REST application on Ophenshift

Question

I created a REST application through netbeans, and now I want to upload it to Openshift.

I’m using eclipselink to make data persistence, so I use a class AbstractFacade<T> to make the basic CRUD, as follows:

public abstract class AbstractFacade<T> {
private final Class<T> entityClass;

public AbstractFacade(Class<T> entityClass) {
    this.entityClass = entityClass;
}

protected abstract EntityManager getEntityManager();

public void create(T entity) {
    getEntityManager().persist(entity);
}

public void edit(T entity) {
    getEntityManager().merge(entity);
}

public void remove(T entity) {
    getEntityManager().remove(getEntityManager().merge(entity));
}

public T find(Object id) {
    return getEntityManager().find(entityClass, id);
}

public List<T> findAll() {
    javax.persistence.criteria.CriteriaQuery cq = getEntityManager().getCriteriaBuilder().createQuery();
    cq.select(cq.from(entityClass));
    return getEntityManager().createQuery(cq).getResultList();
}

public List<T> findRange(int[] range) {
    [...]
}

public int count() {
    [...]
}

}

Then I inherit this class to the class I wish to run CRUD, for example:

@Stateless
@Path("categoria")
public class CategoriaFacadeREST extends AbstractFacade<Categoria> {
@PersistenceContext(unitName = "api_api_war_1.0PU")
private EntityManager em;

public CategoriaFacadeREST() {
    super(Categoria.class);
}

@POST
@Override
@Consumes({"application/xml", "application/json"})
public void create(Categoria entity) {
    super.create(entity);
}

@PUT
@Path("{id}")
@Consumes({"application/xml", "application/json"})
public void edit(@PathParam("id") Integer id, Categoria entity) {
    super.edit(entity);
}

@DELETE
@Path("{id}")
public void remove(@PathParam("id") Integer id) {
    super.remove(super.find(id));
}

@GET
@Path("{id}")
@Produces({"application/xml", "application/json"})
public Categoria find(@PathParam("id") Integer id) {
    return super.find(id);
}

@GET
@Override
@Produces({"application/xml", "application/json"})
public List<Categoria> findAll() {
    return super.findAll();
}

[...]

}

as you can see I use the annotation @Path("categoria"), since I am using a REST API and I have a legacy of the Application class with the annotation @javax.ws.rs.ApplicationPath("/api").

But when I try to access meuhost.com/api/categoria, for example, I get the following error:

HTTP Status 500 - java.lang.Nullpointerexception

**exception**

javax.servlet.ServletException: java.lang.NullPointerException
org.glassfish.jersey.servlet.WebComponent.service(WebComponent.java:421)
    org.glassfish.jersey.servlet.ServletContainer.service(ServletContainer.java:386)
    org.glassfish.jersey.servlet.ServletContainer.service(ServletContainer.java:335)
    org.glassfish.jersey.servlet.ServletContainer.service(ServletContainer.java:222)
org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:52)

**root cause**

java.lang.NullPointerException
    com.rhcloud.api.encontreoferta.model.service.AbstractFacade.findAll(AbstractFacade.java:42)
    com.rhcloud.api.encontreoferta.model.service.CategoriaFacadeREST.findAll(CategoriaFacadeREST.java:68)
sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57)
    sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
java.lang.reflect.Method.invoke(Method.java:606)
    org.glassfish.jersey.server.model.internal.ResourceMethodInvocationHandlerFactory$1.invoke(ResourceMethodInvocationHandlerFactory.java:81)
    org.glassfish.jersey.server.model.internal.AbstractJavaResourceMethodDispatcher$1.run(AbstractJavaResourceMethodDispatcher.java:164)
        org.glassfish.jersey.server.model.internal.AbstractJavaResourceMethodDispatcher.invoke(AbstractJavaResourceMethodDispatcher.java:181)
    org.glassfish.jersey.server.model.internal.JavaResourceMethodDispatcherProvider$TypeOutInvoker.doDispatch(JavaResourceMethodDispatcherProvider.java:203)
    org.glassfish.jersey.server.model.internal.AbstractJavaResourceMethodDispatcher.dispatch(AbstractJavaResourceMethodDispatcher.java:101)
    org.glassfish.jersey.server.model.ResourceMethodInvoker.invoke(ResourceMethodInvoker.java:389)
    org.glassfish.jersey.server.model.ResourceMethodInvoker.apply(ResourceMethodInvoker.java:347)
    org.glassfish.jersey.server.model.ResourceMethodInvoker.apply(ResourceMethodInvoker.java:102)
org.glassfish.jersey.server.ServerRuntime$2.run(ServerRuntime.java:305)
org.glassfish.jersey.internal.Errors$1.call(Errors.java:271)
org.glassfish.jersey.internal.Errors$1.call(Errors.java:267)
org.glassfish.jersey.internal.Errors.process(Errors.java:315)
org.glassfish.jersey.internal.Errors.process(Errors.java:297)
org.glassfish.jersey.internal.Errors.process(Errors.java:267)
    org.glassfish.jersey.process.internal.RequestScope.runInScope(RequestScope.java:317)
org.glassfish.jersey.server.ServerRuntime.process(ServerRuntime.java:288)
    org.glassfish.jersey.server.ApplicationHandler.handle(ApplicationHandler.java:1110)
org.glassfish.jersey.servlet.WebComponent.service(WebComponent.java:401)
    org.glassfish.jersey.servlet.ServletContainer.service(ServletContainer.java:386)
    org.glassfish.jersey.servlet.ServletContainer.service(ServletContainer.java:335)
    org.glassfish.jersey.servlet.ServletContainer.service(ServletContainer.java:222)
org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:52)

---

My problem comes down to EJB.

I really wanted to separate the logic on one server and the interface on another... And a few more things. So I thought I’d use EJB.

However the Openshift server is Tomcat, but Tomcat is only a Servlet Container, that is, it implements the Servlets specifications and JSP. Tomcat does not implement EJB.

As described in http://solucoestecnologia.blogspot.com.br/2013/02/diferencas-entre-ejb-tomcat-e-glassfish.html

And that’s why my application doesn’t run on Openshift, I need to use glassfish to meet the requirements of my project...

In my case the EntityManager comes null, why it was not possible to do the injection of the EJB correctly.

I would like to thank the Bruno César for the great help.