Inject HttpServletRequest in CDI SessionScoped bean

Question

I've got a session scoped CDI bean, and I need to somehow access the HttpServletRequest object in this bean's @PostConstruct method. Is it possible? I've tried to Inject such an object, but it results in:

WELD-001408 Unsatisfied dependencies for type [HttpServletRequest] with qualifiers     [@Default] at injection point [[field] @Inject ...]

As I understood while googling, the Seam framework has such a functionality, but I have a standard Java EE application on a GlassFish server.

Is it even possible to somehow pass the request to a CDI bean's @PostConstruct method?

Answer 1

As per your comment, you want access to the user principal. You can just inject it like this: @Inject Principal principal; or @Resource Principal principal;, see Java EE 6 Tutorial.

Update

I'll answer your direct question. In Java EE 7 (CDI 1.1) injection of HttpServletRequest is supported out of the box. In Java EE 6 (CDI 1.0) however, this is not supported out of the box. To get it working, include the class below into your web-app:

import javax.enterprise.inject.Produces;
import javax.servlet.ServletRequest;
import javax.servlet.ServletRequestEvent;
import javax.servlet.ServletRequestListener;
import javax.servlet.annotation.WebListener;

@WebListener
public class CDIServletRequestProducingListener implements ServletRequestListener {

    private static ThreadLocal<ServletRequest> SERVLET_REQUESTS = new ThreadLocal<>();

    @Override
    public void requestInitialized(ServletRequestEvent sre) {
        SERVLET_REQUESTS.set(sre.getServletRequest());
    }

    @Override
    public void requestDestroyed(ServletRequestEvent sre) {
        SERVLET_REQUESTS.remove();
    }

    @Produces
    private ServletRequest obtain() {
        return SERVLET_REQUESTS.get();
    }

}

Note: Tested only on GlassFish 3.1.2.2

Answer 2

When using the code from rdcrng be aware of the following:
* The producer-method obtain is dependent-scoped, thus is only called once for application scoped beans (and will resolve to problems for every other request except the first)
* You can solve this with @RequestScoped
* When RequestScoped annotated, you will only get a proxy, and thus you cannot cas it to HttpServletRequest. So you maybe want a producer for HttpServletRequest.

Also note: As per CDI specification link passage 3.6, java ee beans are NOT consideres managed beans. Thus you will end up with two instances of CDIServletRequestProducingListener - one managed by the Java EE container, one managed by the CDI-container. It only works because SERVLET_REQUESTS is static.

Following the modified code for your convenience.

import javax.enterprise.context.RequestScoped;
import javax.enterprise.inject.Produces;
import javax.servlet.ServletRequest;
import javax.servlet.ServletRequestEvent;
import javax.servlet.ServletRequestListener;
import javax.servlet.annotation.WebListener;
import javax.servlet.http.HttpServletRequest;

@WebListener
public class CDIServletRequestProducingListener implements ServletRequestListener {

private static ThreadLocal<ServletRequest> SERVLET_REQUESTS = new ThreadLocal<ServletRequest>();

@Override
public void requestInitialized(ServletRequestEvent sre) {
    SERVLET_REQUESTS.set(sre.getServletRequest());
}

@Override
public void requestDestroyed(ServletRequestEvent sre) {
    SERVLET_REQUESTS.remove();
}

@RequestScoped
@Produces
private HttpServletRequest obtainHttp() {
    ServletRequest servletRequest = SERVLET_REQUESTS.get();
    if (servletRequest instanceof HttpServletRequest) {
        return (HttpServletRequest) servletRequest;
    } else {
        throw new RuntimeException("There is no HttpServletRequest avaible for injection");
    }
}

}