Utils.java

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package com.sun.jersey.server.impl.cdi;

import java.util.Collections;
import java.util.Set;
import javax.enterprise.context.spi.CreationalContext;
import javax.enterprise.inject.AmbiguousResolutionException;
import javax.enterprise.inject.spi.Bean;
import javax.enterprise.inject.spi.BeanManager;

/**
  * Utility methods for CDI BeanManager and Bean classes.
  *
  * @author robc
  * @author Paul.Sandoz@Sun.Com
  */
public class Utils {

    private Utils() {}
    
    public static Bean<?> getBean(BeanManager bm, Class<?> c) {
        final Set<Bean<?>> bs = bm.getBeans(c);
        if (bs.isEmpty()) {
            return null;
        }

        try {
            return bm.resolve(bs);
        } catch(AmbiguousResolutionException ex) {
            // Check if there is a shared base class of c
            // If so reduce the set of beans whose class equals c and resolve
            if (isSharedBaseClass(c, bs)) {
                try {
                    return bm.resolve(getBaseClassSubSet(c, bs));
                } catch (AmbiguousResolutionException ex2) {
                    return null;
                }
            }
            return null;
        }
    }

    public static <T> T getInstance(BeanManager bm, Class<T> c) {
        Bean<?> b = getBean(bm, c);
        if (b == null) {
            return null;
        }
        
        CreationalContext<?> cc = bm.createCreationalContext(b);
        return c.cast(bm.getReference(b, c, cc));
    }
    
    private static boolean isSharedBaseClass(Class<?> c, Set<Bean<?>> bs) {
        for (Bean<?> b : bs) {
            if (!c.isAssignableFrom(b.getBeanClass())) {
                return false;
            }
        }
        return true;
    }

    private static Set<Bean<?>> getBaseClassSubSet(Class<?> c, Set<Bean<?>> bs) {
        for (Bean<?> b : bs) {
            if (c == b.getBeanClass()) {
                return Collections.<Bean<?>>singleton(b);
            }
        }
        return bs;
    }

}