需求背景

最近有一需求，原本项目中由于某些原因使用嵌入式数据库H2，鉴于嵌入式数据库可靠性以及不方便管理等因素，需要将数据库迁移到Mysql。

环境说明

SpringBoot：3.0.2
JDK：17
H2：2.1.214
spring-boot-starter-data-jpa：3.0.2

Mysql：8.0.32

实现过程

配置调整

原配置

pom.xml

<!-- 省略其他依赖... -->
<dependency><groupId>com.h2database</groupId><artifactId>h2</artifactId><version>2.1.214</version><scope>runtime</scope>
</dependency>

dev.yml

spring:datasource:url: jdbc:h2:file:./data/cloak-abdriver-class-name: org.h2.Driverusername: rootpassword: root789456jpa:database: h2hibernate:ddl-auto: updateshow-sql: trueh2:console:path: /h2-consoleenabled: truesettings:web-allow-others: truetrace: true

修改配置

修改后pom.xml

<!-- 省略其他依赖... -->
<dependency><groupId>mysql</groupId><artifactId>mysql-connector-java</artifactId><version>8.0.32</version>
</dependency>
<dependency><groupId>com.h2database</groupId><artifactId>h2</artifactId><version>2.1.214</version><scope>runtime</scope>
</dependency>

修改后dev.yml

spring:datasource:url: jdbc:mysql://192.168.0.80:3306/cloak_ab?useUnicode=true&characterEncoding=utf-8&useSSL=true&serverTimezone=GMT%2B8&allowMultiQueries=truedriver-class-name: com.mysql.cj.jdbc.Driverusername: rootpassword: root789456jpa:# 此处有修改database: mysqlhibernate:ddl-auto: updateshow-sql: trueh2:console:path: /h2-consoleenabled: truesettings:web-allow-others: truetrace: true

主要修改点有三处：

①添加Mysql连接依赖
②数据库的连接地址和数据库驱动
③jpa使用的数据库

代码调整

新增DatasourceConfig配置类

配置Mysql主数据源，H2次数据源
DatasourceConfig.java

import lombok.Data;
import org.springframework.beans.factory.annotation.Qualifier;
import org.springframework.boot.context.properties.ConfigurationProperties;
import org.springframework.boot.jdbc.DataSourceBuilder;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import org.springframework.context.annotation.Primary;
import org.springframework.jdbc.core.JdbcTemplate;import javax.sql.DataSource;@Configuration
public class DatasourceConfig {@Data@Configuration@ConfigurationProperties(prefix="spring.datasource")public static class MasterDatasourceProperties {private String url;private String driverClassName;private String username;private String password;}@Bean@Primarypublic DataSource dataSource(MasterDatasourceProperties masterDatasourceProperties) {return DataSourceBuilder.create().driverClassName(masterDatasourceProperties.getDriverClassName()).url(masterDatasourceProperties.getUrl()).username(masterDatasourceProperties.getUsername()).password(masterDatasourceProperties.getPassword()).build();}@Primary@Bean(name = "jdbcTemplate")public JdbcTemplate jdbcTemplate(@Qualifier("dataSource") DataSource dataSource) {return new JdbcTemplate(dataSource);}@Bean(name = "secondaryDataSource")@Qualifier("secondaryDataSource")public DataSource secondaryDataSource() {return DataSourceBuilder.create().url("jdbc:h2:file:./data/cloak-ab").driverClassName("org.h2.Driver").username("root").password("root789456").build();}@Bean(name = "secondaryJdbcTemplate")public JdbcTemplate secondaryJdbcTemplate(@Qualifier("secondaryDataSource") DataSource secondaryDataSource) {return new JdbcTemplate(secondaryDataSource);}}

Mysql主数据源添加@Primary注解，jpa使用的默认是主数据源，如此一来jpa操作的就是Mysql数据库了。

使用secondaryJdbcTemplate

	@Autowiredprivate AppParamDao appParamDao;@Autowired@Qualifier("secondaryJdbcTemplate")protected JdbcTemplate secondaryJdbcTemplate;@Overridepublic void h2ToMysql() {String sql = "select * from app_param";List<AppParam> appParams = secondaryJdbcTemplate.query(sql, new BeanPropertyRowMapper<>(AppParam.class));appParamDao.saveAllAndFlush(appParams);}

此时secondaryJdbcTemplate操作的就是H2数据库，而appParamDao操作的就是Mysql数据库

AppParamDao.java

import org.springframework.data.domain.Page;
import org.springframework.data.domain.Pageable;
import org.springframework.data.jpa.repository.JpaRepository;
import org.springframework.data.repository.CrudRepository;
import org.springframework.stereotype.Repository;import java.util.List;
import java.util.Optional;
import java.util.Set;@Repository
public interface AppParamDao extends CrudRepository<AppParam, Long>, JpaRepository<AppParam, Long> {
}