Java Persistence API (JPA)

What

  • An API specification (ie hibernate is written to)

  • https://en.wikipedia.org/wiki/Java_Persistence_API

  • A persistence entity is a lightweight Java class whose state is typically persisted to a table in a relational database

  • Use of POJOs as entities

    • The pojos will need a zero arg constructor to work

    • It will need an id, which is for the jpa to interact with the database

  • Handles all the JDBC and sql implementations

Advantages

Negatives

  • Add one more thing you have to worry about (if you have a complex database interactions).

  • JPA Have limitations, that is the reason for have a Native interface, you can send Native SQL sentences to database soooooo, you can survive without JPA or any ORM.

  • It’s heavyweight, it creates a complete environment that you almost never need.

  • Forces domain objects to hold database specific knowledge

Linkage

  • Need to override Equals and Hashcode, due to id field in entity

    • We will use the id to determine the object equality

Mappings

  • Linking entity pojos, with each other in code which will be mimicd in the database ie parent child many to many

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