Advanced Workflows

This section describes different use cases for constructing your own custom GraphQL requests and how to approach it. You may want to construct your own GraphQL request if you want to

• retrieve only a subset of the data to reduce data transfer
• retrieve nested objects at a depth that you choose
• combine multiple operations into a single request
• send custom headers to your AppSync endpoint

A GraphQL request is automatically generated for you when using AWSAPIPlugin with the existing workflow. For example, if you have a Todo model, a mutation request to save the Todo will look like this:

1Todo todo = Todo.builder()
2    .name("My first todo")
3    .description("todo description")
4    .build();
5
6Amplify.API.mutate(ModelMutation.create(todo),
7    result -> Log.i("ApiDemo", "Mutation succeeded."),
8    failure -> Log.e("ApiDemo", "Mutation failed.", failure)
9);

Underneath the covers, a request is generated with a GraphQL document and variables and sent to the AppSync service.

1{
2  "query": "mutation createTodo($input: CreateTodoInput!) {
3    createTodo(input: $input) {
4      id
5      name
6      description
7    }
8  }",
9  "variables": "{
10    "input": {
11      "id": "[UNIQUE-ID]",
12      "name": "my first todo",
13      "description": "todo description"
14    }
15  }
16}

The different parts of the document are described as follows

• mutation - the operation type to be performed, other operation types are query and subscription
• createTodo($input: CreateTodoInput!) - the name and input of the operation.
• $input: CreateTodoInput! - the input of type CreateTodoInput! referencing the variables containing JSON input
• createTodo(input: $input) - the mutation operation which takes a variable input from $input
• the selection set containing id, name, and description are fields specified to be returned in the response

You can learn more about the structure of a request from GraphQL Query Language and AppSync documentation. To test out constructing your own requests, open the AppSync console using amplify console api and navigate to the Queries tab.

Subset of data

The selection set of the document specifies which fields are returned in the response. For example, if you are displaying a view of the Todo without the description, you can construct the document to omit the field. You can learn more about selection sets here.

1query getTodo($id: ID!) {
2  getTodo(id: $id) {
3    id
4    name
5  }
6}

The response data will look like this

1{
2  "data": {
3    "getTodo": {
4      "id": "111",
5      "name": "my first todo"
6    }
7  }
8}

First, create your own GraphQLRequest

1private GraphQLRequest<Todo> getTodoRequest(String id) {
2    String document = "query getTodo($id: ID!) { "
3        + "getTodo(id: $id) { "
4            + "id "
5            + "name "
6        + "}"
7    + "}";
8    return new SimpleGraphQLRequest<>(
9            document,
10            Collections.singletonMap("id", id),
11            Todo.class,
12            new GsonVariablesSerializer());
13}

Then, query for the Todo by a todo id

1Amplify.API.query(getTodoRequest("[TODO_ID]"),
2    response -> Log.d("MyAmplifyApp", "response" + response),
3    error -> Log.e("MyAmplifyApp", "error" + error)
4);

Nested Data

If you have a relational model, you can retrieve the nested object by creating a GraphQLRequest with a selection set containing the nested object's fields. For example, in this schema, the Post can contain multiple comments and notes.

1enum PostStatus {
2  ACTIVE
3  INACTIVE
4}
5
6type Post @model {
7  id: ID!
8  title: String!
9  rating: Int!
10  status: PostStatus!
11  comments: [Comment] @hasMany(indexName: "byPost", fields: ["id"])
12  notes: [Note] @hasMany(indexName: "byNote", fields: ["id"])
13}
14
15type Comment @model {
16  id: ID!
17  postID: ID! @index(name: "byPost", sortKeyFields: ["content"])
18  post: Post! @belongsTo(fields: ["postID"])
19  content: String!
20}
21
22type Note @model {
23  id: ID!
24  postID: ID! @index(name: "byNote", sortKeyFields: ["content"])
25  post: Post! @belongsTo(fields: ["postID"])
26  content: String!
27}

If you only want to retrieve the comments, without the notes, create a GraphQLRequest for the Post with nested fields only containing the comment fields.

1private GraphQLRequest<Post> getPostWithCommentsRequest(String id) {
2    String document = "query getPost($id: ID!) { "
3        + "getPost(id: $id) { "
4            + "id "
5            + "title "
6            + "rating "
7            + "status "
8            + "comments { "
9                + "items { "
10                    + "id "
11                    + "postID "
12                    + "content "
13                + "} "
14            + "} "
15        + "} "
16    + "}";
17    return new SimpleGraphQLRequest<>(
18            document,
19            Collections.singletonMap("id", id),
20            Post.class,
21            new GsonVariablesSerializer());
22}

Then query for the Post:

1Amplify.API.query(getPostWithCommentsRequest("[POST_ID]"),
2    response -> Log.d("MyAmplifyApp", "response" + response),
3    error -> Log.e("MyAmplifyApp", "error" + error)
4);

Combining multiple GraphQL operations in a single request

GraphQL allows you to run multiple GraphQL operations (queries/mutations) as part of a single network request from the client code. To perform multiple operations in a single request, you can place them within the same GraphQL document. For example, to retrieve a Post and a Todo:

1private GraphQLRequest<String> getPostAndTodo(String postId, String todoId) {
2    String document = "query get($postId: ID!, $todoId: ID!) { "
3        + "getPost(id: $postId) { "
4            + "id "
5            + "title "
6            + "rating "
7        + "} "
8        + "getTodo(id: $todoId) { "
9            + "id "
10            + "name "
11        + "} "
12    + "}";
13    Map<String, Object> variables = new HashMap<>();
14    variables.put("postId", postId);
15    variables.put("todoId", todoId);
16    return new SimpleGraphQLRequest<>(
17            document,
18            variables,
19            String.class,
20            new GsonVariablesSerializer());
21}

Adding Headers to Outgoing Requests

By default, the API plugin includes appropriate authorization headers on your outgoing requests. However, you may have an advanced use case where you wish to send additional request headers to AppSync.

To specify your own headers, use the configureClient() configuration option on the AWSApiPlugin's builder. Specify the name of one of the configured APIs in your amplifyconfiguration.json. Apply customizations to the underlying OkHttp instance by providing a lambda expression as below.

1AWSApiPlugin plugin = AWSApiPlugin.builder()
2    .configureClient("yourApiName", okHttpBuilder -> {
3        okHttpBuilder.addInterceptor(chain -> {
4            Request originalRequest = chain.request();
5            Request updatedRequest = originalRequest.newBuilder()
6                .addHeader("customHeader", "someValue")
7                .build();
8            return chain.proceed(updatedRequest);
9        });
10    })
11    .build();
12Amplify.addPlugin(plugin);