Spring Boot 学习笔记 5 : JPA

1. 在 pom.xml 文件中添加依赖：

   <dependency>
       <groupId>mysqlgroupId>
       <artifactId>mysql-connector-javaartifactId>
       <scope>runtimescope>
   dependency>
   <dependency>
       <groupId>org.springframework.bootgroupId>
       <artifactId>spring-boot-starter-data-jpaartifactId>
   dependency>

   由于使用 HikariCP 连接池，添加下面依赖：

   <dependency>
       <groupId>com.zaxxergroupId>
       <artifactId>HikariCPartifactId>
   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 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：

   

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("[email protected]");
            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。

    定位异常原因可能是数据库中 hibernate_sequence 这张表中 next_val 这列的值重复所导致。