GuiceDependencyIterator.java

/*
 * Copyright 2010 Proofpoint, Inc.
 *
 * 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 io.airlift.jmx;

import com.google.inject.ConfigurationException;
import com.google.inject.Key;
import com.google.inject.TypeLiteral;
import com.google.inject.spi.Dependency;
import com.google.inject.spi.InjectionPoint;

import java.util.HashSet;
import java.util.Iterator;
import java.util.NoSuchElementException;
import java.util.Set;

/**
 * Utility for iterating over dependent classes in a Guice injector
 */
class GuiceDependencyIterator implements Iterator<Class<?>>, Iterable<Class<?>>
{
    private final Set<Key<?>> visited;
    private final Iterator<Dependency<?>> currentDependencyIterator;
    private final TypeLiteral<?> creationTypeLiteral;
    private final Class<?> creationClass;

    private Class<?> currentClass = null;

    /**
     * @param typeLiteral the type literal to iterate over
     */
    public GuiceDependencyIterator(TypeLiteral<?> typeLiteral)
    {
        this(null, typeLiteral, new HashSet<Key<?>>());
    }

    /**
     * @param clazz the class to iterate over
     */
    public GuiceDependencyIterator(Class<?> clazz)
    {
        this(clazz, null, new HashSet<Key<?>>());
    }

    /**
     * Returns whether or not there was an injection point for the type/class
     *
     * @return true/false
     */
    public boolean hasInjectionPoint()
    {
        return (currentDependencyIterator != null);
    }

    /**
     * Use an external set of visited classes - this is used to avoid recursive iteration
     *
     * @param visited the visited set. A copy is _not_ made. The original instance will be mutated
     * @return new iterator that uses the given visited set instance
     */
    public GuiceDependencyIterator substituteVisitedSet(Set<Key<?>> visited)
    {
        return new GuiceDependencyIterator(creationClass, creationTypeLiteral, visited);
    }

    @Override
    public Iterator<Class<?>> iterator()
    {
        return new GuiceDependencyIterator(creationClass, creationTypeLiteral, visited);
    }

    @Override
    public boolean hasNext()
    {
        if (currentDependencyIterator != null) {
            while ((currentClass == null) && currentDependencyIterator.hasNext()) {
                currentClass = GuiceInjectorIterator.parseKey(visited, currentDependencyIterator.next().getKey());
            }
        }

        return (currentClass != null);
    }

    @Override
    public Class<?> next()
    {
        if (!hasNext()) {
            throw new NoSuchElementException();
        }
        Class<?> localClass = currentClass;
        currentClass = null;
        return localClass;
    }

    @Override
    public void remove()
    {
        throw new UnsupportedOperationException();
    }

    private GuiceDependencyIterator(Class<?> clazz, TypeLiteral<?> typeLiteral, Set<Key<?>> visited)
    {
        this.creationClass = clazz;
        this.creationTypeLiteral = typeLiteral;
        this.visited = visited;

        // must be called last
        currentDependencyIterator = initInjectionPoint();
    }

    private Iterator<Dependency<?>> initInjectionPoint()
    {
        try {
            InjectionPoint injectionPoint;
            if (creationTypeLiteral != null) {
                injectionPoint = InjectionPoint.forConstructorOf(creationTypeLiteral);
            }
            else {
                injectionPoint = InjectionPoint.forConstructorOf(creationClass);
            }

            return injectionPoint.getDependencies().iterator();
        }
        catch (ConfigurationException dummy) {
            // ignore
        }

        return null;
    }
}