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HTTP data source for a resolver

  • Artikkel

APPLIES TO: All API Management tiers

The http-data-source resolver policy configures the HTTP request and optionally the HTTP response to resolve data for an object type and field in a GraphQL schema. The schema must be imported to API Management as a GraphQL API.

Note

Set the policy's elements and child elements in the order provided in the policy statement. Learn more about how to set or edit API Management policies.

Policy statement

<http-data-source> 
    <http-request>
        <get-authorization-context>...get-authorization-context policy configuration...</get-authorization-context>
        <set-backend-service>...set-backend-service policy configuration...</set-backend-service>
        <set-method>...set-method policy configuration...</set-method> 
        <set-url>URL</set-url>
        <include-fragment>...include-fragment policy configuration...</include-fragment>
        <set-header>...set-header policy configuration...</set-header>
        <set-body>...set-body policy configuration...</set-body>
        <authentication-certificate>...authentication-certificate policy configuration...</authentication-certificate>  
    </http-request> 
    <backend>
        <forward-request>...forward-request policy configuration...</forward-request>
    <http-response>
        <set-body>...set-body policy configuration...</set-body>
        <xml-to-json>...xml-to-json policy configuration...</xml-to-json>
        <find-and-replace>...find-and-replace policy configuration...</find-and-replace>
        <publish-event>...publish-event policy configuration...</publish-event>
        <include-fragment>...include-fragment policy configuration...</include-fragment>
    </http-response>
</http-data-source>

Elements

Name Description Required
http-request Specifies a URL and child policies to configure the resolver's HTTP request. Yes
backend Optionally forwards the resolver's HTTP request to a backend service, if specified. No
http-response Optionally specifies child policies to configure the resolver's HTTP response. If not specified, the response is returned as a raw string. No

http-request elements

Note

Except where noted, each child element may be specified at most once. Specify elements in the order listed.

Element Description Required
get-authorization-context Gets an authorization context for the resolver's HTTP request. No
set-backend-service Redirects the resolver's HTTP request to the specified backend. No
include-fragment Inserts a policy fragment in the policy definition. If there are multiple fragments, then add additional include-fragment elements. No
set-method Sets the method of the resolver's HTTP request. Yes
set-url Sets the URL of the resolver's HTTP request. Yes
set-header Sets a header in the resolver's HTTP request. If there are multiple headers, then add additional header elements. No
set-body Sets the body in the resolver's HTTP request. No
authentication-certificate Authenticates using a client certificate in the resolver's HTTP request. No

backend element

Element Description Required
forward-request Forwards the resolver's HTTP request to a configured backend service. No

http-response elements

Note

Except where noted, each child element may be specified at most once. Specify elements in the order listed.

Name Description Required
set-body Sets the body in the resolver's HTTP response. No
xml-to-json Transforms the resolver's HTTP response from XML to JSON. No
find-and-replace Finds a substring in the resolver's HTTP response and replaces it with a different substring. No
publish-event Publishes an event to one or more subscriptions specified in the GraphQL API schema. No
include-fragment Inserts a policy fragment in the policy definition. If there are multiple fragments, then add additional include-fragment elements. No

Usage

Usage notes

  • To configure and manage a resolver with this policy, see Configure a GraphQL resolver.
  • This policy is invoked only when resolving a single field in a matching GraphQL operation type in the schema.

Examples

Resolver for GraphQL query

The following example resolves a query by making an HTTP GET call to a backend data source.

Example schema

type Query {
    users: [User]
}

type User {
    id: String!
    name: String!
}

Example policy

<http-data-source>
    <http-request>
        <set-method>GET</set-method>
        <set-url>https://data.contoso.com/get/users</set-url>
    </http-request>
</http-data-source>

Resolver for a GraqhQL query that returns a list, using a liquid template

The following example uses a liquid template, supported for use in the set-body policy, to return a list in the HTTP response to a query. It also renames the username field in the response from the REST API to name in the GraphQL response.

Example schema

type Query {
    users: [User]
}

type User {
    id: String!
    name: String!
}

Example policy

<http-data-source>
    <http-request>
        <set-method>GET</set-method>
        <set-url>https://data.contoso.com/users</set-url>
    </http-request>
    <http-response>
        <set-body template="liquid">
            [
                {% JSONArrayFor elem in body %}
                    {
                        "name": "{{elem.username}}"
                    }
                {% endJSONArrayFor %}
            ]
        </set-body>
    </http-response>
</http-data-source>

Resolver for GraphQL mutation

The following example resolves a mutation that inserts data by making a POST request to an HTTP data source. The policy expression in the set-body policy of the HTTP request modifies a name argument that is passed in the GraphQL query as its body. The body that is sent will look like the following JSON:

{
    "name": "the-provided-name"
}

Example schema

type Query {
    users: [User]
}

type Mutation {
    makeUser(name: String!): User
}

type User {
    id: String!
    name: String!
}

Example policy

<http-data-source>
    <http-request>
        <set-method>POST</set-method>
        <set-url>https://data.contoso.com/user/create </set-url>
        <set-header name="Content-Type" exists-action="override">
            <value>application/json</value>
        </set-header>
        <set-body>@{
            var args = context.GraphQL.Arguments;  
            JObject jsonObject = new JObject();
            jsonObject.Add("name", args["name"])
            return jsonObject.ToString();
        }</set-body>
    </http-request>
</http-data-source>

Resolver for GraphQL union type

The following example resolves the orderById query by making an HTTP GET call to a backend data source and returns a JSON object that includes the customer ID and type. The customer type is a union of RegisteredCustomer and GuestCustomer types.

Example schema

type Query {
  orderById(orderId: Int): Order
}

type Order {
  customerId: Int!
  orderId: Int!  
  customer: Customer
}

enum AccountType {
  Registered
  Guest
}

union Customer = RegisteredCustomer | GuestCustomer

type RegisteredCustomer {
  accountType: AccountType!
  customerId: Int!
  customerGuid: String!
  firstName: String!
  lastName: String!
  isActive: Boolean!
}

type GuestCustomer {
  accountType: AccountType!
  firstName: String!
  lastName: String!
}

Example policy

For this example, we mock the customer results from an external source, and hard code the fetched results in the set-body policy. The __typename field is used to determine the type of the customer.

<http-data-source>
    <http-request>
        <set-method>GET</set-method>
        <set-url>https://data.contoso.com/orders/</set-url>
    </http-request>
    <http-response>
        <set-body>{"customerId": 12345, "accountType": "Registered", "__typename": "RegisteredCustomer" }
        </set-body>
    </http-response>
</http-data-source>

Related content

For more information about working with policies, see: