我有一个带有DateTime列作为主键的表：
USE [idatest]
GO
CREATE TABLE [dbo].[DatesTbl](
[creationDate] [datetime] NOT NULL
CONSTRAINT [PK_DatesTbl] PRIMARY KEY CLUSTERED
(
[creationDate] ASC
))
GO
当我做entityManager.merge时，我得到重复，因为datetime保留3位数代表毫秒，但PK违反，但是hibernet将其转换为datetime2，保留7位数。在Java代码中，我使用的LocaDatetime可以保存10毫秒的数字。
我已经尝试过在 Hibernate MSSQL datetime2 mapping，但无效： Java代码如下所示： pom.xml
<parent>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-parent</artifactId>
<version>2.0.3.RELEASE</version>
</parent>
<groupId>com.example</groupId>
<artifactId>spring-jap-test</artifactId>
<version>1.0-SNAPSHOT</version>
<build>
<plugins>
<plugin>
<groupId>org.apache.maven.plugins</groupId>
<artifactId>maven-compiler-plugin</artifactId>
<configuration>
<source>1.8</source>
<target>1.8</target>
</configuration>
</plugin>
</plugins>
</build>
<dependencies>
<dependency>
<groupId>org.hibernate</groupId>
<artifactId>hibernate-entitymanager</artifactId>
</dependency>
<dependency>
<groupId>com.microsoft.sqlserver</groupId>
<artifactId>mssql-jdbc</artifactId>
<version>7.0.0.jre8</version>
</dependency>
<dependency>
<groupId>org.springframework.data</groupId>
<artifactId>spring-data-jpa</artifactId>
</dependency>
<dependency>
<groupId>org.projectlombok</groupId>
<artifactId>lombok</artifactId>
</dependency>
</dependencies>
DatesTbl类
@Entity
@NoArgsConstructor
@AllArgsConstructor
public class DatesTbl {
@Column(columnDefinition = "DATETIME", nullable = false)
@Id
private LocalDateTime creationDate;
}
主班
@EnableTransactionManagement
public class Main {
public static void main(String[] args) {
ApplicationContext context = new AnnotationConfigApplicationContext(Main.class);
EntityManagerFactory entityManagerFactory = context.getBean(EntityManagerFactory.class);
final EntityManager entityManager = entityManagerFactory.createEntityManager();
final LocalDateTime creationDate = LocalDateTime.of(2018, 12, 26, 8, 10, 40, 340);
entityManager.getTransaction().begin();
final DatesTbl datesTbl = entityManager.merge(new DatesTbl(creationDate));
entityManager.getTransaction().commit();
System.out.println("test");
}
@Bean
@Primary
public DataSource getDataSource() {
SQLServerDataSource ds = null;
try {
ds = new SQLServerDataSource();
ds.setServerName("localhost");
ds.setDatabaseName("idatest");
ds.setIntegratedSecurity(true);
} catch (Exception ex) {
System.out.println(ex.getMessage());
}
return ds;
}
@Bean
public JpaVendorAdapter jpaVendorAdapter() {
HibernateJpaVendorAdapter hibernateJpaVendorAdapter = new HibernateJpaVendorAdapter();
hibernateJpaVendorAdapter.setShowSql(true);
hibernateJpaVendorAdapter.setGenerateDdl(true);
hibernateJpaVendorAdapter.setDatabase(Database.SQL_SERVER);
return hibernateJpaVendorAdapter;
}
@Bean
public LocalContainerEntityManagerFactoryBean abstractEntityManagerFactoryBean(
JpaVendorAdapter jpaVendorAdapter) {
Properties properties = new Properties();
properties.setProperty(FORMAT_SQL, String.valueOf(true));
properties.setProperty(SHOW_SQL, String.valueOf(true));
properties.setProperty(DIALECT, ModifiedSQLServerDialect.class.getTypeName());
LocalContainerEntityManagerFactoryBean localContainerEntityManagerFactoryBean =
new LocalContainerEntityManagerFactoryBean();
localContainerEntityManagerFactoryBean.setDataSource(getDataSource());
localContainerEntityManagerFactoryBean.setJpaVendorAdapter(jpaVendorAdapter);
localContainerEntityManagerFactoryBean.setJpaProperties(properties);
localContainerEntityManagerFactoryBean.setPackagesToScan("enteties");
return localContainerEntityManagerFactoryBean;
}
@Bean
public PlatformTransactionManager platformTransactionManager(EntityManagerFactory emf) {
return new JpaTransactionManager(emf);
}
}
public class ModifiedSQLServerDialect extends SQLServer2012Dialect {
public ModifiedSQLServerDialect () {
super();
registerColumnType(Types.TIMESTAMP, "timestamp");
registerColumnType(Types.DATE, "timestamp");
registerColumnType(Types.TIME, "timestamp");
registerHibernateType(Types.TIMESTAMP, "timestamp");
registerHibernateType(Types.DATE, "timestamp");
registerHibernateType(Types.TIME, "timestamp");
}
}
但是我仍然在SQLServer profiler中看到：
exec sp_executesql N'select datestbl0_.creationDate as creation1_0_0_ from DatesTbl datestbl0_ where datestbl0_.creationDate=@P0 ',N'@P0 `datetime2`','2018-12-26 08:10:40.0000003'
解决方案出了什么问题？
答案 0 :(得分：2)
我认为使用DATETIME列作为PK并不是一个好主意。在同一纳秒内可能会创建两个实体，这会产生冲突。
您应该使用IDENTITY列或SEQUENCE，而只需索引DATETIME列即可加快查询速度。
这是一个旧系统-我无法更改。主键由int和此datetime列的2个字段组成。
在这种情况下，您需要使用复合标识符。检出this article for more details。
此外，我认为您不需要这些：
registerColumnType(Types.TIMESTAMP, "timestamp");
registerColumnType(Types.DATE, "timestamp");
registerColumnType(Types.TIME, "timestamp");
registerHibernateType(Types.TIMESTAMP, "timestamp");
registerHibernateType(Types.DATE, "timestamp");
registerHibernateType(Types.TIME, "timestamp");
SQL Server方言应提供正确的类型映射。
如果这不起作用，请尝试使用此test case template复制问题，然后打开一个Jira问题。
答案 1 :(得分：2)
该问题与mssql-jdbc（版本4.x和6.x）PreparedStatement.setTimestamp(index, timestamp, calendar) has datatype conversion issues中的问题有关，该问题始终将LocalDateTime数据类型的datetime2参数发送到SQL Server（忽略表的列类型）。由于datetime（0.00333秒）和datetime2（100纳秒）的精度不同，并且将datetime用作PK，因此Hibernate在这种情况下工作不正确。
在运行主程序时，creationDate的值为 2018-12-26 08：10：40.000000340 ，并且该值另存为 2018-12-26数据库中的08：10：40.000 ，因为Hibernate在数据库中找不到具有相同键的记录。当我们再次运行主程序时，Hibernate首先使用
'从DatesTbl datetbl0_中选择datestbl0_.creationDate作为creation1_0_0_，其中datestbl0_.creationDate=@P0'，N'@ P0'datetime2''，'2018-12-26 08：10：40.0000003'
似乎SQL Server将表中的datetime值上载到datetime2进行比较，并且没有返回记录。因此，Hibernate再次插入记录，并导致主键冲突。
如Vlad Mihalcea所建议，将DATETIME列用作PK不是一个好主意。
但是，假设我们仍然需要datetime列作为PK，则以下解决方法应该起作用。解决此问题的关键是使datetime和datetime2之间的比较返回true。为此，我们可以将datetime2的值截断/舍入为相应的datetime的值，然后再传递给DB。使用SQL Server 2012 Express测试了对主程序的以下更改，没有错误。
public static void main(String[] args) {
ApplicationContext context = new AnnotationConfigApplicationContext(Main.class);
EntityManagerFactory entityManagerFactory = context.getBean(EntityManagerFactory.class);
final EntityManager entityManager = entityManagerFactory.createEntityManager();
LocalDateTime creationDate0 = LocalDateTime.of(2018, 12, 26, 8, 10, 40, 341340340);
LocalDateTime creationDate3 = LocalDateTime.of(2018, 12, 26, 8, 10, 40, 343340340);
LocalDateTime creationDate7 = LocalDateTime.of(2018, 12, 26, 8, 10, 40, 346670340);
LocalDateTime creationDate10 = LocalDateTime.of(2018, 12, 26, 8, 10, 40, 349670340);
entityManager.getTransaction().begin();
final DatesTbl datesTbl0 = entityManager.merge(new DatesTbl(roundNanoSecForDateTime(creationDate0)));
final DatesTbl datesTbl3 = entityManager.merge(new DatesTbl(roundNanoSecForDateTime(creationDate3)));
final DatesTbl datesTbl7 = entityManager.merge(new DatesTbl(roundNanoSecForDateTime(creationDate7)));
final DatesTbl datesTbl10 = entityManager.merge(new DatesTbl(roundNanoSecForDateTime(creationDate10)));
entityManager.getTransaction().commit();
System.out.println("test");
}
private static LocalDateTime roundNanoSecForDateTime(LocalDateTime localDateTime) {
int nanoSec = localDateTime.getNano();
// The rounding is based on following results on SQL server 2012 express
// select cast(cast('2018-12-26 08:10:40.3414999' as datetime2) as datetime);
// 2018-12-26 08:10:40.340
// select cast(cast('2018-12-26 08:10:40.3415000' as datetime2) as datetime);
// select cast(cast('2018-12-26 08:10:40.3444999' as datetime2) as datetime);
// 2018-12-26 08:10:40.343
// select cast(cast('2018-12-26 08:10:40.3445000' as datetime2) as datetime);
// select cast(cast('2018-12-26 08:10:40.3484999' as datetime2) as datetime);
// 2018-12-26 08:10:40.347
// select cast(cast('2018-12-26 08:10:40.3485000' as datetime2) as datetime);
// 2018-12-26 08:10:40.350
int last7DigitOfNano = nanoSec - (nanoSec / 10000000) * 10000000;
int roundedNanoSec = 0;
if (last7DigitOfNano < 1500000) {
roundedNanoSec = nanoSec - last7DigitOfNano;
} else if (last7DigitOfNano < 4500000) {
roundedNanoSec = nanoSec - last7DigitOfNano + 3000000;
} else if (last7DigitOfNano < 8500000) {
roundedNanoSec = nanoSec - last7DigitOfNano + 7000000;
} else {
roundedNanoSec = nanoSec - last7DigitOfNano + 10000000;
}
System.out.println("Before Rounding" + nanoSec);
System.out.println("After Rounding" + roundedNanoSec);
return localDateTime.withNano(roundedNanoSec);
}
参考：
1. DateTime2 vs DateTime in SQL Server
2. Date and Time Data Types and Functions (Transact-SQL)