WA1802 SOA for Architects Using WebSphere ESB. Student Labs. Web Age Solutions Inc.

Transcription

1 WA1802 SOA for Architects Using WebSphere ESB Student Labs Web Age Solutions Inc. 1

2 Table of Contents Lab 7 - Service Composition Pattern...3 2

3 Lab 7 - Service Composition Pattern Service composition is a collection of patterns that invoke operations of multiple low level services to achieve a goal. Service composition is essentially service reuse. The idea is that when you have a set of reusable low level services, one can compose a high lever service by using them as building blocks. As an added bonus, most vendors allow you to compose service with little or no coding. In this lab, we will use composition to implement the following patterns: 1. Data enrichment pattern. 2. Notification pattern. Enrichment pattern appears when the consumer of a service does not have all the required information for the request message. An enricher service is used to supply the missing information. The flow of the request message goes as follows. Service Consumer Enricher Service Enrichment pattern Service Provider Enrichment pattern can also be seen as a data transformation pattern. You can also use a complicated data map to retrieve and fill in missing information in a message. It is better to develop an enricher service instead. Complex data map will most certainly be vendor proprietary and non-reusable in another vendor's platform. An enricher web service will be more reusable. Notification pattern appears when a message needs to be sent to multiple applications. Typically notification is sent regarding an event. For example, when product data changes, all applications that keep a copy of that data is notified. Applications that receive the notification are called sink applications. Notification is sent by invoking a one-way operation. The notifier does not receive any reply back. Service Consumer Sink 1 Sink 2 Notification pattern 3

4 Part 1 - Business Use Case For complex problems, always write the use case first. This describes the message flow. this will help us identify the required services. Description A retail company uses many software applications that keep a copy of the product data. Whenever information about a product changes, the updated information needs to be propagated to all applications. An attribute of the product data is inventory. Only the warehouse application has access to this data. How can a consumer initiate propagation of updated product data when inventory of the product is not known to it? We will use an enricher service to retrieve and supply that information. Precondition When product data changes, a consumer invokes a message flow to begin the use case. The following information about a product is sent as request. SKU Name Main Flow The request message is first sent to an enricher service. As input message, the product's SKU and name is sent. The enricher service retrieves the product's inventory and returns it. The following product information is then sent as notification to all recipient applications. The list of recipients can change from time to time. At this point, the following applications need to be notified. 1. Accounting 2. Web site To keep things simple, all services will be implemented using Java classes. In future labs, we will compose web services. Part 2 - Create the Module 1. From the menubar select File > New > Mediation Module. 2. Enter CompositionTest as the name. 3. Set target runtime to WebSphere ESB Server Uncheck Create mediation component. 4

5 5. Click Finish. Part 3 - Create the Product Data Type 1. Right click Data Types and select New > Business Object. 2. Enter Product as the name. 3. Click Finish. 4. Read the use case and try to figure out the various attributes of the product. The table below shows the solution. Add the following fields to the data type. Name SKU Name Inventory Type string string int 5. Save and close. Part 4 - Identify and Specify Services What services do we need to solve this problem? The answer lies in the use case. List all 5

6 the actions or verbs in the use case: 1. Propagate product data The consumer invokes this to start the message flow. 2. Enrich inventory data The message flow invokes this 3. Propagate product data The message flow invokes this for every recipient application. Action #1 and #3 are the same in their intention and can be merged into one. Essentially, we need to define two service interfaces. 1. InventoryEnricher Has an operation that will take as input a Product obejct and return a Product object with the inventory field filled in. 2. ProductDataSink Any service that receives a notification of product data update will implement this interface. It has a one-way operation that takes as input the product's data. According to the use case, we need to develop these four services. 1. The mediation flow implements ProductSink 2. Inventory enricher service implements InventoryEnricher 3. Accounting software - implements ProductSink 4. Web site - implements ProductSink. We will first define the InventoryEnricher interface. 1. Right click Interfaces and select New > Interface. 2. Enter InventoryEnricher as the name and click Finish. 3. Click the Add Request Response Operation toolbar button to create a two-way operation. 4. Make these changes to the operation. Change the name of the operation to supplyinventory Change the name of the input parameter to product and data type to Product Change the name of the output parameter to product and data type to Product 6

7 5. Save and close the interface. Now, we will define the ProductSink interface. 6. Create a new interface and call it ProductSink 7. Add a one-way operation. 8. Make these changes to the operation. Change the name of the operation to updateproduct Change the name of the input parameter to product and data type to Product 9. Save and close. Part 5 - Implement the Message Flow Our message flow design will closely follow the use case. it is recommended that you draw the conceptual flow on a piece of paper. It should look something like this. Service Consumer Inventory Enricher Accounting Web Site 1. Right click Integration Logic and select New > Mediation Flow. 2. Enter PropagateProductChange as the name. 3. Click Next. 4. As the source interface add ProductSink. 5. Click Finish. Note the following about the mediation flow: 7

8 It does not have any target interface. A target interface is used when a service operation is invoked at the end of the request message flow. That is called a call out. We can consider the sink applications as targets. We could use call out to notify them. In this lab we will use the Service Invoke primitive instead. Also, note that the updateproduct source operation has no response message flow. Why is that? It is because the operation is one-way. Remember, notification operations are often one-way. For each service invoked by the mediation flow, we need to add a reference partner. That is a standard SCA programming practice. 6. In the top pane of the mediation flow editor, click the Add Reference button. 7. Select the InventoryEnricher interface. Accept the default name for the partner InventoryEnricherPartner. 8. Click OK. 9. Similarly, add the following references. Name AccountingRef WebSiteRef Interface ProductSink ProductSink We will now add a bunch of service invoke primitives. Each one will invoke one service operation of a reference partner. 10. Click the updateproduct operation in the source interface to select it. 8

9 11. The Request: updateproduct pane will open. 12. Click the Routing folder in the tool palette and locate the Service Invoke item. 13. Drag the Service Invoke primitive and drop it on the message flow. Note the mouse pointer may look like is not available. 14. Select InventoryEnricherPartner, the operation will change to supplyinventory. 9

10 15. Click OK. 16. Change the name of the invoke primitive to EnrichInventory 17. Similarly add two more service invoke primitives with the following specifications. Partner reference Operation Primitive's Name AccountingRef updateproduct AccountingSystem WebSiteRef updateproduct WebSite 18. Connect the output terminal of updateproduct : ProductSink to the input of EnrichInventory. WID will insert a XSL transformer in the middle. 10

11 19. Connect the output terminal of EnrichInventory to the input of AccountingSystem. Another XSL transformer will be inserted. Make sure you use the out terminal of EnrichInventory and not the timeout terminal. 20. Connect the output of XSLTransformer2 to the input of WebSite. 21. Verify the message flow design. Note that the output of XSLTransformation2 is connected to multiple input terminals. That is one way of implementing notification or broadcast. Another more powerful way to do this is using Fan Out primitive. We will use that in a future lab. 22. Save changes. Part 6 - Design the Data Maps 1. Select the first transformer XSLTransformation1. 2. In the Properties view, select the Details tab. 3. Click New. 4. Accept all defaults and click Finish. 5. In the map editor, connect the two Product objects as shown below. 11

12 6. Save and close the map. 7. Select the second transformer XSLTransformation2. 8. In the Properties view, select the Details tab. 9. Click New. 10. Accept all defaults and click Finish. 11. In the map editor, connect the two Product objects as shown below. 12. Save and close the map. 13. Save the mediation flow. Verify that the problems view has no error messages. Part 7 - Implement the Services We have identified the need for four services. Out of that the mediation flow has been already implemented. We will implement the rest using basic Java classes. In real life they will be probably web services. We have already covered how to invoke a web service from a mediation flow. To keep things simple we will not get into that again this time. 1. Open the assembly diagram. 2. Right click the white area and select Add > Java. 3. Change the name of the component to InventoryEnricher 4. Right click it and select Add > Interface. 5. Select InventoryEnricher and click OK. 6. Right click the component again and select Generate Implementation. 7. Select (default package) and click OK. 8. Change the supplyinventory method as follows. public DataObject supplyinventory(dataobject product) { System.out.println("Setting inventory value"); 12

13 product.setint("inventory", 200); } return product; 9. Save and close. 10. Right click the white area and select Add > Java. 11. Change the name of the component to AccountingSystem 12. Right click it and select Add > Interface. 13. Select ProductSink and click OK. 14. Right click the component again and select Generate Implementation. 15. Select (default package) and click OK. 16. Change the updateproduct method as follows. public void updateproduct(dataobject product) { System.out.println("Updating product in accounting system."); System.out.println("Current inventory level: " + product.getint("inventory")); } 17. Save and close. 18. Right click the white area and select Add > Java. 19. Change the name of the component to WebSite 20. Right click it and select Add > Interface. 21. Select ProductSink and click OK. 22. Right click the component again and select Generate Implementation. 23. Select (default package) and click OK. 24. Change the updateproduct method as follows. public void updateproduct(dataobject product) { System.out.println("Updating product in web site."); System.out.println("Current inventory level: " + product.getint("inventory")); } 25. Save and close. 26. Save the assembly diagram but leave it open. 13

14 Part 8 - Wire the Solution 1. Drag PropagateProductChange mediation flow and drop it on the assembly diagram. 2. Study each one of its three reference partners by moving the mouse over it and opening the tooltip. 3. Set up these wirings: Reference Partner Name InventoryEnricherPartner AccountingRef WebSiteRef Wire to Java Component InventoryEnricher AccountingSystem WebSite 4. Save changes. Make sure that there are no errors in the problems view. Part 9 - Test 1. Make sure the server is started in the Servers view and start it if it is not. 2. Right click the server in Servers view and select Add Remove Projects. 3. Click Remove All to undeploy all existing applications. 4. Add the CompositionTestApp. 5. Click Finish. 6. Wait for publishing to end. 14

15 7. Right click in the white area of the assembly diagram and select Test Module. 8. Carefully choose PropagateProductChange mediation flow as the component to be tested. 9. In the input area, enter some values. Leave the inventory as Click the Continue button in the test editor. 11. Expand WebSphere ESB Server 6.2 and Choose WebSphere ESB Server 6.2 at localhost as the runtime. Also check to use it as default. Click Finish. 12. Click OK in the user id and password if prompted. 13. In the Console view, verify the message logs shows the progress of the message flow. Note that the sink services received the correct inventory value. 14. Close the test but do not save. 15. Close any other open files. Part 10 - Review In this lab, we used service composition to implement two separate pattern. We used a service to supply missing information (inventory) in the request message. We then broadcast or notify the request message to multiple recipient or sink services. The mediation flow composed three lower level services to create a solution. In addition, due to the complexity of the business problem, we followed a structure methodology to solve the problem. First, we described the message flow in a use case. We designed the Product data type from the use case. We identified various service interfaces and required services from the use case. 15

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