Creating API event handlers

An API event occurs when an API method manipulates a human task. Use the API event handler plug-in service provider interface (SPI) to create plug-ins to handle the task events sent by the API or the internal events that have equivalent API events.

Why and when to perform this task

Complete the following steps to create an API event handler.

Steps for this task

  1. Write a class that implements the APIEventHandlerPlugin2 interface or extends the APIEventHandler implementation class. This class can invoke the methods of other classes.
    • If you use the APIEventHandlerPlugin2 interface, you must implement all of the methods of the APIEventHandlerPlugin2 interface and the APIEventHandlerPlugin interface.
    • If you extend the SPI implementation class, overwrite the methods that you need.

    This class runs in the context of a Java 2 Enterprise Edition (J2EE) Enterprise JavaBeans (EJB) application. Ensure that this class and its helper classes follow the EJB specification.

    Tip: If you want to call the HumanTaskManagerService interface from this class, do not call a method that updates the task that produced the event. This action results in a database deadlock.
  2. Assemble the plug-in class and its helper classes into a JAR file.

    If the helper classes are used by several J2EE applications, you can package these classes in a separate JAR file that you register as a shared library.

  3. Create a service provider configuration file for the plug-in in the META-INF/services/ directory of your JAR file.

    The configuration file provides the mechanism for identifying and loading the plug-in. This file conforms to the Java 2 service provider interface specification.

    1. Create a file with the name com.ibm.task.spi.plug-in_nameAPIEventHandlerPlugin, where plug-in_name is the name of the plug-in.

      For example, if your plug-in is called Customer and it implements the com.ibm.task.spi.APIEventHandlerPlugin interface, the name of the configuration file is com.ibm.task.spi.CustomerAPIEventHandlerPlugin.

    2. In the first line of the file that is neither a comment line nor a blank line, specify the fully qualified name of the plug-in class that you created in step 1.

      For example, if your plug-in class is called MyAPIEventHandler and it is in the com.customer.plugins package, then the first line of the configuration file must contain the following entry: com.customer.plugins.MyAPIEventHandler.

Result

You have an installable JAR file that contains a plug-in that handles API events and a service provider configuration file that can be used to load the plug-in.
Tip: You only have one eventHandlerName property available to register both API event handlers and notification event handlers. If you want to use both an API event handler and a notification event handler, the plug-in implementations must have the same name, for example, Customer as the event handler name for the SPI implementation.

You can implement both plug-ins using a single class, or two separate classes. In both cases, you need to create two files in the META-INF/services/ directory of your JAR file, for example, com.ibm.task.spi.CustomerNotificationEventHandlerPlugin and com.ibm.task.spi.CustomerAPIEventHandlerPlugin.

Package the plug-in implementation and the helper classes in a single JAR file.

What to do next

You now need to install and register the plug-in so that it is available to the human task container at runtime. You can register API event handlers with a task instance, a task template, or an application component.

Copyright IBM Corporation 2005, 2006.
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