4.1 Getting Started

How the Policy Engine Interacts with a Condition Extension

When the policy engine processes a policy and encounters a condition marked as an extension, it instantiates an object that must comply with the NxpeConditionFactory interface. It then calls the getInstance method and expects an NxpeCondition object from the extension unless NxpeException is thrown by the NxpeConditionFactory object.

This process is illustrated in the following code snippet:

public interface NxpeConditionFactory
{
    NxpeCondition getInstance()
        throws NxpeException;
} /* NxpeConditionFactory */

The policy engine then calls the NxpeCondition.initialize method and sends an NxpeParameterList object for configuration parameters. Configuration parameters are used to initialize the NxpeCondition object. The extension needs these parameters for evaluating the condition. Values for these parameters are retrieved at evaluation from the NxpeInformationContext object that is sent by the policy engine.

The initialize method is called before any other method, followed by a method that sets an ID for the condition.

The following code snippet illustrates this process:

public interface NxpeCondition
{
    void initialize(
            NxpeParameterList   configurationValues)
        throws NxpeException;

        NxpeResult evaluate(
                        NxpeInformationContext   informationContext,
                        NxpeResponseContext      responseContext)
                throws NxpeException;
    
    void setInterfaceId(
            String interfaceId)
        throws NxpeException;
}

How the Policy Engine Interacts with a Data Extension

When the policy engine is processing a policy and encounters a data element marked as an extension, the engine instantiates an object that must comply with the NxpeContextDataElementFactory interface. The engine then calls the getInstance() method, passing the name, enumerativeValue, and parameter as arguments, and expects the extension to return an NxpeContextDataElement object unless the NxpeContextDataElementFactory object throws an NxpeException. The following code snippet illustrates this process:

public interface NxpeContextDataElementFactory
{
     NxpeContextDataElement getInstance(
            String    name,
            int       enumerativeValue,
            String    parameter)
        throws NxpeException;

} /* NxpeContextDataElementFactory */

During the next part of the configuration phase, the policy engine calls the NxpeContextDataElement.initialize() method, passing an NxpeParameterList object with configureParameters. The configureParameters are used to initialize the NxpeContextDataElement object and are the parameters required during policy evaluation. It is expected that the values for these configureParameters are retrieved from the NxpeInformationContext object passed by the policy engine.

The following code snippet illustrates this process:

public interface NxpeContextDataElement
{
    void initialize(
            NxpeParameterList   configurationValues)
        throws NxpeException;

    String getName();

    int getEnumerativeValue();

    String getParameter();

    Object getValue(
            NxpeInformationContext  informationContext,
            NxpeResponseContext     responseContext)
        throws NxpeException;

} /* NxpeContextDataElement */

The policy engine calls the NxpeContextDataElement.intialize() method to initialize a component in preparation for policy evaluation. Derived classes are required to implement this method. This method is guaranteed to be called before any other method is called, because it is part of object construction.

The configurationValues parameter contains a list of the configuration data required by the external ContextDataElement handler. If the context data element wants to preserve configuration data, it must maintain a reference to the configuration value parameters.

How the Policy Engine Interacts with an Action Extension

When the policy engine is processing a policy and encounters an action marked as an extension, the engine instantiates an object that must comply with the NxpeActionFactory interface. The engine then calls the getInstance() method, and expects the extension to return an NxpeAction object unless the NxpeActionFactory object throws an NxpeException.

This process is illustrated in the following code snippet:

public interface NxpeActionFactory
{
        NxpeAction   getInstance()
        throws NxpeException;

} /* NxpeActionFactory */

During the next part of the configuration phase, the policy engine calls the NxpeAction.initialize() method, passing an NxpeParameterList object with the configureParameters. The configureParameters are used to initialize the NxpeAction object. The configureParameters are those parameters needed during NxpePolicy.evaluate(). It is expected that the values for these configureParameters are retrieved from the NxpeInformationContext passed by the policy engine.The following code snippet illustrates this process:

public interface NxpeAction
{
        void initialize(
            NxpeParameterList   configurationValues)
        throws NxpeException;

The NxpeParameterList is a list of configuration data required by the external action extension. If the action extension wants to preserve configuration data, the extension must maintain a reference to the configuration value parameters.

The second method called is the setInterfaceId method, which sets up a value for trace evaluation. The interfaceId parameter sets a unique sting value for the action. The following code snippet illustrates this last step in the NxpeAction interface.

    void setInterfaceId(
            String   interfaceId)
        throws NxpeException;

} /* NxpeAction */

The policy engine calls the doAction method to initiate the action. It has the following parameters:

This method returns an NxpeResult, which contains an error code, permit, deny, or obligation. Derived classes are require to override this method to implement the supported action.

The following code snippet illustrates this process:

    NxpeResult doAction(
            NxpeInformationContext  informationCtx,
            NxpeResponseContext     responseCtx)
        throws NxpeException;