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Introduction to Java Repository

In the Java Spring framework, JPA-based repositories are commonly used. These repositories are crucial in managing database operations and are a part of the Spring Data JPA module. Repositories define a new elegant method of storing, updating, and extracting the data stored from JAVA applications in the backend. All of the CRUD (Create, read, update, and delete) operations can be implemented with the help of a repository interface. JPA is an abbreviation for JAVA Persistence API (Application program interface). As the name suggests, JPA helps in persisting the java objects in relational databases. There are two ways of doing this, and they are:

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Relational tables are mapped to subsystems using map classes.

EntityManager API.

In this article, we will be reading about syntax and the use of JPA repositories for CRUD operations.


Once all the necessary libraries have been imported and linked to Spring, Persistence objects, and Java EE in the classpath of the project, the next step is to create an interface by extending the “JpaRepository” interface. This is an extension of the repository library and contains other repositories like CrudRepository and PagingAndSortingRepository, along with the basic functions of repositories.

Note: chúng tôi should be present in your project to use JPA applications.


import; import org.springframework.stereotype.Repository; import net.guides.springboot.jparepository.model.Employee; @Repository { } private repositoryname RepositoryName; @Override public void run(String…... arguments) throws Exception { TableName("Data1", "Data2", "Data3")); TableName("Data1", "Data2", "Data3")); TableName("Data1", "Data2", "Data3")); TableName("Data1", "Data2", "Data3"));"number of elements in table now: {}", RepositoryName.count()); How does the JPA Repository Work?

These implementations are crucial for enabling persistence in web or desktop applications developed using Java. To have these interfaces working, all the dependent libraries must be loaded in the classpath. Once the interface is created, then functions like “save(),” “count(),” “info(),” “findAll(),” “sort(),” and others are used to accomplish the data query or required data manipulation. We need to have a database set up to insert, update, or delete the values from tables beneath via a java application. Using repositories brings easy handling of data from databases along with secure transactions.

Examples of Java Repository

Implementing a JPA repository is a complex time project for beginners. All linked libraries, JARs, dependencies, server setup, and database setup are prerequisites.

File: pom.xml

Note: Assuming that the database with a table named “user” is already present in the H2 database with two columns, “Id” and “Name.” “Id” is the primary key generated automatically by the system.



package test.controller; import test.model.User import test.repository.UserJpaRespository; import org.springframework.beans.factory.annotation.Autowired; import org.springframework.web.bind.annotation.*; import java.util.List; @RestController @RequestMapping("/users") public class UsersControl { @Autowired private UserJpaRespository userJpaRespository; @GetMapping(value = "/all") return userJpaRespository.findAll(); } @PostMapping(value = "/load") public User load(@RequestBody final User users) {; return userJpaRespository.findByName(users.getName()); } }



package test.model import test.controller; import javax.persistence.Entity; import javax.persistence.Id; import javax.persistence.GeneratedValue; @Entity public class User { private Long id; private String name; @Id @GeneratedValue public Long getId() { return id;} public void setId(Long id) { = id;} public String getName() { return name;} public void setName(String name) { = name;} }



package test.repository; import test.controller; import package.model.User; import; import org.springframework.stereotype.Component; @Component }

package test.implementation; import static; import static org.springframework.test.web.servlet.request.MockMvcRequestBuilders.get; import static; import static org.springframework.test.web.servlet.result.MockMvcResultMatchers.status; import java.util.ArrayList; import java.util.List; import test.controller; import org.junit.Before; import org.junit.*; import org.springframework.beans.factory.annotation.Autowired; import org.springframework.boot.test.autoconfigure.web.servlet.WebMvcTest; import org.springframework.test.context.junit4.SpringRunner; import org.springframework.test.web.servlet.MockMvc; import org.springframework.test.web.servlet.MvcResult; import com.fasterxml.jackson.databind.ObjectMapper; import test.model.user; import com.fasterxml.jackson.databind.ObjectMapper; import test.repository.UserJpaRespository; @RunWith(SpringRunner.class) public class Implementation { private User user; @MockBean private UserJpaRespository userJpaRespository; @Before public void setUp() { user = new User(); user.setId(1l); user.setName("Virat"); } }


Here the value is inserted into the database.


The first file, “UserControl” contains details regarding extracting or storing the values using JPA functions like “@GetMapping()” and “@PostMapping” which require some base files to support it to work. These support files are chúng tôi and

The file “” maintains the structure of the database in the form of Java objects, allowing access to the database using Java persistence objects. To start working on the project, you must generate the “pom.xml” file using the provided source code in Step 1. In the provided output, the “pom.xml” file is responsible for setting up all the dependencies required for the project. Dependencies contain “spring framework” related data and persistence object-related data. chúng tôi file provides the initiation of a JPA repository by extending the built-in library JpaRepository.


JPA repositories are very useful as it provides a generic platform to create queries in the JAVA language but can be used with any database beneath. It reduces the number of code lines by providing elegant functions to accomplish the tasks backed up by libraries. It reduces the use of “boiler plate” code, thus improving the look and speed of execution.

Recommended Articles

This is a guide to Java Repository. Here we discuss an Introduction to Java Repository and How does the JPA Repository Work with code implementation. You may also have a look at the following articles to learn more-

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