/*
* LensKit, an open source recommender systems toolkit.
* Copyright 2010-2014 LensKit Contributors. See CONTRIBUTORS.md.
* Work on LensKit has been funded by the National Science Foundation under
* grants IIS 05-34939, 08-08692, 08-12148, and 10-17697.
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU Lesser General Public License as
* published by the Free Software Foundation; either version 2.1 of the
* License, or (at your option) any later version.
*
* This program is distributed in the hope that it will be useful, but WITHOUT
* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
* FOR A PARTICULAR PURPOSE. See the GNU General Public License for more
* details.
*
* You should have received a copy of the GNU General Public License along with
* this program; if not, write to the Free Software Foundation, Inc., 51
* Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
*/
package org.grouplens.lenskit.inject;
import com.google.common.base.Predicate;
import org.grouplens.grapht.Component;
import org.grouplens.grapht.Dependency;
import org.grouplens.grapht.InjectionException;
import org.grouplens.grapht.Injector;
import org.grouplens.grapht.graph.DAGEdge;
import org.grouplens.grapht.graph.DAGNode;
import org.grouplens.grapht.reflect.Desire;
import org.grouplens.grapht.reflect.Desires;
import org.grouplens.grapht.reflect.QualifierMatcher;
import org.grouplens.grapht.reflect.Qualifiers;
import javax.annotation.Nullable;
import java.lang.annotation.Annotation;
/**
* A Grapht injector that uses a precomputed graph.
*
* @author <a href="http://www.grouplens.org">GroupLens Research</a>
*/
public class StaticInjector implements Injector {
private final NodeInstantiator instantiator;
private DAGNode<Component, Dependency> graph;
/**
* Create a new static injector.
*
* @param g The object graph.
*/
public StaticInjector(DAGNode<Component,Dependency> g) {
graph = g;
instantiator = NodeInstantiator.create();
}
@Override
public <T> T getInstance(Class<T> type) throws InjectionException {
Desire d = Desires.create(null, type, true);
DAGEdge<Component, Dependency> e =
graph.getOutgoingEdgeWithLabel(Dependency.hasInitialDesire(d));
if (e != null) {
return type.cast(instantiator.instantiate(e.getTail()));
} else {
DAGNode<Component, Dependency> node = findSatisfyingNode(Qualifiers.matchDefault(), type);
if (node != null) {
return type.cast(instantiator.instantiate(node));
} else {
return null;
}
}
}
public <T> T getInstance(Class<? extends Annotation> qual, Class<T> type) throws InjectionException {
return getInstance(Qualifiers.match(qual), type);
}
public <T> T getInstance(QualifierMatcher qmatch, Class<T> type) throws InjectionException {
DAGNode<Component, Dependency> node = findSatisfyingNode(qmatch, type);
if (node != null) {
return type.cast(instantiator.instantiate(node));
} else {
return null;
}
}
/**
* Find a node with a satisfaction for a specified type. Does a breadth-first
* search to find the closest matching one.
*
* @param type The type to look for.
* @return A node whose satisfaction is compatible with {@code type}.
* @review Decide how to handle qualifiers and contexts
*/
@Nullable
private DAGNode<Component,Dependency> findSatisfyingNode(final QualifierMatcher qmatch, final Class<?> type) {
Predicate<DAGEdge<Component,Dependency>> pred = new Predicate<DAGEdge<Component, Dependency>>() {
@Override
public boolean apply(@Nullable DAGEdge<Component, Dependency> input) {
return input != null
&& type.isAssignableFrom(input.getTail()
.getLabel()
.getSatisfaction()
.getErasedType())
&& qmatch.apply(input.getLabel()
.getInitialDesire()
.getInjectionPoint()
.getQualifier());
}
};
DAGEdge<Component, Dependency> edge = graph.findEdgeBFS(pred);
if (edge != null) {
return edge.getTail();
} else {
return null;
}
}
@Override
public <T> T getInstance(Annotation qualifier, Class<T> type) throws InjectionException {
return getInstance(Qualifiers.match(qualifier), type);
}
}