Rejoiner
- Creates a uniform GraphQL schema from microservices
- Allows the GraphQL schema to be flexibly defined and composed as shared components
- Generates GraphQL types from Proto definitions
- Populates request Proto based on GraphQL query parameters
- Supplies a DSL to modify the generated schema
- Joins data sources by annotating methods that fetch data
- Creates Proto FieldMasks based on GraphQL selectors
Experimental Features
These features are actively being developed.
- Expose any GraphQL schema as a gRPC service.
- Lossless end to end proto scalar types when using gRPC.
- Relay support [Example]
- GraphQL Stream (based on gRPC streaming) [Example]
Schema Module
SchemaModule is a Guice module that is used to generate parts of a GraphQL
schema. It finds methods and fields that have Rejoiner annotations when it's
instantiated. It then looks at the parameters and return type of these methods
in order to generate the appropriate GraphQL schema. Examples of queries,
mutations, and schema modifications are presented below.
GraphQL Query
final class TodoQuerySchemaModule extends SchemaModule {
@Query("listTodo")
ListenableFuture<ListTodoResponse> listTodo(ListTodoRequest request, TodoClient todoClient) {
return todoClient.listTodo(request);
}
}
In this example request is of type ListTodoRequest (a protobuf message), so
it's used as a parameter in the generated GraphQL query. todoService isn't a
protobuf message, so it's provided by the Guice injector.
This is useful for providing rpc services or database access objects for
fetching data. Authentication data can also be provided here.
Common implementations for these annotated methods:
- Make gRPC calls to microservices which can be implemented in any language
- Load protobuf messages directly from storage
- Perform arbitrary logic to produce the result
GraphQL Mutation
final class TodoMutationSchemaModule extends SchemaModule {
@Mutation("createTodo")
ListenableFuture<Todo> createTodo(
CreateTodoRequest request, TodoService todoService, @AuthenticatedUser String email) {
return todoService.createTodo(request, email);
}
}
Adding edges between GraphQL types
In this example we are adding a reference to the User type on the Todo type.
final class TodoToUserSchemaModule extends SchemaModule {
@SchemaModification(addField = "creator", onType = Todo.class)
ListenableFuture<User> todoCreatorToUser(UserService userService, Todo todo) {
return userService.getUserByEmail(todo.getCreatorEmail());
}
}
In this case the Todo parameter is the parent object which can be referenced to
get the creator's email.
This is how types are joined within and across APIs.
Removing a field
final class TodoModificationsSchemaModule extends SchemaModule {
@SchemaModification
TypeModification removePrivateTodoData =
Type.find(Todo.getDescriptor()).removeField("privateTodoData");
}
Building the GraphQL schema
import com.google.api.graphql.rejoiner.SchemaProviderModule;
public final class TodoModule extends AbstractModule {
@Override
protected void configure() {
// Guice module that provides the generated GraphQLSchema instance
install(new SchemaProviderModule());
// Install schema modules
install(new TodoQuerySchemaModule());
install(new TodoMutationSchemaModule());
install(new TodoModificationsSchemaModule());
install(new TodoToUserSchemaModule());
}
}
Getting started
Dependency information
Apache Maven
<dependency>
<groupId>com.google.api.graphql</groupId>
<artifactId>rejoiner</artifactId>
<version>0.0.4</version>
</dependency>
Gradle/Grails
compile 'com.google.api.graphql:rejoiner:0.0.4'
Scala SBT
libraryDependencies += "com.google.api.graphql" % "rejoiner" % "0.0.4"
Supported return types
All generated proto messages extend Message.
- Any subclass of
Message ImmutableList<? extends Message>ListenableFuture<? extends Message>ListenableFuture<ImmutableList<? extends Message>>
Project information
- Rejoiner is built on top of GraphQL-Java which provides the core
GraphQL capabilities such as query parsing, validation, and execution. - Java code is formatted using google-java-format.
- Note: This is not an official Google product.