These are specifications of a generic Java Persistence API. Meanwhile, the JCP with a lot of input from Hibernate and other ORM tool vendors was developing JSR 220 (Java Specification Request) which resulted in JPA 1.0 (2006) and eventually JSR 317 which is JPA 2.0 (2009). Hence the need for a generic persistence API. The fundamental issue now is that your code becomes tightly coupled with a specific vendor(Hibernate) for what a lot of people thought should be more generic. Hibernate provided an implementation to do this and the API to drive the implementation either through XML config or annotations. You notify hibernate about your Entity objects and it automatically generates the strategy to persist them. Hibernate (in 2003) provided a way to abstract SQL and allow developers to think more in terms of persisting objects (ORM). For various reasons that function may become part of the Java JDK through the JCP (Java Community Process) Often there are third parties that develop packages that perform a function or fill a gap that are not part of the official JDK. Some things are too hard to understand without a historical perspective of the language and understanding of the JCP. Is there a book that takes a problem/solution approach to JPA2? "Pro JPA2" seems more like a bible and reference on JPA2 (It doesn't get into Queries until the later half of the book). Can you recommend a good practical JPA2 book.Is JPA2 supposed to be used with a "JPA Provider" e.g TopLink or Hibernate? If so, then what's the benefit of using JPA2 + Hibernate as compared to JPA2 alone, or compared to Hibernate alone ?.Using JPA2 alone can I fetch data from DB by simply annotating my POJO's.This confuses me so I have a few questions: If you think a feature should be standardized, you should speak up I picked up Pro JPA2 book and it keeps referring to "JPA provider". I have experience using iBatis and now I'm trying to learn either Hibernate or JPA2. But from a practical point of view, what really is the difference? Also, I understand that Hibernate has more features than JPA 2. I understand that JPA 2 is a specification and Hibernate is a tool for ORM. It is not currently accepting new answers or interactions. This question and its answers are locked because the question is off-topic but has historical significance. This encryption/decryption logic can be kept in setters and getters. E.g.: you want to have some arbitrary logic like encrypting and decrypting the fields before and after they persisted and fetched to/from database. Sometimes you might want JPA to access the fields through setters/getters even Id or EmbeddedId annotation is kept on a field and not on setters/getters. So when you placed your Id or EmbeddedId annotation on a field, all access will happen through the fields, when you apply it on the getter/setter methods, all fields will use the getter/setter methods. By default the access type is defined by the place where you put your mandatory id property of the POJO with Id or EmbeddedId. JPA can access the fields of Entity class, Embeddable class and Id class or any other class which is in the JPA scope, directly or through setters and getters. We can pass AccessType.FIELD or AccessType.PROPERTY values.ĪccessType.PROPERTY: Access will be through setters and getters Means Access annotation is class level and as well as member level annotation. You can also use the annotation to override the access strategy of individual properties. If you set on the class/entity level, JPA accesses all properties of the class according to the selected strategy irrespective of place of Id/EmeddedId annotation. JPA provides annotation for overriding the default behavior, by using AccessType.FIELD and AccessType.PROPERTY. JPA Annotation - AccessType.FIELD and AccessType.PROPERTY
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