Spring Boot JpaRepository 教程 · ZetCode 中文系列教程

# Spring Boot `JpaRepository` 教程 > 原文： [http://zetcode.com/springboot/jparepository/](http://zetcode.com/springboot/jparepository/) SpringBoot `JpaRepository`教程展示了如何使用`JpaRepository`在 Spring Boot 应用中管理数据。 Spring 是流行的 Java 应用框架。 Spring Boot 致力于以最小的努力创建独立的，基于生产级别的基于 Spring 的应用。 ## Spring Data Spring Data 是用于数据访问的基于 Spring 的编程模型。它减少了使用数据库和数据存储所需的代码量。它由几个模块组成。 Spring Data JPA 简化了使用 JPA 技术的 Spring 应用的开发。使用 Spring Data，我们为应用中的每个域实体定义了一个存储库接口。存储库包含用于执行 CRUD 操作，对数据进行排序和分页的方法。 `@Repository`是标记注解，指示基础接口是存储库。通过扩展特定的存储库接口（例如`CrudRepository`，`PagingAndSortingRepository`或`JpaRepository`）来创建存储库。 Spring Data 已与 Spring MVC 控制器进行了高级集成，并提供了从存储库方法名称派生的动态查询。 ## `JpaRepository` `JpaRepository`是`Repository`的 JPA 特定扩展。它包含`CrudRepository`和`PagingAndSortingRepository`的完整 API。因此，它包含用于基本 CRUD 操作的 API，以及用于分页和排序的 API。 ## Spring Boot `JpaRepository` 示例以下 Spring Boot 应用使用`JpaRepository`管理`City`实体。数据保存在 H2 数据库中。该应用是一个控制台程序。 ```java pom.xml src ├───main │ ├───java │ │ └───com │ │ └───zetcode │ │ │ Application.java │ │ │ MyRunner.java │ │ ├───model │ │ │ City.java │ │ └───repository │ │ CityRepository.java │ └───resources │ application.properties └───test └───java ``` 这是项目结构。 `pom.xml` ```java <?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"> <modelVersion>4.0.0</modelVersion> <groupId>com.zetcode</groupId> <artifactId>springbootjparepository</artifactId> <version>1.0-SNAPSHOT</version> <packaging>jar</packaging> <properties> <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding> <maven.compiler.source>11</maven.compiler.source> <maven.compiler.target>11</maven.compiler.target> </properties> <parent> <groupId>org.springframework.boot</groupId> <artifactId>spring-boot-starter-parent</artifactId> <version>2.1.1.RELEASE</version> </parent> <dependencies> <dependency> <groupId>org.springframework.boot</groupId> <artifactId>spring-boot-starter-data-jpa</artifactId> </dependency> <dependency> <groupId>com.h2database</groupId> <artifactId>h2</artifactId> <scope>runtime</scope> </dependency> </dependencies> <build> <plugins> <plugin> <groupId>org.springframework.boot</groupId> <artifactId>spring-boot-maven-plugin</artifactId> </plugin> </plugins> </build> </project> ``` 这是 Maven 构建文件。 `spring-boot-starter-data-jpa`是将 Spring Data JPA 与 Hibernate 结合使用的入门工具。 `resources/application.properties` ```java spring.main.banner-mode=off logging.pattern.console=%clr(%d{yy-MM-dd E HH:mm:ss.SSS}){blue} %clr(%-5p) %clr(%logger{0}){blue} %clr(%m){faint}%n ``` `application.properties`是主要的 Spring Boot 配置文件。使用`spring.main.banner-mode`属性，我们可以关闭 Spring 横幅。 `logging.pattern.console`定义控制台的日志模式。 `com/zetcode/model/City.java` ```java package com.zetcode.model; import java.util.Objects; import javax.persistence.Entity; import javax.persistence.GeneratedValue; import javax.persistence.GenerationType; import javax.persistence.Id; import javax.persistence.Table; @Entity @Table(name = "cities") public class City { @Id @GeneratedValue(strategy = GenerationType.AUTO) private Long id; private String name; private int population; public City() { } public City(String name, int population) { this.name = name; this.population = population; } public Long getId() { return id; } public void setId(Long id) { this.id = id; } public String getName() { return name; } public void setName(String name) { this.name = name; } public int getPopulation() { return population; } public void setPopulation(int population) { this.population = population; } @Override public int hashCode() { int hash = 7; hash = 79 * hash + Objects.hashCode(this.id); hash = 79 * hash + Objects.hashCode(this.name); hash = 79 * hash + this.population; return hash; } @Override public boolean equals(Object obj) { if (this == obj) { return true; } if (obj == null) { return false; } if (getClass() != obj.getClass()) { return false; } final City other = (City) obj; if (this.population != other.population) { return false; } if (!Objects.equals(this.name, other.name)) { return false; } return Objects.equals(this.id, other.id); } @Override public String toString() { var builder = new StringBuilder(); builder.append("City{id=").append(id).append(", name=") .append(name).append(", population=") .append(population).append("}"); return builder.toString(); } } ``` 这是`City`实体。它包含以下属性：`id`，`name`和`population`。 `com/zetcode/repository/CityRepository.java` ```java package com.zetcode.repository; import com.zetcode.model.City; import org.springframework.data.jpa.repository.JpaRepository; import org.springframework.stereotype.Repository; @Repository public interface CityRepository extends JpaRepository<City, Long> { } ``` `CityRepository`从`JpaRepository`延伸。它提供了实体的类型及其主键。 > **注意**：在Java企业应用中，定义与存储库一起使用的服务层是一个好习惯。为简单起见，我们跳过服务层。 `com/zetcode/MyRunner.java` ```java package com.zetcode; import com.zetcode.model.City; import com.zetcode.repository.CityRepository; import org.slf4j.Logger; import org.slf4j.LoggerFactory; import org.springframework.beans.factory.annotation.Autowired; import org.springframework.boot.CommandLineRunner; import org.springframework.data.domain.Sort; import org.springframework.stereotype.Component; @Component public class MyRunner implements CommandLineRunner { private static final Logger logger = LoggerFactory.getLogger(MyRunner.class); @Autowired private CityRepository cityRepository; @Override public void run(String... args) throws Exception { cityRepository.save(new City("Bratislava", 432000)); cityRepository.save(new City("Budapest", 1759000)); cityRepository.save(new City("Prague", 1280000)); cityRepository.save(new City("Warsaw", 1748000)); cityRepository.save(new City("Los Angeles", 3971000)); cityRepository.save(new City("New York", 8550000)); cityRepository.save(new City("Edinburgh", 464000)); logger.info("# of cities: {}", cityRepository.count()); logger.info("All cities unsorted:"); var cities = cityRepository.findAll(); logger.info("{}", cities); logger.info("------------------------"); logger.info("All cities sorted by name in descending order"); var sortedCities = cityRepository.findAll(new Sort(Sort.Direction.DESC, "name")); logger.info("{}", sortedCities); logger.info("------------------------"); logger.info("Deleting all cities"); cityRepository.deleteAllInBatch(); logger.info("# of cities: {}", cityRepository.count()); } } ``` 在`MyRunner`中，我们使用`JpaRepository`的各种方法。 ```java @Autowired private CityRepository cityRepository; ``` 我们将`CityRepository`注入`cityRepository`字段。 ```java cityRepository.save(new City("Bratislava", 432000)); ``` 使用`save()`插入一个新城市。 ```java logger.info("# of cities: {}", cityRepository.count()); ``` 我们用`count()`计算城市数。 ```java logger.info("All cities unsorted:"); var cities = cityRepository.findAll(); logger.info("{}", cities); ``` 使用`findAll()`，我们可以到达所有城市。 ```java logger.info("All cities sorted by name in descending order"); var sortedCities = cityRepository.findAll(new Sort(Sort.Direction.DESC, "name")); logger.info("{}", sortedCities); ``` 通过将`Sort`对象传递给`findAll()`方法，我们得到了所有城市的降序排列。 ```java logger.info("Deleting all cities"); cityRepository.deleteAllInBatch(); ``` 我们使用`deleteAllInBatch()`批量删除所有城市。 `com/zetcode/Application.java` ```java package com.zetcode; import org.springframework.boot.SpringApplication; import org.springframework.boot.autoconfigure.SpringBootApplication; @SpringBootApplication public class Application { public static void main(String[] args) { SpringApplication.run(Application.class, args); } } ``` `Application`设置 Spring Boot 应用。 ```java ... 19-06-25 Tue 12:47:14.593 INFO MyRunner # of cities: 7 19-06-25 Tue 12:47:14.593 INFO MyRunner All cities unsorted: 19-06-25 Tue 12:47:14.652 INFO MyRunner [City{id=1, name=Bratislava, population=432000}, City{id=2, name=Budapest, population=1759000}, City{id=3, name=Prague, population=1280000}, City{id=4, name=Warsaw, population=1748000}, City{id=5, name=Los Angeles, population=3971000}, City{id=6, name=New York, population=8550000}, City{id=7, name=Edinburgh, population=464000}] 19-06-25 Tue 12:47:14.652 INFO MyRunner ------------------------ 19-06-25 Tue 12:47:14.652 INFO MyRunner All cities sorted by name in descending order 19-06-25 Tue 12:47:14.667 INFO MyRunner [City{id=4, name=Warsaw, population=1748000}, City{id=3, name=Prague, population=1280000}, City{id=6, name=New York, population=8550000}, City{id=5, name=Los Angeles, population=3971000}, City{id=7, name=Edinburgh, population=464000}, City{id=2, name=Budapest, population=1759000}, City{id=1, name=Bratislava, population=432000}] 19-06-25 Tue 12:47:14.668 INFO MyRunner ------------------------ 19-06-25 Tue 12:47:14.668 INFO MyRunner Deleting all cities 19-06-25 Tue 12:47:14.681 INFO MyRunner # of cities: 0 ... ``` 这是一个示例输出。在本教程中，我们使用`JpaRepository`管理了应用数据。您可能也对相关教程感兴趣： [Spring Boot `CrudRepository`教程](/springboot/crudrepository/)， [Spring Boot Data JPA `@Query`教程](/springboot/datajpaquery/)， [Spring Boot Data JPA `@NamedQuery`教程](/springboot/datajpanamedquery/)，[Java 教程](/lang/java/)。列出[所有 Spring Boot 教程](/all/#springboot)。