WebSphere Business Integration Message Broker Basics

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4.3.2 Modifying the BookstoreFlow message flow

The BookstoreFlow message flow currently contains three nodes:

򐂰 An MQInput node to retrieve the input message from the IN queue

򐂰 A Compute node to process the input message to generate an output

message

򐂰 An MQOutput node to put the output message on the OUT queue.

The Compute node in the BookstoreFlow is capable of modifying the message

and generating a new message. However, all information about the message

structure is held in the message itself (the XML message is self-defining), so the

Compute node must be programmed, using ESQL, to perform the processing on

the message. The more complex the processing, the more complex the ESQL

must be, which makes the message flow more complex to maintain and debug.

If the logical structure of the XML message is externally defined in a message

set, you do not have to program such complex ESQL to manipulate the message.

The message flow refers, instead, to the external message set for information

about each message that it processes. If you create a message set, you can use

a Mapping node instead of the Computer node.

The Mapping node enables you to load into the Mapping editor the input

message (BookStoreOrder) and output message (ShippingDetails) structures

from the message set. You can then simply drag and drop elements from the

input message onto elements in the output message to show which data should

be used from the input message to create the output message.

Mapping fields from one message to another is useful if, for example, the

business application that sends the message to the broker structures the data in

the message differently from the business application that will receive the

message. If the first business application positions the customer’s first name

before their last name but the second business application expects the

customer’s last name to precede their first name in the message, the Mapping

node can map the fields so that each business application can understand the

message.

In the BookstoreFlow message flow, in addition to replacing the Compute node,

edit the properties of the MQInput node so that it uses the correct message set to

parse input messages. In addition, to avoid conflict between the original version

of the BookstoreFlow message flow and the new version of BookstoreFlow

message flow in the broker, before you deploy the new version of the

BookstoreFlow message flow, you must create a new execution group and two

new WebSphere MQ local queues.

Chapter 4. Application development 117

Replacing the Compute node with a Mapping node

To modify the BookstoreFlow message flow by replacing the Compute node with

a Mapping node:

1. In the Resource Navigator view, double-click BookstoreFlow.msgflow to

open the BookstoreFlow message flow in the Message Flow Editor.

2. In the Message Flow Editor, right-click the Compute node, then click Delete.

The Compute node is deleted from the BookstoreFlow message flow.

3. From the node palette, select the Mapping node and add it to the canvas

between the MQInput node and the MQOutput node.

4. Connect the nodes (Figure 4-23), then save BookstoreFlow.msgflow.

Figure 4-23 Modified BookstoreFlow message flow

Editing the MQInput node properties

To add information about the Bookstore message that is set to the MQInput

node:

1. In the Message Flow Editor, right-click the MQInput node, then click

Properties.

2. On the Default page of the Properties dialog box, edit the properties as shown

in Figure 4-24 on page 118:

a. From the Message Domain list, select MRM.

b. From the Message Set list, select the unique identifier of the message set

that you created. (The value shown in the figure is different from the

identifier that you are using.)

c. In the Message Type field, type BookStoreOrder.

d. From the Message Format list, select XML1.

3. Click OK to close the Properties dialog.

4. Save BookstoreFlow.msgflow.

118 WebSphere Business Integration Message Broker Basics

Figure 4-24 Editing the MQInput node properties to specify message set details

Configuring the Mapping node

The Mapping node enables you to drag and drop fields of the input message,

BookStoreOrder, onto fields of the output message, ShippingDetails, to map the

content of the input message onto the output message.

To configure the Mapping node:

1. In BookstoreFlow.msgflow, right-click the Mapping node, then click Open

Mappings. A mappings file called BookstoreFlow_Mapping.mfmap is

created. BookstoreFlow_Mapping.mfmap automatically opens in the Mapping

editor (Figure 4-25 on page 119).