Thanks Christian! That are good news... Especially, your future planning regarding "TransactionTemplate" sounds really interesting.
Can you plase provide a small example for your alternative solutions. How can I obtain a "UserTransaction" to create the transaction? Best regards, Jens Gesendet: Samstag, 22. April 2017 um 13:22 Uhr Von: "Christian Schneider" <[email protected]> An: [email protected] Betreff: Re: Consistent entity updates without exposing JpaTemplate For now this is a good pattern. I plan to add a pure TransactionTemplate or similar to cover this case outside of JPATemplate. Alternatively you can inject a UserTransaction and use it to create the transaction. Christian 2017-04-21 16:49 GMT+02:00 Jens Offenbach <[email protected][mailto:[email protected]]>:Hallo, I am sorry, but I am still in trouble with JpaTemplate and API design. I am trying to hide JpaTemplate in my service implementation, but I am not sure, if this is the recommended approach. Unfortuantely, I cannot find any complex examples in the web. Let me explain the problem with the help of the TaskService example (https://github.com/apache/aries/blob/trunk/jpa/examples/tasklist-ds/src/main/java/org/apache/aries/jpa/example/tasklist/ds/impl/TaskServiceImpl.java[https://github.com/apache/aries/blob/trunk/jpa/examples/tasklist-ds/src/main/java/org/apache/aries/jpa/example/tasklist/ds/impl/TaskServiceImpl.java]): Task task = taskService.getTask(1); task.setTitle("New Title#1"); Both calls must be done under transaction control to keep the database consistent (Thanks Christian), so the only correct way would be: jpa.tx(em -> { Task task = taskService.getTask(1); task.setTitle("New Title#1"); }); The problem is, that service users must have the JpaTemplate reference for consistent entity updates. The only way to hide JpaTemplate would be to extend TaskService like this: public interface TaskService { void tx(Runnable runnable); Task getTask(Integer id); void addTask(Task task); void updateTask(Task task); void deleteTask(Integer id); Collection<Task> getTasks(); } @Component public class TaskServiceImpl implements TaskService { @Reference(target = "(osgi.unit.name[http://osgi.unit.name]=tasklist)") private JpaTemplate jpa; @Override public void tx(Runnable runnable) { jpa.tx(em -> runnable.run()); } } The resulting user code that updates an entity consistently (hopefully) would look like this: @Component(immediate = true) public class TasklistUpdater { @Reference TaskService taskService; @Activate public void addDemoTask() { if (taskService.getTask(1) == null) { Task task = new Task(); task.setId(1); task.setTitle("Task1"); taskService.addTask(task); } updateDemoTask(); } private void updateDemoTask() { taskService.tx(() -> { Task task = taskService.getTask(1); task.setDescription("A description"); task.setTitle("A title"); }); } } I am not sure, if this approach works as expected and if JpaTemplate calls can be nested as shown above. What about overhead? Are there any best practices known regarding API design in respect to JpaTemplate? I am thankful for any comments or ideas for improvement? Thank you very much, Jens -- -- Christian Schneider http://www.liquid-reality.de[https://owa.talend.com/owa/redir.aspx?C=3aa4083e0c744ae1ba52bd062c5a7e46&URL=http%3a%2f%2fwww.liquid-reality.de] Open Source Architect http://www.talend.com[https://owa.talend.com/owa/redir.aspx?C=3aa4083e0c744ae1ba52bd062c5a7e46&URL=http%3a%2f%2fwww.talend.com]
