127 lines
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4.5 KiB
Markdown
127 lines
No EOL
4.5 KiB
Markdown
# graphql_server
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[](https://pub.dartlang.org/packages/graphql_server)
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[](https://travis-ci.org/angel-dart/graphql)
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Base package for implementing GraphQL servers.
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You might prefer [`package:angel_graphql`](https://github.com/angel-dart/graphql),
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the fastest way to implement GraphQL backends in Dart.
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`package:graphql_server` does not require any specific
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framework, and thus can be used in any Dart project.
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## Ad-hoc Usage
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The actual querying functionality is handled by the
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`GraphQL` class, which takes a schema (from `package:graphql_schema`).
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In most cases, you'll want to call `parseAndExecute`
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on some string of GraphQL text. It returns either a `Stream`
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or `Map<String, dynamic>`, and can potentially throw
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a `GraphQLException` (which is JSON-serializable):
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```dart
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try {
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var data = await graphQL.parseExecute(responseText);
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if (data is Stream) {
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// Handle a subscription somehow...
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} else {
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response.send({'data': data});
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}
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} on GraphQLException catch(e) {
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response.send(e.toJson());
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}
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```
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Consult the API reference for more:
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https://pub.dartlang.org/documentation/graphql_server/latest/graphql_server/GraphQL/parseAndExecute.html
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If you're looking for functionality like `graphQLHttp`
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in `graphql-js`, that is not included in this package, because
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it is typically specific to the framework/platform you are using.
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The `graphQLHttp` implementation in `package:angel_graphql` is
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a good example:
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https://github.com/angel-dart/graphql/blob/master/angel_graphql/lib/src/graphql_http.dart
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## Subscriptions
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GraphQL queries involving `subscription` operations can return
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a `Stream`. Ultimately, the transport for relaying subscription
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events to clients is not specified in the GraphQL spec, so it's
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up to you.
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Note that in a schema like this:
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```graphql
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type TodoSubscription {
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onTodo: TodoAdded!
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}
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type TodoAdded {
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id: ID!
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text: String!
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isComplete: Bool
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}
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```
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Your Dart schema's resolver for `onTodo` should be
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a `Map` *containing an `onTodo` key*:
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```dart
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field(
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'onTodo',
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todoAddedType,
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resolve: (_, __) {
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return someStreamOfTodos()
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.map((todo) => {'onTodo': todo});
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},
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);
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```
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For the purposes of reusing existing tooling (i.e. JS clients, etc.),
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`package:graphql_server` rolls with an implementation of Apollo's
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`subscriptions-transport-ws` spec.
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**NOTE: At this point, Apollo's spec is extremely out-of-sync with the protocol their client actually expects.**
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**See the following issue to track this:**
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**https://github.com/apollographql/subscriptions-transport-ws/issues/551**
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The implementation is built on `package:stream_channel`, and
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therefore can be used on any two-way transport, whether it is
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WebSockets, TCP sockets, Isolates, or otherwise.
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Users of this package are expected to extend the `Server`
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abstract class. `Server` will handle the transport and communication,
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but again, ultimately, emitting subscription events is up to your
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implementation.
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Here's a snippet from `graphQLWS` in `package:angel_graphql`.
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It runs within the context of one single request:
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```dart
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var channel = IOWebSocketChannel(socket);
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var client = stw.RemoteClient(channel.cast<String>());
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var server =
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_GraphQLWSServer(client, graphQL, req, res, keepAliveInterval);
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await server.done;
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```
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See `graphQLWS` in `package:angel_graphql` for a good example:
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https://github.com/angel-dart/graphql/blob/master/angel_graphql/lib/src/graphql_ws.dart
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## Introspection
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Introspection of a GraphQL schema allows clients to query the schema itself,
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and get information about the response the server expects. The `GraphQL`
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class handles this automatically, so you don't have to write any code for it.
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However, you can call the `reflectSchema` method to manually reflect a schema:
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https://pub.dartlang.org/documentation/graphql_server/latest/introspection/reflectSchema.html
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## Mirrors Usage
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By default, `dart:mirrors` is not required, but it can be optionally used.
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The `mirrorsFieldResolver` can resolve fields from concrete objects, instead of you
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first having to serialize them:
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https://pub.dartlang.org/documentation/graphql_server/latest/graphql_server.mirrors/mirrorsFieldResolver.html
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You can also use `convertDartType` to convert a concrete Dart type into a `GraphQLType`. However,
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the ideal choice is `package:graphql_generator`.
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* https://pub.dartlang.org/documentation/graphql_server/latest/graphql_server.mirrors/convertDartType.html
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* https://pub.dartlang.org/packages/graphql_generator |