WebLogic Tuxedo Connector Programmer's Guide

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Developing WebLogic Tuxedo Connector Client EJBs

Note: For more information on the WebLogic Tuxedo Connector JATMI, view the Javadocs for WebLogic Classes. The WebLogic Tuxedo Connector classes are located in the weblogic.wtc.jatmi and weblogic.wtc.gwt packages.

The following sections describe how to create client EJBs that take user input and send service requests to a server process or outbound object that offers a requested service.

WebLogic Tuxedo Connector JATMI client classes are used to create clients that access services found in Tuxedo.

 


Joining and Leaving Applications

Tuxedo and WebLogic Tuxedo Connector have different approaches to connect to services.

Joining an Application

The following section compares how Tuxedo and WebLogic Tuxedo Connector join an application:

Leaving an Application

The following section compares how Tuxedo and WebLogic Tuxedo Connector leave an application:

 


Basic Client Operation

A client process uses Java and JATMI primitives to provide the following basic application tasks:

A client may send and receive any number of service requests before leaving the application.

Get a Tuxedo Object

Establish a connection to a remote domain by looking up "tuxedo.services.TuxedoConnection" in the JNDI tree to get TuxedoConnectionFactory, and use it to get a TuxedoConnection object.

Perform Message Buffering

Use the following TypedBuffers when sending and receiving messages between your application and Tuxedo:

Table 2-1 TypedBuffers
Buffer Type
Description
TypedString
Buffer type used when the data is an array of characters that terminates with the null character. Tuxedo equivalent: STRING.
TypedCArray
Buffer type used when the data is an undefined array of characters (byte array), any of which can be null. Tuxedo equivalent: CARRAY.
TypedFML
Buffer type used when the data is self-defined. Each data field carries its own identifier, an occurrence number, and possibly a length indicator. Tuxedo equivalent: FML.
TypedFML32
Buffer type similar to TypeFML but allows for larger character fields, more fields, and larger overall buffers. Tuxedo equivalent: FML32.
TypedXML
Buffer type used when data is an XML based message. Tuxedo equivalent: XML for Tuxedo Release 7.1 and higher.
TypedView
Buffer type used when the application uses a Java structure to define the buffer structure using a view description file. Tuxedo equivalent: View
TypedView32
Buffer type similar to View but allows for larger character fields, more fields, and larger overall buffers. Tuxedo equivalent: View32.
TypedMBString
Buffer type used when the data is a wide array of characters to support multibyte characters. Tuxedo equivalent: MBSTRING.

Send and Receive Messages

WebLogic Tuxedo Connector clients support three types of communications with Tuxedo service applications:

Request/Response Communication

Note: WebLogic Tuxedo Connector does not provide a JATMI primitive to support setting the priority of a message request. All messages originating from a WebLogic Tuxedo Connector client have a message priority of 50.

Use the following JATMI primitives to request and receive response messages between your WebLogic Tuxedo Connector client application and Tuxedo:

Table 2-2 JATMI Primitives
Name
Operation
tpacall
Use for asynchronous invocations of a Tuxedo service.This JATMI primitive has two forms:
  • deferred synchronous
  • asynchronous
tpcall
Use for synchronous invocation of a Tuxedo service.
tpgetrply
Use for retrieving replies from deferred synchronous calls to a Tuxedo service.
tpcancel
Use to cancel an outstanding message reply for a call descriptor returned by tpacall.

Note: You can not use tpcancel to cancel a call descriptor associated with a transaction.

Using Synchronous Service Calls

Use tpcall to send a request to a service and synchronously await for the reply. The service specified must be advertised by your Tuxedo application. Logically, tpcall() has the same functionality as calling tpacall() and immediately calling tpgetreply().

Using Deferred Synchronous Service Calls

A deferred synchronous tpacall allows you to send a request to a Tuxedo service and not immediately wait for the reply. This allows you to send a request, perform other work, and then retrieve the reply.

A deferred tpacall() service call sends a request to a Tuxedo service and immediately returns from the call. The service specified must be advertised by your Tuxedo application. Upon successful completion of the call, tpacall() returns an object that serves as a descriptor. The calling thread is now available to perform other tasks. You can use the call descriptor to:

When you are ready to retrieve the reply, use tpgetreply() to dequeue the reply using the call descriptor returned by tpacall(). If the reply is not immediately available, the calling thread polls for the reply.

If tpacall() is in a transaction, you must receive the reply using tpgetreply() before the transaction can commit. You can not use tpcancel to cancel a call descriptor associated with a transaction. For example: If you make three tpacall() requests in a transaction, you must make three tpgetreply() calls and successfully dequeue a reply for each of the three requests for the transaction to commit.

Using Asynchronous Calls

The asynchronous tpacall allows you to send a request to a Tuxedo service and release the thread resource that performed the call to the thread pool. This allows a very large number of outstanding requests to be serviced with a much smaller number of threads.

An asynchronous tpacall() service call sends a request to a Tuxedo service. The service specified must be advertised by your Tuxedo application. Upon successful completion of the call, asynchronous tpacall() returns an object that serves as a descriptor. The calling thread is now available to perform other tasks. You can use the call descriptor to identify the correct message reply from TpacallAsynchReply for a sent message request or cancel an outstanding message reply using tpcancel().

Note: You can not use the call descriptor to invoke tpgetreply().

When the service reply is ready, the callback object is invoked on a different thread. If the original request succeeded, the TpacallAsynchReply.sucess method returns the reply from the service. If the original request failed, the TpacallAsynchReply.failure method returns a failure code.

You should implement the callback object using the following guidelines:

Conversational Communication

Note: For more information on Conversational Communication, see WebLogic Tuxedo Connector JATMI Conversations.

Use the following conversational primitives when creating conversational clients that communicate with Tuxedo services:

Table 2-3 WebLogic Tuxedo Connector Conversational Client Primitives
Name
Operation
tpconnect
Use to establish a connection to a Tuxedo conversational service.
tpdiscon
Use to abort a connection and generate a TPEV_DISCONIMM event when executed by the process controlling the conversation.
tprecv
Use to receive data across an open connection from a Tuxedo application.
tpsend
Use to send data across an open connection to a Tuxedo application.

Enqueuing and Dequeuing Messages

Use the following JATMI primitives to enqueue and dequeue messages between your WebLogic Tuxedo Connector client application and Tuxedo /Q:

Table 2-4 JATMI Primitives
Name
Operation
tpdequeue
Use for receiving messages from a Tuxedo /Q.
tpenqueue
Use for placing a message on a Tuxedo /Q.

Close a Connection to a Tuxedo Object

Use tpterm() to close a connection to an object and prevent future operations on this object.

 


Example Client EJB

The following Java code provides an example of the ToupperBean.java client EJB which sends a string argument to a server and receives a reply string from the server.

Listing 2-2 Example Client Application
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public String Toupper(String toConvert)
   throws TPException, TPReplyException
{
     Context ctx;
     TuxedoConnectionFactory tcf;
     TuxedoConnection myTux;
     TypedString myData;
      Reply myRtn;
     int status;

     log("toupper called, converting " + toConvert);

     try {
           ctx = new InitialContext();
          tcf = (TuxedoConnectionFactory) ctx.lookup(
                 "tuxedo.services.TuxedoConnection");
     }
     catch (NamingException ne) {
          // Could not get the tuxedo object, throw TPENOENT
            throw new TPException(TPException.TPENOENT, "Could not get TuxedoConnectionFactory : " + ne);
      }

     myTux = tcf.getTuxedoConnection();

     myData = new TypedString(toConvert);

     log("About to call tpcall");
      try {
          myRtn = myTux.tpcall("TOUPPER", myData, 0);
}
     catch (TPReplyException tre) {
          log("tpcall threw TPReplyExcption " + tre);
           throw tre;
     }
      catch (TPException te) {
           log("tpcall threw TPException " + te);
           throw te;
      }
      catch (Exception ee) {
           log("tpcall threw exception: " + ee);
           throw new TPException(TPException.TPESYSTEM, "Exception: " + ee);
      }
     log("tpcall successfull!");

      myData = (TypedString) myRtn.getReplyBuffer();

      myTux.tpterm(); // Closing the association with Tuxedo

      return (myData.toString());
}
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