# Add a custom subject mapper to a Permissioning Service blade

A Java-based Liberator Permissioning Service blade can contain a custom subject mapper, which resides in Liberator’s Permissioning Auth Module. Here we explain how to add the custom subject mapper to the blade.

**📌 NOTE**\
For an explanation of subject mapping in the context of permissioning, see the online documentation **[Additional permissioning capabilities](../platform-architecture/additional-permissioning-capabilities.md)**.

You develop a custom subject mapper by implementing the `SubjectMapper` interface of the Permissioning Integration API in the [Caplin Integration Suite](../cis-toolkit/index.md). Having created a JAR file containing the subject mapper, your Permissioning Service blade needs to

know its location. To specify this (assuming the JAR is called _mycustommapper.jar_):

1. Add the custom mapper JAR to the blade by copying it to the blade’s _Liberator/lib/java/_ directory.
2. Specify the class path of the custom mapper in the blade’s _Liberator/etc/java.conf_ directory, as in this example:

   ```
   add-javaclass
       class-name   example.permissioning.SimplePermissioning
       class-id     authenticator
       classpath    "${ccd}/../lib/java/mycustommapper.jar"
       classpath    "${ccd}/../lib/java/SimplePermissioning.jar"
   end-javaclass
   ```

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**See also:**

* [Create a Java-based Liberator Permissioning Service blade](cdf-create-a-java-based-liberator-permissioning-service-blade.md)
* [Permissioning Overview And Concepts](https://docs.caplin.com/developer/docs/PermissioningOverviewAndConcepts_62.pdf) (PDF)