Provides the application programming interface (API) for managing task-related objects in the Human Task Manager. You can create application programs that use the API to manage information related to tasks. You can:
The API contains a stateless session bean HumanTaskManager for local and remote access. The HumanTaskManagerService interface describes the functions that can be called locally and remotely. It exposes the functions that can be called by an application program. The application program can be any Java program, including another EJB.
The application program accesses the HumanTaskManager session bean through the bean's home and remote or local interfaces. A reference must be added to your application deployment descriptor. For example, for client applications such as a J2EE client application add the reference to the application-client.xml, for a Web application to the web.xml, and for an EJB application to the ejb-jar.xml.
Add the reference to the remote interface as in the following example:
<ejb-ref> <ejb-ref-name>ejb/HumanTaskManagerHome</ejb-ref-name> <ejb-ref-type>Session</ejb-ref-type> <home>com.ibm.task.api.HumanTaskManagerHome</home> <remote>com.ibm.task.api.HumanTaskManager</remote> </ejb-ref>
Add the reference to the local interface as in the following example:
<ejb-local-ref> <ejb-ref-name>ejb/LocalHumanTaskManagerHome</ejb-ref-name> <ejb-ref-type>Session</ejb-ref-type> <local-home>com.ibm.task.api.LocalHumanTaskManagerHome</local-home> <local>com.ibm.task.api.LocalHumanTaskManager</local> </ejb-local-ref>
If you are using the remote interface, then the generated API stubs must be packaged with your application:
Note: If you are using the remote interface, the XSD's describing your messages must be on the classpath.
The HumanTaskManager bean's local or remote home interface is then made available to the client through JNDI by the container where the HumanTaskManager session bean is deployed. To access the remote interface:
// Obtain the default initial JNDI context Context initialContext= new InitialContext(); // Lookup the remote home interface of the HumanTaskManager bean Object result= initialContext.lookup("java:comp/env/ejb/HumanTaskManagerHome"); // Convert the lookup result to the proper type HumanTaskManagerHome home= (HumanTaskManagerHome)javax.rmi.PortableRemoteObject.narrow(result,HumanTaskManagerHome.class);To access the local interface:
// Obtain the default initial JNDI context Context initialContext= new InitialContext(); // Lookup the local home interface of the HumanTaskManager bean LocalHumanTaskManagerHome home= (LocalHumanTaskManagerHome)initialContext.lookup("java:comp/env/ejb/LocalHumanTaskManagerHome");
The home interface contains a create method that returns the HumanTaskManager session bean's remote or local interface. For example, access the remote interface of the session bean:
HumanTaskManager manager= home.create();For example, access the local interface of the session bean:
LocalHumanTaskManager manager= home.create();
When the HumanTaskManager session bean is accessed, the application program can call any of the business functions exposed by the API. For example:
manager.claim(tkiid);
When an instance of the HumanTaskManager session bean is created, the container associates a session context with the instance of the session bean. The session context contains the caller's principal ID and an indication whether the caller belongs to the group of HTM system administrators or monitors. This information is used by both the container and the task manager to check the caller's authorization for each call.
Authorization is always checked by the Human Task Manager, even when checking global security is unset. In the latter case, the caller's principal ID is 'UNAUTHENTICATED' and handled like a normal user ID.
Calls are executed as transactions. A transaction is either established and ended explicitly by the application program, or established by the container when the application progam calls the task manager and ended by the container when the application program receives the result (the deployment descriptor specifies TX_REQUIRED). For example, the application program can establish and end a transaction as follows:
// Obtain user transaction interface UserTransaction transaction= (UserTransaction)intialContext.lookup("jta/usertransaction"); // Begin a transaction transaction.begin(); // Human Task Manager calls ... // On successful return, commit the transaction transaction.commit();Design your own transactions to prevent database deadlocks when multiple transaction instances are running concurrently. For example, the following transaction may result in database deadlocks when run concurrently:
UserTransaction transaction= (UserTransaction)intialContext.lookup("jta/usertransaction"); transaction.begin(); manager.getTask(tkiid); // read-locks the task manager.claim(tkiid); // write-locks the task to update the state transaction.commit();