Your First REST Endpoint

• Writing @Path, @GET, @POST, returning JSON, and injecting services.

1. How do you create a simple REST endpoint in Quarkus?

Answer:
Add the quarkus-rest extension (or quarkus-rest-jackson for JSON) and annotate a class with @Path:

import jakarta.ws.rs.GET;
import jakarta.ws.rs.Path;
import jakarta.ws.rs.Produces;
import jakarta.ws.rs.core.MediaType;

@Path("/hello")
public class GreetingResource {

    @GET
    @Produces(MediaType.TEXT_PLAIN)
    public String hello() {
        return "Hello, Quarkus!";
    }
}

Run with quarkus dev and visit http://localhost:8080/hello.

---

2. How do you return JSON from an endpoint?

Answer:
Use @Produces(MediaType.APPLICATION_JSON) and return a POJO. Quarkus serializes it automatically with Jackson (or JSON-B depending on extension).

@Path("/users")
@Produces(MediaType.APPLICATION_JSON)
public class UserResource {

    @GET
    @Path("/{id}")
    public User getUser(@PathParam("id") Long id) {
        return new User(id, "Alice", "alice@example.com");
    }
}

public class User {
    public Long id;
    public String name;
    public String email;
    // constructor, getters/setters
}

Extension needed: quarkus-rest-jackson

---

3. How do you inject a service (CDI bean) into a resource?

Answer:
Annotate the service with a CDI scope (@ApplicationScoped, @RequestScoped) and inject with @Inject:

@ApplicationScoped
public class GreetingService {
    public String greet(String name) {
        return "Hello, " + name + "!";
    }
}

@Path("/greet")
public class GreetingResource {

    @Inject
    GreetingService service;

    @GET
    @Path("/{name}")
    @Produces(MediaType.TEXT_PLAIN)
    public String greet(@PathParam("name") String name) {
        return service.greet(name);
    }
}

---

4. How do you handle POST requests with a JSON body?

Answer:
Use @POST, @Consumes(MediaType.APPLICATION_JSON), and accept the body as a method parameter:

@POST
@Consumes(MediaType.APPLICATION_JSON)
@Produces(MediaType.APPLICATION_JSON)
public Response createUser(User user) {
    // save user...
    return Response.status(201).entity(user).build();
}

With Bean Validation:

@POST
public Response createUser(@Valid User user) {
    // user fields validated automatically
}

public class User {
    @NotBlank
    public String name;

    @Email
    public String email;
}

---

5. What HTTP methods are commonly used and how are they mapped?

Answer:

HTTP Method	Annotation	Typical Use
GET	@GET	Read resource
POST	@POST	Create resource
PUT	@PUT	Full update
PATCH	@PATCH	Partial update
DELETE	@DELETE	Delete resource

---

6. How do you read query parameters and path parameters?

Answer:

@GET
@Path("/{id}")
public User getById(
    @PathParam("id") Long id,           // /users/42
    @QueryParam("verbose") boolean v    // /users/42?verbose=true
) {
    return service.find(id, v);
}

Other injection points:

@HeaderParam("Authorization") String token   // Request header
@CookieParam("session") String session       // Cookie value
@FormParam("username") String username       // Form field

---

Summary Table

Task	Annotation / Approach
Define resource class	@Path("/route")
GET endpoint	@GET
POST endpoint	@POST + @Consumes
Return JSON	@Produces(APPLICATION_JSON)
Path variable	@PathParam("name")
Query string	@QueryParam("key")
Inject service	@Inject
Validate body	@Valid on parameter