http://www.w3.org/1999/02/22-rdf-syntax-ns#type'
+      format: resource
+  uid:
+    target_id:
+      predicate: 'http://example.com/fruit/uid'
+      format: 'xsd:integer'
+  label:
+    value:
+      predicate: 'http://example.com/fruit/label'
+      format: t_literal
+graph:
+  default: 'http://example.com/fruit/published'
diff --git a/modules/rdf_export/tests/modules/rdf_export_test/config/install/rdf_entity.rdfentity.fruit.yml b/modules/rdf_export/tests/modules/rdf_export_test/config/install/rdf_entity.rdfentity.fruit.yml
new file mode 100644
index 00000000..aca72646
--- /dev/null
+++ b/modules/rdf_export/tests/modules/rdf_export_test/config/install/rdf_entity.rdfentity.fruit.yml
@@ -0,0 +1,7 @@
+langcode: en
+status: true
+dependencies: {  }
+third_party_settings: {  }
+name: Fruit
+rid: fruit
+description: ''
diff --git a/modules/rdf_export/tests/modules/rdf_export_test/config/install/rest.resource.entity.rdf_entity.yml b/modules/rdf_export/tests/modules/rdf_export_test/config/install/rest.resource.entity.rdf_entity.yml
new file mode 100644
index 00000000..4a9600e3
--- /dev/null
+++ b/modules/rdf_export/tests/modules/rdf_export_test/config/install/rest.resource.entity.rdf_entity.yml
@@ -0,0 +1,21 @@
+langcode: en
+status: true
+dependencies:
+  module:
+    - rdf_export
+    - serialization
+    - user
+id: entity.rdf_entity
+plugin_id: 'entity:rdf_entity'
+granularity: resource
+configuration:
+  methods:
+    - GET
+  formats:
+    - jsonld
+    - rdfxml
+    - ntriples
+    - turtle
+    - n3
+  authentication:
+    - cookie
diff --git a/modules/rdf_export/tests/modules/rdf_export_test/rdf_export_test.info.yml b/modules/rdf_export/tests/modules/rdf_export_test/rdf_export_test.info.yml
new file mode 100644
index 00000000..eceb9ae8
--- /dev/null
+++ b/modules/rdf_export/tests/modules/rdf_export_test/rdf_export_test.info.yml
@@ -0,0 +1,8 @@
+name: 'RDF Entity Export test'
+type: module
+description: 'Provides a testing RDF Entity Export module.'
+core: 8.x
+package: Testing
+dependencies:
+- rdf_export
+- rest
diff --git a/modules/rdf_export/tests/src/Functional/RdfExportTest.php b/modules/rdf_export/tests/src/Functional/RdfExportTest.php
new file mode 100644
index 00000000..2dbb7190
--- /dev/null
+++ b/modules/rdf_export/tests/src/Functional/RdfExportTest.php
@@ -0,0 +1,98 @@
+<?php
+
+namespace Drupal\Tests\rdf_export\Functional;
+
+use Drupal\rdf_entity\Entity\Rdf;
+use Drupal\Tests\BrowserTestBase;
+use Drupal\Tests\rdf_entity\Traits\RdfDatabaseConnectionTrait;
+
+/**
+ * Tests the RDF export functionality.
+ *
+ * @group rdf_entity
+ */
+class RdfExportTest extends BrowserTestBase {
+
+  use RdfDatabaseConnectionTrait;
+
+  /**
+   * {@inheritdoc}
+   */
+  protected static $modules = ['rdf_export_test'];
+
+  /**
+   * Testing entity.
+   *
+   * @var \Drupal\rdf_entity\RdfInterface
+   */
+  protected $entity;
+
+  /**
+   * {@inheritdoc}
+   */
+  protected function setUp() {
+    $this->setUpSparql();
+    parent::setUp();
+
+    $this->entity = Rdf::create([
+      'rid' => 'fruit',
+      'id' => 'http://example.com/apple',
+      'label' => 'Apple',
+    ]);
+    $this->entity->save();
+  }
+
+  /**
+   * Tests the RDF export functionality.
+   */
+  public function testRdfExport() {
+    $this->drupalLogin($this->drupalCreateUser(['export rdf metadata']));
+
+    $this->drupalGet($this->entity->toUrl('rdf-export'));
+    $page = $this->getSession()->getPage();
+    $assert_session = $this->assertSession();
+    $page->clickLink('Turtle Terse RDF Triple Language');
+    $assert_session->statusCodeEquals(200);
+    $assert_session->responseContains('ns0:fruit "Apple"');
+
+    $this->drupalGet($this->entity->toUrl('rdf-export'));
+    $page = $this->getSession()->getPage();
+    $assert_session = $this->assertSession();
+    $page->clickLink('RDF/XML');
+    $assert_session->statusCodeEquals(200);
+    $assert_session->responseContains('<ns0:fruit>Apple</ns0:fruit>');
+  }
+
+  /**
+   * Tests content negotiation.
+   */
+  public function testContentNegotiation() {
+    $serializers = [
+      'jsonld' => 'application/ld+json',
+      'n3' => 'text/n3; charset=UTF-8',
+      'ntriples' => 'application/n-triples',
+      'rdfxml' => 'application/rdf+xml',
+      'turtle' => 'text/turtle; charset=UTF-8',
+    ];
+
+    $this->drupalLogin($this->drupalCreateUser(['view rdf entity']));
+
+    foreach ($serializers as $format => $content_type) {
+      $url = $this->entity->toUrl('canonical', ['query' => ['_format' => $format]]);
+      $this->drupalGet($url);
+      $content = $this->getSession()->getPage()->getContent();
+      $expected_content = trim(file_get_contents(__DIR__ . "/../../fixtures/content-negotiation/$format"));
+      $this->assertEquals($expected_content, $content);
+      $this->assertSession()->responseHeaderEquals('Content-Type', $content_type);
+    }
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function tearDown() {
+    $this->entity->delete();
+    parent::tearDown();
+  }
+
+}

From f66229a7900e50bc710b407bed6b93f0713c9233 Mon Sep 17 00:00:00 2001
From: Claudiu Cristea <clau.cristea@gmail.com>
Date: Tue, 4 Dec 2018 17:03:48 +0200
Subject: [PATCH 12/12] Provide the ml/json-ld library.

---
 composer.json                                      |  3 ++-
 .../tests/src/Functional/RdfExportTest.php         | 14 ++++++++------
 tests/travis-ci/fixtures/composer.json.dist        |  3 ++-
 3 files changed, 12 insertions(+), 8 deletions(-)

diff --git a/composer.json b/composer.json
index c2fe6749..5eca7571 100644
--- a/composer.json
+++ b/composer.json
@@ -10,7 +10,8 @@
     "license": "GPL-2.0+",
     "require": {
         "php": ">=7.1",
-        "easyrdf/easyrdf": "0.10.0-alpha.1 as 0.9.2"
+        "easyrdf/easyrdf": "0.10.0-alpha.1 as 0.9.2",
+        "ml/json-ld": "^1.0"
     },
     "autoload": {
         "classmap": [
diff --git a/modules/rdf_export/tests/src/Functional/RdfExportTest.php b/modules/rdf_export/tests/src/Functional/RdfExportTest.php
index 2dbb7190..b126aed3 100644
--- a/modules/rdf_export/tests/src/Functional/RdfExportTest.php
+++ b/modules/rdf_export/tests/src/Functional/RdfExportTest.php
@@ -50,17 +50,19 @@ public function testRdfExport() {
 
     $this->drupalGet($this->entity->toUrl('rdf-export'));
     $page = $this->getSession()->getPage();
-    $assert_session = $this->assertSession();
     $page->clickLink('Turtle Terse RDF Triple Language');
-    $assert_session->statusCodeEquals(200);
-    $assert_session->responseContains('ns0:fruit "Apple"');
+    $this->assertSession()->statusCodeEquals(200);
+    $actual_content = $page->getContent();
+    $expected_content = trim(file_get_contents(__DIR__ . "/../../fixtures/content-negotiation/turtle"));
+    $this->assertEquals($expected_content, $actual_content);
 
     $this->drupalGet($this->entity->toUrl('rdf-export'));
     $page = $this->getSession()->getPage();
-    $assert_session = $this->assertSession();
     $page->clickLink('RDF/XML');
-    $assert_session->statusCodeEquals(200);
-    $assert_session->responseContains('<ns0:fruit>Apple</ns0:fruit>');
+    $this->assertSession()->statusCodeEquals(200);
+    $actual_content = $page->getContent();
+    $expected_content = trim(file_get_contents(__DIR__ . "/../../fixtures/content-negotiation/rdfxml"));
+    $this->assertEquals($expected_content, $actual_content);
   }
 
   /**
diff --git a/tests/travis-ci/fixtures/composer.json.dist b/tests/travis-ci/fixtures/composer.json.dist
index 1d22cc9c..f7150608 100644
--- a/tests/travis-ci/fixtures/composer.json.dist
+++ b/tests/travis-ci/fixtures/composer.json.dist
@@ -8,7 +8,8 @@
     "drupal/core": "~8",
     "drupal/rdf_entity": "*",
     "drush/drush": "~9",
-    "easyrdf/easyrdf": "0.10.0-alpha.1 as 0.9.2"
+    "easyrdf/easyrdf": "0.10.0-alpha.1 as 0.9.2",
+    "ml/json-ld": "^1.0"
   },
   "require-dev": {
     "behat/mink-goutte-driver": "~1.2",