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Hibernate 랑 JPA가 뭐지?

Hibernate/JPA CRUD (1)

  • What is Hibernate?
  • Benefits of Hibernate?
  • What is JPA?
  • Benefits of JPA?
  • Code Snippets

What is Hibernate?

  • A framework for persisting / saving Java objects in a database
  • www.hibernate.org/orm

    save(), pertsist()?

  • save() - Persist the given transient instance, first assigning a generated identifier. (Or using the current value of the identifier property if the assigned generator is used.) This operation cascades to associated instances if the association is mapped with cascade=”save-update”.
  • persist() - Make a transient instance persistent. This operation cascades to associated instances if the association is mapped with cascade=”persist”. The semantics of this method are defined by JSR-220.
Key save() persist()
Basic It stores object in database It also stores object in database
Return Type It return generated id and return type is serializable It does not return anything. Its void return type.
Transaction Boundaries It can save object within boundaries and outside boundaries It can only save object within the transaction boundaries
Detached Object It will create a new row in the table for detached object It will throw persistence exception for detached object
Supported by It is only supported by Hibernate It is also supported by JPA

Benefits of Hibernate

  • Hibernate handles all of the low-level SQL
  • Minimizes the amount of JDBC code you have to develop
  • Hibernate provides the Object-to-Relational Mapping(ORM)

What is JDBC?

  • JDBC stands for Java Database Connectivity. It is a Java library/specification released by sun microsystems.
  • It enables Java applications to communicate with databases.
  • A JDBC driver is an implementation of the above-mentioned specification i.e. it contains the classes and interfaces to communicate with the database.
  • Using JDBC driver and JDBC API you can write Java applications which will send a request to the database and retrieve the results.
  • I.e. you can connect to the database, create SQL statements, Execute the SQL statements, access and modify the resultant tables using this library.
  • Fundamentally, JDBC is a specification that provides a complete set of interfaces that allows for portable access to an underlying database.
  • Java can be used to write different types of executables, such as −
    • Java Applications
    • Java Applets
    • Java Servlets
    • Java ServerPages (JSPs)
    • Enterprise JavaBeans (EJBs).
  • All of these different executables are able to use a JDBC driver to access a database, and take advantage of the stored data.
  • JDBC provides the same capabilities as ODBC, allowing Java programs to contain database-independent code.

Object-TO-Relational Mapping(ORM)

  • The developer defines mapping between Java class and database table

What is JPA?

  • Jakarta Persistence API(JPA) … previously known as Java Persistence API
    • Standard API for Object-to-Relational-Mapping(ORM)
  • Only a specification
    • Defines a set of interfaces
    • Requires an implementation tobe usable

JPA - Vendor Implementations

What are Benefits of JPA

  • By having a standard API, you are not locked to vendor’s implementation
  • Maintain portable, flexible code by coding to JPA spec(interfaces)
  • Can theoretically switch vendor implementations
    • For example, if Vendor ABC stops supporting their product
    • You could switch to Vendor XYZ without vendor lock in

    • JPA - Vendor Implementations

Saving a Java Object with JPA

Retrieving a Java Object with JPA

Querying for Java Objects

JPA/Hibernate CRUD Apps

  • Create objects
  • Read objects
  • Update objects
  • Delete objects

출처 : luv2code.com , https://www.tutorialspoint.com/difference-between-save-and-persist-in-hibernate, https://www.tutorialspoint.com/what-is-jdbc

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