Authorization backends in CDAP are implemented as extensions, and are loaded and executed in their own Java classloader.

The reason for implementing them as extensions is that a variety of existing authorization systems can then be plugged into CDAP, and can execute using their own classloader without having to worry about conflicts with CDAP's system classloader. Each authorization extension is designed to be a fully self-contained JAR file, packaged with the required versions of all its dependencies.

This is similar to how CDAP applications are packaged. Having the required dependencies loaded from a separate class loader constructed using the provided JAR file ensures that there will be no conflicts, even if CDAP itself uses a different version of the library than the one that the extension requires.

Writing Your Own Authorization Extension

CDAP provides an authorization SPI (Service Provider Interface) for users to implement their own authorization extensions. To implement an authorization extension:

• Create a Maven project using the CDAP Application Archetype, as described in Creating an Application.

• Implement your authorization extension by extending the AbstractAuthorizer class.

• This class must be specified as the Main-Class attribute in the extension JAR's manifest file. This will be done automatically if you specify the app.main.class property to be the fully qualified class name in the pom.xml of the Maven project generated using the archetype.

• The class that extends AbstractAuthorizer must have a default constructor, as that default constructor is the one that will be invoked by CDAP.

• All dependencies of the class must be packaged within the JAR file containing the authorizer class. This is also done automatically by the CDAP Application Archetype.

• The AbstractAuthorizer class provides lifecycle methods for authorization extensions. Any initialization code should be implemented by overriding the initialize method. Cleanup code should be implemented by overriding the destroy method.

• The initialize method provides an AuthorizationContext object. This object can be used to obtain access to—and perform admin operations on—CDAP Datasets and Secure Keys.

• If the authorization extension requires configuration parameters, they are provided in the AuthorizationContext object as a Java Properties object via the getProperties method. The Properties object is populated with configuration parameters from cdap-site.xml with the prefix security.authorization.extension.config.

  Note: In the Properties object, these configuration parameters are available with the security.authorization.extension.config prefix removed. For example: security.authorization.extension.config.example.property in the cdap-site.xml will be available as example.property in the Properties object.