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Weld's implementation of CDI
There is a newer version: 3.0.0.Alpha6
/*
 * 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.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.inject.WeldInstance;
import org.jboss.weld.logging.BeanManagerLogger;
import org.jboss.weld.manager.BeanManagerImpl;
import org.jboss.weld.util.Function;
import org.jboss.weld.util.cache.ComputingCache;
import org.jboss.weld.util.cache.ComputingCacheBuilder;
import org.jboss.weld.util.collections.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 implements WeldInstance {

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

    private final ComputingCache> 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());
        names.add(CompositeCDIProvider.class.getName());
        this.knownClassNames = names.build();
        this.instanceCache = ComputingCacheBuilder.newBuilder().build(new Function>() {

            @Override
            public WeldInstance apply(BeanManagerImpl beanManager) {
                return cast(beanManager.getInstance(beanManager.createCreationalContext(null)));
            }
        });
    }

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

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

    @Override
    public WeldInstance select(Annotation... qualifiers) {
        return instanceInternal().select(qualifiers);
    }

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

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

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

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

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

    @Override
    public Handler getHandler() {
        return instanceInternal().getHandler();
    }

    @Override
    public boolean isResolvable() {
        return instanceInternal().isResolvable();
    }

    @Override
    public Iterable> handlers() {
        return instanceInternal().handlers();
    }

    /**
     * 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();
    }

    private WeldInstance instanceInternal() {
        checkState();
        return getInstance();
    }

    /**
     * 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 WeldInstance getInstance() {
        return instanceCache.getValue(BeanManagerProxy.unwrap(getBeanManager()));
    }

    /**
     * Check whether the container is in a "valid" state, no-op by default.
     * 
     * Subclasses are allowed to override the default behavior, i.e. to check whether a container is running.
     */
    protected void checkState(){
      //no-op
    }

}