For your use case where the application runs on one server and the database runs on another, the choice between EJB and Spring is irrelevant. Every platforms supports this, be it a Java SE application, a simple Servlet container like Tomcat or Jetty, PHP, Ruby on Rails, or whatever. You don’t need any kind of … Read more
Updating maven project after importing it has fixed this issue for me: Right click on the project –> Maven –> Update project.
I think the best way is to put a break point in the constructor of java.lang.TypeNotPresentException and check the second argument of type Throwable to know the root cause
What you do is called a projection. That’s when you return only a scalar value that belongs to one entity. You can do this with JPA. See scalar value. I think in this case, omitting the entity type altogether is possible: Query query = em.createNativeQuery( “select id from users where username = ?”); query.setParameter(1, “lt”); … Read more
Although you are getting valid results, the SQL query fetches all data and it’s not as efficient as it should. So, you have two options. Fixing the issue with two SQL queries that can fetch entities in read-write mode The easiest way to fix this issue is to execute two queries: . The first query … Read more
The terms “jta-datasource” and “resouce-local datasource” are a little vague to me. I guess you actually refer to the jta-datasource and non-jta-datasource elements. In short: if the transaction type of the persistence unit is JTA, the jta-datasource element is used to declare the JNDI name of the JTA data source that will be used to … Read more
Fixed it by removing CascadeType.MERGE on Permission entity
There won’t be much difference between EJB3 and Spring based on Performance. We chose Spring for the following reasons (not mentioned in the question): Spring drives the architecture in a direction that more readily supports unit testing. For example, inject a mock DAO object to unit test your business layer, or utilize Spring’s MockHttpRequest object … Read more
The error occurs because the object’s ID is set. Hibernate distinguishes between transient and detached objects and persist works only with transient objects. If persist concludes the object is detached (which it will because the ID is set), it will return the “detached object passed to persist” error. You can find more details here and … Read more
Spring was developed as an alternative to EJB right from its inception, so the answer is of course you can use Spring in place of EJBs. If there’s an “advantage” to using EJBs, I’d say that it would depend on the skills of your team. If you have no Spring expertise, and lots of EJB … Read more