CDI/Weld beans.xml XSD/DTD

Dominik Dorn — Fri, 20 Aug 2010 14:21:09 +0000

As I’m often looking for the correct header of the beans.xml file required for Web Beans / Context and Dependency Injection (CDI) to work, I decided to share this simple header here with you.

If you don’t have anything to declare, create an empty beans.xml like this one


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" />
 
If you have to declare alternatives or interceptors, do it like this
 lang='xml'>

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">
    >
        >
            com.dominikdorn.dc.passwordReset.PasswordResetService
        >
        >com.dominikdorn.dc.passwordReset.StudyGuruPasswordReset>
    >
>

A good IDE will help you with creating a proper beans.xml as soon as you specify the xml namespace.

Popular implementations of CDI are

CDI/Weld manual lookup

Dominik Dorn — Wed, 21 Apr 2010 18:04:28 +0000

So, you’re ended up in a situation, where you are somewhere (e.g. a javax.faces.Converter) where you are unable to simple @Inject SomeClass ?

I had the problem, that I had a FacesConverter like this:

import javax.annotation.ManagedBean;
import javax.annotation.PostConstruct;
import javax.enterprise.context.RequestScoped;
import javax.faces.component.UIComponent;
import javax.faces.context.FacesContext;
import javax.faces.convert.Converter;
import javax.faces.convert.FacesConverter;
import javax.inject.Inject;
 
 
@FacesConverter(forClass = AvailableCountry.class)
@ManagedBean // does not help :(
@RequestScoped // does not help :(
public class AvailableCountryConverter implements Converter
{
	@Inject
	AvailableCountryDao dao;
 
	@PostConstruct
	public void postConstruct()
	{
		System.out.println("calling postConstruct");
	}
 
	public Object getAsObject(FacesContext facesContext, UIComponent
			component, String value) {
		if (value == null || value.length() == 0) {
			return null;
		}
		return dao.find(getKey(value));
	}
 
	Long getKey(String value) {
		Long key;
		key = Long.valueOf(value);
		return key;
	}
 
	String getStringKey(long value) {
		StringBuffer sb = new StringBuffer();
		sb.append(value);
		return sb.toString();
	}
 
	public String getAsString(FacesContext facesContext, UIComponent
			component, Object object) {
		if (object == null) {
			return null;
		}
		if (object instanceof AvailableCountry) {
			AvailableCountry o = (AvailableCountry) object;
			return getStringKey(o.getCountry().getId());
		} else {
			throw new IllegalArgumentException("object " + object + "
					is of type " + object.getClass().getName() + "; expected type: " +
					AvailableCountry.class.getName());
		}
	}
}

But my DAO was not injected, nor was the postConstruct method triggered by CDI.

Why?
Because the bean is not managed by CDI, not even when annotating it with @ManagedBean because it gets created by the JSF-Lifecycle and not by CDI.

Well.. but how to manually lookup a Bean with CDI / Weld?

First, you need to get the BeanManager. When you have a FacesContext (like in the converter above), you can get it like this:

    public BeanManager getBeanManager()
    {
        return (BeanManager) 
              ((ServletContext) facesContext.getExternalContext().getContext())
                   .getAttribute("javax.enterprise.inject.spi.BeanManager"); 
    }

If you don’t have access to a FacesContext, ServletContext or similar, you can lookup the BeanManager through JNDI

    public BeanManager getBeanManager()
    {
        try{
            InitialContext initialContext = new InitialContext();
            return (BeanManager) initialContext.lookup("java:comp/BeanManager");
        catch (NamingException e) {
            log.error("Couldn't get BeanManager through JNDI");
            return null;
        }
    }

After you’ve got your BeanManager, simply lookup your Bean like this:
(In my case, I wanted to lookup a bean with the type AvailableCountryDao)
Type-based CDI manual lookup

    public AvailableCountryDao getFacade()
    {
        BeanManager bm = getBeanManager();
        Bean<AvailableCountryDao> bean = (Bean<AvailableCountryDao>) bm.getBeans(AvailableCountryDao.class).iterator().next();
        CreationalContext<AvailableCountryDao> ctx = bm.createCreationalContext(bean);
        AvailableCountryDao dao = (AvailableCountryDao) bm.getReference(bean, AvailableCountryDao.class, ctx); // this could be inlined, but intentionally left this way
        return dao;
    }

Thanks to my friend Lincoln Baxter, III for the snipped.

Name-based CDI manual lookup

    public Object getBeanByName(String name) // eg. name=availableCountryDao
    {
        BeanManager bm = getBeanManager();
        Bean bean = bm.getBeans(name).iterator().next();
        CreationalContext ctx = bm.createCreationalContext(bean); // could be inlined below
        Object o = bm.getReference(bean, bean.getClass(), ctx); // could be inlined with return
        return o;
    }

So, now you’re able to manually lookup beans with CDI.
In case you have the same problem (with Converters/Validators) like I had above, checkout Seam Faces, where this problem already is fixed,
meaning your @ManagedBean annotated Converter/Validator is working as expected with @Inject, @PostConstruct & @PreDestroy

dominikdorn.com » Dependency Injection

CDI/Weld beans.xml XSD/DTD

CDI/Weld manual lookup