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Weld's implementation of CDI
There is a newer version: 6.0.0.Final
/*
 * JBoss, Home of Professional Open Source
 * Copyright 2014, Red Hat, Inc., and individual contributors
 * by the @authors tag. See the copyright.txt in the distribution for a
 * full listing of individual contributors.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 * http://www.apache.org/licenses/LICENSE-2.0
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package org.jboss.weld;

import static org.jboss.weld.util.cache.LoadingCacheUtils.getCastCacheValue;
import static org.jboss.weld.util.reflection.Reflections.cast;

import java.lang.annotation.Annotation;
import java.util.Iterator;
import java.util.Set;

import javax.enterprise.inject.Instance;
import javax.enterprise.inject.spi.CDI;
import javax.enterprise.inject.spi.Unmanaged;
import javax.enterprise.util.TypeLiteral;

import org.jboss.weld.bean.builtin.BeanManagerProxy;
import org.jboss.weld.logging.BeanManagerLogger;
import org.jboss.weld.manager.BeanManagerImpl;

import com.google.common.cache.CacheBuilder;
import com.google.common.cache.CacheLoader;
import com.google.common.cache.LoadingCache;
import com.google.common.collect.ImmutableSet;

/**
 * Abstract implementation of CDI which forwards all Instance methods to a delegate. Furthermore, it allows the calling class to be identified using the
 * {@link #getCallingClassName()} method.
 *
 * @author Jozef Hartinger
 *
 * @param 
 */
public abstract class AbstractCDI extends CDI {

    // CDI API / IMPL classes calling CDI.current()
    // used for caller detection
    protected final Set knownClassNames;

    private final LoadingCache> instanceCache;

    public AbstractCDI() {
        ImmutableSet.Builder names = ImmutableSet.builder();
        for (Class clazz = getClass(); clazz != CDI.class; clazz = clazz.getSuperclass()) {
            names.add(clazz.getName());
        }
        names.add(Unmanaged.class.getName());
        this.knownClassNames = names.build();
        this.instanceCache = CacheBuilder.newBuilder().build(new CacheLoader>() {

            @Override
            public Instance load(BeanManagerImpl beanManager) throws Exception {
                return cast(beanManager.getInstance(beanManager.createCreationalContext(null)));
            }
        });
    }

    @Override
    public Iterator iterator() {
        return getInstance().iterator();
    }

    @Override
    public T get() {
        return getInstance().get();
    }

    @Override
    public Instance select(Annotation... qualifiers) {
        return getInstance().select(qualifiers);
    }

    @Override
    public  Instance select(Class subtype, Annotation... qualifiers) {
        return getInstance().select(subtype, qualifiers);
    }

    @Override
    public  Instance select(TypeLiteral subtype, Annotation... qualifiers) {
        return getInstance().select(subtype, qualifiers);
    }

    @Override
    public boolean isUnsatisfied() {
        return getInstance().isUnsatisfied();
    }

    @Override
    public boolean isAmbiguous() {
        return getInstance().isAmbiguous();
    }

    @Override
    public void destroy(T instance) {
        getInstance().destroy(instance);
    }

    /**
     * Examines {@link StackTraceElement}s to figure out which class invoked a method on {@link CDI}.
     */
    protected String getCallingClassName() {
        boolean outerSubclassReached = false;
        for (StackTraceElement element : Thread.currentThread().getStackTrace()) {
            // the method call that leads to the first invocation of this class or its subclass is considered the caller
            if (!knownClassNames.contains(element.getClassName())) {
                if (outerSubclassReached) {
                    return element.getClassName();
                }
            } else {
                outerSubclassReached = true;
            }
        }
        throw BeanManagerLogger.LOG.unableToIdentifyBeanManager();
    }

    /**
     * Subclasses are allowed to override the default behavior, i.e. to cache instance per BeanManager.
     *
     * @return the {@link Instance} the relevant calls are delegated to
     */
    protected Instance getInstance() {
        return getCastCacheValue(instanceCache, BeanManagerProxy.unwrap(getBeanManager()));
    }

}