Adding URL parameters in WSO2 APIManager

It is a common use case, where users might want to add URL parameters  which are evaluated dynamically in their endpoints.
We can use same approach what we do in ESB, but it may confuse users on how to implement it in APIManager.
APIManager supports adding custom sequences for the API mediation logic. There are few ways available to add custom mediation plugins.
One, which we can simply use for this requirement is, store the mediation logic in registry as a sequence and select that in the in/out flow of the API invocation when publishing API.

Eg:

If we want to invoke the API with something like(note: we pass PhoneNumber parameter)
http://localhost:8280/dimtry/1.0?PhoneNumber=+16506697051 and send to the backend: http://ws.cdyne.com/phoneverify/phoneverify.asmx/CheckPhoneNumber? PhoneNumber=+16506697051&LicenseKey=0"

In the above example, backend service expects two URL parameters for the GET call to return proper response. But user will pass only one parameter(i.e.: phone number). We need to extract that user parameter and within api mediation logic we need to add another license key parameter too.

To achieve this, When publish an API define HTTP endpoint with parameters and assign values to those parameters in the custom sequence.

Eg: <http uri-template=" http://ws.cdyne.com/phoneverify/phoneverify.asmx/CheckPhoneNumber?Phonenumber={uri.var.PhoneNumber}&LicenseKey={uri.var.LicenseKey}"/>


Here, you need to pass two parameters, which can be passed through the custom sequence. Edit the existing log-in message sequence like below and save;(you can create new sequence and save it)

<sequence xmlns="http://ws.apache.org/ns/synapse" name="log_in_message">

                <property name="uri.var.LicenseKey" value="0" scope="default" type="STRING"/>

                <property name="uri.var.PhoneNumber" expression="substring-after(get-property('To'),'/dimtry/1.0?PhoneNumber=')" scope="default" type="STRING"/>

</sequence>

If you check above sequence,  phonumber is extracted from incoming request using an xpath and hardcoded a value for licensekey, which user can modify according to his requirement.
Now when  we create and publish the api, select above insequence.

APIConfiguration:

Send a GET request for the API like;

http://localhost:8280/dimtry/1.0?PhoneNumber=+16506697051

You will get response;