KumuluzEE JAX-RS REST service sample

Develop a REST service using standard JAX-RS 2 API and pack it as a KumuluzEE microservice.

The objective of this sample is to show how to develop a REST service using standard JAX-RS 2 API and pack it as a KumuluzEE microservice. The tutorial will guide you through the necessary steps. You will add KumuluzEE dependencies into build.gradle. To develop the REST service, you will use the standard JAX-RS 2 API. Required knowledge: basic familiarity with JAX-RS 2 and basic concepts of REST and JSON.

Requirements

In order to run this example you will need the following:

1. Java 8 (or newer), you can use any implementation:

   • If you have installed Java, you can check the version by typing the following in a command line:

     java -version
     

2. Gradle:

   • If you have installed Gradle, you can check the version by typing the following in a command line:

     gradle -version
     

3. Git:

   • If you have installed Git, you can check the version by typing the following in a command line:

     git --version
     

Prerequisites

This sample does not contain any prerequisites and can be started on its own.

Usage

The example uses Gradle to build and run the microservice.

1. Build the sample using Gradle:

   $ cd jax-rs
   $ gradle clean buildKumuluzee

2. Run the sample:

• Uber-jar:

  $ gradle runJar

• Exploded:

  Not yet fully supported.

The application/service can be accessed on the following URL:

• JAX-RS REST resource - http://localhost:8080/v1/customers

To shut down the example simply stop the processes in the foreground.

Tutorial

This tutorial will guide you through the steps required to create a simple REST service using standard JAX-RS 2 API and pack it as a KumuluzEE microservice. We will develop a simple Customer REST service with the following resources:

• GET http://localhost:8080/v1/customers - list of all customers
• GET http://localhost:8080/v1/customers/{customerId} – details of customer with ID {customerId}
• POST http://localhost:8080/v1/customers – add a customer
• DELETE http://localhost:8080/v1/customers/{customerId} – delete customer with ID {customerId}

We will follow these steps:

• Create a Gradle project in the IDE of your choice (Eclipse, IntelliJ, etc.)
• Add Gradle dependencies to KumuluzEE and include KumuluzEE components (Core, Servlet and JAX-RS)
• Implement the service using standard JAX-RS 2 API
• Build the microservice
• Run it

Add Gradle dependencies

Add the KumuluzEE BOM module dependency to your pom.xml file:

implementation 'com.kumuluz.ee:kumuluzee-bom:3.1.0'

Add the kumuluzee-core, kumuluzee-servlet-jetty and kumuluzee-jax-rs-jersey dependencies:

implementation 'com.kumuluz.ee:kumuluzee-core:3.1.0'
implementation 'com.kumuluz.ee:kumuluzee-servlet-jetty:3.1.0'
implementation 'com.kumuluz.ee:kumuluzee-jax-rs-jersey:3.1.0'

Alternatively, we could add the kumuluzee-microProfile-1.0, which adds the MicroProfile 1.0 dependencies (JAX-RS, CDI, JSON-P, and Servlet).

Implement the service

Register your module as JAX-RS service and define the application path. You could do that in web.xml or for example with @ApplicationPath annotation:

@ApplicationPath("v1")
public class CustomerApplication extends Application {
}

Implement JAX-RS resource, for example, to implement resource customers which will return all customers by default on GET request:

@Consumes(MediaType.APPLICATION_JSON)
@Produces(MediaType.APPLICATION_JSON)
@Path("customers")
public class CustomerResource {

    @GET
    public Response getAllCustomers() {
        List<Customer> customers = Database.getCustomers();
        return Response.ok(customers).build();
    }

    @GET
    @Path("{customerId}")
    public Response getCustomer(@PathParam("customerId") String customerId) {
        Customer customer = Database.getCustomer(customerId);
        return customer != null
                ? Response.ok(customer).build()
                : Response.status(Response.Status.NOT_FOUND).build();
    }

    @POST
    public Response addNewCustomer(Customer customer) {
        Database.addCustomer(customer);
        return Response.noContent().build();
    }

    @DELETE
    @Path("{customerId}")
    public Response deleteCustomer(@PathParam("customerId") String customerId) {
        Database.deleteCustomer(customerId);
        return Response.noContent().build();
    }
}

Implement the Customer Java class, which is a POJO:

public class Customer {

    private String id;

    private String firstName;

    private String lastName;

    // TODO: implement get and set methods
}

In the example above, we use Database class to access data. A sample implementation which simulates persistance layer, can be implemented as follows:

public class Database {
    private static List<Customer> customers = new ArrayList<>();

    public static List<Customer> getCustomers() {
        return customers;
    }

    public static Customer getCustomer(String customerId) {
        for (Customer customer : customers) {
            if (customer.getId().equals(customerId))
                return customer;
        }

        return null;
    }

    public static void addCustomer(Customer customer) {
        customers.add(customer);
    }

    public static void deleteCustomer(String customerId) {
        for (Customer customer : customers) {
            if (customer.getId().equals(customerId)) {
                customers.remove(customer);
                break;
            }
        }
    }
}

Build the microservice and run it

To build the microservice and run the example, use the commands as described in previous sections.