Learner Series: Build/Consume HTTP REST Services in SOA 11g (with example)

Today REST (Representational State Transfer) has become a norm for building services on the web. REST brings along its own merits & demerits - choice of REST vs SOAP/WSDL, when and where is an architectural decision. So, how does Oracle SOA BPEL support HTTP based RESTful web services.

For all HTTP based interactions, Oracle SOA 11g provides an out-of-box HTTP Binding adapter.

This post will illustrate the following;

a) Expose a SOA 11g BPEL process as a HTTP REST service
b) Consume/Invoke a HTTP REST service from a SOA 11g BPEL process [We will consume service that we will build as part of (a)]

As part of this exercise, we will build a REST service that will take customer name & id as input and greets the customer.

Before dunking into building the SOA composites, let's quickly take a look at the XML schema that will form the REST service contract.

Exposing SOA 11g BPEL Process as HTTP REST service:

Step 1: Create a SOA Project with empty composite and name it "HttpGetRestService"

Step 2: Drag and Drop a HTTP Binding adapter on the "Exposed Services" swimlane in the SOA composite (SCA)

Step 3: Choose Next in the Welcome page of the wizard

Step 4: Enter service name

 Step 5: Choose "Define from operation and schema (specified later)" option

Step 6: Choose the following options and click Next

Type: Service [You will choose "Reference" if you need to consume a HTTP REST service]
Operation Type: Request-Response [For 2-way communication. Choose One-way if the service doesn't return a response]
Operation Name: Defaults to Request-Response [You can change it as you please]
Verb: GET [This specifies the HTTP method. You have 2 options GET/POST]
Payload Type: url-encoded [For HTTP GET method, SOA 11g support only payload type of url-encoded (name-value pairs). For HTTP POST, you get 2 options url-encoded and XML]

Step 7: In the Messages dialog, select the GreetCustomer.xsd, <CustomerInput> and <Response> XML elements for "Request Message Schema" & "Response Message Schema" respectively.

Step 8: In the summary page, click "Finish" to complete service

Now, drag and drop a BPEL Process on the "Components" section.

Name the process as "GreetCustomerProcess" and choose to define service later.

You can now proceed to build the BPEL process as you please. As part of this sample, I have concatenated the customer name input with "Welcome" prefix so that the service returns the greeting as response.

Finally, deploy this project to your SOA server.

On deployment you can notice that the service is exposed both as a WSDL based webservice and HTTP based REST service. This will enable clients to interface through either standards.

You can test this service either via Enterprise Manager (EM) console - test mode or via normal browser.

For testing your SOA 11g based HTTP service refer to my blog entry here

Consuming a HTTP REST service in SOA 11g BPEL process:

Step 1: Create a SOA Project with empty composite and name it "InvokeHttpGetService"

Step 2: Drag and Drop a HTTP Binding adapter on to the "External References" swimlane in the SOA composite (SCA)

Step 3: Choose Next in the Welcome page of the wizard

Step 4: Enter service name

 Step 5: Choose "Define from operation and schema (specified later)" option

Step 6: Choose the following options and click Next

Type: Reference [Since we are consuming a HTTP REST service]
Operation Type: Request-Response [Default selection for references]
Operation Name: Request-Response [Default]
Verb: GET [This specifies the HTTP method. You have 2 options GET/POST]
Payload Type: url-encoded [Default]
Endpoint: Provide the HTTP URL for the REST service to be invoked. In this case, you can obtain the HTTP URL from enterprise manager console.

Step 7: In the Messages dialog, select the GreetCustomer.xsd, <CustomerInput> and <Response> XML elements for "Request Message Schema" & "Response Message Schema" respectively.

Step 8: In the summary screen, click Finish to complete the service adapter

Now, drag and drop a BPEL Process on to the Components section of your SOA composite. Provide a name to the process, accept other defaults and click OK

Wire the BPEL process with the HTTP Binding adapter in the SOA composite.

Inside the BPEL process, just map the input payload element to the <Name> element of the greeting rest service and deploy to SOA server.

You can now test and check both SOA services in action. One will expose itself as a REST service and the other will invoke it.

Source code can be downloaded here

Let me know your thoughts in comments section.

Testing SOA 11g based HTTP REST services (Resolving Invalid Query String Error)

When a SOA 11g service is exposed as a HTTP service (using HTTP Binding adapter), it can be easily tested through Enterprise Manager (EM) console. Refer here to find out more on how to build/consume/trigger HTTP based REST services in SOA 11g.

However, the purpose of exposing the service accessible via HTTP standard is to ensure it can be directly consumed over a browser.

Typically for a HTTP-GET service, parameters (if any) to the service are passed as query strings (name-value pairs).

From the EM console, HTTP Endpoint for the deployed service can be obtained.

But just invoking the service endpoint via browser along with query string throws the following exception;
 "Invalid Query String"

To resolve this issue, pass the "operationName" query string (mandatory parameter) along.

For eg., if your current endpoint looks like:

http://localhost:7001/soa-infra/services/default/HttpGetRestService/HttpGet?name=Sathya

Modify this to:

http://localhost:7001/soa-infra/services/default/HttpGetRestService/HttpGet?name=Sathya&operationName=Request-Response

Here operation name value is the operation name that was specified during the HTTP Binding adapter creation. By default operation name defaults to "Request-Response".