Relationships.java

/*
 * JBoss, Home of Professional Open Source.
 * Copyright 2011, Red Hat Middleware LLC, and individual contributors
 * as indicated by the @author tags. See the copyright.txt file in the
 * distribution for a full listing of individual contributors.
 *
 * This 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 software 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
 * Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public
 * License along with this software; if not, write to the Free
 * Software Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA
 * 02110-1301 USA, or see the FSF site: http://www.fsf.org.
 */

package org.jboss.capedwarf.jpa;

import javax.persistence.EntityManager;
import javax.persistence.Query;
import java.lang.reflect.Method;
import java.lang.reflect.ParameterizedType;
import java.lang.reflect.Type;
import java.util.Arrays;
import java.util.Collection;
import java.util.List;
import java.util.Map;
import java.util.concurrent.ConcurrentHashMap;

/**
 * Handle relationships.
 *
 * @author <a href="mailto:ales.justin@jboss.org">Ales Justin</a>
 */
class Relationships {
    /**
     * The get entity id mapping
     */
    private static Map<Class<?>, Map<Class<?>, Method>> getIdMapping = new ConcurrentHashMap<Class<?>, Map<Class<?>, Method>>();

    /**
     * The set entity id mapping
     */
    private static Map<Class<?>, Map<Class<?>, Method>> setIdMapping = new ConcurrentHashMap<Class<?>, Map<Class<?>, Method>>();

    /**
     * The one-to-many queries
     */
    private static Map<String, String> otmQueries = new ConcurrentHashMap<String, String>();

    static Object handleManyToOne(Object entity, Method method, Object[] args, ManyToOne otm, EntityManagerProvider provider) throws Throwable {
        String methodName = method.getName();
        if (methodName.startsWith("get"))
            return getMTO(method, otm, entity, provider);
        else {
            if (args == null || args.length != 1 || args[0] == null)
                throw new IllegalArgumentException("Illegals args: " + Arrays.toString(args));

            setMTO(method, otm, entity, args[0]);
            return null;
        }
    }

    @SuppressWarnings({"unchecked"})
    static Collection handleOneToMany(Object entity, Method method, OneToMany otm, ProxyingHelper helper) throws Throwable {
        if (entity instanceof Entity == false)
            throw new IllegalArgumentException("Entity is not an entity: " + entity);

        Class<?> ownerClass = entity.getClass();
        String key = ownerClass.getName() + "::" + method.getName();
        String queryString = otmQueries.get(key);
        if (queryString == null) {
            Class<?> entityClass = otm.element();
            if (entityClass == Void.class) {
                Type rt = method.getGenericReturnType();
                if (rt instanceof ParameterizedType == false)
                    throw new IllegalArgumentException("Cannot get exact type: " + rt);

                ParameterizedType pt = (ParameterizedType) rt;
                Type[] ats = pt.getActualTypeArguments();
                if (ats == null || ats.length != 1 || (ats[0] instanceof Class == false))
                    throw new IllegalArgumentException("Illegal actual type: " + Arrays.toString(ats));

                entityClass = (Class) ats[0];
            }

            String joinName = otm.join();
            if (joinName == null || joinName.length() == 0) {
                String ownerName = ownerClass.getSimpleName().toLowerCase();
                joinName = ownerName + "Id";
            }

            StringBuilder builder = new StringBuilder("select e from ");
            builder.append(entityClass.getSimpleName());
            builder.append(" e where e.").append(joinName).append(" = ?1 ");
            builder.append(otm.orderBy());

            queryString = builder.toString().trim();
            otmQueries.put(key, queryString);
        }

        Object id = ((Entity) entity).getId();
        EntityManagerProvider provider = helper.getProvider();
        EntityManager em = provider.getEntityManager();
        try {
            Query query = em.createQuery(queryString);
            query.setParameter(1, id);
            List result = query.getResultList();
            Collection collection = otm.type().newInstance();
            if (ProxyingUtils.isDisabled()) {
                collection.addAll(result);
            } else {
                for (Object obj : result)
                    collection.add(helper.wrap(obj));
            }
            return collection;
        } finally {
            provider.close(em);
        }
    }

    private static Object getMTO(Method method, ManyToOne mto, Object entity, EntityManagerProvider provider) throws Throwable {
        Object rel = method.invoke(entity);
        if (rel == null) {
            Class<?> ec = entity.getClass();
            String methodName = method.getName();
            Class<?> entityClass = method.getReturnType();
            Map<Class<?>, Method> map = getIdMapping.get(ec);
            if (map == null) {
                map = new ConcurrentHashMap<Class<?>, Method>();
                getIdMapping.put(ec, map);
            }
            Method idMethod = map.get(entityClass);
            if (idMethod == null) {
                String idName = mto.id();
                if (idName == null || idName.length() == 0) {
                    idName = methodName + "Id";
                }
                idMethod = ec.getMethod(idName);
                map.put(entityClass, idMethod);
            }
            Object id = idMethod.invoke(entity); // get rel id
            if (id == null) {
                return null;
            }
            EntityManager em = provider.getEntityManager();
            try {
                rel = em.find(entityClass, id);
            } finally {
                provider.close(em);
            }

            Method setter = ec.getMethod("s" + methodName.substring(1), entityClass);
            setter.invoke(entity, rel); // set rel
        }
        return rel;
    }

    private static void setMTO(Method method, ManyToOne mto, Object entity, Object value) throws Throwable {
        if (value instanceof Entity == false)
            throw new IllegalArgumentException("Value is not an entity: " + value);

        Class<?> ec = entity.getClass();
        String methodName = method.getName();
        Class<?> entityClass = method.getParameterTypes()[0];
        Map<Class<?>, Method> map = setIdMapping.get(ec);
        if (map == null) {
            map = new ConcurrentHashMap<Class<?>, Method>();
            setIdMapping.put(ec, map);
        }
        Method idMethod = map.get(entityClass);
        if (idMethod == null) {
            String idName = mto.id();
            if (idName == null || idName.length() == 0) {
                idName = methodName + "Id";
            }
            idMethod = ec.getMethod(idName, Long.class);
            map.put(entityClass, idMethod);
        }
        Object id = ((Entity) value).getId();
        idMethod.invoke(entity, id); // set rel id
    }
}