IsisJdoSupport.java

/*
 *  Licensed to the Apache Software Foundation (ASF) under one
 *  or more contributor license agreements.  See the NOTICE file
 *  distributed with this work for additional information
 *  regarding copyright ownership.  The ASF licenses this file
 *  to you 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.apache.isis.applib.services.jdosupport;

import java.util.Collection;
import java.util.List;
import java.util.Map;

import javax.jdo.PersistenceManager;

import org.datanucleus.query.typesafe.BooleanExpression;
import org.datanucleus.query.typesafe.TypesafeQuery;

import org.apache.isis.applib.annotation.Programmatic;


/**
 * Service that provide a number of workarounds when using JDO/DataNucleus. 
 */
public interface IsisJdoSupport {

    /**
     * Force a reload (corresponding to the JDO <tt>PersistenceManager</tt>'s <tt>refresh()</tt> method)
     * of a domain objects.
     * 
     * <p>
     * In fact, this may just reset the lazy-load state of the domain object, but the effect is the same: 
     * to cause the object's state to be reloaded from the database.
     * 
     * <p>
     * The particular example that led to this method being added was a 1:m bidirectional relationship,
     * analogous to <tt>Customer <-> * Order</tt>.  Persisting the child <tt>Order</tt> object did not cause
     * the parent <tt>Customer</tt>'s collection of orders to be updated.  In fact, JDO does not make any
     * such guarantee to do so.  Options are therefore either to maintain the collection in code, or to
     * refresh the parent.
     */
    @Programmatic
    <T> T refresh(T domainObject);
    
    @Programmatic
    void ensureLoaded(Collection<?> collectionOfDomainObjects);
    
    @Programmatic
    PersistenceManager getJdoPersistenceManager();

    @Programmatic
    List<Map<String, Object>> executeSql(String sql);

    @Programmatic
    Integer executeUpdate(String sql);

    /**
     * Force the deletion of all instances of the specified class.
     * 
     * <p>
     * Note: this is intended primarily for testing purposes, eg clearing existing data as part of
     * installing fixtures.  It will generate a <tt>SQL DELETE</tt> for each instance.  To perform
     * a bulk deletion with a single <tt>SQL DELETE</tt>, use {@link #executeUpdate(String)}.  
     * 
     * <p>
     * Implementation note: It can occasionally be the case that Isis' internal adapter for the domain object is
     * still in memory.  JDO/DataNucleus seems to bump up the version of the object prior to its deletion, 
     * which under normal circumstances would cause Isis to throw a concurrency exception.  Therefore
     * To prevent this from happening (ie to <i>force</i> the deletion of all instances), concurrency checking
     * is temporarily disabled while this method is performed. 
     */
    @Programmatic
    void deleteAll(Class<?>... pcClasses);

    /**
     * To perform the most common use-case of executing a (type-safe) query against the specified class,
     * filtering using the provided {@link BooleanExpression}, then automatically cloning the returned list
     * and closing the query.
     *
     * <p>
     *     Typical usage:
     *     <pre>
     *          final QToDoItem q = QToDoItem.candidate();
     *          return executeQuery(ToDoItem.class,
     *                              q.atPath.eq(atPath).and(
     *                              q.description.indexOf(description).gt(0))
     *                              );
     *     </pre>
     * </p>
     */
    @Programmatic
    <T> List<T> executeQuery(final Class<T> cls, final BooleanExpression booleanExpression);

    /**
     * To support the execution of type-safe queries using DataNucleus' lower-level APIs
     * (eg for group by and so on).
     *
     * <p>
     *     Responsibility for cloning any result sets and closing the query is the responsibility
     *     of the caller.
     * </p>
     */
    @Programmatic
    <T> TypesafeQuery<T> newTypesafeQuery(Class<T> cls);
}