Spring Data JPA

     It is used to develop persistence logic in our application.

-> The logic which is responsible to communicate with database is called as Persistence Logic.

-> Already we have JDBC, Spring JDBC, Hibernate, Spring ORM to develop persistence logic.

-> If we use JDBC or Spring JDBC or Hibernate or Spring ORM then we should common logics in all DAO classes to perform CURD Operations.

-> Data JPA simplified persistence logic development by providing pre-defined interfaces with methods.

-> Data JPA provided Repository methods to perform CURD operations.

Note: If we use Data JPA then we don't need to write logic to perform curd operations bcz Data JPA will take care of that.

-> Data JPA provided Repository interfaces to perform CURD operations

1) CrudRepository  (Methods to perform Crud Operations)

2) JpaRepository (Methods to perform Crud Operations + Pagination + Sorting + QBE)

Hibernate Vs Data JPA

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-> In Hibernate we should implement all methods to perform CRUD operations.

-> Data JPA providing predefined methods to perform CRUD Operations.

-> In Hibernate we should boiler plate code (same code in multiple classes).

-> In Data JPA we don't need to write any method because JPA Repositories providing methods for us.

Environment Setup

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1) MySQL Database (Server s/w)

2) MySQL  Workbench (Client s/w)

MySQL DB Properties

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Host : localhost

Port : 3306

Username : admin

Password : Tiger@123

Entity Class

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-> The java class which is mapped with DB table is called as Entity class.

-> To map java class with DB table we will use below annotations.

@Entity : It represents our class as Entity class. (It is mandatory annotation)

@Table : It is used to map our class with DB Table name

Note : @Table is optional if our class name and table is same. If we don't give @Table then it will consider class name as table name.

@Id : It represents variable mapping with primary column in table (It is mandatory annotation).

@Column : It is used to map our class variables with DB table column names

Note: @Column is optional if class variable name and DB table column names are same. If we don't give @Column then it will consider variable name as column name.

Note: For every table we should create one Entity class. Entity class represents  DB operations should be performed in which table.

@Entity

@Table(name="CRICKET_PLAYERS")

public class Player {

@Id

@Column(name="PLAYER_ID")

private Integer playerId;

@Column(name="PLAYER_NAME")

private String playerName;

@Column(name="PLAYER_AGE")

private Integer playerAge;

@Column(name="LOCATION")

private String location;

}

Note: One entity class will be mapped with only one DB table.

Repository Interfaces

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-> JPA provided repository interfaces to perform Curd Operations.

-> For Every DB table we will create one Repository interface by extending JPA Repository

Syntax: 

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public interface PlayerRepository extends CrudRepository<Entity, ID>{  }

Example

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public interface PlayerRepository extends CrudRepository<Player, Serializable>{  }

Note: When our interface extending properties from JPA Repository interfaces then JPA will provide implementation for our interface in Runtime using Proxy Design Pattern.

Datasource properties

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-> Datasource properties represents with which database we want connect

- DB URL

- DB Uname

- DB Pwd

- DB Driver Class

-> We will configure datasource properties in application.properties file or application.yml file.

ORM Properties

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-> Hibernate provided some additional benefits while developing persistence logic.

-> Tables can be created dynamically  using "auto-ddl" property.

-> We are calling JPA methods to perform DB operations. Those methods will generate queries to execute. To print those queries on console we can use 'show-sql' property.

Jpa First Example with Oracle : https://youtu.be/99FG2QEmbJQ

Build First App using Data JPA

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1) Create spring boot application with below dependencies

a) starter-data-jpa

b) mysql-connector

2) Create Entity class using Annotations.

3) Create Repository interface by extending CrudRepository.

4) Configure DataSource & ORM properties in application.properties file.

5) Call Repository methods in start class to perform DB operations.