JAVA API FOR XML MESSAGING

The conventional method for sending and receiving XML documents is not
yet well defined. Using custom interfaces and API wrappers is common in
many organizations due to a lack of available and practical standards. 
In
order to provide a standard approach to sending and receiving XML
messages, the Java Community Process has produced a Java Specification 
Request
called Java API for XML Messaging (JAXM).

MESSAGES IN A BOTTLENECK

The widespread adoption of XML as the data format of the Internet age
has prompted many organizations to jump in feet first. Unfortunately, 
many
of them are not swimming as well as expected. Several organizations 
have
created their own technology and mechanisms for sharing their XML data
with the rest of the world, with unpredictable results.

The business message has become an atomic set of data that can be
shared; this includes invoices, purchase orders, and order 
confirmations. Due
to the rapid adoption of XML as a data format, many companies are still
trying to build their XML infrastructure around these business 
messages,
with less than stellar results.

JAXM OVERVIEW

The Java API for XML Messaging is set to provide a solution that
standardizes how companies share XML messages. The format of the 
messages may be
specified by some agreed-upon XML vocabulary, but the transportation of
the message is handled by JAXM. JAXM is built on familiar technologies,
such as the Simple Object Access Protocol (SOAP).

JAXM provides two methods for sending and receiving XML messages. These
methods are based upon common synchronous and asynchronous messaging
models. A synchronous model uses a request/response approach. This 
means that
when a message is sent, it is processed as a request. The object that
makes the request waits (or 'blocks') until the receiver sends a 
response
message in return. The response message is synchronized in the request
call. One cannot occur (or succeed) without the other.

An asynchronous method uses a one-way model. This means that an object
may send a message to a receiver and not wait for a response. If a
response is sent back to the original caller, it is sent as a second 
one-way
message. In this way, the request and the response are not 
synchronized. A
message can be sent successfully without receiving any response. In 
fact,
in some instances, a response may not even be necessary.

CONNECTIONS

JAXM provides two types of connections for sending and receiving
messages. All XML messages must be sent using one of the following 
provider
types: SOAPConnection or ProviderConnection. The SOAPConnection allows 
the
sender to transfer a message using the SOAP protocol, while the
ProviderConnection uses a 'messaging provider' to assist with message 
delivery.

All connections using SOAPConnection are synchronous. Using the
SOAPConnection's call() method, the sender can call another 
application, send a
request to a specific endpoint, and wait for a response. The request 
and
response are synchronized through the SOAPConnection's call() method.

The ProviderConnection is asynchronous. Unlike a SOAPConnection, which
provides communication between two applications, a ProviderConnection 
uses
a middleman known as a messaging provider, which accepts delivery of a
message on behalf of the receiver. A ProviderConnection is more complex
than a SOAPConnection because of the messaging provider.

Because a ProviderConnection doesn't connect two applications directly,
it provides a level of abstraction not available using the
SOAPConnection. The ProviderConnection also takes care of holding and 
resending a
message when a recipient is not available, allowing the sending 
application to
continue.

A provider can also handle more sophisticated aspects of message
handling, such as routing and intermediate destinations. This means 
that the
messaging provider may route an order to the appropriate users for 
approval,
to the inventory system to check stock, and to the fulfillment system 
to
send the order. At each point, the messaging provider is able to send
status messages back to the source system.

FIND OUT MORE

JAXM is a new technology, which will continue to change and add more
value to the process of sending and receiving XML messages. Find out 
more
about JAXM download tools, documentation, and tutorials.
http://clickthru.online.com/Click?q=0a-ZnICIrrwc4r83ltdwUbiSIvH6sRR 

SUMMARY

Although there are many technologies and approaches available for
sending and receiving XML messages, until now there has not been a 
definable
standard that could be used. JAXM provides the technology necessary to
create a standard method for transmitting XML messages.

Brian Schaffner is a senior consultant for DMR Consulting, a Fujitsu
company. He provides architecture, design, and development support for 
DMR's
Telcom360 group.

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