woensdag 12 juni 2013

Oracle BPEL and Java. A comparison of different interaction options

When building BPEL processes in Oracle SOA Suite 11g, it sometimes happens some of the required functionality can't easily be created by using provided activities, flow control options and adapters. Often there are Java libraries available which can fill these gaps. This blog post provides an evaluation of different options for making interaction between BPEL and Java possible.

In the examples provided in this post, I'm using the JsonPath library (https://code.google.com/p/json-path/) inside a BPEL process. A usecase for this could be that a webclient calls the BPEL process with a JSON message and BPEL needs to extract fields from that message.

The Java code to execute, is the following;

package ms.testapp;

import com.jayway.jsonpath.JsonPath;

public class JsonPathUtils {
   
    public String ExecuteJsonPath(String jsonstring, String jsonpath) {
        String result = JsonPath.read(jsonstring, jsonpath).toString();
        return result;
    }
    
    public JsonPathUtils() {
        super();
    }
}

Of course small changes were necessary for the specific integration methods. I provided code samples at the end of this post for every method.

Integration methods

Embedding

Oracle has provided an extension activity for BPEL which allows Java embedding. By using this activity, Java code can be used directly from BPEL. The JsonPath libraries to use in the embedding activity can be put in different locations such as the domain library directory or be deployed as part of the BPEL process. Different classloaders will be involved. To check whether this matters I've tried both locations.

Performance
The Java call happens within the same component engine. Below are measures from when using JSON libraries deployed as part of the BPEL process (in SCA-INF/lib).
Below are measures from when putting the libraries in the domain library folder.
As you can see from the measures, the performance is very comparable. The location where the BPEL process gets it's classes from has no clear measurable consequences for the performance.

Re-use potential
When the libraries are placed in the domain lib folder, they can be reused by almost everything deployed on the applications server. This should be considered. When deploying as part of the composite, there is no re-use potential outside the composite except possibly indirectly by calling the composite.

Maintenance considerations
Embedded Java code is difficult to maintain and debug. When deployed as part of a BPEL process, changes to the library require redeployment of the process. When libraries are put in the domain library directory, changes to it, impact all applications using it and might require a restart.

XPath

XPath extension functions can be created and used in BPEL (+ other components) and JDeveloper. This is nicely described on; https://blogs.oracle.com/reynolds/entry/building_your_own_path.

Performance
The custom XPath library is included as part of the SOA infrastructure and does not leave this context. As can be seen, the performance is comparable to the Java embedding method.

Re-use potential
The reuse potential is high. The custom XPath library can be used in different locations/engines, dependent on the descriptor file.

Maintenance considerations
Reuse by different developers in JDeveloper requires minimal local configuration, but this allows GUI support of the custom library. There are no specific changes to BPEL code thus low maintenance overhead. Changing the library on the application server requires a restart of the server.

Spring component

The Java code can be called as a Spring component inside a composite. Here another component within the composite is called. The Java code is executed outside the BPEL engine.

Performance


Re-use potential
The following blog posts links to options with the Spring Framework; https://blogs.oracle.com/rammenon/entry/spring_framework_samples. When deployed inside a composite, reuse is limited to the composite. It is possible to define global Spring beans however, increasing re-use. The code can be created/debugged outside an embedding activity.

Maintenance considerations
The Spring component is relatively new to Oracle SOA Suite so some developers might not know how to work with this option yet. It's maintenance options are better then for the BPEL embedding activity. It is however still deployed as part of a composite.

External webservice

Java code can be externalized completely by for example providing it as a JAX-WS webservice or an EJB.

Performance
Performance is poor compared to the solutions described above. This is most likely due to the overhead of leaving soa-infra and the layers the message needs to pass to be able to be called from BPEL.

Re-use potential
Re-use potential is highest for this option. Even external processes can call the webservice so re-use is not limited to the same application server.

Maintenance considerations
Since the code is completely externalized, this option provides the best maintenance options. It can be developed separately by Java developers and provided to be used by an Oracle SOA developer. Also it can be replaced without requiring a server restart or composite redeploy.

Conclusion

The technical effort required to implement the different methods is comparable. Depending on the usecase/requirements, different options might be relevant. If performance is very important, embedding and XPath expressions might be your best choice. If maintenance and reuse are important, then externalizing the Java code in for example an external webservice might be the better option.

Summary of results
This is of course a personal opinion.


The used code with examples of all embedding options can be downloaded here; https://dl.dropboxusercontent.com/u/6693935/blog/TestJavaEmbedding.zip