Spring Boot - Restful webservices with Jersey

In the previous posts, we have created a Spring Boot QuickStart, customized the embedded server and properties and running specific code after spring boot application starts.

Now in this post, we will create Restful webservices with Jersey deployed on Undertow as a Spring Boot Application.

Adding dependencies in pom.xml

We will add spring-boot-starter-parent as parent of our maven based project. The added benefit of this is version management for spring dependencies.

<parent>
  <groupId>org.springframework.boot</groupId>
  <artifactId>spring-boot-starter-parent</artifactId>
  <version>1.5.0.RELEASE</version>
</parent>

Adding spring-boot-starter-jersey dependency

This will add/ configure the jersey related dependencies.

<dependency>
  <groupId>org.springframework.boot</groupId>
  <artifactId>spring-boot-starter-jersey</artifactId>
</dependency>

Adding spring-boot-starter-undertow dependency

<dependency>
  <groupId>org.springframework.boot</groupId>
  <artifactId>spring-boot-starter-undertow</artifactId>
</dependency>

These are all the necessary spring-boot-starters we require to create Restful webservices with Jersey.

Creating a Root resource/ Controller class

What are Root resource classes?

Root resource classes are POJOs that are either annotated with @Path or have at least one method annotated with @Path or a request method designator, such as @GET, @PUT, @POST, or @DELETE.

@Component
@Path("/books")
public class BookController {
  private BookService bookService;

  public BookController(BookService bookService) {
    this.bookService = bookService;
  }

  @GET
  @Produces("application/json")
  public Collection getAllBooks() {
    return bookService.getAllBooks();
  }

  @GET
  @Produces("application/json")
  @Path("/{oid}")
  public Book getBook(@PathParam("oid") String oid) {
    return bookService.getBook(oid);
  }

  @POST
  @Produces("application/json")
  @Consumes("application/json")
  public Response addBook(Book book) {
    bookService.addBook(book);
    return Response.created(URI.create("/" + book.getOid())).build();
  }

  @PUT
  @Consumes("application/json")
  @Path("/{oid}")
  public Response updateBook(@PathParam("oid") String oid, Book book) {
    bookService.updateBook(oid, book);
    return Response.noContent().build();
  }

  @DELETE
  @Path("/{oid}")
  public Response deleteBook(@PathParam("oid") String oid) {
    bookService.deleteBook(oid);
    return Response.ok().build();
  }
}

We have created a BookController class and used JAX-RS annotations.

• @Path is used to identify the URI path (relative) that a resource class or class method will serve requests for.
• @PathParam is used to bind the value of a URI template parameter or a path segment containing the template parameter to a resource method parameter, resource class field, or resource class bean property. The value is URL decoded unless this is disabled using the @Encoded annotation.
• @GET indicates that annotated method handles HTTP GET requests.
• @POST indicates that annotated method handles HTTP POST requests.
• @PUT indicates that annotated method handles HTTP PUT requests.
• @DELETE indicates that annotated method handles HTTP DELETE requests.
• @Produces defines a media-type that the resource method can produce.
• @Consumes defines a media-type that the resource method can accept.

You might have noticed that we have annotated BookController with @Component which is Spring's annotation and register it as bean. We have done so to benefit Spring's DI for injecting BookService service class.

Creating a JerseyConfiguration class

@Configuration
@ApplicationPath("rest")
public class JerseyConfiguration extends ResourceConfig {
  public JerseyConfiguration() {
  
  }
 
  @PostConstruct
  public void setUp() {
    register(BookController.class);
    register(GenericExceptionMapper.class);
  }
}

We created a JerseyConfiguration class which extends the ResourceConfig from package org.glassfish.jersey.server which configures the web application. In the setUp(), we registered BookController and GenericExceptionMapper.

@ApplicationPath identifies the application path that serves as the base URI for all the resources.

Registering exception mappers

Could there be a case that some exceptions occurs in the resource methods (Runtime/ Checked). You can write your own custom exception mappers to map Java exceptions to javax.ws.rs.core.Response.

@Provider
public class GenericExceptionMapper implements ExceptionMapper {

  @Override
  public Response toResponse(Throwable exception) {
    return Response.serverError().entity(exception.getMessage()).build();
  }
}

We have created a generic exception handler by catching Throwable. Ideally, you should write finer-grained exception mapper.

What is @Provider annotation?

It marks an implementation of an extension interface that should be discoverable by JAX-RS runtime during a provider scanning phase.

We have also created service BookService, model Book also. You can grab the full code from Githib.

Running the application

You can use maven to directly run it with mvn spring-boot:run command or can create a jar and run it.

Testing the rest endpoints

I have used PostMan extension available in chrome brower to test rest services. You can use any package/ API/ software to test it.

This is how we create Restful web-services with Jersey in conjuction with Spring Boot. I hope you find this post informative and helpful to create your first but not last Restful web-service.