Spring Boot 学习笔记 5 : JPA

时间：2022-01-06 16:07:13

  1. 在 pom.xml 文件中添加依赖：

    <dependency>
    <groupId>mysql</groupId>
    <artifactId>mysql-connector-java</artifactId>
    <scope>runtime</scope>
</dependency>
<dependency>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-starter-data-jpa</artifactId>
</dependency>

    由于使用 HikariCP 连接池，添加下面依赖：

    <dependency>
    <groupId>com.zaxxer</groupId>
    <artifactId>HikariCP</artifactId>
</dependency>

  2. 在 application.yml 文件中添加配置：

    spring:
    datasource:
        driver-class-name: com.mysql.jdbc.Driver
        url: jdbc:mysql://localhost:3306/test?useUnicode=true&characterEncoding=utf8&useSSL=false
        username: root
        password:
        type: com.zaxxer.hikari.HikariDataSource
    jpa:
        database: mysql
        database-platform: MYSQL
        show-sql: true
        format-sql: true
        hibernate:
            ddl-auto: update
            naming:
                strategy: org.springframework.boot.orm.jpa.hibernate.SpringNamingStrategy

  3. 编写配置类：

    import com.mj.wcs.domain.User;
import com.mj.wcs.repository.UserRepository;
import org.springframework.boot.autoconfigure.domain.EntityScan;
import org.springframework.context.annotation.Configuration;
import org.springframework.data.jpa.repository.config.EnableJpaRepositories;
import org.springframework.transaction.annotation.EnableTransactionManagement;

/** * @author smileorsilence * @date 2018/03/28 */
@Configuration
@EntityScan(basePackageClasses = User.class)
@EnableJpaRepositories(basePackageClasses = UserRepository.class)
@EnableTransactionManagement
public class HibernateJpaConfiguration {

}

  4. 编写实体类：

    import com.fasterxml.jackson.annotation.JsonIgnore;
import lombok.Data;

import javax.persistence.*;
import javax.validation.constraints.NotNull;
import java.io.Serializable;

/** * @author smileorsilence */
@Data
@Entity
@Table(name = "user")
public class User implements Serializable {

    @Id
    @GeneratedValue
    private Long id;

    @NotNull
    @Column(name = "username")
    private String username;

    @NotNull
    @JsonIgnore
    @Column(name = "password")
    private String password;

    @Column(name = "email", unique = true)
    private String email;

}

  5. 编写Repository类：

    import com.mj.wcs.domain.User;
import org.springframework.data.jpa.repository.JpaRepository;
import org.springframework.stereotype.Repository;

import java.util.Optional;

/** * @author smileorsilence * @date 2018/03/28 */
@Repository
public interface UserRepository extends JpaRepository<User, Long> {

    Optional<User> findOneByEmail(String email);
}

  6. 编写Service类：

    import com.mj.wcs.domain.User;
import com.mj.wcs.repository.UserRepository;
import com.mj.wcs.service.util.MD5Util;
import lombok.extern.slf4j.Slf4j;
import org.springframework.stereotype.Service;
import org.springframework.transaction.annotation.Transactional;

import javax.inject.Inject;

/** * @author smileorsilence * @date 2018/03/28 */
@Slf4j
@Service
@Transactional
public class UserService {

    @Inject
    private UserRepository userRepository;

    public User saveUser() {
        User user = new User();
        user.setUsername("爱他明月好");
        user.setPassword(MD5Util.encodeByMD5("憔悴也相关"));
        user = userRepository.save(user);
        log.info("saveUser, user : {}", user);
        return user;
    }

}

  7. 编写Controller类：

    import com.mj.wcs.domain.User;
import com.mj.wcs.service.UserService;
import io.swagger.annotations.Api;
import io.swagger.annotations.ApiOperation;
import lombok.extern.slf4j.Slf4j;
import org.springframework.stereotype.Controller;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RequestMethod;
import org.springframework.web.bind.annotation.ResponseBody;

import javax.inject.Inject;

/** * @author smileorsilence * @date 2018/03/28 */
@Api("test")
@Slf4j
@Controller
@RequestMapping("/api")
public class UserController {

    @Inject
    private UserService userService;

    @ApiOperation(value = "测试saveUser方法")
    @RequestMapping(value = "/user/save", method = RequestMethod.GET)
    @ResponseBody
    public User saveUser() {
        log.info("saveUser");
        return userService.saveUser();
    }
}

  8. 运行程序，抛出异常：

    2018-03-28 16:47:37.032 ERROR 1744 --- [           main] o.s.boot.SpringApplication               : Application startup failed

org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'entityManagerFactory' defined in class path resource [org/springframework/boot/autoconfigure/orm/jpa/HibernateJpaAutoConfiguration.class]: Invocation of init method failed; nested exception is org.hibernate.service.spi.ServiceException: Unable to create requested service [org.hibernate.engine.jdbc.env.spi.JdbcEnvironment]
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.initializeBean(AbstractAutowireCapableBeanFactory.java:1628) ~[spring-beans-4.3.10.RELEASE.jar:4.3.10.RELEASE]
    ... ？ common frames omitted
Caused by: org.hibernate.service.spi.ServiceException: Unable to create requested service [org.hibernate.engine.jdbc.env.spi.JdbcEnvironment]
    at org.hibernate.service.internal.AbstractServiceRegistryImpl.createService(AbstractServiceRegistryImpl.java:264) ~[hibernate-core-5.0.12.Final.jar:5.0.12.Final]
    ... ？ common frames omitted
Caused by: org.hibernate.boot.registry.selector.spi.StrategySelectionException: Unable to resolve name [MYSQL] as strategy [org.hibernate.dialect.Dialect]
    at org.hibernate.boot.registry.selector.internal.StrategySelectorImpl.selectStrategyImplementor(StrategySelectorImpl.java:113) ~[hibernate-core-5.0.12.Final.jar:5.0.12.Final]
    ... ？ common frames omitted

    定位异常原因是 application.yml 配置文件中 JPA 配置错误：

    spring:
    jpa:
        database-platform: MYSQL

    修改为如下：

    spring:
    jpa:
        database-platform: org.hibernate.dialect.MySQL5InnoDBDialect

    抛出异常：

    2018-03-28 18:10:00.899 ERROR 7904 --- [           main] o.s.boot.SpringApplication               : Application startup failed

org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'entityManagerFactory' defined in class path resource [org/springframework/boot/autoconfigure/orm/jpa/HibernateJpaAutoConfiguration.class]: Invocation of init method failed; nested exception is javax.persistence.PersistenceException: [PersistenceUnit: default] Unable to build Hibernate SessionFactory
Caused by: javax.persistence.PersistenceException: [PersistenceUnit: default] Unable to build Hibernate SessionFactory
    at org.hibernate.jpa.boot.internal.EntityManagerFactoryBuilderImpl.persistenceException(EntityManagerFactoryBuilderImpl.java:954) ~[hibernate-entitymanager-5.0.12.Final.jar:5.0.12.Final]
    ... ? common frames omitted
Caused by: com.zaxxer.hikari.pool.HikariPool$PoolInitializationException: Failed to initialize pool: Unknown database 'nmgyj-wcs'
    at com.zaxxer.hikari.pool.HikariPool.checkFailFast(HikariPool.java:512) ~[HikariCP-2.5.1.jar:na]
    ... ? common frames omitted
Caused by: com.mysql.jdbc.exceptions.jdbc4.MySQLSyntaxErrorException: Unknown database 'nmgyj-wcs'
    at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method) ~[na:1.8.0_111]
    ... ? common frames omitted

    定位异常原因是 MySQL 数据库中找不到 nmgyj-wcs 数据库错误：

    创建对应数据库即可。

  9. 使用Postman测试：

    Spring Boot 学习笔记 5 : JPA

  10. 编写Junit单元测试：

    import com.mj.wcs.domain.User;
import com.mj.wcs.repository.UserRepository;
import com.mj.wcs.service.util.MD5Util;
import lombok.extern.slf4j.Slf4j;
import org.junit.Test;
import org.junit.runner.RunWith;
import org.springframework.boot.test.context.SpringBootTest;
import org.springframework.test.context.junit4.SpringJUnit4ClassRunner;

import javax.inject.Inject;

/** * @author smileorsilence * @date 2018/03/28 */
@Slf4j
@RunWith(SpringJUnit4ClassRunner.class)
@SpringBootTest
public class UserServiceTest {

    @Inject
    private UserRepository userRepository;

    @Test
    public void saveUser() throws Exception {
        User user = new User();
        user.setUsername("爱他明月好");
        user.setPassword(MD5Util.encodeByMD5("憔悴也相关"));
        user.setEmail("shakespeare@163.com");
        user = userRepository.save(user);
        log.info("saveUser, user : {}", user);
    }

}

    运行测试方法，抛出异常：

    2018-03-28 19:25:49.669  INFO 8324 --- [           main] com.mj.wcs.service.UserServiceTest       : Started UserServiceTest in 15.072 seconds (JVM running for 16.826)
Hibernate: 
    select
        next_val as id_val 
    from
        hibernate_sequence for update

Hibernate: 
    update
        hibernate_sequence 
    set
        next_val= ? 
    where
        next_val=?
Hibernate: 
    insert 
    into
        user
        (email, password, username, id) 
    values
        (?, ?, ?, ?)
2018-03-28 19:25:50.003  WARN 8324 --- [           main] o.h.engine.jdbc.spi.SqlExceptionHelper   : SQL Error: 1062, SQLState: 23000
2018-03-28 19:25:50.003 ERROR 8324 --- [           main] o.h.engine.jdbc.spi.SqlExceptionHelper   : Duplicate entry '1' for key 'PRIMARY'
2018-03-28 19:25:50.006  INFO 8324 --- [           main] o.h.e.j.b.internal.AbstractBatchImpl     : HHH000010: On release of batch it still contained JDBC statements

org.springframework.dao.DataIntegrityViolationException: could not execute statement; SQL [n/a]; constraint [PRIMARY]; nested exception is org.hibernate.exception.ConstraintViolationException: could not execute statement
    ... ? more
Caused by: org.hibernate.exception.ConstraintViolationException: could not execute statement
    ... ? more
Caused by: com.mysql.jdbc.exceptions.jdbc4.MySQLIntegrityConstraintViolationException: Duplicate entry '1' for key 'PRIMARY'
    ... ? more

    定位异常原因可能是 User 实体类中使用 Lombok 提供的 @Data 注解导致 equals() 方法和 hashCode() 方法重写不正确，使用 IDEA 重新生成即可。

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