Java EE 5 / Servlet 2.5将EJB注入ServletFilter

Question

I want to inject session beans into my ServletFilter, which seems not to work. Can you please tell me how to achieve this?

public class MyExample implements Filter {
    @EJB
    private MyBean someEjb;

    @Override
    public void destroy() {
    }

    @Override
    public void init(FilterConfig filterConfig) throws ServletException {
    }

    @Override
    public void doFilter(ServletRequest servletRequest, ServletResponse servletResponse,
                     FilterChain filterChain) throws IOException, ServletException{
        someEjb.toString();
    }
}

Results in NullPointerException because myEjb is null. The platform used is JBoss 5.1 MyBean can be accessed correctly from other EJBs or from Servlets.

Thank you.

---

Problem Solved (though I do not know why):

The application consists of three artifacts: - A jar containing the EJBs - A war containing servlets - An ear containing both the above

If i package the Filter in the jar, the problem occurs. If i package it along with the servlets in the war, the problem does not occur.

So, immediate problem solved but not understood.

Maybe someone can help me understand that?

Answer 1

If both the servlet and EJB are not in a single ear file, one must use @EJB(mappedName="name") while injecting EJB. Check this post for more details.

Related links: Injection from outside modules

Of course, Filter is a kinda Servlet , therefore known as "Servlet Filter". And both Servlet and Filter are web component, hence belongs to web archive, .war , not Java archive, .jar . Filter in jar will not be scanned to inject that kinda annotations and will be dealt as any other regular Java class.

Answer 2

We faced a similar problem, we had some @WebFilter and @WebListener components packaged inside a Jar that weren´t readed (the annotations weren´t processed).

The objetive was to tell the container to scan other jars looking for other annotated components.

We achive the goal adding the attribute metadata-complete to web.xml declaration. Example:

 <?xml version="1.0" encoding="UTF-8"?> <web-app version="3.0" 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/web-app_3_0.xsd" metadata-complete="false"> ...NORMAL_CONTENT_HERE... </web-app> 

Hope it helps.