Set GraphQL resolver (retired)

Important

• The set-graphql-resolver policy is retired. Customers using the set-graphql-resolver policy must migrate to the managed resolvers for GraphQL APIs, which provide enhanced functionality.
• After you configure a managed resolver for a GraphQL field, the gateway skips the set-graphql-resolver policy in any policy definitions. You can't combine use of managed resolvers and the set-graphql-resolver policy in your API Management instance.

The set-graphql-resolver policy retrieves or sets data for a GraphQL field in an object type specified in a GraphQL schema. The schema must be imported to API Management. Currently the data must be resolved using an HTTP-based data source (REST or SOAP 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

<set-graphql-resolver parent-type="type" field="field"> 
    <http-data-source> 
        <http-request> 
            <set-method>...set-method policy configuration...</set-method> 
            <set-url>URL</set-url>
            <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> 
        <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>
        </http-response>
      </http-data-source> 
</set-graphql-resolver> 

Attributes

Attribute	Description	Required	Default
parent-type	An object type in the GraphQL schema.	Yes	N/A
field	A field of the specified parent-type in the GraphQL schema.	Yes	N/A

Note

Currently, the values of parent-type and field aren't validated by this policy. If they aren't valid, the policy is ignored, and the GraphQL query is forwarded to a GraphQL endpoint (if one is configured).

Elements

Name	Description	Required
http-data-source	Configures the HTTP request and optionally the HTTP response that are used to resolve data for the given parent-type and field.	Yes
http-request	Specifies a URL and child policies to configure the resolver's HTTP request.	Yes
http-response	Optionally specifies child policies to configure the resolver's HTTP response. If not specified, the response is returned as a raw string.

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
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

http-response elements

Note

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

Usage

• Policy sections: backend
• Policy scopes: global, workspace, product, API, operation
• Gateways: dedicated

Usage notes

• This policy is invoked only when a matching GraphQL query is executed.
• The policy resolves data for a single field. To resolve data for multiple fields, configure multiple occurrences of this policy in a policy definition.

GraphQL context

• The context for the HTTP request and HTTP response (if specified) differs from the context for the original gateway API request:
  • context.ParentResult is set to the parent object for the current resolver execution.
  • The HTTP request context contains arguments that are passed in the GraphQL query as its body.
  • The HTTP response context is the response from the independent HTTP call made by the resolver, not the context for the complete response for the gateway request. The context variable that is passed through the request and response pipeline is augmented with the GraphQL context when used with <set-graphql-resolver> policies.

ParentResult

The context.ParentResult is set to the parent object for the current resolver execution. Consider the following partial schema:

type Comment {
    id: ID!
    owner: string!
    content: string!
}

type Blog {
    id: ID!
    title: string!
    content: string!
    comments: [Comment]!
    comment(id: ID!): Comment
}

type Query {
    getBlog(): [Blog]!
    getBlog(id: ID!): Blog
}

Also, consider a GraphQL query for all the information for a specific blog:

query {
    getBlog(id: 1) {
        title
        content
        comments {
            id
            owner
            content
        }
    }
}

If you set a resolver for parent-type="Blog" field="comments", you will want to understand which blog ID to use. You can get the ID of the blog using context.ParentResult.AsJObject()["id"].ToString(). The policy for configuring this resolver would resemble:

<set-graphql-resolver parent-type="Blog" field="comments">
    <http-data-source>
        <http-request>
            <set-method>GET</set-method>
            <set-url>@{
                var blogId = context.ParentResult.AsJObject()["id"].ToString();
                return $"https://data.contoso.com/api/blog/{blogId}";
            }</set-url>
        </http-request>
    </http-data-source>
</set-graphql-resolver>

Arguments

The arguments for a parameterized GraphQL query are added to the body of the request. For example, consider the following two queries:

query($id: Int) {
    getComment(id: $id) {
        content
    }
}

query {
    getComment(id: 2) {
        content
    }
}

These queries are two ways of calling the getComment resolver. GraphQL sends the following JSON payload:

{
    "query": "query($id: Int) { getComment(id: $id) { content } }",
    "variables": { "id": 2 }
}

{
    "query": "query { getComment(id: 2) { content } }"
}

When the resolver is executed, the arguments property is added to the body. You can define the resolver as follows:

<set-graphql-resolver parent-type="Blog" field="comments">
    <http-data-source>
        <http-request>
            <set-method>GET</set-method>
            <set-url>@{
                var commentId = context.Request.Body.As<JObject>(true)["arguments"]["id"];
                return $"https://data.contoso.com/api/comment/{commentId}";
            }</set-url>
        </http-request>
    </http-data-source>
</set-graphql-resolver>

More 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

<set-graphql-resolver parent-type="Query" field="users">
    <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>
</set-graphql-resolver>

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

<set-graphql-resolver parent-type="Query" field="users">
    <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>
</set-graphql-resolver>

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

<set-graphql-resolver parent-type="Mutation" field="makeUser">
    <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.Request.Body.As<JObject>(true)["arguments"];  
                JObject jsonObject = new JObject();
                jsonObject.Add("name", args["name"])
                return jsonObject.ToString();
            }</set-body>
        </http-request>
    </http-data-source>
</set-graphql-resolver>

Related policies

• API Management policies for GraphQL APIs

Related content

For more information about working with policies, see:

• Tutorial: Transform and protect your API
• Policy reference for a full list of policy statements and their settings
• Policy expressions
• Set or edit policies
• Reuse policy configurations
• Policy snippets repo
• Author policies using Microsoft Copilot for Azure