Spring Boot TestEntityManager 教程展示了如何在 JPA 测试中使用 TestEntityManager。 TestEntityManager 提供了 EntityManager 方法的子集，可用于测试以及用于常见测试任务（例如 persist 或 find）的辅助方法。
Spring 是用于创建企业应用的流行 Java 应用框架。 Spring Boot 是 Spring 框架的演进，可帮助您轻松创建独立的，生产级的基于 Spring 的应用。
TestEntityManager
TestEntityManager允许在测试中使用EntityManager。 Spring Repository是EntityManager的抽象； 它使开发人员免受 JPA 底层细节的困扰，并带来了许多便捷的方法。 但是 Spring 允许在应用代码和测试中需要时使用EntityManager。
在我们的测试中，我们可以从应用中注入 DataSource，@ JdbcTemplate，@ EntityManager 或任何 Spring Data 存储库。
Spring TestEntityManager示例
以下应用使用TestEntityManager以测试方法保存了一些城市实体。
pom.xmlsrc├───main│ ├───java│ │ └───com│ │ └───zetcode│ │ │ Application.java│ │ │ MyRunner.java│ │ ├───model│ │ │ City.java│ │ └───repository│ │ CityRepository.java│ └───resources└───test └───java └───com └───zetcode └───repository CityRepositoryTest.java
这是项目结构。
pom.xml
<?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>springboottestentitymanager</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>org.springframework.boot</groupId> <artifactId>spring-boot-starter-test</artifactId> <scope>test</scope> </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>
Maven POM 文件包含 Spring Data JPA，测试和 H2 数据库的依赖项。
com/zetcode/model/City.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。
com/zetcode/repository/CityRepository.java
package com.zetcode.repository;import com.zetcode.model.City;import org.springframework.data.repository.CrudRepository;import org.springframework.stereotype.Repository;import java.util.List;@Repositorypublic interface CityRepository extends CrudRepository<City, Long> { List<City> findByName(String name);}CityRepository包含自定义的findByName()方法。 Spring 检查方法的名称，并从其关键字派生查询。
com/zetcode/MyRunner.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.stereotype.Component;@Componentpublic 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 { logger.info("Saving cities"); cityRepository.save(new City("Bratislava", 432000)); cityRepository.save(new City("Budapest", 1759000)); cityRepository.save(new City("Prague", 1280000)); cityRepository.save(new City("Warsaw", 1748000)); logger.info("Retrieving cities"); var cities = cityRepository.findAll(); cities.forEach(city -> logger.info("{}", city)); }}在MyRunner中，我们使用CityRepository保存和检索实体。 数据存储在内存中的 H2 数据库中。
Note: In Java enterprise applications it is a good practice to define a service layer that works with repositories. For simplicity reasons, we skip the service layer.
com/zetcode/Application.java
package com.zetcode;import org.springframework.boot.SpringApplication;import org.springframework.boot.autoconfigure.SpringBootApplication;@SpringBootApplicationpublic class Application { public static void main(String[] args) { SpringApplication.run(Application.class, args); }}Application设置 Spring Boot 应用。 @SpringBootApplication启用自动配置和组件扫描。
com/zetcode/repository/CityRepositoryTest.java
package com.zetcode.repository;import com.zetcode.model.City;import org.junit.Test;import org.junit.runner.RunWith;import org.springframework.beans.factory.annotation.Autowired;import org.springframework.boot.test.autoconfigure.orm.jpa.DataJpaTest;import org.springframework.boot.test.autoconfigure.orm.jpa.TestEntityManager;import org.springframework.test.context.junit4.SpringRunner;import static org.assertj.core.api.Assertions.assertThat;import static org.junit.Assert.assertEquals;@RunWith(SpringRunner.class)@DataJpaTestpublic class CityRepositoryTest { @Autowired private TestEntityManager entityManager; @Autowired private CityRepository repository; @Test public void testFindByName() { entityManager.persist(new City("Bratislava", 432000)); entityManager.persist(new City("Budapest", 1759000)); entityManager.persist(new City("Prague", 1280000)); entityManager.persist(new City("Warsaw", 1748000)); var cities = repository.findByName("Bratislava"); assertEquals(1, cities.size()); assertThat(cities).extracting(City::getName).containsOnly("Bratislava"); }}在CityRepositoryTest中，我们测试了自定义 JPA 方法。
@Autowiredprivate TestEntityManager entityManager;
我们注入TestEntityManager。
@RunWith(SpringRunner.class)@DataJpaTestpublic class CityRepositoryTest {@DataJpaTest用于测试 JPA 信息库。 它与@RunWith（SpringRunner.class）结合使用。 注解会禁用完全自动配置，并且仅应用与 JPA 测试相关的配置。 默认情况下，用@DataJpaTest 注解的测试使用嵌入式内存数据库。
entityManager.persist(new City("Bratislava", 432000));entityManager.persist(new City("Budapest", 1759000));entityManager.persist(new City("Prague", 1280000));entityManager.persist(new City("Warsaw", 1748000));我们用EntityManager's persist()方法保存了四个城市。
var cities = repository.findByName("Bratislava");assertEquals(1, cities.size());我们测试findByName()方法返回一个城市。
assertThat(cities).extracting(City::getName).containsOnly("Bratislava");在这里，我们测试城市的名称。
$ mvn spring-boot:test
我们运行测试。
在本教程中，我们在测试中使用了TestEntityManager。
