#Java spring annotations cheat sheet how to
#Java spring annotations cheat sheet code

I don't know any examples in Java but in. When you reflect a type of a class in your code, you can access the attributes and act according to the information found there. Similarly, methods can be marked obsolete.

#Java spring annotations cheat sheet code

One typical Java example, has no effect on the code but it can be used by the compiler to generate a warning (or error) if the decorated method doesn't actually override another method.

No, but VB and C# have attributes which are the same thing. Of course, this approach tends to create and release the EntityManagerFactory very often, so it may become a performance problem in production.Also, are they unique to Java, is there a C++ equivalent? I wrapped the DAO functions in an AutoCloseable class which can be used in a try-with-resources block. The following example takes a different approach. So it might be a good idea to put them in a SessionScoped bean and release the resources in an method. This is the shortest running version I successfully tested:: Configuring JPA with as little XML as possibleĪccording to the Javadoc, both the EntityManager and the EntityManagerFactory must be released after use. If you use the standard directory layout of Maven, that's src/main/resources. Put the persistence.xml into the META-INF of the classpath. In the meantime, we can do with a very minimalist persistence.xml.

#Java spring annotations cheat sheet how to

If you know how to get rid of the persistence.xml file, please drop me a note. There are a couple of vague hints in the internet, and it's obviously possible: Spring does it (at least internally). Again, I was surprised I didn't find out how to configure a JPA PersistenceUnit without at least a few lines of XML. Now let's have a look at the standard approach. Transaction transaction = session.beginTransaction() For the sake of brevity, I omit them here: Again, make sure you close it correctly in a try.finally block. Persisting data requires a transaction manager. I've grown up with SQL, so it matches my mind model better. I know about the criteria API, but I prefer the older SQL-like style. Session session = sessionFactory.openSession() The session object doesn't implement the AutoClosable interface, so take care to close the connection correctly (even and especially if an exception is thrown): However, it can be closed, so probably it's a better idea to put it in an ApplicationScoped bean and release the SessionFactory in a method annotated by Reading and writing entities (native Hibernate style)

The SessionFactory has immutable state, so I suppose you can safely use it in a static final variable without opening a memory leak. However, you can automate this with a few lines of reflection. The drawback of this approach is that you have to add each Entity individually. SessionFactory = config.buildSessionFactory(ssrb.build()) StandardServiceRegistryBuilder ssrb = new StandardServiceRegistryBuilder() addAnnotatedClass(MyBusinessClass.class) setProperty('hibernate.show_sql', 'true') Private static SessionFactory sessionFactory Ĭonfiguration config = new Configuration() Instead, use Configuration#addAnnotatedClass(): This method requires an *.hbm file for each and every entity. prefix to the property name.ĭon't add the entity classes via Configuration#addClass(). The properties - such as the SQL dialect, the name of the datasource and whether to create the database from scratch each time the server is started - are set by calling Configuration#setProperty(). There's nothing worse than an administrator modifying the database configuration in production without telling the development team.īasically, you need a Configuration object. I like this version better because I can debug it. Instead, I resorted to a pure Java solution. Probably I could have moved it to the classes folder. My application wouldn't start because it didn't find the configuration file. Configuring an XML file is all good and well - until I uploaded my app to a server with a different folder layout.