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[utils] / test / enterprise / src / main / java / org / wamblee / support / persistence / JpaBuilder.java

diff --git a/test/enterprise/src/main/java/org/wamblee/support/persistence/JpaBuilder.java b/test/enterprise/src/main/java/org/wamblee/support/persistence/JpaBuilder.java
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+++ b/test/enterprise/src/main/java/org/wamblee/support/persistence/JpaBuilder.java
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+package org.wamblee.support.persistence;
+
+import java.util.Map;
+import java.util.TreeMap;
+import java.util.logging.Level;
+import java.util.logging.Logger;
+
+import javax.naming.InitialContext;
+import javax.naming.NamingException;
+import javax.persistence.EntityManager;
+import javax.persistence.EntityManagerFactory;
+import javax.persistence.EntityTransaction;
+import javax.persistence.Persistence;
+import javax.sql.DataSource;
+
+import org.wamblee.support.jndi.StubInitialContextFactory;
+
+
+/**
+ * Utility for building an appropriately configured EntityManagerFactory. The
+ * idea is that a persistence.xml is used unchanged from the production version.
+ * This utility will then add the additional properties required for execution
+ * in a standalone environment.
+ * 
+ * The other purpose is to to shield dependencies of the test code on a
+ * particular JPA provider.
+ */
+public class JpaBuilder {
+
+       private static final Logger LOGGER = Logger.getLogger(JpaBuilder.class
+                       .getName());
+
+       /**
+        * Callback interface to execute some JPA code within a transaction with the
+        * entitymanager to use provided as input.
+        */
+       public static interface JpaUnitOfWork<T> {
+               /**
+                * Executes the unit of work. A transaction has been started.  
+                * @param em Entity manager. 
+                * @return Result of the execute method. If you don't want to return anything use
+                *  <code>Void</code> for the return type and return null from the implementation. 
+                */
+               T execute(EntityManager em);
+       }
+
+       private PersistenceUnitDescription persistenceUnit;
+       private DataSource dataSource;
+       private EntityManagerFactory factory;
+
+       /**
+        * Constructs the builder.
+        * 
+        * @param aDataSource
+        *            Datasource of database.
+        * @param aPersistenceUnit
+        *            Persistence unit.
+        */
+       public JpaBuilder(DataSource aDataSource,
+                       PersistenceUnitDescription aPersistenceUnit) {
+               persistenceUnit = aPersistenceUnit;
+               dataSource = aDataSource;
+               StubInitialContextFactory.register();
+       }
+
+       /**
+        * Starts the builder, which in particular, mocks JNDI, binds the datasource
+        * the JNDI where the persistence unit expects it, creates the entity
+        * manager factory, and forces creation of the database schema.
+        */
+       public void start() throws Exception {
+               try {
+                       InitialContext ctx = new InitialContext();
+                       ctx.bind(persistenceUnit.getJndiName(), dataSource);
+               } catch (NamingException e) {
+                       throw new RuntimeException("JNDI problem", e);
+               }
+               factory = createFactory();
+               execute(new JpaUnitOfWork<Void>() {
+                       public Void execute(EntityManager em) {
+                               // Empty, just to trigger database schema creation.
+                               return null;
+                       }
+               });
+       }
+
+       /**
+        * Stops the entity manager factory and disables JNDI mocking. 
+        */
+       public void stop() {
+               StubInitialContextFactory.unregister();
+               factory.close();
+       }
+
+       /**
+        * Creates a new entity manager factory. Typically not used by test code. 
+        * @return Entity manager factory. 
+        */
+       public EntityManagerFactory createFactory() {
+               Map<String, String> jpaProps = new TreeMap<String, String>();
+       
+               JpaCustomizerBuilder.getCustomizer().customize(persistenceUnit, jpaProps);
+               
+               //jpaProps.put("javax.persistence.provider", HibernatePersistence.class.getName());
+               EntityManagerFactory factory = Persistence.createEntityManagerFactory(persistenceUnit
+                               .getUnitName(), jpaProps);
+               
+               LOGGER.info("Using " + factory.getClass());
+               return factory;
+       }
+
+       /**
+        * Executes a unit of work. This creates an entitymanager and runs the 
+        * {@link JpaUnitOfWork#execute(EntityManager)} within a transaction, passing
+        * it the entity manager. Use of this method saves a lot of typing for applications. 
+        * 
+        * @param aWork Work to execute. 
+        * @return The return value of the execute method of the unit of work. 
+        */
+       public <T> T execute(JpaUnitOfWork<T> aWork) throws Exception {
+               EntityManager em = factory.createEntityManager();
+               EntityTransaction transaction = em.getTransaction();
+               transaction.begin();
+               try {
+                       T value = aWork.execute(em);
+                       transaction.commit();
+                       return value; 
+               } catch (Exception e) {
+                       LOGGER.log(Level.WARNING, "Exception occured", e);
+                       transaction.rollback();
+                       throw e; 
+               } finally {
+                       em.close();
+               }
+       }
+}