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Order Service - Services Layer

In this chapter we are going to create service layer which exposes backend functionality via REST services with JSON transport.

REST API

First we create the REST API as interface in api/src/main/java/org/example/app/ordermanagement/service/api/rest/OrdermanagementRestService

@Path("/ordermanagement/v1")
@Consumes(MediaType.APPLICATION_JSON)
@Produces(MediaType.APPLICATION_JSON)
public interface OrdermanagementRestService {

  @GET
  @Path("/order/{id}/")
  OrderEto findOrder(@PathParam("id") long id);

  // ...
}

REST Implementation

Now we create a REST implementation class in core/src/main/java/org/example/app/ordermanagement/service/impl/rest/OrdermanagementRestServiceImpl.

Simply implement your REST interface as Java class and annotate it with @Named:

@Named
public class OrdermanagementRestServiceImpl implements OrdermanagementRestService {

  @Inject
  private Ordermanagement ordermanagement;

  public OrderEto findOrder(long id) {
	// TODO
  }

  // ...
}

Testing of service layer

The URL of the service should be like this (what will retrive order with ID 1 as JSON): http://localhost:8081/services/rest/ordermanagement/v1/order/1

Simple GET requests can be easily tested via URL in your browser. For testing other methods such as POST or DELETE see rest testing.

Integration-Test (optional)

If you have time left, create an automated integration test. Therefore, we define a subsystem tests in core/src/test/java/org/example/app/ordermanagement/service/impl/rest/OrdermanagementRestServiceTest

public class OrdermanagementRestServiceTest extends RestServiceTest {
  @Test
  public void testFindOrder() {

    String login = "admin";
    String password = "admin";
    OrdermanagementRestService service = getServiceClientFactory().create(OrdermanagementRestService.class,
        new ServiceClientConfigBuilder().host("localhost").authBasic().userLogin(login).userPassword(password)
            .buildMap());
    OrderEto order = service.findOrder(1L);
    assertThat(order.getPrice()).isEqualTo(new BigDecimal("25.50"));
  }

}

At the first look this appears to be the same as our test of the use-case or repository. However, technically here a full server with HTTP stack is started within JUnit. The JUnit test itself invokes the server via HTTP GET request and de-serializes the JSON from the server response back to OrderEto. Besides authentication and all such aspects are also tested.

To make this work you need to ensure you have a proper service client implementation available. Therefore add the following dependency to core/pom.xml:

<dependency>
  <groupId>com.devonfw.java.starters</groupId>
  <artifactId>devon4j-starter-cxf-client-rest</artifactId>
</dependency>

The same infrastructure with ServiceClientFactory can also be used for microservices.