What is Spring Data JPA - Tutorial | Projects | Example

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Spring Data JPA API offers the JpaTemplate class, which helps connect Spring applications with JPA. JPA, short for Java Persistent API, is a standard way of storing objects in enterprise applications. It's a set of rules everyone follows to save and manage data without using complicated entity beans anymore. The following article will discuss in depth about this JPA. 

What is Spring Data JPA?

Before we dive into Spring Data JPA or JPA, let's understand ORM, which stands for Object-Relational Mapping. It's a way of saving Java objects directly into database tables. The object's name becomes the table name, and its fields become columns in that table. Each row in the table represents a record in your application.

The Java Persistence API (JPA) is like a guidebook for saving, reading, and handling data in your Java programs. It helps you connect your Java objects with tables in a database. JPA lays down the rules and tips for creating interfaces that meet these standards. Simply put, JPA is all about following guidelines to use Object-Relational Mapping (ORM) without writing the actual code. Now, the Spring Data JPA project is an element of the Spring framework. Its main aim is to reduce the repetitive code you need to write for accessing data in different databases.

It is important to note that Spring Data JPA isn't a database provider itself; it's more like an extra tool that sits on top of JPA providers like Hibernate. Moreover, it adds an extra layer to simplify data access.

Difference Between JPA and Hibernate

In this data JPA tutorial, we will learn the prime concept, JPA VS Hibernate. The following section will elaborate on the same. 

Application of Spring JPA

Here, we will discuss various advantages of spring data JPA.
 

• POJO Based: Spring lets you use Plain Old Java Objects (POJOs) to build powerful applications without needing complex server software like EJB containers. You can run your app on simpler servers like Tomcat.
• Modular: Spring is organized in a modular way. You only need to focus on the parts of Spring you need for your project and ignore the rest.
• Integration: Instead of inventing new technologies, Spring works well with existing ones like ORM frameworks, logging tools, Java EE, and more. As a result, it makes it easier to use what you're already familiar with.
• Testability: Spring makes it easy to test your code because it separates environment-specific code. You can use JavaBean-style POJOs for dependency injection, which simplifies testing by allowing you to inject test data.
• Web MVC: Spring's web framework is well-designed and a good alternative to other web frameworks like Struts. It's simpler and more efficient.
• Central Exception Handling: Spring provides a helpful feature for handling exceptions consistently across different technologies like JDBC, Hibernate, etc. As a result, it makes error handling easier.
• Lightweight: Spring's Inversion of Control (IoC) containers are lightweight compared to other containers like EJB. However, it is significant for building and running applications on systems with limited resources.

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Spring Framework

Spring is a toolbox for developers. It's lightweight and supports many other tools (frameworks) like Struts, Hibernate, etc. It is a prominent solution provider for technical problems. The Spring framework has different parts called modules. These modules help with things like managing objects (IOC), handling aspects of programming (AOP), accessing databases (DAO), managing application contexts, dealing with ORM (Object-Relational Mapping), and handling web development (WEB MVC). Each module focuses on a specific task to make development more organized. 

Advantages
 

• Predefined Templates: Spring has ready-to-use templates for handling technologies like JDBC, Hibernate, and JPA. In other words, you don't have to write multiple codes for basic tasks like exception handling, creating connections, and managing transactions. For example, with JdbcTemplate, you only need to write the query execution code, saving you from writing lots of JDBC code.
• Loose Coupling: Spring applications are loosely coupled, thanks to dependency injection. In short, components in your application are not tightly bound to each other, making it easier to modify and maintain.
• Easy Testing: Dependency Injection in Spring makes testing simpler. Unlike EJB or Struts, Spring doesn't need a server to run your application, making testing faster and more straightforward.
• Lightweight: Spring is lightweight because it uses Plain Old Java Objects (POJOs) without forcing you to inherit specific classes or implement interfaces. As a result, it makes Spring non-invasive and efficient.
• Fast Development: Spring's Dependency Injection feature and support for various frameworks speed up Java EE application development.
• Powerful Abstraction: Spring provides a powerful abstraction for Java EE specifications like JMS, JDBC, JPA, and JTA. Moreover, it makes it easier to work with these technologies.
• Declarative Support: Spring offers declarative support for tasks like caching, validation, transactions, and formatting, simplifying development and maintenance.

Spring Boot

Spring Boot simplifies the process of creating standalone Spring applications that are ready for production without a lot of hassle. We have a specific way of looking at the Spring platform and other libraries. So you can start your project with minimal effort. Many Spring Boot applications require very little configuration compared to traditional setups. 

Features

Now, we will describe some features of the boot.
 

• Spring Boot allows you to create standalone applications without needing a separate server setup.
• You can directly embed web servers like Tomcat, Jetty, or Undertow into your Spring Boot application, eliminating the need to deploy WAR files separately.
• Data JPA in Spring Boot offers pre-configured dependencies that simplify your build configuration, making it easier to get started with your project.
• Spring Boot automatically configures Spring and other third-party libraries whenever possible, reducing manual setup and configuration.
• It includes production-ready features like metrics, health checks, and externalized configuration, making your application ready for deployment in production environments.
• Spring Boot avoids code generation and eliminates the need for XML configuration files, keeping your development process clean and efficient.

Spring Data JPA Example

Here, we will elaborate on examples of Spring JPA.
 

• Example: This project provides various sample packages demonstrating various ways to use Spring Data JPA. The "simple" package is the most basic setup. It also includes examples running on Virtual Threads.
• Interceptors: This example shows how to enhance repositories using Aspect-Oriented Programming (AOP).
• JPA21: This project shows support for specific features of JPA 2.1, such as stored procedures.
• Multiple-datasources: Here, you can find examples of using Spring JPA with multiple data sources.
• Query-by-example: This project showcases the usage of Query by Example with Spring Data JPA.
• Security: It demonstrates integrating Spring Data JPA Repositories with Spring Security.
• Showcase: This is a refactoring showcase. Additionally, it illustrates how to improve a plain-JPA-based persistence layer by adopting Spring JPA, which significantly reduces implementation code. Refer to the demo.txt file for detailed instructions.
• Vavr: This project exhibits support for Vavr collection types as return types for query methods.

Each of these projects provides insights into specific aspects or features of using Spring Data JPA with Spring Boot and EclipseLink. Moreover, it makes it easier for developers to understand and implement these technologies effectively. 

What Does Spring Data JPA do?

Spring Data JPA is all about using JPA to save data in a database.
 

• One of its best features is that it can automatically create implementations for your repository interfaces while the application is running.
• For instance, let's say you have a CustomerRepository interface with a method like findByLastName(). 
• Normally, in Java, you'd have to write a class that implements CustomerRepository and includes the logic for findByLastName(). 
• But with Spring Data, you don't have to do that. When you run your application, Spring Data JPA takes care of creating the implementation for you. This makes coding much faster and easier.

Conclusion

In summary, Spring Data JPA makes it easier to work with databases in Java programs. It cuts down on repetitive code by automatically creating database access code for you. Moreover, you can define specific ways to query data using simple method signatures. In addition, it also works well with different database technologies like Hibernate. Using data JPA in spring boot saves time, keeps code neat, and makes database tasks smoother for Java developers.

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