StackCheats

Retrieve (Custom) API Properties

Access Custom API Properties in Mediation Sequences

September 26, 2020

wso2mediatorsynapse-sequenceapi-properties

Stratagem

As out-of-the-box, the WSO2 API Manager supports adding and creating custom API properties. You can learn more about managing custom API properties from here. In this cheat, we will be looking at how to access these custom API properties from mediation sequences.

For demo, we have introduced a custom property named transparent-token in one of our published API, and we have a requirement to log this property in the logs whenever this API is invoked.

Quick Note

The following illustrations are developed considering an All-In-One deployment environment of the API Manager server. In a distributed environment, the Gateway component will not have access to the registry space of the Publisher component unless it is shared and configured under the master-datasources.xml and registry.xml.

          fn:concat(
<sequence name="custom-sequence" 
  xmlns="http://ws.apache.org/ns/synapse">
  <log level="custom">
      <property 
        name="prop" 
        expression="get-property('registry')" 
        value="value-to-be-printed" 
      />
  </log>
</sequence>
          fn:concat(
  'gov:/apimgt/applicationdata/provider/',
        expression="get-property('registry')" 
          fn:concat(
            'gov:/apimgt/applicationdata/provider/',
  'gov:/apimgt/applicationdata/provider/',
          fn:concat(
            'gov:/apimgt/applicationdata/provider/',

All introduced custom API properties are stored and persisted inside the local registry of the API Manager. We are going to implement a mediation sequence to retrieve our transparent-token custom property from the local registry space of the API Manager.

Since, our requirement is to only log the property, we are going to start implementing a custom mediation sequence with a simple log mediator.

Change the log mediator to use expression in order to use the get-property() method to retrieve our custom API property. As the introduced custom property is available in the registry space, we are going to specify the scope of our get-property() with the registry scope.

Now let’s construct the registry path to access our transparent-token custom property. The registry path is constructed with the use of existing context properties. The fn:concat function is used to join the strings and the properties to build a complete registry path.

Following are the usages of the specified context properties

  • $ctx:api.ut.apiPublisher: Publisher of the API
  • $ctx:api.ut.api: API name
  • $ctx:api.ut.version: API version

We have now successfully developed a custom mediation sequence to retrieve our custom API property from the registry space and to print the value in the logs.

Upload the sequence as an in-mediation sequence to the API from the Publisher portal and, Save and Publish, Invoke and check the logs.

Given below is the complete Synapse sequence (in-sequence), we developed to access our custom property named transparent-token from the local registry space of the API Manager.

<sequence name="custom-sequence" xmlns="http://ws.apache.org/ns/synapse">
  <log level="custom">
      <property 
        name="prop"
        expression="get-property('registry', 
          fn:concat(
            'gov:/apimgt/applicationdata/provider/',
            $ctx:api.ut.apiPublisher, '/',
            $ctx:api.ut.api, '/',
            $ctx:api.ut.version, '/',
            'api@api_meta.transparent-token'
          ))" />
  </log>
</sequence>
Athiththan Kathirgamasegaran