Spring Boot JpaRepository 示例

Spring Boot建立在 Spring 之上，包含 Spring 的所有功能。由于其快速的生產(chǎn)就緒環(huán)境，使開發(fā)人員能夠直接專注于邏輯，而不必費(fèi)力配置和設(shè)置，因此如今它正成為開發(fā)人員的最愛。Spring Boot 是一個(gè)基于微服務(wù)的框架，在其中創(chuàng)建生產(chǎn)就緒的應(yīng)用程序只需很少的時(shí)間。以下是 Spring Boot 的一些功能：

• 它可以避免 Spring 中繁重的 XML 配置。
• 它提供了 REST 端點(diǎn)的輕松維護(hù)和創(chuàng)建。
• 它包括一個(gè)嵌入式的 Tomcat 服務(wù)器。
• 部署很簡單，war和jar文件可以輕松地部署在Tomcat服務(wù)器中。

有關(guān)更多信息，請參閱本文：Spring Boot 簡介。在本文中，我們將討論如何使用JpaRepository來管理 Spring Boot 應(yīng)用程序中的數(shù)據(jù)。

Jpa存儲庫

JpaRepository 是 Repository 的一個(gè)JPA（Java 持久性 API）特定擴(kuò)展。它包含CrudRepository 和 PagingAndSortingRepository的完整 API?。因此，它包含用于基本 CRUD 操作的 API 以及用于分頁和排序的 API。

句法：

public interface JpaRepository<T,ID> 
extends PagingAndSortingRepository<T,ID>, QueryByExampleExecutor<T>  

這里：

• T：存儲庫管理的域類型（通常是實(shí)體/模型類名）
• ID：存儲庫管理的實(shí)體的 id 類型（通常是在實(shí)體/模型類中創(chuàng)建的 @Id 的包裝類）

插圖：

public interface DepartmentRepository extends JpaRepository<Department, Long> {}

方法

JpaRepository 中的一些最重要的方法如下

方法 1：saveAll()：

保存所有給定的實(shí)體。

句法：

<S extends T> List<S> saveAll(Iterable<S> entities)

參數(shù)：實(shí)體，注意它們不能為空，也不能包含空。

返回類型：已保存的實(shí)體；永遠(yuǎn)不會為空。返回的 Iterable 將與作為參數(shù)傳遞的 Iterable 具有相同的大小。

拋出異常：如果給定的實(shí)體或其某個(gè)實(shí)體為空，則會拋出IllegalArgumentException 。

方法 2：getById()：

返回具有給定標(biāo)識符的實(shí)體的引用。根據(jù) JPA 持久性提供程序的實(shí)現(xiàn)方式，這很可能始終返回一個(gè)實(shí)例并在首次訪問時(shí)拋出 EntityNotFoundException。其中一些會立即拒絕無效標(biāo)識符。

句法：

T getById(ID id)

參數(shù)：id – 不能為空。

返回類型：對具有給定標(biāo)識符的實(shí)體的引用。

方法 3：flush()：

刷新數(shù)據(jù)庫中所有待處理的更改。

句法：

void flush()

方法 4：saveAndFlush()：

保存實(shí)體并立即刷新更改。

句法：

<S extends T> S saveAndFlush(S entity)

參數(shù)：要保存的實(shí)體。不能為空。

返回類型：已保存的實(shí)體

方法 5：deleteAllInBatch()：

批量刪除給定實(shí)體，這意味著它將創(chuàng)建單個(gè)查詢。此類操作會導(dǎo)致 JPA 一級緩存和數(shù)據(jù)庫不同步。在調(diào)用此方法之前，請考慮刷新 EntityManager。

句法：

 void deleteAllInBatch(Iterable<T> entities)

參數(shù)：要?jiǎng)h除的實(shí)體，不能為空。

實(shí)現(xiàn)：

讓我們考慮一個(gè)使用 JpaRepository 管理 Department 實(shí)體的 Spring Boot 應(yīng)用程序。數(shù)據(jù)保存在 H2 數(shù)據(jù)庫中。我們使用 RESTful 控制器。

步驟1：使用IntelliJ IDEA創(chuàng)建Spring Boot項(xiàng)目，創(chuàng)建一個(gè)Spring Boot項(xiàng)目。

第 2 步：添加以下依賴項(xiàng)

• Spring Web
• H2 Database
• Lombok
• Spring Data JPA

示例：這是pom.xml文件的完整代碼。

<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0"
? ? ? ? ?xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
? ? ? ? ?xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
? ??
? ? <!-- Model version -->
? ? <modelVersion>4.0.0</modelVersion>
? ??
? ? <!-- Parent configuration for Spring Boot -->
? ? <parent>
? ? ? ? <groupId>org.springframework.boot</groupId>
? ? ? ? <artifactId>spring-boot-starter-parent</artifactId>
? ? ? ? <version>3.0.0</version>
? ? ? ? <relativePath/> <!-- lookup parent from repository -->
? ? </parent>
? ??
? ? <!-- Project metadata -->
? ? <groupId>com.amiya</groupId>
? ? <artifactId>Spring-Boot-Demo-Project</artifactId>
? ? <version>1.0.0-SNAPSHOT</version>
? ? <name>Spring-Boot-Demo-Project</name>
? ? <description>Demo project for Spring Boot</description>
? ??
? ? <!-- Java version property -->
? ? <properties>
? ? ? ? <java.version>17</java.version>
? ? </properties>
? ??
? ? <!-- Dependencies required for the project -->
? ? <dependencies>
? ? ? ? <!-- Spring Boot Starter Web: To build web applications -->
? ? ? ? <dependency>
? ? ? ? ? ? <groupId>org.springframework.boot</groupId>
? ? ? ? ? ? <artifactId>spring-boot-starter-web</artifactId>
? ? ? ? </dependency>
? ? ? ??
? ? ? ? <!-- Spring Boot Starter Data JPA: To work with JPA for data access -->
? ? ? ? <dependency>
? ? ? ? ? ? <groupId>org.springframework.boot</groupId>
? ? ? ? ? ? <artifactId>spring-boot-starter-data-jpa</artifactId>
? ? ? ? </dependency>
? ? ? ??
? ? ? ? <!-- Spring Boot Starter Validation: For Jakarta EE bean validation -->
? ? ? ? <dependency>
? ? ? ? ? ? <groupId>org.springframework.boot</groupId>
? ? ? ? ? ? <artifactId>spring-boot-starter-validation</artifactId>
? ? ? ? </dependency>
? ? ? ??
? ? ? ? <!-- H2 Database: In-memory database for development and testing -->
? ? ? ? <dependency>
? ? ? ? ? ? <groupId>com.h2database</groupId>
? ? ? ? ? ? <artifactId>h2</artifactId>
? ? ? ? ? ? <scope>runtime</scope>
? ? ? ? </dependency>
? ? ? ??
? ? ? ? <!-- Lombok: To reduce boilerplate code in Java classes -->
? ? ? ? <dependency>
? ? ? ? ? ? <groupId>org.projectlombok</groupId>
? ? ? ? ? ? <artifactId>lombok</artifactId>
? ? ? ? ? ? <optional>true</optional>
? ? ? ? </dependency>
? ? </dependencies>
? ??
? ? <!-- Build configuration -->
? ? <build>
? ? ? ? <plugins>
? ? ? ? ? ? <!-- Spring Boot Maven Plugin: To package the application as a jar/war -->
? ? ? ? ? ? <plugin>
? ? ? ? ? ? ? ? <groupId>org.springframework.boot</groupId>
? ? ? ? ? ? ? ? <artifactId>spring-boot-maven-plugin</artifactId>
? ? ? ? ? ? ? ? <configuration>
? ? ? ? ? ? ? ? ? ? <excludes>
? ? ? ? ? ? ? ? ? ? ? ? <!-- Exclude Lombok from the final build -->
? ? ? ? ? ? ? ? ? ? ? ? <exclude>
? ? ? ? ? ? ? ? ? ? ? ? ? ? <groupId>org.projectlombok</groupId>
? ? ? ? ? ? ? ? ? ? ? ? ? ? <artifactId>lombok</artifactId>
? ? ? ? ? ? ? ? ? ? ? ? </exclude>
? ? ? ? ? ? ? ? ? ? </excludes>
? ? ? ? ? ? ? ? </configuration>
? ? ? ? ? ? </plugin>
? ? ? ? </plugins>
? ? </build>
</project>

步驟 3：創(chuàng)建下面列出的 4 個(gè)包，并在這些包中創(chuàng)建一些類和接口，如下圖所示

• entity
• repository
• service
• controller

注意：

• 綠色圓形圖標(biāo)“I”按鈕是界面
• 藍(lán)色圓形圖標(biāo)“C”按鈕屬于類

步驟 4：實(shí)體包內(nèi)部

在 Department.java 文件中創(chuàng)建一個(gè)簡單的POJO 類。

package com.amiya.springbootdemoproject.entity;

import jakarta.persistence.Entity;
import jakarta.persistence.GeneratedValue;
import jakarta.persistence.GenerationType;
import jakarta.persistence.Id;
import lombok.AllArgsConstructor;
import lombok.Builder;
import lombok.Data;
import lombok.NoArgsConstructor;

/**
?* Represents a Department entity in the application.
?*/
@Entity
@Data // Generates getters, setters, toString, equals, and hashCode methods.
@NoArgsConstructor // Generates a no-args constructor.
@AllArgsConstructor // Generates a constructor with all arguments.
@Builder // Generates a builder pattern for creating instances.
public class Department {
? ? @Id // Specifies the primary key of the entity.
? ? @GeneratedValue(strategy = GenerationType.AUTO) // Auto-generates the primary key value.
? ? private Long departmentId; // Unique identifier for the department.
? ? private String departmentName; // Name of the department.
? ? private String departmentAddress; // Address of the department.
? ? private String departmentCode; // Code representing the department.
}
?

步驟 5：存儲庫包內(nèi)部

創(chuàng)建一個(gè)簡單的接口，并將該接口命名為 DepartmentRepository。正如我們上面討論的那樣，這個(gè)接口將擴(kuò)展JpaRepository 。

例子：

// Java Program to Illustrate DepartmentRepository File

// Importing necessary packages
package com.amiya.springbootdemoproject.repository;

import com.amiya.springbootdemoproject.entity.Department;
import org.springframework.data.jpa.repository.JpaRepository;
import org.springframework.stereotype.Repository;

/**
?* Repository interface for Department entity.
?* Provides CRUD operations and custom query methods through JpaRepository.
?*/
@Repository // Indicates that this interface is a Spring Data repository.
public interface DepartmentRepository extends JpaRepository<Department, Long> {}
?

步驟 6：服務(wù)包內(nèi)

在包內(nèi)創(chuàng)建一個(gè)名為DepartmentService 的接口和一個(gè)名為DepartmentServiceImpl 的類。

示例 1-A：

// Java Program to Demonstrate DepartmentService File

// Importing required packages
package com.amiya.springbootdemoproject.service;

import com.amiya.springbootdemoproject.entity.Department;
import java.util.List;

/**
?* Service interface for Department entity.
?* Defines methods for CRUD operations and additional business logic.
?*/
public interface DepartmentService {
? ? /**
? ? ?* Saves a department entity.
? ? ?* @param department the department to save
? ? ?* @return the saved department
? ? ?*/
? ? Department saveDepartment(Department department);

? ? /**
? ? ?* Fetches the list of all department entities.
? ? ?* @return a list of departments
? ? ?*/
? ? List<Department> fetchDepartmentList();

? ? /**
? ? ?* Updates an existing department entity.
? ? ?* @param department the department with updated information
? ? ?* @param departmentId the ID of the department to update
? ? ?* @return the updated department
? ? ?*/
? ? Department updateDepartment(Department department, Long departmentId);

? ? /**
? ? ?* Deletes a department entity by its ID.
? ? ?* @param departmentId the ID of the department to delete
? ? ?*/
? ? void deleteDepartmentById(Long departmentId);
}
?

示例 1-B：

// Java Program to Illustrate DepartmentServiceImpl File

package com.amiya.springbootdemoproject.service;

import com.amiya.springbootdemoproject.entity.Department;
import com.amiya.springbootdemoproject.repository.DepartmentRepository;
import java.util.List;
import java.util.Objects;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Service;

/**
?* Implementation of DepartmentService.
?* Provides business logic for handling department-related operations.
?*/
@Service // Marks this class as a Spring service component.
public class DepartmentServiceImpl implements DepartmentService {

? ? @Autowired
? ? private DepartmentRepository departmentRepository; // Injects the DepartmentRepository dependency.

? ? @Override
? ? public Department saveDepartment(Department department) {
? ? ? ? // Saves and returns the department entity.
? ? ? ? return departmentRepository.save(department);
? ? }

? ? @Override
? ? public List<Department> fetchDepartmentList() {
? ? ? ? // Retrieves and returns a list of all department entities.
? ? ? ? return (List<Department>) departmentRepository.findAll();
? ? }

? ? @Override
? ? public Department updateDepartment(Department department, Long departmentId) {
? ? ? ? // Finds the existing department by ID.
? ? ? ? Department depDB = departmentRepository.findById(departmentId).get();
? ? ? ??
? ? ? ? // Updates fields if they are not null or empty.
? ? ? ? if (Objects.nonNull(department.getDepartmentName()) && !"".equalsIgnoreCase(department.getDepartmentName())) {
? ? ? ? ? ? depDB.setDepartmentName(department.getDepartmentName());
? ? ? ? }
? ? ? ? if (Objects.nonNull(department.getDepartmentAddress()) && !"".equalsIgnoreCase(department.getDepartmentAddress())) {
? ? ? ? ? ? depDB.setDepartmentAddress(department.getDepartmentAddress());
? ? ? ? }
? ? ? ? if (Objects.nonNull(department.getDepartmentCode()) && !"".equalsIgnoreCase(department.getDepartmentCode())) {
? ? ? ? ? ? depDB.setDepartmentCode(department.getDepartmentCode());
? ? ? ? }
? ? ? ??
? ? ? ? // Saves and returns the updated department entity.
? ? ? ? return departmentRepository.save(depDB);
? ? }

? ? @Override
? ? public void deleteDepartmentById(Long departmentId) {
? ? ? ? // Deletes the department entity by its ID.
? ? ? ? departmentRepository.deleteById(departmentId);
? ? }
}
?

步驟 7：控制器包裝內(nèi)部

在包內(nèi)創(chuàng)建一個(gè)名為DepartmentController 的類。

// Java Program to Demonstrate DepartmentController File

package com.amiya.springbootdemoproject.controller;

import com.amiya.springbootdemoproject.entity.Department;
import com.amiya.springbootdemoproject.service.DepartmentService;
import java.util.List;
import jakarta.validation.Valid;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.web.bind.annotation.*;

/**
?* REST controller for managing Department entities.
?* Handles HTTP requests and routes them to the appropriate service methods.
?*/
@RestController // Marks this class as a RESTful controller.
public class DepartmentController {

? ? @Autowired
? ? private DepartmentService departmentService; // Injects the DepartmentService dependency.

? ? /**
? ? ?* Handles POST requests to save a new department.
? ? ?* @param department the department entity to be saved
? ? ?* @return the saved department entity
? ? ?*/
? ? @PostMapping("/departments")
? ? public Department saveDepartment(@Valid @RequestBody Department department) {
? ? ? ? return departmentService.saveDepartment(department);
? ? }

? ? /**
? ? ?* Handles GET requests to fetch the list of all departments.
? ? ?* @return a list of department entities
? ? ?*/
? ? @GetMapping("/departments")
? ? public List<Department> fetchDepartmentList() {
? ? ? ? return departmentService.fetchDepartmentList();
? ? }

? ? /**
? ? ?* Handles PUT requests to update an existing department.
? ? ?* @param department the department entity with updated information
? ? ?* @param departmentId the ID of the department to be updated
? ? ?* @return the updated department entity
? ? ?*/
? ? @PutMapping("/departments/{id}")
? ? public Department updateDepartment(@RequestBody Department department, @PathVariable("id") Long departmentId) {
? ? ? ? return departmentService.updateDepartment(department, departmentId);
? ? }

? ? /**
? ? ?* Handles DELETE requests to remove a department by ID.
? ? ?* @param departmentId the ID of the department to be deleted
? ? ?* @return a success message
? ? ?*/
? ? @DeleteMapping("/departments/{id}")
? ? public String deleteDepartmentById(@PathVariable("id") Long departmentId) {
? ? ? ? departmentService.deleteDepartmentById(departmentId);
? ? ? ? return "Deleted Successfully";
? ? }
}
?

步驟 8：下面是 application.properties 文件的代碼

server.port=8082# H2 Database
spring.h2.console.enabled=true
spring.datasource.url=jdbc:h2:mem:dcbapp
spring.datasource.driverClassName=org.h2.Driver
spring.datasource.username=sa
spring.datasource.password=password
spring.jpa.database-platform=org.hibernate.dialect.H2Dialect

現(xiàn)在運(yùn)行您的應(yīng)用程序，讓我們在 Postman 中測試端點(diǎn)并參考我們的 H2 數(shù)據(jù)庫。

在 Postman 中測試端點(diǎn)

端點(diǎn) 1：?POST – http://localhost:8082/departments/

端點(diǎn) 2：?GET – http://localhost:8082/departments/

端點(diǎn) 3：?PUT – http://localhost:8082/departments/1

端點(diǎn) 4：刪除 – http://localhost:8082/departments/1

H2數(shù)據(jù)庫如下：