EverRest Example

This is sample of using EverRest to launch JAX-RS services.

We will create simple books service. It should be able give access to books by id, get list all available books and add new book in storage. Service supports JSON format for transfer data to/from client.

Add required context-param

<context-param>
  <param-name>javax.ws.rs.Application</param-name>
  <param-value>org.everrest.sample.book.BookApplication</param-value>   
</context-param>

javax.ws.rs.Application: This is FQN of Java class that extends javax.ws.rs.core.Application and provides set of classes and(or) instances of JAX-RS components.

Add bootstrap listeners

Need add two listeners. First one initializes BookStorage and adds it to servlet context. The second one initializes common components of EverRest frameworks.

<listener>
   <listener-class>org.everrest.sample.book.BookServiceBootstrap</listener-class>
</listener>
<listener>
   <listener-class>org.everrest.core.servlet.EverrestInitializedListener</listener-class>
</listener>

Add EverrestServlet

<servlet>
   <servlet-name>EverrestServlet</servlet-name>
   <servlet-class>org.everrest.core.servlet.EverrestServlet</servlet-class>
</servlet>
<servlet-mapping>
   <servlet-name>EverrestServlet</servlet-name>
   <url-pattern>/*</url-pattern>
</servlet-mapping>

EverRest components

org.everrest.sample.book.BookApplication - application deployer.

public class BookApplication extends Application {
   @Override
   public Set<Class<?>> getClasses() {
      Set<Class<?>> cls = new HashSet<Class<?>>(1);
      cls.add(BookService.class);
      return cls;
   }

   @Override
   public Set<Object> getSingletons() {
      Set<Object> objs = new HashSet<Object>(1);
      objs.add(new BookNotFoundExceptionMapper());
      return objs;
   }
}

org.everrest.sample.book.Book - simple Java Bean that will be used to transfer data via JSON.
org.everrest.sample.book.BookNotFoundException - exception that will be thrown by org.everrest.sample.book.BookService if client requested book that does not exist in storage.

org.everrest.sample.book.BookNotFoundExceptionMapper - JAX-RS component that intercepts org.everrest.sample.book.BookNotFoundException and send correct response to client.

@Provider
public class BookNotFoundExceptionMapper implements ExceptionMapper<BookNotFoundException> {
   Response toResponse(BookNotFoundException exception) {
      return Response.status(404).entity(exception.getMessage()).type("text/plain").build();
   }
}

org.everrest.sample.book.BookService - JAX-RS service that process client's requests. Instance of BookStorage will be injected automatically thanks to org.everrest.core.Inject annotation

@Path("books")
public class BookService {
   @Inject
   private BookStorage bookStorage;

   @Path("{id}")
   @GET
   @Produces("application/json")
   public Book get(@PathParam("id") String id) throws BookNotFoundException {
      Book book = bookStorage.getBook(id);
      if (book == null)
         throw new BookNotFoundException(id);
      return book;
   }

   @GET
   @Produces("application/json")
   public Collection<Book> getAll() {
      return bookStorage.getAll();
   }

   @PUT
   @Consumes("application/json")
   public Response put(Book book, @Context UriInfo uriInfo) {
      String id = bookStorage.putBook(book);
      URI location = uriInfo.getBaseUriBuilder().path(getClass()).path(id).build();
      return Response.created(location).entity(location.toString()).type("text/plain").build();
   }
}

org.everrest.sample.book.BookStorage - storage of Books.

public class BookStorage {

   private static int idCounter = 100;

   public synchronized String generateId() {
      idCounter++;
      return Integer.toString(idCounter);
   }

   private Map<String, Book> books = new ConcurrentHashMap<String, Book>();

   public BookStorage() {
      init();
   }

   private void init() {
      Book book = new Book();
      book.setTitle("JUnit in Action");
      book.setAuthor("Vincent Masson");
      book.setPages(386);
      book.setPrice(19.37);
      putBook(book);
   }

   public Book getBook(String id) {
      return books.get(id);
   }

   public String putBook(Book book) {
      String id = book.getId();
      if (id == null || id.trim().length() == 0)
      {
         id = generateId();
         book.setId(id);
      }
      books.put(id, book);
      return id;
   }

   public Collection<Book> getAll() {
      return books.values();
   }

   public int numberOfBooks() {
      return books.size();
   }
}

Request mapping

GET book-service/books/{id}: get books with specified id. Just after server start only one book in storage and it can be accessed via id 101
GET book-service/books/: get all books from storage.
PUT book-service/books/: add new book in storage. The body of request must contains book's description in JSON format. The Content-type header must be set to application/json

How to try

Build project.

mvn clean install

Run it with Jetty server.

mvn jetty:run

Point you web browser to http://localhost:8080/book-service/books/101

If you are under linux or other unix like OS the you can use curl utility (often it is already installed). Binary build of this utility available for windows also at http://curl.haxx.se/download.html. With curl you able to add new book in storage via command:

curl -X PUT \
     -H "Content-type:application/json" \
     -d '{"author":"My Author","title":"My Title","price":1.00,"pages":100}' \
     http://localhost:8080/book-service/books/