Jena API with REST webservice using Jersey - rest

Question

I am using Jena API to get RDF data from Allegrograph Server. I have written a REST webservice using Jersey jar to get this data.
My java code for the webservice is as shown below:
#GET
#Path("/JENA")
#Produces({ MediaType.APPLICATION_XML, MediaType.APPLICATION_JSON })
public String getData() throws RepositoryException {
AGGraphMaker maker = new AGGraphMaker(conn);
AGGraph graph = maker.getGraph();
AGModel model = new AGModel(graph);
AGQuery agQuery = AGQueryFactory.create(query);
QueryExecution qe = AGQueryExecutionFactory.create(agQuery, model);
String result = null;
ByteArrayOutputStream byteArrayOutputStream = null;
try {
ResultSet rs = qe.execSelect();
While(rs.hasNext()){
byteArrayOutputStream = new ByteArrayOutputStream();
if("JSON".equalsIgnoreCase(outputFormat)){
ResultSetFormatter.outputAsJSON(byteArrayOutputStream, rs);
result = byteArrayOutputStream.toString();
System.out.println("Result is "+result);
} else if("XML".equalsIgnoreCase(outputFormat)){
ResultSetFormatter.outputAsXML(byteArrayOutputStream, rs);
result = byteArrayOutputStream.toString();
}else if("CSV".equalsIgnoreCase(outputFormat)){
ResultSetFormatter.outputAsCSV(byteArrayOutputStream, rs);
result = byteArrayOutputStream.toString();
}
}
} catch (Exception e) {
System.out.println(e.getMessage());
}
}
I get no results for the SPARQL query when I deploy this web service on Tomcat server and test it using REST client app on Chrome and firefox.
But the same code(absolutely no difference in webservice code and this main method code) if I write in a plain java class and run its main method, i am getting 36 results. I am not sure what the issue is.
Please help me in this regard.

Answer 1

You need to separate the concerns:
Move the service logic - the bit that actually queries Allegro graph - to a separate class so that it's properly encapsulated. The API for the class should reflect its responsibilities in your application, not the way that it happens to be working at the moment.
Write JUnit tests for the service class. This is important - it gives you confidence that your service is performing its job correctly, and keeps on doing so as you develop your application.
Write your Jersey method to invoke any service object that conforms to the API of your service class.
Write one or more HTTPUnit (or similar) tests to invoke your REST API. Ideally, you'll use a mock or test double instead of the actual service. What you want to test is whether the HTTP request reaches the right method, and that method delegates to the service object with the right arguments. You're then testing (and debugging!) a smaller number of concerns.
It's much better to work with small units of functionality with a clear idea of what their responsibilities are. And you should definitely learn to work with tests - it's a big win in the medium term, even if it means a bit more learning up front!