Table of contents
1.
Introduction
2.
JPA Versions
3.
JPA and Hibernate
4.
What is Java ORM?
5.
JPA with NoSQL
6.
Configuring the Java ORM layer
7.
Data persistence in Java
8.
Data persistence with JDBC
8.1.
1. Load the JDBC driver
8.2.
2. Establish a database connection
8.3.
3. Create & execute SQL statements
8.4.
4. Process the results
8.5.
5. Close the resources
9.
Data persistence with JPA
9.1.
1. Define entity classes
9.2.
2. Configure the persistence unit
9.3.
3. Obtain an EntityManager
9.4.
4. Perform database operations
9.5.
5. Query the database
9.6.
6. Close the EntityManager
10.
Metadata annotations in JPA.
10.1.
1. `@Entity`
10.2.
2. `@Table`
10.3.
3. `@Id`
10.4.
4. `@GeneratedValue`
10.5.
5. `@Column`
10.6.
6. `@OneToOne`, `@OneToMany`, `@ManyToOne`, `@ManyToMany`
10.7.
7. `@JoinColumn`
10.8.
8. `@Enumerated`
10.9.
9. `@Temporal`
11.
Configuring JPA
11.1.
1. Create a persistence.xml file
11.2.
2. Define the persistence unit
11.3.
3. Specify the JPA provider:
11.4.
4. Configure the database connection:
11.5.
5. Configure JPA properties:
11.6.
6. List the entity classes:
12.
Frequently Asked Questions
12.1.
What is the difference between JPA and Hibernate?
12.2.
Can JPA handle inheritance mapping?
12.3.
How can I define relationships between entities in JPA?
13.
Conclusion
Last Updated: Jul 20, 2024
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JPA Java

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Introduction

Java Persistence API, or JPA, is a way to manage data in Java applications that helps developers work with databases more easily. Instead of writing complex SQL queries, you can use simple Java objects to store & retrieve data, with JPA acting as a bridge between the Java application & the database. 

JPA Java

In this article, we will discuss the key features of JPA, including different versions, how it works with Hibernate, the benefits of using an Object-Relational Mapping (ORM) tool, setting up JPA in your Java project, & working with different databases, including NoSQL. 

JPA Versions

JPA has evolved over time, with multiple versions released to add new features & improve performance. The most widely used versions are JPA 1.0, JPA 2.0, JPA 2.1, & JPA 2.2.

JPA 1.0, released in 2006, laid the foundation for object-relational mapping in Java. It introduced basic annotations like @Entity, @Id, & @Table to define how Java classes map to database tables.

JPA 2.0, released in 2009, added more advanced features such as criteria queries, metamodel API, & support for embedded objects. This version made it easier to write complex queries & work with object hierarchies.

JPA 2.1, released in 2013, focused on improving performance & scalability. It introduced features like stored procedures, schema generation, & entity graphs to optimize database access.

The latest version, JPA 2.2, was released in 2017. It added support for Java 8 features like Date & Time API, Stream API, & repeatable annotations. It also introduced better caching support & compatibility with Java EE 8.

JPA and Hibernate

JPA is a specification that defines how object-relational mapping should be done in Java. It provides a set of interfaces & annotations that can be used to map Java objects to database tables. However, JPA itself is not an implementation. That's where Hibernate comes in.

Hibernate is one of the most popular implementations of JPA. It is an open-source ORM framework that provides a complete solution for mapping Java classes to database tables. Hibernate follows the JPA specification & provides additional features & optimizations on top of it.

When you use Hibernate as your JPA implementation, you get access to all the features defined in the JPA specification. You can use annotations like @Entity, @Id, & @Table to define your mappings. Hibernate takes care of generating the necessary SQL queries to interact with the database.

Hibernate also provides its own query language called Hibernate Query Language (HQL), which is similar to SQL but works with Java objects instead of database tables. You can use HQL to write complex queries & retrieve data from the database.

One of the key benefits of using Hibernate with JPA is that it abstracts away the database-specific details. You can switch between different databases (e.g., MySQL, PostgreSQL, Oracle) without having to change your Java code. Hibernate takes care of generating the appropriate SQL queries based on the configured database dialect.

What is Java ORM?

Object-Relational Mapping (ORM) is a technique that allows you to map Java objects to database tables. It bridges the gap between the object-oriented world of Java & the relational world of databases.

In traditional JDBC programming, you need to write a lot of boilerplate code to interact with the database. You have to create database connections, execute SQL queries, & map the result sets to Java objects manually. This can be time-consuming & error-prone, especially for complex object hierarchies.

ORM frameworks like Hibernate simplify this process by providing a mapping layer between Java objects & database tables. You define the mappings using annotations or XML configuration files. The ORM framework takes care of generating the necessary SQL queries & mapping the results back to Java objects.

Here's a simple example of how you can define a Java class using JPA annotations:

@Entity
@Table(name = "employees")
public class Employee {
    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private Long id;
    @Column(name = "first_name")
    private String firstName;
    @Column(name = "last_name")
    private String lastName;
    // Getters and setters
}


In this example, the `Employee` class is annotated with `@Entity`, indicating that it is a persistent entity. The `@Table` annotation specifies the name of the database table. The `id` field is annotated with `@Id`, making it the primary key. The `firstName` & `lastName` fields are mapped to the corresponding columns in the table using the `@Column` annotation.

With ORM, you can perform database operations using Java objects. For example, to persist a new employee to the database, you can simply create an instance of the `Employee` class, set its properties, & save it using the `EntityManager`:

Employee employee = new Employee();
employee.setFirstName("Rahul");
employee.setLastName("Sharma");
EntityManager entityManager = entityManagerFactory.createEntityManager();
entityManager.getTransaction().begin();
entityManager.persist(employee);
entityManager.getTransaction().commit();


The ORM framework takes care of generating the appropriate SQL `INSERT` statement & executing it to persist the employee to the database.

ORM frameworks like Hibernate also provide features like lazy loading, caching, & cascading, which help optimize performance & simplify the management of object relationships.

JPA with NoSQL

While JPA is primarily designed for working with relational databases, it can also be used with NoSQL databases. NoSQL databases, such as MongoDB, Cassandra, & Couchbase, provide a different approach to data storage & retrieval compared to traditional relational databases.

JPA has evolved to support NoSQL databases through the use of custom persistence providers. These providers extend the JPA specification to work with specific NoSQL databases.

One popular JPA provider for NoSQL databases is Hibernate OGM (Object/Grid Mapper). Hibernate OGM allows you to use JPA annotations & APIs to map Java objects to NoSQL databases. It supports a wide range of NoSQL databases, including MongoDB, Cassandra, Neo4j, & more.

Let’s see an example of how you can configure JPA to work with MongoDB using Hibernate OGM:

Properties properties = new Properties();
properties.put("hibernate.ogm.datastore.provider", "mongodb");
properties.put("hibernate.ogm.datastore.database", "mydb");
properties.put("hibernate.ogm.datastore.host", "localhost");
properties.put("hibernate.ogm.datastore.port", "27017");

EntityManagerFactory emf = Persistence.createEntityManagerFactory("myPersistenceUnit", properties);


In this example, we create a `Properties` object & set the necessary configuration properties for Hibernate OGM. We specify the datastore provider as "mongodb", the database name, host, & port. Then, we create an `EntityManagerFactory` using the `Persistence.createEntityManagerFactory()` method, passing in the persistence unit name & the configuration properties.

Once configured, you can use the standard JPA annotations & APIs to map your Java objects to MongoDB collections. For example:

@Entity
@Table(name = "products")
public class Product {
    @Id
    private String id;
    private String name;
    private double price;
    // Getters and setters
}


In this example, the `Product` class is annotated with `@Entity`, indicating that it is a persistent entity. The `@Table` annotation specifies the name of the MongoDB collection. The `id` field is annotated with `@Id`, making it the primary key.

You can then use the `EntityManager` to perform database operations, just like with a relational database:

Product product = new Product();
product.setId("1");
product.setName("Laptop");
product.setPrice(999.99);
EntityManager entityManager = emf.createEntityManager();
entityManager.getTransaction().begin();
entityManager.persist(product);
entityManager.getTransaction().commit();


Hibernate OGM takes care of mapping the Java object to the appropriate MongoDB document & persisting it to the database.

Using JPA with NoSQL databases allows you to leverage the familiar JPA programming model while working with non-relational data stores. It provides a level of abstraction & portability across different NoSQL databases.

Configuring the Java ORM layer

To use JPA in your Java application, you need to configure the ORM layer. This involves setting up the necessary dependencies, configuring the persistence unit, & specifying the database connection details.

First, you need to add the required JPA dependencies to your project. If you're using Maven, you can add the following dependencies to your `pom.xml` file:

<dependencies>
    <dependency>
        <groupId>org.hibernate</groupId>
        <artifactId>hibernate-core</artifactId>
        <version>5.5.7.Final</version>
    </dependency>
    <dependency>
        <groupId>org.hibernate</groupId>
        <artifactId>hibernate-entitymanager</artifactId>
        <version>5.5.7.Final</version>
    </dependency>
    <dependency>
        <groupId>mysql</groupId>
        <artifactId>mysql-connector-java</artifactId>
        <version>8.0.26</version>
    </dependency>
</dependencies>


In this example, we're using Hibernate as the JPA implementation & MySQL as the database. You can adjust the dependencies based on your specific requirements.

Next, you need to create a persistence unit configuration file named `persistence.xml` in the `META-INF` directory of your project. Here's an example configuration:

<?xml version="1.0" encoding="UTF-8"?>
<persistence xmlns="http://xmlns.jcp.org/xml/ns/persistence"
             xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
             xsi:schemaLocation="http://xmlns.jcp.org/xml/ns/persistence
                                 http://xmlns.jcp.org/xml/ns/persistence/persistence_2_2.xsd"
             version="2.2">
    <persistence-unit name="myPersistenceUnit">
        <provider>org.hibernate.jpa.HibernatePersistenceProvider</provider>
        <properties>
            <property name="javax.persistence.jdbc.url" value="jdbc:mysql://localhost:3306/mydatabase"/>
            <property name="javax.persistence.jdbc.driver" value="com.mysql.cj.jdbc.Driver"/>
            <property name="javax.persistence.jdbc.user" value="root"/>
            <property name="javax.persistence.jdbc.password" value="password"/>
            <property name="hibernate.dialect" value="org.hibernate.dialect.MySQL8Dialect"/>
            <property name="hibernate.show_sql" value="true"/>
            <property name="hibernate.hbm2ddl.auto" value="update"/>
        </properties>
    </persistence-unit>
</persistence>


In this configuration, we define a persistence unit named "myPersistenceUnit". We specify Hibernate as the persistence provider using the `<provider>` element. Inside the `<properties>` section, we configure the database connection details, such as the JDBC URL, driver class, username, & password. We also set Hibernate-specific properties like the dialect, SQL logging, & database schema generation strategy.

Finally, you can create an `EntityManagerFactory` using the persistence unit configuration:

EntityManagerFactory emf = Persistence.createEntityManagerFactory("myPersistenceUnit");


The `EntityManagerFactory` is responsible for creating `EntityManager` instances, which you can use to perform database operations.

With the ORM layer configured, you can start defining your entity classes using JPA annotations & use the `EntityManager` to persist, retrieve, update, & delete objects from the database.

Data persistence in Java

Data persistence refers to the process of storing & retrieving data from a persistent storage medium, such as a database. In Java, there are different approaches to achieve data persistence, each with its own advantages & use cases.

One common approach is using the Java Database Connectivity (JDBC) API. JDBC provides a low-level interface for interacting with relational databases. It allows you to establish database connections, execute SQL queries, & process result sets. With JDBC, you have full control over the database interactions, but it requires writing a lot of boilerplate code & manual mapping between result sets & Java objects.

Another approach is using Object-Relational Mapping (ORM) frameworks like Java Persistence API (JPA) & Hibernate. ORM frameworks provide a higher-level abstraction over JDBC & simplify the process of mapping Java objects to database tables. They use annotations or XML configuration to define the mapping between entities & tables. ORM frameworks take care of generating the necessary SQL queries & provide features like lazy loading, caching, & object-relational mapping.

The choice between JDBC & ORM depends on the complexity of your application, performance requirements, & the level of control you need over the database interactions. JDBC is suitable for low-level database access & when you need fine-grained control over the SQL queries. ORM frameworks like JPA & Hibernate are preferred when you want to work with objects & have a higher-level abstraction over the database.

In addition to relational databases, Java also supports data persistence with NoSQL databases. NoSQL databases, such as MongoDB, Cassandra, & Redis, provide alternative data models & are designed for scalability & high-performance use cases. Java has various libraries & frameworks, such as Spring Data, Morphia, & Redisson, that simplify the integration with NoSQL databases.

When choosing a data persistence approach, consider factors like the type of data you're dealing with, scalability requirements, performance needs, & the complexity of your application. Relational databases with JDBC or ORM are suitable for structured data & complex relationships, while NoSQL databases are often used for handling large amounts of unstructured or semi-structured data.

Regardless of the approach you choose, it's important to follow best practices for data persistence. This includes proper connection management, transaction handling, error handling, & security considerations. Proper design & optimization of your data access layer can significantly impact the performance & maintainability of your application.

Data persistence with JDBC

JDBC (Java Database Connectivity) is a standard API provided by Java for interacting with relational databases. It allows you to establish a connection to a database, execute SQL queries, & retrieve results.

To use JDBC, you need to follow these basic steps:

1. Load the JDBC driver

You need to load the appropriate JDBC driver for your database. For example, if you're using MySQL, you would load the MySQL Connector/J driver.

try {
    Class.forName("com.mysql.cj.jdbc.Driver");
} catch (ClassNotFoundException e) {
    e.printStackTrace();
}

2. Establish a database connection

Create a connection to the database using the `DriverManager` class & provide the necessary connection details.

String url = "jdbc:mysql://localhost:3306/mydatabase";
String username = "root";
String password = "password";
try (Connection connection = DriverManager.getConnection(url, username, password)) {
    // Perform database operations
} catch (SQLException e) {
    e.printStackTrace();
}

3. Create & execute SQL statements

Use the `Connection` object to create `Statement` or `PreparedStatement` objects. Execute SQL queries using methods like `executeQuery()` for `SELECT` statements & `executeUpdate()` for `INSERT`, `UPDATE`, or `DELETE` statements.

String sql = "SELECT * FROM employees";
try (Statement statement = connection.createStatement();
     ResultSet resultSet = statement.executeQuery(sql)) {
    
    while (resultSet.next()) {
        int id = resultSet.getInt("id");
        String name = resultSet.getString("name");
        // Process the retrieved data
    }
} catch (SQLException e) {
    e.printStackTrace();
}

4. Process the results

If the SQL query returns a result set (e.g., `SELECT` statement), you can iterate over the `ResultSet` object & retrieve the data using getter methods like `getInt()`, `getString()`, etc.

5. Close the resources

It's important to close the JDBC resources (Connection, Statement, ResultSet) when you're done to release the database connections & avoid resource leaks. You can use try-with-resources statements to automatically close the resources.

JDBC provides a low-level, flexible approach to interact with relational databases. However, it requires writing a lot of boilerplate code for mapping result sets to Java objects & handling database-specific details.

To simplify database interactions & reduce boilerplate code, many developers choose to use higher-level frameworks & libraries built on top of JDBC, such as Spring JDBC, Apache DBUtils, or JOOQ. These frameworks provide abstractions & utilities that make working with JDBC easier & more productive.

Data persistence with JPA

JPA (Java Persistence API) is a standard specification for object-relational mapping (ORM) in Java. It provides a higher-level abstraction over JDBC & simplifies the process of persisting & retrieving objects from a relational database.

To use JPA, you need to follow these basic steps:

1. Define entity classes

Create Java classes that represent the entities in your database. Annotate them with JPA annotations like `@Entity`, `@Table`, `@Id`, `@Column`, etc., to define the mapping between the class & the database table.

@Entity
@Table(name = "employees")
public class Employee {
    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private Long id;
    @Column(name = "first_name")
    private String firstName;
    @Column(name = "last_name")
    private String lastName;
    // Getters and setters
}

2. Configure the persistence unit

Create a `persistence.xml` file in the `META-INF` directory of your project. Configure the persistence unit by specifying the database connection details, JPA provider (e.g., Hibernate), & other properties.

<persistence xmlns="http://xmlns.jcp.org/xml/ns/persistence"
             xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
             xsi:schemaLocation="http://xmlns.jcp.org/xml/ns/persistence
                                 http://xmlns.jcp.org/xml/ns/persistence/persistence_2_2.xsd"
             version="2.2">

    <persistence-unit name="myPersistenceUnit">
        <!-- Configuration properties -->
    </persistence-unit>
</persistence>

3. Obtain an EntityManager

Use the `EntityManagerFactory` to create an `EntityManager` instance. The `EntityManager` is responsible for managing the persistence context & interacting with the database.

EntityManagerFactory emf = Persistence.createEntityManagerFactory("myPersistenceUnit");
EntityManager entityManager = emf.createEntityManager();

4. Perform database operations

Use the `EntityManager` to perform database operations such as persisting, retrieving, updating, & deleting objects. JPA provides methods like `persist()`, `find()`, `merge()`, & `remove()` for these operations.

Employee employee = new Employee();
employee.setFirstName("Rahul");
employee.setLastName("Sharma");

entityManager.getTransaction().begin();
entityManager.persist(employee);
entityManager.getTransaction().commit();

5. Query the database

JPA provides a query language called JPQL (Java Persistence Query Language) for querying the database. You can create typed or untyped queries using the `EntityManager` & retrieve the results.

String jpql = "SELECT e FROM Employee e WHERE e.firstName = :firstName";
TypedQuery<Employee> query = entityManager.createQuery(jpql, Employee.class);
query.setParameter("firstName", "Rahul");
List<Employee> employees = query.getResultList();

6. Close the EntityManager

After performing the database operations, close the `EntityManager` to release the resources.

entityManager.close();
emf.close();


JPA provides a higher-level, object-oriented approach to data persistence compared to JDBC. It abstracts away the low-level details & provides features like object-relational mapping, query language, & transaction management.

JPA is an API specification, & there are various implementations available, such as Hibernate, EclipseLink, & OpenJPA. These implementations provide additional features & optimizations on top of the JPA specification.

Metadata annotations in JPA.

JPA uses annotations to provide metadata about the mapping between Java classes & database tables. These annotations are used to define the object-relational mapping & specify how the entities should be persisted in the database.

Let’s see some commonly used JPA annotations:

1. `@Entity`

Marks a Java class as an entity, indicating that it should be mapped to a database table.

@Entity
public class Employee {
    // Class members
}

2. `@Table`

Specifies the name of the database table to which the entity is mapped. If not specified, the default table name is the same as the class name.

@Entity
@Table(name = "employees")
public class Employee {
    // Class members
}

3. `@Id`

Marks a field or property as the primary key of the entity.

@Id
@GeneratedValue(strategy = GenerationType.IDENTITY)
private Long id;

4. `@GeneratedValue`

Specifies the strategy for generating the primary key value. Common strategies include `IDENTITY`, `SEQUENCE`, & `AUTO`.

5. `@Column`

Maps a field or property to a database column. You can specify the column name, length, nullable constraint, & other attributes.

@Column(name = "first_name", length = 50, nullable = false)
private String firstName;

6. `@OneToOne`, `@OneToMany`, `@ManyToOne`, `@ManyToMany`

Define the relationship between entities. These annotations specify the cardinality & mapping of the relationships.

@OneToMany(mappedBy = "employee")
private List<Address> addresses;

7. `@JoinColumn`

Specifies the joining column for a relationship when the foreign key is in the same table as the referencing entity.

@ManyToOne
@JoinColumn(name = "department_id")
private Department department;

8. `@Enumerated`

Specifies how an enumerated type should be persisted in the database. It can be stored as an ordinal value or as a string representation.

@Enumerated(EnumType.STRING)
private EmploymentStatus status;

9. `@Temporal`

Specifies the temporal type of a date or time field. It can be `DATE`, `TIME`, or `TIMESTAMP`.

@Temporal(TemporalType.DATE)
private Date joinDate;


These are just a few examples of the annotations available in JPA. There are many more annotations for handling inheritance, embeddable types, transient fields, lazy loading, & other mapping scenarios.

By using these annotations, you can define the mapping metadata directly in the Java code, making it easier to understand & maintain the object-relational mapping.

JPA annotations eliminate the need for separate XML configuration files & provide a more intuitive & readable way to define the mapping between Java objects & database tables.

Configuring JPA

To use JPA in your Java application, you need to configure it properly. The configuration involves setting up the persistence unit, specifying the database connection details, & configuring other JPA properties.

Here are the steps to configure JPA:

1. Create a persistence.xml file

   - Create a file named `persistence.xml` in the `META-INF` directory of your project.

   - This file contains the configuration for the persistence unit & the JPA properties.

2. Define the persistence unit

   - Inside the `persistence.xml` file, define a `<persistence-unit>` element with a unique name.

   - Specify the transaction type (`JTA` or `RESOURCE_LOCAL`) based on your application's requirements.

<persistence xmlns="http://xmlns.jcp.org/xml/ns/persistence"
             xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
             xsi:schemaLocation="http://xmlns.jcp.org/xml/ns/persistence
                                 http://xmlns.jcp.org/xml/ns/persistence/persistence_2_2.xsd"
             version="2.2">

    <persistence-unit name="myPersistenceUnit" transaction-type="RESOURCE_LOCAL">
        <!-- Configuration properties -->
    </persistence-unit>
</persistence>

3. Specify the JPA provider:

   - Inside the `<persistence-unit>` element, specify the JPA provider using the `<provider>` element.

   - Common JPA providers include Hibernate, EclipseLink, & OpenJPA.

<provider>org.hibernate.jpa.HibernatePersistenceProvider</provider>

4. Configure the database connection:

   - Specify the database connection details using the appropriate properties.

   - Common properties include `javax.persistence.jdbc.url`, `javax.persistence.jdbc.driver`, `javax.persistence.jdbc.user`, & `javax.persistence.jdbc.password`.

<properties>
    <property name="javax.persistence.jdbc.url" value="jdbc:mysql://localhost:3306/mydatabase"/>
    <property name="javax.persistence.jdbc.driver" value="com.mysql.cj.jdbc.Driver"/>
    <property name="javax.persistence.jdbc.user" value="root"/>
    <property name="javax.persistence.jdbc.password" value="password"/>
</properties>

5. Configure JPA properties:

   - Set any additional JPA properties based on your requirements.

   - Common properties include `hibernate.dialect`, `hibernate.show_sql`, & `hibernate.hbm2ddl.auto`.

<property name="hibernate.dialect" value="org.hibernate.dialect.MySQL8Dialect"/>
<property name="hibernate.show_sql" value="true"/>
<property name="hibernate.hbm2ddl.auto" value="update"/>

6. List the entity classes:

   - If you want to explicitly list the entity classes, you can use the `<class>` element inside the `<persistence-unit>`.

   - Alternatively, you can use package scanning by specifying the package name using the `<exclude-unlisted-classes>` element.

<class>com.example.Employee</class>
<class>com.example.Department</class>


or

<exclude-unlisted-classes>false</exclude-unlisted-classes>


By configuring JPA using the `persistence.xml` file, you provide the necessary information for the JPA provider to establish a connection to the database & manage the persistence of your entities.

Once the configuration is in place, you can obtain an `EntityManagerFactory` using the `Persistence.createEntityManagerFactory()` method & start using JPA in your application.

Frequently Asked Questions

What is the difference between JPA and Hibernate?

JPA is a specification that defines a standard API for object-relational mapping in Java. Hibernate is one of the most popular implementations of the JPA specification, providing additional features & optimizations on top of the standard API.

Can JPA handle inheritance mapping?

Yes, JPA supports inheritance mapping. It provides different strategies for mapping inheritance hierarchies to database tables, such as single table, joined table, & table per class. You can use annotations like @Inheritance & @DiscriminatorColumn to define the inheritance mapping.

How can I define relationships between entities in JPA?

JPA provides annotations to define relationships between entities, such as @OneToOne, @OneToMany, @ManyToOne, & @ManyToMany. You can use these annotations on the entity fields or properties to specify the cardinality & mapping of the relationships. Additionally, you can use annotations like @JoinColumn & @JoinTable to configure the joining columns & tables for the relationships.

Conclusion

In this article, we talked about the Java Persistence API (JPA) & its role in simplifying data persistence in Java applications. We learned about the different versions of JPA, its integration with Hibernate, & the benefits of using an Object-Relational Mapping (ORM) tool. We also discussed how to configure JPA in a Java project & work with various databases, including NoSQL. JPA provides a standard & efficient way to map Java objects to database tables, reducing the boilerplate code & improving productivity. 

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