CDI Producer causes stackoverflow

Question

I want to create a producer to choose an implementation of my Interface Hello dynamically.

public interface Hello extends Serializable{

     public String sayHello();
}

Hello Impls:

public class HelloBanned implements Hello{

    @Override
    public String sayHello() {
        return "Get out!!!";
    }  
}

public class HelloCoolGuy implements Hello{

   @Override
   public String sayHello() {
       return "Welcome";
   }   
}

My sessionBean, where I want the producer method:

public class UsuarioHandler implements Serializable{

    @Inject
    private Usuario usuario;
    @Inject
    @Preferred
    Hello hello;
    @EJB
    UsuarioBeanLocal userEJB;

    public String login(){
        usuario.setId(2L);
        return userEJB.efetuarLogin(usuario);
    }
    @Produces
    @Preferred
    public Hello getHello(@New HelloBanned ban,
                      @New HelloCoolGuy cool){
        if (usuario.isBannedFlag()){
            return ban;
        }
        return cool;
    }
}

This code result on StackOverFlow. I can't find what can be causing it.

Answer 1

In CDI producers support injection. Since, your class UsuarioHandler is both the producer and the injection target a stack overflow is the expected result. Think about it:

1. After UsuarioHandler is instantiated as a managed bean, @Preferred Hello hello needs to be injected.
2. Then the producer for @Preferred Hello hello needs instantiated, also your UsuarioHandler .
3. But the producer itself needs an instance of @Preferred Hello hello injected as well.
4. So another producer is instantiated, and so on.

Since the cope for your UsuarioHandler is @Default , the container doesn't proxy it, therefore creating a new instance each time one is needed, as producer or as a managed bean.

Answer 2

Make your Producer Method "getHello" static (can even be private) and pass the Usuario as a parameter.

@Produces
@Preferred
private static  Hello getHello(@New HelloBanned ban,
                      @New HelloCoolGuy cool, Usuario usuario){
    if (usuario.isBannedFlag()){
       return ban;
    }
    return cool;
}

Answer 3

I find the most common issue with CDI not working in a project is the fact that the XML bean descriptor for CDI is missing. Add the beans.xml into your META-INF/beans.xml or WEB-INF/beans.xml

The descriptor can be empty like so:

    <?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://java.sun.com/xml/ns/javaee"
       xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
       xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/beans_1_0.xsd">
</beans>

To find out more about the beans.xml file please refer to this link: http://www.seamframework.org/Documentation/WhatIsBeansxmlAndWhyDoINeedIt

If this is not the issue then please paste in your stacktrace so we can see what the error you're getting is.