How to connect with SAP S/4HANA OData Services from SAP APIM? – OAuth 2.0 Based Authentication

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Assuming that you have enabled the API Management capability in Integration Suite, I will start with API Provider creation.

1. Create API Proxy – To Generate OAuth Authentication Token

Create an API Proxy with URL type, 

2. Add Policy – To generate OAuth 2.0 Authentication

OAuth v2.0 – To generate the Access Token for the ac

<OAuthV2 async=”false” continueOnError=”false” enabled=”true” xmlns=”http://www.sap.com/apimgmt”>
<ExternalAuthorization>false</ExternalAuthorization>
<Operation>GenerateAccessToken</Operation>
<GenerateResponse enabled=”true”/>
<SupportedGrantTypes>
<GrantType>client_credentials</GrantType>
</SupportedGrantTypes>
<Tokens/>
</OAuthV2>

3. Create API Provider

Connection

Catalog Service Settings

Test connection:

4. Create Key Value Map to store the credentials to S/4HANA

5. Create API Proxy – To call the OData Service from S/4HANA

Select the API Provider, click on Discover to select the API which you wanted to use

Select the API & then click on Create.

6. Add Policies to the API Proxy created to call the OData target endpoint on S/4HANA side

Verify API Key – To verify the key which you are going to pass while calling the API.
Where do you get the API? – When you create the Product, and a Subscription, after creating a Subscription in the Developer Hub you will get a Key. That key is to be provided to the Consumer, and this Policy will verify the key sent by the consumer.

<!–Specify in the APIKey element where to look for the variable containing the api key–>
<VerifyAPIKey async=’true’ continueOnError=’false’ enabled=’true’
xmlns=’http://www.sap.com/apimgmt’>
<APIKey ref=’request.header.apikey ‘/>
</VerifyAPIKey>

OAuth 2.0 – To verify OAuth Token generated

<OAuthV2 async=”false” continueOnError=”false” enabled=”true” xmlns=”http://www.sap.com/apimgmt”>
<ExternalAuthorization>false</ExternalAuthorization>
<!– valid values are GenerateAccessToken, GenerateAccessTokenImplicitGrant, GenerateAuthorizationCode ,
RefreshAccessToken , VerifyAccessToken , InvalidateToken , ValidateToken –>
<Operation>VerifyAccessToken</Operation>
<GenerateResponse enabled=”true”/><SupportedGrantTypes/>
<Tokens/>
</OAuthV2>

Assign Message – Before setting up basic authentication in a later step, we need to remove the existing Authorization header. I’ve used the Assign Message policy to achieve this with the following configuration:

<!– This policy can be used to create or modify the standard HTTP request and response messages –>
<AssignMessage async=”false” continueOnError=”true” enabled=”true” xmlns=’http://www.sap.com/apimgmt’>
<Remove>
<Headers>
<Header name=”Authorization”></Header>
</Headers>
</Remove>
<IgnoreUnresolvedVariables>true</IgnoreUnresolvedVariables>
<AssignTo createNew=”false” type=”request”></AssignTo>
</AssignMessage>

Key Value Map Operations – To fetch the credentials saved in the Key Value Mapping

<KeyValueMapOperations mapIdentifier=”SAP_S4HANA_Credentials” async=”true” continueOnError=”false” enabled=”true” xmlns=”http://www.sap.com/apimgmt”>
<Get assignTo=”private.usernameFromKVM” index=”1″>
<Key>
<Parameter>Username</Parameter>
</Key>
</Get>
<Get assignTo=”private.passwordFromKVM” index=”1″>
<Key>
<Parameter>Password</Parameter>
</Key>
</Get>
<Scope>environment</Scope>
</KeyValueMapOperations>

Basic Authentication – To pass the credentials fetched in the previous step.

<BasicAuthentication async=’true’ continueOnError=’false’ enabled=’true’ xmlns=’http://www.sap.com/apimgmt’>
<Operation>Encode</Operation>
<IgnoreUnresolvedVariables>false</IgnoreUnresolvedVariables>
<User ref=’private.usernameFromKVM’></User>
<Password ref=’private.passwordFromKVM’></Password>
<AssignTo>request.header.Authorization</AssignTo>
</BasicAuthentication>

Assign Message – So you get an error as, “{“fault”:{“faultstring”:”Unsupported Encoding “br””,”detail”:{“errorcode”:”protocol.http.UnsupportedEncoding”}}}“. 
BR is a data format Brotli which is often defined by backend for webpage loading and not accepted by default. And this Assign Message will help your message reach the target.

<!– This policy can be used to create or modify the standard HTTP request and response messages –>
<AssignMessage async=”false” continueOnError=”false” enabled=”true” xmlns=’http://www.sap.com/apimgmt’>

<!– Sets a new value to the existing parameter –>
<Set>
<Headers>
<Header name=”Accept-Encoding”>gzip,deflate</Header>
</Headers>
</Set>
<IgnoreUnresolvedVariables>false</IgnoreUnresolvedVariables>
<AssignTo createNew=”false” type=”request”></AssignTo>
</AssignMessage>

7. Create Product & Add the both the API Proxies

8. Create a Subscription for the Product created

7. It’s time to test!

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