This document covers the following topics:
In the properties file, only one input and one output queue can be specified. These are the default queues used by the WebSphere MQ RPC Server. The queue name can also be specified on each call, using a dynamic parameter. Since different queue names can be specified on different calls, multiple input or output queues are supported. The default input and output queues can also be used with the dynamic parameter. Queues specified by a dynamic parameter are opened when they are used for the first time and closed when the WebSphere MQ RPC Server terminates.
A synchronous request/reply call to MQ is possible. In this case, the
remote procedure call has to have both INPUT and OUTPUT parameters, or an INOUT
parameter has to be specified. The WebSphere MQ RPC Server issues an MQ PUT call
with message type "Request" on the default output
queue. The Reply To Queue Name field is set to the name
of the default input queue. After the PUT call, the WebSphere MQ RPC Server issues
an MQ GET on the default input queue and then it waits for the reply message
(note that for this scenario the input queue must be different from the output
queue).
Dynamic queue names can also be used for the request/reply scenario. Use
the MQ_QUEUE_NAME parameter for the output (request)
queue and the MQ_REPLY_QUEUE parameter for the input
(reply) queue.
You can also use the dynamic Reply To Queue parameter to indicate that
a reply is expected for this message. In this case, sending the message and
receiving the reply is decoupled and is performed by two separate RPC
requests.
The request and reply messages are correlated by the correlation ID. The reply message has to have the same correlation ID as the request message.
With the WebSphere MQ RPC Server it is possible that certain parameters of a remote procedure call are dynamic parameters which are evaluated by the WebSphere MQ RPC Server. Dynamic parameters have a fixed name; they can be defined only on level 1 in the parameter definition in the IDL file and before any variable length parameter, and have a specific format. The WebSphere MQ RPC Server uses the following parameters:
| Parameter | Format | Description |
|---|---|---|
Queue name (MQ_QUEUE_NAME) |
A48 |
Overrides the default input or output queue name
specified in the properties file. IN parameter only.
|
Correlation ID (MQ_CORREL_ID) |
A48 |
The MQ Correlation ID can be used in Request Reply scenarios. If
it is an IN (or INOUT) parameter, it is assigned to the correlationId parameter
of the MQ message which is sent to MQ. If it is an OUT (or INOUT) parameter, it
contains the corresponding value of the received MQ message. This parameter is
defined of type alphanumeric but its contents is an hexadecimal encoded binary
array.
|
Reply To Queue (MQ_REPLY_QUEUE) |
A48 |
The replyToQueueName parameter of the MQ message.If it is an IN
(or INOUT) parameter, it specifies that the MQ message is of type Request. If
it is an OUT (or INOUT) parameter, it contains the corresponding value of the
received MQ message.
|
Wait Interval (MQ_WAIT_INTERVAL) |
A with fixed length | The wait interval in milliseconds for an MQ GET call. Overrides
the default value entirex.wmqbridge.waittime from the properties file. IN
parameter only.
|
MQRFH Header data (MQ_RFH_*) |
A with fixed length | Arbitrary number of parameters. The names following the prefix
"MQ_RFH_" are used as the names of the name value pairs of the MQRFH
header.
|
If dynamic parameters are to be used, generate a properties file from
the corresponding Software AG IDL file and specified with the
entirex.bridge.names.file property. To generate
this property file, use the template bridge.tpl in the
template subdirectory of the EntireX installation. For
batch generation, run erxidl.bat (Windows) or
erxidl.bsh (UNIX) with the parameters "-t
<path to template directory>/bridge.tpl
<idlFile>".
Alternatively, you can also use the EntireX Workbench. Go to the Preferences for EntireX and create a new custom wrapper. Specify a name and browse to the bridge.tpl template. If the Custom Wrapper has been created (and the Workbench restarted), you can generate the properties file from an IDL file, using the context menu item .
The correlation ID can be explicitly used in get message and put message
operations using the dynamic parameter MQ_CORREL_ID.
For Request Reply scenarios there is also an implicit usage of the
correlation ID by the WebSphere MQ RPC Server: If
MQ_CORREL_ID is not explicitly specified, MQ is
instructed to generate a correlation ID. The option
MQPMO_NEW_CORREL_ID is set internally to achieve this.
When reading the reply the option MQMO_MATCH_CORREL_ID
is specified, thus the reply message has to use the same correlation as
specified in the request message.
MQ messages may have custom specific headers. The MQRFH header (rules
and formatting header) consists basically of name value pairs. Restriction:
only one header per MQ message is possible; MQ allows an arbitrary number of
headers per message.
When sending a message to MQ: a MQRFH header is built if at least one
parameter in the IDL file has a name with prefix "MQ_RFH_". All IN (or INOUT)
parameters with this prefix are used to build the header. If for example the
IDL file contains two fields MQ_RFH_H1 and
MQ_RFH_H2 with the values v1 and v2, the resulting
MQRFH header will have two name value pairs, H1 v1 and H2 v2.
If a message is received from MQ: if the message has a MQRFH header, all
value entries in the name value pairs are copied to the corresponding OUT (or
INOUT) parameter in the IDL file. The name has to match the part of the IDL
parameter name after the prefix. In the above example consider that the MQ
message has two name value pairs, H1 v11 and H3 v22. Then the value v11
will be assigned to the parameter MQ_RFH_H1, the parameter MQ_RFH_H2 gets
no value assigned, and the entry for H3 will be ignored.
When the WebSphere MQ RPC Server is exchanging messages via the EntireX Broker with an RPC client (or server), the usual rules apply. By default, the message is exchanged between the WebSphere MQ RPC Server and EntireX using the platform encoding of the JVM which executes the WebSphere MQ RPC Server.
If the payload of the MQ message is in XML format
(property entirex.bridge.xmm has been set), the
WebSphere MQ RPC Server converts the XML payload to the encoding used for the
remote procedure call. If the WebSphere MQ RPC Server has to create the XML
payload, it will use UTF-8.
If the payload of the MQ message is of type text, the translation of the MQ message payload is done by the IBM MQ Java classes. When sending a message, the WebSphere MQ RPC Server converts the message to a Unicode string and the MQ classes convert the Unicode string to the encoding specified by the CCSID (Coded Character Set IDentification) of the queue manager. When receiving a message the IBM MQ Java classes return a Unicode string.
WebSphere MQ does not have a clearly defined message layout, it is basically a stream of bytes. In general it is up to the MQ application to know the exact semantics of an MQ message. This might include application-specific headers and formatting rules. The WebSphere MQ RPC Server supports a general but simplified model of message processing.
To better handle application specific message layout details a user exit
(or callback routine) can be used. The user exit is working on the WebSphere MQ
Java representation of an MQ message (class com.ibm.mq.MQMessage) and can
change the MQ message. The user exit gets control:
after an MQ message has been constructed by the WebSphere MQ RPC Server and before the message is put to the MQ queue,
after an MQ message has been read from an MQ queue and before it is processed by the WebSphere MQ RPC Server.
The user exit can be used for example for an application specific
processing of the MQRFH, MQRFH2 or even custom headers.
To enable a user exit, use the property entirex.wmqbridge.userexit to specify the class name of the user
exit implementation. The class will be loaded using the standard classpath. You
can specify a separate classpath with the property
entirex.wmqbridge.userexit.classpath. Note that
for the classpath a file or HTTP URL must be specified. Your user exit class
must implement the Java interface
com.softwareag.entirex.rpcbridge.WMQBridgeExit. This Java
interface has the following methods:
/** ** This method is called after the message has been created by the WMQBridge ** and before the message is sent to an MQ queue (MQPUT). ** The Message object and/or the MessageOptions object can be changed. ** ** @param msg The MQ message object. ** @param pmo The MQPutMessageOptions object. **/ public void beforePut(com.ibm.mq.MQMessage msg, com.ibm.mq.MQPutMessageOptions pmo); /** ** This method is called before a message is retrieved from an ** MQ queue (MQGET). The MessageOptions object can be changed. ** ** @param gmo The MQGetMessageOptions object. **/ public void beforeGet(com.ibm.mq.MQGetMessageOptions gmo); /** ** This method is called after a message has been retrieved from an ** MQ queue (MQGET) and before the message will be processed by the WMQBridge. ** The Message object can be changed. ** ** @param msg The MQ message object. **/ public void afterGet(com.ibm.mq.MQMessage msg);
Calls to MQ Series are non-transactional by default. Thus the request
operates outside the normal unit-of-work protocols. When reading a message with
MQ GET, the message is deleted from the queue immediately.
If an error occurs
in the further processing of the message within the WebSphere MQ RPC Server (for
example the translation to RPC or XML results in an error), the message cannot
be made available again. The same applies to sending a message, the MQ PUT
operation makes the message available immediately.
If the RPC client application uses conversational RPC, the MQ calls are
issued transactional (using the SYNCPOINT option).
A Backout Conversation will
send a backout to the queue manager, and a Commit Conversation will send a
commit to the queue manager.
To understand the level of guaranteed delivery provided by the WebSphere MQ RPC Server we present the flow of control when reading a message from a queue or writing a message to a queue. Sending a message to an MQ queue:
To send a message to an MQ Queue
The RPC client application sends a send request to the WebSphere MQ RPC Server.
The WebSphere MQ RPC Server creates a corresponding MQ message and puts the message on the queue. If the remote procedure call is part of an RPC conversation, the message is not committed.
The WebSphere MQ RPC Server returns a positive acknowledgment back to the RPC client. If something fails in step 2, an error is returned to the RPC client.
To receive a message from an MQ Queue
The RPC client application sends a receive request to the WebSphere MQ RPC Server.
The WebSphere MQ RPC Server reads a message from the queue. If no message is available, an error is returned to the RPC client. If the remote procedure call is part of an RPC conversation, the message is not committed.
The WebSphere MQ RPC Server creates a corresponding RPC reply which is sent back to the RPC client. If something fails in step 2, an error is returned to the RPC client.
If the send or receive call is part of a conversational RPC, the MQ transaction will get a commit or backout when the RPC conversation is closed, depending on the type of the endConversation call.
