1. First, we create a User POJO:

public class User implements Serializable{

    private String name;
    private String email;

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public String getEmail() {
        return email;
    }

    public void setEmail(String email) {
        this.email = email;
    }   
}

2. Then we create a class with two methods (endpoints) for returning User:

@Path("userService")
public class UserService {
    
    @GET
    @Path("getUserCoupled/{name}/{email}")
    @Produces(MediaType.APPLICATION_JSON)
    public Response getUserCoupled(
            @PathParam("name") String name, 
            @PathParam("email") String email){
        //GET USER CODE
        
        return Response.ok().build();
    }
    
    @GET
    @Path("getUserDecoupled")
    @Produces(MediaType.APPLICATION_JSON)
    public Response getUserDecoupled(@HeaderParam("User") 
    User user){
        //GET USER CODE
        
        return Response.ok().build();
    }
}

3. Finally, we create another service (another project) to consume UserService:

@Path("doSomethingService")
public class DoSomethingService {
    
    private final String hostURI = "http://localhost:8080/";
    private Client client;
    private WebTarget target;

    @PostConstruct
    public void init() {
        client = ClientBuilder.newClient();
        target = client.target(hostURI + "ch08-decoupled-user/");
    } 
    
    @Path("doSomethingCoupled")
    @Produces(MediaType.APPLICATION_JSON)
    public Response doSomethingCoupled(String name, String email){
        WebTarget service = 
        target.path("webresources/userService/getUserCoupled");
        service.queryParam("name", name);
        service.queryParam("email", email);

        Response response;
        try {
            response = service.request().get();
        } catch (ProcessingException e) {
            return Response.status(408).build();
        }

        return 
        Response.ok(response.readEntity(String.class)).build();
    }
    
    @Path("doSomethingDecoupled")
    @Produces(MediaType.APPLICATION_JSON)
    public Response doSomethingDecoupled(User user){
        WebTarget service = 
        target.path("webresources/userService/getUserDecoupled");

        Response response;
        try {
            response = service.request().header("User", 
            Entity.json(user)).get();
        } catch (ProcessingException e) {
            return Response.status(408).build();
        }

        return 
        Response.ok(response.readEntity(String.class)).build();
    } 
}