Message broker nodes are used in
Message flows. A message flow node is a processing step in a message
flow.
A message flow node receives a message, performs a set of actions against the
message, and optionally passes the message on to the next node in the message
flow. A message flow node can be a built-in node, a user-defined node, or a
subflow node.
A built-in node is a message flow node that is
supplied by WebSphere Message Broker. The built-in nodes provide input and
output, manipulation and transformation, decision making, collating requests,
and error handling and reporting functions.
A user-defined node is an extension to the broker
that provides a new message flow node in addition to those supplied with the
product. It must be written to the user-defined node API provided by WebSphere
Message Broker for both C and Java languages.
A subflow is a directed graph that is composed of
message flow nodes and connectors and is designed to be embedded in a message
flow or in another subflow. A subflow must include at least one Input node or
one Output node. A subflow can be executed by a broker only as part of the
message flow in which it is embedded, and therefore cannot be independently
deployed.
A message flow node has a fixed number of input and output points known as terminals.
You can make connections between the terminals to define the routes that a
message can take through a message flow.
Input and output nodes define points in the message flow to which client applications
send messages, and from which client applications receive messages.Client
applications interact with these nodes by putting messages to, or getting
messages from, the I/O resource that is specified by the node as the source or
target of the messages. Although a message flow must include at least one input
node, it does not need to include an output node.
Overview of all the nodes available
in WMB v6.0, 6.1 and 7.0
Input Nodes:
MQInput
Use an MQInput node if the messages arrive at the broker on
a WebSphere MQ queue, and the node is to be at the start of a message flow.
MQGet
Use an MQGet node if the messages arrive at the broker on a
WebSphere MQ queue and the node is not to be at the start of a message flow.
SCADAInput
Use a SCADAInput node if the messages are sent by a
telemetry device.
HTTPInput
Use an HTTPInput node if the messages are sent by a Web
services client.
Real-timeInput or Real-timeOptimizedFlow
Use one of these nodes if the messages are sent by a JMS or
multicast application. The Real-timeInput node is an input
node and the Real-timeOptimizedFlow node is a complete message flow that
provides a high performance publish/subscribe message flow.
JMSInput
Use a JMSInput node if the messages are sent by a JMS
application.
User-defined input node
Use a user-defined input node if the message source is a
client or application that uses a different protocol or transport.
Input node
If you are creating a message flow that you want to embed in
another message flow (a subflow) that you will not deploy as a stand-alone
message flow, you must include at least one Input node to receive messages into
the subflow.
Output Nodes:
Publication
Use a Publication node to distribute the messages using the
publish/subscribe network for applications that subscribe to the broker across
all supported protocols.
MQOutput
Use an MQOutput node if the target application expects to
receive messages on a WebSphere MQ queue, or on the WebSphere MQ reply-to queue
that is specified in the input message MQMD
MQReply
Use an MQReply node if the target application expects to
receive messages on the WebSphere MQ reply-to queue that is specified in the
input message MQMD.
SCADAOutput
Use a SCADAOutput node if a telemetry device is the target
of the output messages, and the Publication node is not suitable.
HTTPReply
Use an HTTPReply node if the messages are in response to a
Web services client request.
HTTPRequest
Use an HTTPRequest node if your message flow interacts with
a Web service.
Real-timeOptimizedFlow Use a Real-timeOptimizedFlow node if the target application
is a JMS or multicast application.
JMSOutput
Use a JMSOutput node if the messages are for a JMS
destination.
User-defined output node
Use a user-defined output node if the target is a client or
application that uses a different protocol or transport.
Output node
If you are creating a message flow that you want to embed in
another message flow (a subflow) that you will not deploy as a stand-alone
message flow, you must include at least one Output node to propagate messages
to subsequent nodes that you connect to the subflow.
Nodes for manipulating, enhancing,
and transforming messages
Compute
Use the Compute node to:
* Manipulate message content
* Transform the message in some way
* Interact with a database to modify
the content of the message or the database and pass on one or more new messages
JavaCompute
Use the JavaCompute node to:
* Examine an incoming message and,
depending on its content, propagate it unchanged to one of the node’s two
output terminals. The node behaves in a similar way to a Filter node, but uses
Java™ instead of ESQL to decide which output terminal to use.
* Change part of an incoming message
and propagate the changed message to one of the output terminals.
* Create and build a new output
message that is totally independent of the input message.
Mapping
Use the Mapping node to create a new message from the input
message by mapping the content of elements of the output message from elements
of the input message, or from database content. You can also extract parts of
the message, and optionally change their content, to create a new output
message that is a partial copy of the message that is received by the node.
Database
Use the Database node to interact with a database that is
identified by the node properties. The Database node handles both predefined
and self-defining messages.
DataDelete, DataInsert, DataUpdate
The DataDelete, DataInsert, and DataUpdate nodes are
specialized forms of the Database node that provide a single mode of
interaction (deletion of one or more rows, insertion of one or more rows, or
update of one or more existing rows).
Warehouse
The Warehouse node provides a store interface that you can
use to store all or part of the message in a database
XMLTransformation
Use the XMLTransformation node to transform an input XML
message into another format using XSLT style sheets.
It, can perform the following actions:
* Sort the data
* Select data elements to include or exclude based on some
criteria
* Transform the data into another format
JMSMQTransform
Use the JMSMQTransform node to transform a message with a
JMS message tree into a message that has a tree structure that is compatible
with the format of messages that are produced by the WebSphere MQ JMS provider.
MQJMSTransform
Use the MQJMSTransform node to receive messages that have a
WebSphere MQ JMS provider message tree format, and transform them into a format
that is compatible with messages that are to be sent to JMS destinations.
MQOptimizedFlow
Use the MQOptimizedFlow node to replace a publish/subscribe
message flow that consists of an MQInput node connected to a Publication node,
and that uses the JMS over WebSphere MQ transport.
User-defined
Use a user-defined node to handle specific requirements that
are not met by the built-in nodes.
Decision making nodes
Validate
Use the Validate node to check that the message that arrives
on its input terminal is as expected.
Filter
Use the Filter node with an ESQL statement to determine the
next node to which the message is sent by this node.
FlowOrder
You can connect the terminals of this node to force the
message to be processed by one sequence of nodes, followed by a second sequence
of nodes.
Passthrough
Use the Passthrough node to enable version control of a
subflow at run time. Use this node to add a label to your
subflow.
RouteToLabel and Label
Use the RouteToLabel node following a Compute node for
complex routing. Define a list of destinations in a Compute node that are acted
on by the RouteToLabel node, which interrogates the destinations and passes the
message on to the corresponding Label node.
ResetContentDescriptor
Use the ResetContentDescriptor node to set new message
properties that are used when the message bit stream is next parsed by a
subsequent node in the message flow.
Nodes for controlling time-sensitive
operations
TimeoutControl
Use a TimeoutControl node and a TimeoutNotification node
together in a message flow to control events that occur at a specific time or
at defined time intervals. The TimeoutControl node receives an input message
that contains a timeout request. All or part of this input message is validated
and stored to be propagated by an associated TimeoutNotification node in the
message flow. The input message is also propagated unchanged to the next node
in the message flow.
TimeoutNotification
Use a stand-alone TimeoutNotification node to generate
messages that are propagated at configured times or time intervals to the next
node in the message flow for further processing.
Nodes for collating
requests
Use the AggregateControl,
AggregateReply, and AggregateRequest nodes to collate related
requests and responses. Use these nodes to generate several requests in
response to one input message, to control and coordinate the responses that are
received in response to those requests, and to combine the information that is
provided by the responses to continue processing.
Error handling and reporting nodes
Trace
Include a Trace node to generate one or more trace entries
to record what is happening in the message flow at this point.
TryCatch
Include a TryCatch node to control the error processing when
exceptions are thrown.
Throw
Include a Throw node to force an exception to be thrown, and
specify the identity of the exception, to make it easier to diagnose the
problem.
New nodes in v6.1
File and FTP nodes
FileInput node reads files from the local file system or FTP server
FileOutput node writes files to the local file system or FTP server
Route, database route
nodes:
The new Route node provides a
graphical technique to enable incoming requests to be examined, and flow sent
down the appropriate part of the message flow, depending on the specified
criteria.
The DatabaseRoute node provides a similar function to the Route node,
but the routing decision is based on the contents of a relational database.
DatabaseRetrieve node enables data to be retrieved from one of more
relational databases, and use a similar dialogue to the DatabaseRoute node.
New nodes in V7
V7 introduced new nodes for SCA
(service component architecture). These are nodes are basically for use with
websphere process server which uses SCA.
SCA Input Node: A WebSphere Process Server SCA Import component can use
Message Broker as an SCA endpoint. The message received by the broker can be a
SOAP over HTTP message or an MQ message on a queue, depending on the binding
used by the node.
SCA Reply Node: This allows a response message to be sent from the
broker back to the originating Process Server SCA client, in response to a
prior message received by an SCA Input Node.
SCA Request Node: This allows synchronous requests to be made from the
broker, allowing the broker to participate in synchronous message exchange
patterns with a Process Server SCA export component. The message sent by the
broker can be a SOAP message over HTTP, or an MQ message, depending on the
binding used by the node. The node will perform a blocked wait for a specified
time period until a response is received
