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[utils] / test / enterprise / src / main / java / org / wamblee / support / persistence / package-info.java

/*
 * Copyright 2005-2010 the original author or authors.
 * 
 * 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.
 */ 
/**
 * <p>
 * This package provides test library for database testing in general and JPA testing
 * specifically. As part of this it provides a means to transparently start an inmemory 
 * database from a junit test or connect to an external database. Also, given a persistence 
 * unit it is easy to start testing it in a junit test with only a few lines of code.
 * </p> 
 * 
 * <p>
 * The main use cases are explained below:
 * </p> 
 * <ul>
 *   <li> <a href="#db-basic">Basic database testing, transparently connecting to a database</a>  
 *   </li>
 *   <li> <a href="#db-basic-external">Connecting to an external database</a>
 *   </li>
 *   <li> <a href="#db-utils">Executing code within a JDBC transaction</a>
 *   </li>
 *   <li> <a href="#db-unit">Using DB Unit in your tests</a>
 *   </li>
 *   <li> <a href="#db-jpa-basic">Basic JPA testing</a> 
 *   </li>
 *   <li> <a href="#db-jpa-plus-jdbc">JPA testing combined with JDBC and DBUnit</a>
 *   </li>
 *   <li> <a href="#db-jpa-services">Testing a service that requires a transaction</a>
 *   </li>
 * </ul>
 * 
 * <p>
 *   See the <a href="#design-overview">design overview</a> for a an overview of the design.  
 * </p>
 * 
 * <a name="db-basic">
 *   <h2>Basic database testing, transparently connecting to a database</h2>
 * </a>
 * Starting the database: 
 * <pre>
 *      Database db = DatabaseBuilder.getDatabase();
 *      DataSource dataSource = db.start();
 * </pre>
 * If nothing is specified in the user's environment, an inmemory database is started (derby).
 * Using the datasource is just standard JDBC now. 
 * Stopping the database
 * <pre>
 *      db.stop();
 * </pre>
 * 
 * <a name="db-basic-external">
 *   <h2>Connecting to an external database</h2>
 * </a>
 * 
 * Connecting to an external database can be done by requiring the 'external' capability on 
 * the database provider. 
 * <pre>
 *      Database db = DatabaseBuilder.getDatabase(DatabaseProvider.CAPABILITY_EXTERNAL); 
 * </pre>
 * This also requires a number of environment variables or system properties to be set, 
 * see {@link ExternalDatabase}. 
 * 
 * 
 * <a name="db-utils">
 *   <h2>Executing code within a JDBC transaction</h2>
 * </a>
 * <p>
 *   To execute code withing a JDBC transaction, use the {@link DatabaseUtils} and 
 *   use the {@link DatabaseUtils#executeInTransaction(org.wamblee.support.persistence.DatabaseUtils.JdbcUnitOfWork)}
 *   method. 
 * </p>
 * <pre>
 *       DatabaseUtils dbutils = new DatabaseUtils(dataSource);
 *       boolean result = dbutils.executeInTransaction(
 *           new JdbcUnitOfWork&lt;Boolean&gt;() {
 *               &#064;Override
 *               public Boolean execute(Connection aConnection) throws Exception {
 *                   ResultSet res = jpaTester.getDbUtils().executeQuery(
 *                       aConnection, GROUP_QUERY, aGroup);
 *                   return res.next();
 *               }
 *           });
 * </pre>
 * {@link DatabaseUtils} also provides various other utility methods to work with JDBC queries. 
 * 
 * <a name="db-unit">
 *   <h2>Using DB Unit in your tests</h2>
 * </a>
 * 
 * <p>To work with <a href="http://dbunit.org">DBUnit</a>, {@link DatabaseUtils#createDbTester(org.dbunit.dataset.filter.ITableFilterSimple)}
 * must be used passing it in the tables to use in the form of a {@link org.dbunit.dataset.filter.ITableFilterSimple}
 * object. </p>
 * 
 * <pre>
 *      IDatabaseTester dbtester = dbutils.createDbTester(new ITableFilterSimple() {
 *          public boolean accept(String aTableName) throws DataSetException {
 *              return aTableName.startsWith("XYZ_");
 *          }
 *      });
 * </pre>
 * 
 * <p>The reason for using a <code>DatabaseUtils</code> instead of DBUnit directly is that 
 * <code>DatabseUtils</code> will keep track of connections and close them when <code>DatabaseUtils</code>
 * is closed</p>
 * 
 * <a name="db-jpa-basic">
 *   <h2>Basic JPA testing</h2>
 * </a>
 * <p>
 *    First step is to create a {@link PersistenceUnitDescription} that matches the persistence unit you
 *    want to test. 
 * </p>
 * <p>Second step is to make sure that all entities are listed explicitly in your
 *    <pre>persistence.xml</pre>. Currently, class path scanning appears to fail when
 *    run from junit. 
 *    Specifying all entities explicitly is not necessarily a bad thing as it is also more efficient. 
 * </p>
 * 
 * <p>
 *    Now create a <code>JpaTester</code> in your test code: 
 * </p>
 * <pre>
 *      &#064;Before
 *      public void setUp() throws Exception {
 * 
 *          // First we create the JpaTester by telling us which persistence unit we
 *          // are going to test
 *          jpaTester = new JpaTester(new MyPersistenceUnit());
 *          jpaTester.start();     
 *      }
 * </pre>
 * 
 * <p>
 * Then in test code execute some JPA code within a unit of work: 
 * </p>
 * <pre>
 *      jpaTester.getJpaBuilder().execute(new JpaUnitOfWork<Void>() {
 *          public Void execute(EntityManager aEm) {
 *              MyEntity entity = new MyEntity("a", "b");
 *              aEm.persist(entity);
 *              return null;
 *          }
 *      });
 * </pre>
 * 
 * <a name="db-jpa-plus-jdbc">
 *   <h2>JPA testing combined with JDBC and DBUnit</h2>
 * </a>
 * <p>The <code>JPATester</code> provides access to all required object. It is usually convenient to 
 * get them directly from the <code>JPATester</code> after initializing it: 
 * <pre>
 *      builder = jpaTester.getJpaBuilder();
 *      dbtester = jpaTester.getDbUtils().createDbTester(new MyTables());
 *      dbutils = jpaTester.getDbUtils();
 * </pre>
 * 
 * <a name="db-jpa-services">
 *   <h2>Testing a service that requires a transaction</h2>
 * </a>
 * 
 * <p>Using {@link TransactionProxyFactory} it is possible to create a proxy for a given
 * service interface to provide the semantics of 'requires new' transaction semantics. 
 * <pre>
 *      TransactionProxyFactory<Service> factory = new TransactionProxyFactory<Service>(
 *           jpaTester.getJpaBuilder(), Service.class);
 *      Service service = new ServiceImpl(factory.getTransactionScopedEntityManager()); 
 *      Service proxy = factory.getProxy(service);
 *      proxy.execute(...);
 * </pre>
 * 
 * <p>
 * In the above example, the <code>Service</code> POJO requires an {@link EntityManager} in its 
 * constructor and it is passed a transaction scoped entitymanager from the factory. This entitymanager
 * is in fact a so-called contextual reference.
 * Next, the proxy is obtained from the factory. Invoking any method on it will make sure a new 
 * transaction is started and a new entity manager is created for the scope of that transaction.
 * </p> 
 * 
 * <a name="design-overview">
 *   <h2>design overview</h2>
 * </a>
 * 
 * <h3>Database transaparency</h3>
 * 
 * <h3>Testing using JDBC and DBUnit</h3> 
 * 
 * <h3>JPA tester overview</h3>
 * 
 * 
 * 
 */
package org.wamblee.support.persistence;

import static org.mockito.Mockito.*;

import javax.persistence.EntityManager;

import org.junit.Before;
import org.wamblee.support.persistence.JpaBuilder.JpaUnitOfWork;
import org.wamblee.support.persistence.TransactionProxyFactoryTestBase.Service;