What is jpa? What are the advantages of jpa?

The full English name of JPA is "Java Persistence API", which means Java persistence layer API and is a Java persistence specification. It provides Java developers with an object and association mapping tool to manage relationships in Java applications. Data has the advantages of standardization, simplicity and ease of use, and easy integration.

What is JPA?

JPA (Java Persistence API), Chinese name Java persistence layer API, is a Java persistence specification. It provides Java developers with an object/association mapping tool to manage Java applications. relational data in .

The emergence of JPA is mainly to simplify existing persistence development work and integrate ORM technology, ending the current situation in which ORM frameworks such as Hibernate, TopLink, and JDO operate independently.

JPA is developed on the basis of fully absorbing existing ORM frameworks such as Hibernate, TopLink, JDO, etc., and has the advantages of ease of use and strong scalability. In general, JPA includes the following three technologies:

1. ORM mapping metadata

JPA supports both XML and JDK5.0 annotations In the form of metadata, metadata describes the mapping relationship between objects and tables, and the framework persists entity objects into database tables accordingly;

2. Java persistence API

Used to operate entity objects and perform CRUD operations. The framework completes everything for us in the background, freeing developers from cumbersome JDBC and SQL codes.

3. Query Language (JPQL)

This is a very important aspect of persistence operations. Data is queried through object-oriented rather than database-oriented query language. Avoid tightly coupling your program's SQL statements.

What are the advantages of JPA?

1. Standardization

JPA is one of the Java EE standards published by the JCP organization, so any framework that claims to comply with the JPA standard They all follow the same architecture and provide the same access API, which ensures that enterprise applications developed based on JPA can run under different JPA frameworks with a small amount of modifications.

2. Support for container-level features

The JPA framework supports container-level transactions such as large data sets, transactions, and concurrency, which makes JPA go beyond simple persistence. The limitations of the framework play a greater role in enterprise applications.

3. Easy to use and easy to integrate

One of the main goals of JPA is to provide a simpler programming model: create entities and create Java classes under the JPA framework Just as simple, without any constraints or restrictions, just use javax.persistence.Entity for annotation; the JPA framework and interface are also very simple, without many special rules and design pattern requirements, developers can easily master it . JPA is designed based on non-intrusive principles, so it can be easily integrated with other frameworks or containers.

4. Query capabilities comparable to JDBC

JPA’s query language is object-oriented rather than database-oriented. It constructs query statements with object-oriented natural syntax. Can be seen as the equivalent of Hibernate HQL. JPA defines a unique JPQL (Java Persistence Query Language). JPQL is an extension of EJB QL. It is a query language for entities. The operation object is entities, not tables of relational databases, and it can support batch updates and Modification, JOIN, GROUP BY, HAVING and other advanced query features that are usually only provided by SQL can even support subqueries.

5. Support advanced object-oriented features

JPA can support advanced object-oriented features, such as inheritance between classes, polymorphism and inheritance between classes For complex relationships, this support allows developers to maximize the use of object-oriented models to design enterprise applications without having to deal with the persistence of these features in relational databases.

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