DroolsModule.java

/*
 * Copyright 2015 Red Hat, Inc. and/or its affiliates.
 *
 * 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.drools.android.roboguice;

import android.app.Application;
import android.content.Context;
import android.content.res.Resources;
import com.google.inject.AbstractModule;
import com.google.inject.MembersInjector;
import com.google.inject.TypeLiteral;
import com.google.inject.matcher.Matchers;
import com.google.inject.spi.TypeEncounter;
import com.google.inject.spi.TypeListener;
import org.drools.android.DroolsAndroidContext;
import org.drools.android.roboguice.KnowledgeBaseListener;
import org.drools.core.util.DroolsStreamUtils;
import org.kie.api.KieBase;
import org.kie.api.KieServices;
import org.kie.api.cdi.KBase;
import org.kie.api.runtime.KieContainer;
import org.kie.internal.KnowledgeBase;
import org.kie.internal.KnowledgeBaseFactory;
import org.kie.internal.definition.KnowledgePackage;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import roboguice.inject.Nullable;

import java.lang.reflect.Field;
import java.lang.reflect.Modifier;
import java.util.HashMap;
import java.util.List;
import java.util.Map;

/**
 * Custom Roboguice module for preserialized kiebases
 */
public class DroolsModule extends AbstractModule {
    private static final Logger logger = LoggerFactory.getLogger(DroolsModule.class);

    private Application application;

    public DroolsModule(Application ctx) {
        this.application = ctx;
    }

    @Override
    protected void configure() {
        DroolsAndroidContext.setContext(application);
        final KnowledgeBaseListener kbListener = new KnowledgeBaseListener(application);
        bind(KnowledgeBaseListener.class).toInstance(kbListener);
        bindListener(Matchers.any(), kbListener);
    }
}

class KnowledgeBaseListener implements TypeListener {
    private static final Logger logger = LoggerFactory.getLogger(KnowledgeBaseListener.class);

    protected Application application;
    protected Resources resources;

    public KnowledgeBaseListener(Application application) {
        this.application = application;
        this.resources = application.getResources();
    }

    public <I> void hear(TypeLiteral<I> typeLiteral, TypeEncounter<I> typeEncounter) {
        for (Class<?> c = typeLiteral.getRawType(); c != Object.class; c = c.getSuperclass())
            for (Field field : c.getDeclaredFields())
                if (field.isAnnotationPresent(KBase.class) && !Modifier.isStatic(field.getModifiers()))
                    typeEncounter.register(new KnowledgeBaseMembersInjector<I>(field, application, field.getAnnotation(KBase.class)));
    }

    private KieServices ks;
    private KieContainer classpathContainer;
    private Map<String, KieBase> kbases = new HashMap<String, KieBase>();

    protected class KnowledgeBaseMembersInjector<T> implements MembersInjector<T> {

        protected Field field;
        protected Application application;
        protected KBase annotation;

        public KnowledgeBaseMembersInjector(Field field, Application application, KBase annotation) {
            this.field = field;
            this.application = application;
            this.annotation = annotation;
        }

        public void injectMembers(T instance) {
            KieBase knowledgeBase = null;
            try {
                final int id = resources.getIdentifier(annotation.value().toLowerCase(),
                        "raw", application.getPackageName());
                logger.debug("Injecting kbase from : " + id);
                if (id != 0) { //Inject serialized knowledgebase
                    if (!kbases.containsKey(annotation.value())) {
                        logger.debug("Deserializing knowledge base {}", annotation.value());
                        knowledgeBase = KnowledgeBaseFactory.newKnowledgeBase();
                        ((KnowledgeBase) knowledgeBase).addKnowledgePackages(
                                (List<KnowledgePackage>) DroolsStreamUtils.streamIn(resources.openRawResource(id)));
                        kbases.put(annotation.value(), knowledgeBase);
                    }
                    knowledgeBase = kbases.get(annotation.value());
                } else { //inject knowledge base from classpath container
                    if (classpathContainer == null) {
                        ks = KieServices.Factory.get();
                        classpathContainer = ks.getKieClasspathContainer();
                    }
                    knowledgeBase = classpathContainer.getKieBase(annotation.value());
                }

                if (knowledgeBase == null && Nullable.notNullable(field)) {
                    throw new NullPointerException(String.format("Can't inject null value into %s.%s when field is not @Nullable", field.getDeclaringClass(), field
                            .getName()));
                }

                field.setAccessible(true);
                field.set(instance, knowledgeBase);
                logger.debug("Injected Knowledge Base: " + knowledgeBase);
            } catch (IllegalArgumentException f) {
                throw new IllegalArgumentException(String.format("Can't assign %s value %s to %s field %s", knowledgeBase != null ? knowledgeBase.getClass() : "(null)", knowledgeBase,
                        field.getType(), field.getName()));
            } catch (Exception e) {
                throw new RuntimeException(e);
            }
        }

    }
}