Polishing

spring-orm/src/main/java/org/springframework/orm/jpa/DefaultJpaDialect.java

@@ -69,6 +69,9 @@ public class DefaultJpaDialect implements JpaDialect, Serializable {
 		return null;
 	}
 
+	/**
+	 * This implementation simply returns {@code null} for no transaction data.
+	 */
 	@Override
 	@Nullable
 	public Object prepareTransaction(EntityManager entityManager, boolean readOnly, @Nullable String name)
@@ -81,6 +84,7 @@ public class DefaultJpaDialect implements JpaDialect, Serializable {
 	 * This implementation does nothing, since the default {@code beginTransaction}
 	 * implementation does not require any cleanup.
 	 * @see #beginTransaction
+	 * @see #prepareTransaction
 	 */
 	@Override
 	public void cleanupTransaction(@Nullable Object transactionData) {

spring-orm/src/main/java/org/springframework/orm/jpa/JpaDialect.java

@@ -100,7 +100,7 @@ public interface JpaDialect extends PersistenceExceptionTranslator {
 	 * @param readOnly whether the transaction is supposed to be read-only
 	 * @param name the name of the transaction (if any)
 	 * @return an arbitrary object that holds transaction data, if any
-	 * (to be passed into cleanupTransaction)
+	 * (to be passed into {@link #cleanupTransaction})
 	 * @throws jakarta.persistence.PersistenceException if thrown by JPA methods
 	 * @see #cleanupTransaction
 	 */
@@ -117,6 +117,7 @@ public interface JpaDialect extends PersistenceExceptionTranslator {
 	 * @param transactionData arbitrary object that holds transaction data, if any
 	 * (as returned by beginTransaction or prepareTransaction)
 	 * @see #beginTransaction
+	 * @see #prepareTransaction
 	 * @see org.springframework.jdbc.datasource.DataSourceUtils#resetConnectionAfterTransaction
 	 */
 	void cleanupTransaction(@Nullable Object transactionData);

spring-orm/src/main/java/org/springframework/orm/jpa/vendor/EclipseLinkJpaDialect.java

@@ -181,16 +181,18 @@ public class EclipseLinkJpaDialect extends DefaultJpaDialect {
 
 		@Override
 		public Connection getConnection() {
-			if (this.connection == null) {
+			Connection con = this.connection;
+			if (con == null) {
 				transactionIsolationLock.lock();
 				try {
-					this.connection = this.entityManager.unwrap(Connection.class);
+					con = this.entityManager.unwrap(Connection.class);
 				}
 				finally {
 					transactionIsolationLock.unlock();
 				}
+				this.connection = con;
 			}
-			return this.connection;
+			return con;
 		}
 	}