Custom Gateway Executor

Writing a custom Gateway Executor¶

The WSO2 Open Banking Accelerator contains extension points known as Open Banking Executors that can validate and manipulate API requests. The executors can mediate and enforce different policies based on regulatory and other requirements. You can use the executors to perform the following:

• Intercept requests and responses before and after API authentication
• Modify request/response headers and payloads
• Configure custom error messages
• Add custom attributes. For example, data reporting

For the executors, you can configure context attributes (for example, consent ID) provided by swagger definitions. These context attributes are shared through a particular request/response flow. You can also define the order of execution by the flow.

To build your own executor, implement the following interface:

com.wso2.openbanking.accelerator.gateway.executor.core.OpenBankingGatewayExecutor

Use the following data model and implement the interface methods according to your requirements:

Data model¶

preProcessRequest method¶

This method handles the requests before API Authentication.

public void preProcessRequest(OBAPIRequestContext obapiRequestContext);

postProcessRequest method¶

This method handles the requests after API Authentication.

public void postProcessRequest(OBAPIRequestContext obapiRequestContext);

preProcessResponse method¶

This method handles the responses before API Authentication.

public void preProcessResponse(OBAPIResponseContext obapiResponseContext);

postProcessResponse method¶

This method handles the responses after API Authentication.

public void postProcessResponse(OBAPIResponseContext obapiResponseContext);

Use the above methods and the context attributes to implement the necessary logics. However, you can ignore implementing any method and not return anything. Once implemented, build a JAR file for the project.

Configuring a custom executor¶

1. Place the above-created JAR file in the <APIM_HOME>/repository/components/lib directory.

   Note

   If it’s an OSGI JAR file, place it in the <APIM_HOME>/repository/components/dropins directory.

2. Open the <APIM_HOME>/repository/conf/deployment.toml file.

   1. Find the open_banking.gateway.openbanking_gateway_executors.type tags and add/modify them according to the type of your consent. For example, Payments.
   2. Add the Fully Qualified Name (FQN) of the executor under the open_banking.gateway.openbanking_gateway_executors.type.executors tag as shown below:

   [[open_banking.gateway.openbanking_gateway_executors.type]]
   name = "Payments"
   
   [[open_banking.gateway.openbanking_gateway_executors.type.executors]]
   name = "com.wso2.openbanking.accelerator.gateway.executor.impl.api.resource.access.validation.APIResourceAccessValidationExecutor"
   priority = 1
   
   [[open_banking.gateway.openbanking_gateway_executors.type.executors]]
   name = "com.wso2.openbanking.accelerator.gateway.executor.impl.consent.ConsentEnforcementExecutor"
   priority = 2
   
   [[open_banking.gateway.openbanking_gateway_executors.type.executors]]
   name = "com.wso2.openbanking.accelerator.gateway.executor.impl.error.handler.OBDefaultErrorHandler"
   priority = 1000

   Click here to see the order of execution...

   • If only one set of executors are configured for an API flow, the order of execution is as follows:
   • If there is more than one set of executors for an API flow, given below is the order they get executed: For example, if there are 3 sets:
   • The order is: A -> E -> I -> B-> F -> J -> C -> G -> K -> D -> H -> L

   Note

   • The default Request Router only reads the Default tag in <APIM_HOME>/repository/conf/deployment.toml.

   • If you haven’t already configured a custom Request Router make sure to configure it.

     1. Open the <APIM_HOME>/repository/conf/deployment.toml file.
     2. Follow the given sample configurations and configure your router.

        [[open_banking.gateway.openbanking_gateway_executors.type]]
        name = "Accounts"
        [[open_banking.gateway.openbanking_gateway_executors.type.executors]]
        name = "com.wso2.openbanking.accelerator.gateway.executor.impl.api.resource.access.validation.APIResourceAccessValidationExecutor"
        priority = 1
        [[open_banking.gateway.openbanking_gateway_executors.type.executors]]
        name = "com.wso2.openbanking.accelerator.gateway.executor.dcr.DCRExecutor"
        priority = 2
        [[open_banking.gateway.openbanking_gateway_executors.type.executors]]
        name = "com.wso2.openbanking.accelerator.gateway.executor.impl.error.handler.OBDefaultErrorHandler"
        priority = 1000

   • For more information, see Configuring a custom Request Router

3. Save the above configurations and restart the API Manager server.

4. Publish and invoke an API of your choice to ensure that the customer executor is running.

   Tip

   Enable logs for that particular executor class to inspect if the executor is running successfully.