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This article mainly shows you "what is the specification of JPA", the content is easy to understand, clear, hope to help you solve your doubts, the following let the editor lead you to study and learn "what is the specification of JPA" this article.

Overview of JPA

JPA (Java Persistence API), as the ORM specification of the Java EE 5.0 platform standard, will be supported by all Java EE servers. This time, Sun draws on the experience of the painful failure of the previous EJB specification, and obtains an easy-to-use and scalable ORM specification on the basis of fully absorbing the existing ORM framework. Judging from the response of the current development community, JPA has received great support and praise, and JPA's goal as a standardization integrator in the ORM domain should not be difficult to achieve.

JPA describes the object-relational table mapping through JDK 5.0 annotations or XML, and persists runtime entity objects into the database. Figure 1 describes the structure of JPA well:

Sun introduces the new JPA ORM specification for two reasons: first, it simplifies the development of object persistence for existing Java EE and Java SE applications; second, Sun hopes to integrate ORM technology to achieve the unification of the world.

JPA was developed by the EJB 3.0 software expert group as part of the JSR-220 implementation. But it's not limited to EJB 3.0. you can use it in Web applications or even desktop applications. The purpose of JPA is to provide persistence standard specification for POJO. It can be seen that after years of practical exploration, the concept of being able to run independently from the container and facilitate development and testing has been deeply rooted in the hearts of the people. Currently, Hibernate 3.2, TopLink 10.1.3, and OpenJpa all provide an implementation of JPA.

The overall idea of JPA is roughly the same as the existing ORM frameworks such as Hibernate, TopLink,JDO and so on. In general, JPA includes the following three technologies:

ORM maps metadata, JPA supports XML and JDK 5.0Annotation two forms of metadata, metadata describes the mapping relationship between objects and tables, according to which the framework persists entity objects into database tables.

JPA's API is used to manipulate entity objects and perform CRUD operations. The framework does everything for us in the background, and developers are freed from tedious JDBC and SQL code.

Query language, which is a very important aspect of persistence operation, queries data through object-oriented rather than database-oriented query language to avoid tight coupling of SQL statements of the program.

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