有个项目需要作SQL Server到MySQL的数据迁移,而且两边的schema也有不少差异,这时候用工具去迁移就很难了,需要写程序去控制每个字段的变换。于是采用Spring Data JPA来做这件事,自动搞定各种DAO,而且底层的Hibernate也轻松支持SQL Server和MySQL的
做这个事情的第一步就是配置两个数据源,一个连MySQL,一个连SQL Server。很多需要支持读写分离多数据源的和这个类似,只会更简单,因为只用支持MySQL就可以。下面看代码:
配置文件
application.yml的内容是:
spring:
datasource:
mssql:
type: org.apache.tomcat.jdbc.pool.DataSource
driver-class-name: com.microsoft.sqlserver.jdbc.SQLServerDriver
url: jdbc:sqlserver://localhost:1433;database=old;
username: sa
password: password
mysql:
type: org.apache.tomcat.jdbc.pool.DataSource
driver-class-name: com.mysql.jdbc.Driver
url: jdbc:mysql://localhost:3306/new?useUnicode=true&characterEncoding=UTF-8&autoReconnect=true&zeroDateTimeBehavior=convertToNull&useSSL=false
username: root
password: password
jpa:
show-sql: false
可以看到,很清楚的两个数据源配置,下面来看怎样使用这两个配置
DataSource配置类
import org.springframework.boot.autoconfigure.jdbc.DataSourceBuilder;
import org.springframework.boot.context.properties.ConfigurationProperties;
import org.springframework.boot.orm.jpa.EntityManagerFactoryBuilder;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import org.springframework.context.annotation.Primary;
import org.springframework.orm.jpa.JpaTransactionManager;
import org.springframework.orm.jpa.LocalContainerEntityManagerFactoryBean;
import org.springframework.transaction.PlatformTransactionManager;
import javax.sql.DataSource;
import java.util.Properties;
@Configuration
public class DataSourceConfiguration {
@Bean
@Primary
@ConfigurationProperties(prefix = "spring.datasource.mssql")
public DataSource mssqlDataSource() {
return DataSourceBuilder.create().build();
}
@Bean
@ConfigurationProperties(prefix = "spring.datasource.mysql")
public DataSource mysqlDataSource() {
return DataSourceBuilder.create().build();
}
@Bean(name = "mssqlEntityManagerFactory")
@Primary
public LocalContainerEntityManagerFactoryBean mssqlEntityManagerFactory(
EntityManagerFactoryBuilder builder) {
LocalContainerEntityManagerFactoryBean em = builder
.dataSource(mssqlDataSource())
.packages(OldBuy.class)
.persistenceUnit("mssql")
.build();
Properties properties = new Properties();
properties.setProperty("hibernate.physical_naming_strategy", "org.hibernate.boot.model.naming.PhysicalNamingStrategyStandardImpl");
em.setJpaProperties(properties);
return em;
}
@Bean(name = "mysqlEntityManagerFactory")
public LocalContainerEntityManagerFactoryBean mysqlEntityManagerFactory(
EntityManagerFactoryBuilder builder) {
LocalContainerEntityManagerFactoryBean em = builder
.dataSource(mysqlDataSource())
.packages(Buy.class)
.persistenceUnit("mysql")
.build();
Properties properties = new Properties();
properties.setProperty("hibernate.physical_naming_strategy", "org.springframework.boot.orm.jpa.hibernate.SpringPhysicalNamingStrategy");
em.setJpaProperties(properties);
return em;
}
@Bean(name = "mssqlTransactionManager")
@Primary
PlatformTransactionManager mssqlTransactionManager(EntityManagerFactoryBuilder builder) {
return new JpaTransactionManager(mssqlEntityManagerFactory(builder).getObject());
}
@Bean(name = "mysqlTransactionManager")
@Primary
PlatformTransactionManager mysqlTransactionManager(EntityManagerFactoryBuilder builder) {
return new JpaTransactionManager(mysqlEntityManagerFactory(builder).getObject());
}
}
这里主要分三块:
最上面的两个
DataSource
类,根据配置文件产生数据源,注意必须一个是Primary的,不然Spring会报错,因为找到了bean的两个实现,默认不知道选哪个中间的两个
LocalContainerEntityManagerFactoryBean
则是根据两个数据源产生对应的EntityManager
,这里就可以做些hibernate的特定配置了,比如取名策略、sql方言之类的最后两个
PlatformTransactionManager
则是根据两个EntityManager
产生对应的事务管理器,这样我们才能用事务
Repository配置
现在万事俱备,只欠东风了,也就是指定我们哪些Repository
用上面配置好的两套DataSource
、EntityManager
、Transaction Manager
:
SQL Server配置
import org.springframework.context.annotation.Configuration;
import org.springframework.data.jpa.repository.config.EnableJpaRepositories;
import org.springframework.transaction.annotation.EnableTransactionManagement;
@Configuration
@EnableTransactionManagement
@EnableJpaRepositories(
basePackageClasses = MsSQLXXXRepository.class,
entityManagerFactoryRef = "mssqlEntityManagerFactory",
transactionManagerRef = "mssqlTransactionManager"
)
public class MssqlConfiguration {
}
MySQL配置
import org.springframework.context.annotation.Configuration;
import org.springframework.data.jpa.repository.config.EnableJpaRepositories;
import org.springframework.transaction.annotation.EnableTransactionManagement;
@Configuration
@EnableTransactionManagement
@EnableJpaRepositories(
basePackageClasses = MySQLYYYRepository.class,
entityManagerFactoryRef = "mysqlEntityManagerFactory",
transactionManagerRef = "mysqlTransactionManager"
)
public class MysqlConfiguration {
}
上面就是两种Repository
的配置了,很简单。basePackageClasses
指向的那个类,同一个包里面的所有Repository
都会用这个数据源的配置
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