springboot系列学习笔记全部文章请移步值博主专栏**： spring boot 2.X/spring cloud Greenwich。
由于是一系列文章，所以后面的文章可能会使用到前面文章的项目。springboot系列代码全部上传至GitHub：https://github.com/liubenlong/springboot2_demo
本系列环境：Java11；springboot 2.1.1.RELEASE；springcloud Greenwich.RELEASE；MySQL 8.0.5；
文章目录
- 阅读本文前 ，请先阅读笔者另一片文章Spring Boot 源码深入分析
需求描述
在业务开发中，需要读写分离，或者需要配置多个数据源，接下来我们看看在springboot中如何配置多数据源，支持事务。
想知道springboot如何加载配置以及选择使用哪个连接池，请移步springboot 中数据源配置，连接池配置，源码剖析，如何选择连接池
application.properties修改如下，主要是添加双数据源：
spring.datasource.master.url=${jdbc.master.url}
spring.datasource.master.username=${jdbc.username}
spring.datasource.master.password=${jdbc.password}
spring.datasource.master.driverClassName=com.mysql.jdbc.Driver
spring.datasource.master.max-idle=30
spring.datasource.master.max-wait-millis=10000
spring.datasource.master.min-idle=5
spring.datasource.master.initial-size=5
spring.datasource.master.initSQL=SELECT 2
spring.datasource.master.connection-init-sqls=SELECT 1
spring.datasource.master.validation-query=SELECT 1
spring.datasource.master.validation-query-timeout=3000
#spring.datasource.master.test-on-borrow=true
spring.datasource.master.test-while-idle=true
spring.datasource.master.time-between-eviction-runs-millis=10000
spring.datasource.master.max-active=30
spring.datasource.slave.url=${jdbc.slave.url}
spring.datasource.slave.username=${jdbc.username}
spring.datasource.slave.password=${jdbc.password}
spring.datasource.slave.driverClassName=com.mysql.jdbc.Driver
spring.datasource.slave.max-idle=30
spring.datasource.slave.max-wait-millis=10000
spring.datasource.slave.min-idle=5
spring.datasource.slave.initial-size=5
spring.datasource.slave.initSQL=SELECT 2
spring.datasource.slave.connection-init-sqls=SELECT 1
spring.datasource.slave.validation-query=SELECT 1
spring.datasource.slave.validation-query-timeout=3000
#spring.datasource.slave.test-on-borrow=true
spring.datasource.slave.test-while-idle=true
spring.datasource.slave.time-between-eviction-runs-millis=10000
spring.datasource.slave.max-active=30
然后如果想要springboot加载到这两个配置，需要自定义数据源以及事务管理器等：
主库的配置：
import com.netease.generator.EncryptionInterceptor;
import org.apache.ibatis.plugin.Interceptor;
import org.apache.ibatis.session.SqlSessionFactory;
import org.mybatis.spring.SqlSessionFactoryBean;
import org.mybatis.spring.SqlSessionTemplate;
import org.mybatis.spring.annotation.MapperScan;
import org.springframework.beans.factory.annotation.Qualifier;
import org.springframework.boot.autoconfigure.jdbc.DataSourceBuilder;
import org.springframework.boot.context.properties.ConfigurationProperties;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import org.springframework.context.annotation.Primary;
import org.springframework.core.io.support.PathMatchingResourcePatternResolver;
import org.springframework.jdbc.datasource.DataSourceTransactionManager;
import javax.sql.DataSource;
@Configuration
@MapperScan(basePackages = {"repository的包名"}, sqlSessionTemplateRef = "masterSqlSessionTemplate")
public class MybatisMasterDbConfig {
@Bean(name = "masterDataSource")
@ConfigurationProperties(prefix = "spring.datasource.master")
@Primary
public DataSource testDataSource() {
return DataSourceBuilder.create().build();
}
@Bean(name = "masterSqlSessionFactory")
@Primary
public SqlSessionFactory testSqlSessionFactory(@Qualifier("masterDataSource") DataSource dataSource) throws Exception {
SqlSessionFactoryBean bean = new SqlSessionFactoryBean();
bean.setDataSource(dataSource);
bean.setMapperLocations(new PathMatchingResourcePatternResolver().getResources("classpath:mybatis/mapper/master/*.xml"));
bean.setPlugins(new Interceptor[]{new EncryptionInterceptor()});
return bean.getObject();
}
@Bean(name = "masterTransactionManager")
@Primary
public DataSourceTransactionManager testTransactionManager(@Qualifier("masterDataSource") DataSource dataSource) {
return new DataSourceTransactionManager(dataSource);
}
@Bean(name = "masterSqlSessionTemplate")
@Primary
public SqlSessionTemplate testSqlSessionTemplate(@Qualifier("masterSqlSessionFactory") SqlSessionFactory sqlSessionFactory) throws Exception {
return new SqlSessionTemplate(sqlSessionFactory);
}
}
从库的配置类：
import com.netease.generator.EncryptionInterceptor;
import org.apache.ibatis.plugin.Interceptor;
import org.apache.ibatis.session.SqlSessionFactory;
import org.mybatis.spring.SqlSessionFactoryBean;
import org.mybatis.spring.SqlSessionTemplate;
import org.mybatis.spring.annotation.MapperScan;
import org.springframework.beans.factory.annotation.Qualifier;
import org.springframework.boot.autoconfigure.jdbc.DataSourceBuilder;
import org.springframework.boot.context.properties.ConfigurationProperties;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import org.springframework.context.annotation.Primary;
import org.springframework.core.io.support.PathMatchingResourcePatternResolver;
import org.springframework.jdbc.datasource.DataSourceTransactionManager;
import javax.sql.DataSource;
@Configuration
@MapperScan(basePackages = {"repository的包名"}, sqlSessionTemplateRef = "slaveSqlSessionTemplate")
public class MybatisSlaveDbConfig {
@Bean(name = "slaveDataSource")
@ConfigurationProperties(prefix = "spring.datasource.slave")
public DataSource testDataSource() {
return DataSourceBuilder.create().build();
}
@Bean(name = "sqlSessionFactory")
@Primary
public SqlSessionFactory testSqlSessionFactory(@Qualifier("slaveDataSource") DataSource dataSource) throws Exception {
SqlSessionFactoryBean bean = new SqlSessionFactoryBean();
bean.setDataSource(dataSource);
bean.setMapperLocations(new PathMatchingResourcePatternResolver().getResources("classpath:mybatis/mapper/slave/*.xml"));
bean.setPlugins(new Interceptor[]{new EncryptionInterceptor()});
return bean.getObject();
}
@Bean(name = "slaveTransactionManager")
public DataSourceTransactionManager testTransactionManager(@Qualifier("slaveDataSource") DataSource dataSource) {
return new DataSourceTransactionManager(dataSource);
}
@Bean(name = "slaveSqlSessionTemplate")
public SqlSessionTemplate testSqlSessionTemplate(@Qualifier("slaveSqlSessionFactory") SqlSessionFactory sqlSessionFactory) throws Exception {
return new SqlSessionTemplate(sqlSessionFactory);
}
}
可以看到，上述两个配置类，是根据包的路径来区分mapper的【我们这里使用的是mybatis，并且是使用的mapper.xml文件】。所以只需要建两个包路径即可：
**.**.master.mapper
**.**.slave.mapper
假设master的mapper类下有UserMasterMapper.java
假设slave的mapper类下有 UserSlaveMapper.java
这两个mapper读者可以自行使用mysql的自动生成工具生成；对应上面配置类中的@MapperScan指定的basepackage地址。
然后mapper.xml也应该有两个目录【在 masterSqlSessionFactory 中指定的目录地址】：
假设resource/mapper/master下有UserMasterMapper.xml
假设resource/mapper/slave下有UserMasterMapper.xml
经过上面的配置，我们就可以愉快的撸代码了：
@Autowired
private UserMasterMapper userMasterMapper;
@Autowired
private UserSlaveMapper userSlaveMapper ;
#事务
接下来说一下事务问题。上面主从两个数据源的配置类中，各自配置了一个事务管理器masterSqlSessionTemplate和slaveSqlSessionTemplate。
我们在写service方法的时候，一定要标识是使用的哪个事务管理器
@Transactional(rollbackFor = Exception.class, transactionManager = "slaveTransactionManager")
public void testMultiDST(String mobile) {
}
如果不加事务管理器，默认是第一个加载的数据源的事务。为了不出一些不可描述的BUG，强烈建议明确指定使用哪个事务管理器。
配置项说明
在application.properties配置文件中，我们可以看到
#使用DBCP connection pool时，指定初始化时要执行的sql
spring.datasource.slave.connection-init-sqls=SELECT 'x'
#指定获取连接时连接校验的sql查询语句.
spring.datasource.slave.validation-query=SELECT 'x'
# 指定连接校验查询的超时时间.
spring.datasource.slave.validation-query-timeout=3000
#获取连接时候验证，会影响性能（不建议true）
spring.datasource.slave.test-on-borrow=false
#验证连接的有效性
spring.datasource.slave.test-while-idle=true
#空闲连接回收的时间间隔，与test-while-idle一起使用，设置5分钟
spring.datasource.slave.time-between-eviction-runs-millis=10000
master也同样配置了。这几个参数是为了探测MySQL的链接是否存活，
备注：单库的配置
spring.datasource.url=${star.jdbc.url}
spring.datasource.username=${jdbc.username}
spring.datasource.password=${jdbc.password}
spring.datasource.driverClassName=com.mysql.jdbc.Driver
spring.datasource.tomcat.max-active=30
spring.datasource.tomcat.max-idle=30
spring.datasource.tomcat.max-wait=10000
spring.datasource.tomcat.min-idle=5
spring.datasource.tomcat.initial-size=5
spring.datasource.tomcat.initSQL=SELECT 2
spring.datasource.tomcat.validation-query=SELECT 'x'
spring.datasource.tomcat.validation-query-timeout=3000
#spring.datasource.tomcat.test-on-borrow=true
spring.datasource.tomcat.test-while-idle=true
spring.datasource.tomcat.time-between-eviction-runs-millis=10000
logging.level.com.dy.springboot.server.mapper=debug
springboot系列学习笔记全部文章请移步值博主专栏**： spring boot 2.X/spring cloud Greenwich。
由于是一系列文章，所以后面的文章可能会使用到前面文章的项目。springboot系列代码全部上传至GitHub：https://github.com/liubenlong/springboot2_demo
本系列环境：Java11；springboot 2.1.1.RELEASE；springcloud Greenwich.RELEASE；MySQL 8.0.5；
