IBM BPM, V8.0.1, All platforms > Authoring services in Integration Designer > Services and service-related functions > Access external services with messaging systems
Mapping a message to an SCA interface
An import with a messaging binding such as JMS, MQ, MQ JMS or generic JMS that exchanges messages with an export with a messaging binding could be considered as messaging clients to each other. In order for your service component architecture (SCA) application to communicate with an existing JMS, MQ or MQ JMS messaging client, certain SCA artifacts need to be created.
This section describes how to create a business object and an interface that represents your messaging client application in an SCA manner. Imports, exports, and bindings are also discussed. SCA applications use imports with messaging bindings to send messages to messaging clients and use exports with messaging bindings to receive messages from messaging clients.
Verify that a module that contains your service component architecture application exists and that the message format used by the JMS, MQ, or MQ JMS client is known.
These SCA artifacts and their relationship to a JMS client are discussed in the following sections:
Business object
In order for your SCA application to communicate with an existing messaging client, you will need to have a business object that would represent the message that is used by the messaging client.
If the message that is used by the client is in XML format, the XML schema that defines it is used as your business object. If you have this schema, you must import it into your module. The imported XML schema then appears under Data in your module. If you do not have this schema, you can create a business object and add the appropriate attributes to it that will mirror the XML format used by the client.
If the message that is used by the client is not in XML format and there is no XML schema that defines it, create a business object and add the appropriate attributes to it so that it reflects logically the message format used by the JMS client.
For example, if the message conforms to the Enterprise JavaBean (EJB) model, you create a business object and add appropriate attributes to the business object to represent the attributes of the EJB model.
JMS provides a message class that can have one of five body types containing the message in a different format. IBM Integration Designer supports this message class. To reduce your development time, IBM Integration Designer provides a feature in its dependency editor to generate appropriate business objects for each of these JMS body types.
To create the business object...
- Right-click Data in your module, and select New > Business Object from the menu.
- Specify an appropriate name for your business object and click Finish.
- Add the appropriate attributes to your business object to fully describe it, and save the object.
Data bindings, which are discussed later, handle the transformation of data passed in native format from a messaging system or EIS system to a Service Data Object (SDO) in a Service Component Architecture-based (SCA) application.
Interface
In order for your SCA application to communicate to an existing messaging client, you must have an interface that represents the input and output of the messaging client application; that is, the interface represents the interaction with the client.
The interface has business operations to describe the messaging client application operations. The operation style, such as document literal wrapped, document literal, or RPC, to be implemented must be decided. An operation can be one-way, sending a message and not expecting a response, or request-response, sending a message and expecting a returning message.
The type of the operation is the type of the business object that represents the message used by the messaging client.
For example, in the case of employee information, an employeeRecord business object should be used or created. Based on the content of the employee information, it might cause an employee record to be created or an existing employee record to be updated or deleted. So on the interface, you could have three operations: createEmployeeRecord, updateEmployeeRecord, and deleteEmployeeRecord.
To create the interface...
- Right-click Interfaces in the navigation of your module, and select New > Interface from the menu.
- Specify an appropriate name for the interface and click Finish.
- Add the appropriate operations to your interface to fully describe the interaction with the messaging client, and save the interface.
Imports, exports, and bindings
A business object represents the message received and sent from the JMS, MQ, or MQ JMS messaging client, and an interface represents the interaction of the input and output of the messaging client. But how is the data transferred between the client and these SCA artifacts? Business objects and interfaces are found in a module, which is similar to a project container. Imports and exports define the external interfaces or access points of the module. In other words, the messaging client interacts with an SCA application's business objects and interfaces through imports and exports.
Imports identify services outside of a module that can be called from within the module. Exports allow components to listen to requests from external clients. An export allows an external event to be processed. When a message is put on a destination, the associated SCA export processes the event invoking the targeted SCA component. With respect to messaging, imports and exports work as a pair to send and receive messages. An import allows an internal event in the SCA application to be processed. When such a message is put on a destination queue, the associated messaging client processes the event. When a message is put on a destination queue, the associated SCA export processes the event invoking the targeted SCA component.
Binding information, which specifies the means of transporting the data from the modules, is required for an import or an export. Several messaging bindings, including JMS, MQ, and MQ JMS, are available.
The relationship of bindings, messages in the context of imports and exports, and types of operations in interfaces is shown in the following table.
The relationship of bindings and the types of operations in interfaces used in the context of how the client behaves JMS, MQ, or MQ JMS bindings One-way operation in an interface Request-response operation in an interface Import binding Client receives message Client receives and sends message Export binding Client sends message Client sends and receives message To create an import with a messaging binding...
- Open the assembly editor.
- From the import group on the palette, select an import and drag it on to the canvas. An import with no implementation and no interface is created.
- Right-click the import and select Add Interface from the menu.
- Add an interface with at least one operation.
- Generate the binding by right-clicking the import and, from the menu, select Generate Binding > Messaging Binding > < type_of_binding>.
To create an export with a messaging binding...
- Open the assembly editor.
- From the component group on the palette, select an export and drag it on to the canvas. An export with no implementation and no interface is created.
- Right-click the import and select Add Interface from the menu.
- Add an interface with at least one operation.
- Generate the binding by right-clicking the export and, from the menu, select Generate Binding > Messaging Binding > < type_of_binding>.
Access external services with messaging systems
Related concepts:
Java Message Service (JMS)
WebSphere MQ Java Message Service (MQ JMS)
Generic JMS
WebSphere MQ (WMQ)
Related reference:
Recommendations when using messaging bindings
Language support in non-EIS bindings