前言

同一个项目有时会涉及到多个数据库，也就是多数据源。多数据源又可以分为两种情况：

1）两个或多个数据库没有相关性，各自独立，其实这种可以作为两个项目来开发。比如在游戏开发中一个数据库是平台数据库，其它还有平台下的游戏对应的数据库；

2）两个或多个数据库是master-slave的关系，比如有mysql搭建一个 master-master，其后又带有多个slave；或者采用MHA搭建的master-slave复制；

MyBatis多数据源的配置主要有两种方式:

• 通过@MapperScan注解，对不同包下的Mapper使用不同的sqlSessionFactory
• 通过@MapperScan注解加自定义注解，对使用不同注解的Mapper使用不同的sqlSessionFactory

第二种配置相对灵活，示例如下:

package bj;import ch.qos.logback.classic.Level;import ch.qos.logback.classic.Logger;import com.zaxxer.hikari.HikariDataSource;import io.shardingsphere.shardingjdbc.spring.boot.SpringBootConfiguration;import org.apache.ibatis.annotations.Mapper;import org.apache.ibatis.annotations.Select;import org.apache.ibatis.session.SqlSessionFactory;import org.mybatis.spring.SqlSessionFactoryBean;import org.mybatis.spring.annotation.MapperScan;import org.slf4j.LoggerFactory;import org.springframework.boot.SpringApplication;import org.springframework.boot.WebApplicationType;import org.springframework.boot.autoconfigure.SpringBootApplication;import org.springframework.boot.context.event.ApplicationReadyEvent;import org.springframework.context.ApplicationListener;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.annotation.Resource;import javax.sql.DataSource;import java.lang.annotation.ElementType;import java.lang.annotation.Retention;import java.lang.annotation.RetentionPolicy;import java.lang.annotation.Target;import java.util.List;import java.util.Map;/** * Created by BaiJiFeiLong@gmail.com at 2018/12/6 下午9:29 * <p> * MyBatis多数据源演示 */@SpringBootApplication(exclude = {SpringBootConfiguration.class})@Configuration@MapperScan(annotationClass = Mapper.class, basePackageClasses = MyBatisApp.class, sqlSessionFactoryRef = "sqlSessionFactory")public class MyBatisApp implements ApplicationListener<ApplicationReadyEvent> { /** * SecondaryMapper配置 * \@MapperScan 注解一次只能添加一个，所以需要单独再加一个配置类 * 自定义@MapperScan会替换MyBatis自动添加的默认@MapperScan。所以主@MapperScan也必须显式添加 */ @Configuration @MapperScan(annotationClass = SecondaryMapper.class, basePackageClasses = MyBatisApp.class, sqlSessionFactoryRef = "sqlSessionFactorySecond") static class SecondaryMapperConfiguration { } public static void main(String[] args) { new SpringApplication(MyBatisApp.class) {{ setWebApplicationType(WebApplicationType.NONE); }}.run(args); } @Resource private DataSource dataSource; @Resource private DataSource dataSourceSecond; @Resource private JdbcTemplate jdbcTemplate; @Resource private UserMapper userMapper; @Resource private SecondaryUserMapper secondaryUserMapper; private void initLogger() { ((Logger) LoggerFactory.getLogger(MyBatisApp.class)).setLevel(Level.DEBUG); ((Logger) LoggerFactory.getLogger(JdbcTemplate.class)).setLevel(Level.DEBUG); } private void initDatabase() { String oldDatabase = jdbcTemplate.queryForObject("SELECT DATABASE()", String.class); jdbcTemplate.execute("DROP SCHEMA IF EXISTS one"); jdbcTemplate.execute("CREATE SCHEMA one"); jdbcTemplate.execute("USE one"); jdbcTemplate.execute("CREATE TABLE user(id INT AUTO_INCREMENT PRIMARY KEY, name VARCHAR(32) CHARSET 'utf8')"); jdbcTemplate.execute("INSERT INTO user(name) VALUES ('人民的儿子')"); jdbcTemplate.execute("INSERT INTO user(name) VALUES ('人民的孙子')"); jdbcTemplate.execute("INSERT INTO user(name) VALUES ('人民的曾孙子')"); jdbcTemplate.execute("DROP SCHEMA IF EXISTS two"); jdbcTemplate.execute("CREATE SCHEMA two"); jdbcTemplate.execute("USE two"); jdbcTemplate.execute("CREATE TABLE user(id INT AUTO_INCREMENT PRIMARY KEY, name VARCHAR(32) CHARSET 'utf8')"); jdbcTemplate.execute("INSERT INTO user(name) VALUES ('人民的爹')"); jdbcTemplate.execute("INSERT INTO user(name) VALUES ('人民的爷')"); jdbcTemplate.execute("INSERT INTO user(name) VALUES ('人民的太爷')"); jdbcTemplate.execute("INSERT INTO user(name) VALUES ('人民的老太爷')"); jdbcTemplate.execute("USE " + oldDatabase); } @Override public void onApplicationEvent(ApplicationReadyEvent applicationReadyEvent) { initLogger(); initDatabase(); System.out.println("Users:"); userMapper.selectAll().forEach(System.out::println); System.out.println("Secondary users:"); secondaryUserMapper.selectAll().forEach(System.out::println); } /** * 主数据源 * <p> * 如果不添加@Primary注解, MyBatis可以工作，但是JdbcTemplate无法注入 * * @return . */ @Primary @Bean public DataSource dataSource() { return new HikariDataSource() {{ setJdbcUrl("jdbc:mysql://localhost/one?useUnicode=true&characterEncoding=utf8"); setUsername("root"); setPassword("root"); }}; } /** * 副数据源 * * @return . */ @Bean public DataSource dataSourceSecond() { return new HikariDataSource() {{ setJdbcUrl("jdbc:mysql://localhost/two?useUnicode=true&characterEncoding=utf8"); setUsername("root"); setPassword("root"); }}; } /** * 主SqlSessionFactory。使用主数据源。自定义SqlSessionFactory后，MyBatis就不自动添加SqlSessionFactory了，所以必须有 * * @return . * @throws Exception . */ @Bean public SqlSessionFactory sqlSessionFactory() throws Exception { return new SqlSessionFactoryBean() {{ setDataSource(dataSource); }}.getObject(); } /** * 副SqlSessionFactory。使用副数据源 * * @return . * @throws Exception . */ @Bean public SqlSessionFactory sqlSessionFactorySecond() throws Exception { return new SqlSessionFactoryBean() {{ setDataSource(dataSourceSecond); }}.getObject(); } @Mapper interface UserMapper { @Select("SELECT * FROM user") List<Map<String, Object>> selectAll(); } @SecondaryMapper interface SecondaryUserMapper { @Select("SELECT * FROM user") List<Map<String, Object>> selectAll(); } /** * 自定义Mapper注解，用于标识使用的数据源 */ @Target(ElementType.TYPE) @Retention(RetentionPolicy.RUNTIME) @interface SecondaryMapper { }}

控制台输出:

. ____ _ __ _ _
/\\ / ___'_ __ _ _(_)_ __ __ _ \ \ \ \
( ( )\___ | '_ | '_| | '_ \/ _` | \ \ \ \
\\/ ___)| |_)| | | | | || (_| | ) ) ) )
' |____| .__|_| |_|_| |_\__, | / / / /
=========|_|==============|___/=/_/_/_/
:: Spring Boot :: (v2.1.0.RELEASE)

2018-12-07 11:49:02.596 INFO 5154 --- [ main] bj.MyBatisApp : Starting MyBatisApp on MacBook-Air-2.local with PID 5154 (/Users/yuchao/temp/java/hellomaven/target/classes started by yuchao in /Users/yuchao/temp/java/hellomaven)
2018-12-07 11:49:02.633 INFO 5154 --- [ main] bj.MyBatisApp : No active profile set, falling back to default profiles: default
2018-12-07 11:49:05.341 INFO 5154 --- [ main] com.zaxxer.hikari.HikariDataSource : HikariPool-1 - Starting...
2018-12-07 11:49:05.499 INFO 5154 --- [ main] com.zaxxer.hikari.HikariDataSource : HikariPool-1 - Start completed.
2018-12-07 11:49:05.547 INFO 5154 --- [ main] org.quartz.impl.StdSchedulerFactory : Using default implementation for ThreadExecutor
2018-12-07 11:49:05.569 INFO 5154 --- [ main] org.quartz.core.SchedulerSignalerImpl : Initialized Scheduler Signaller of type: class org.quartz.core.SchedulerSignalerImpl
2018-12-07 11:49:05.569 INFO 5154 --- [ main] org.quartz.core.QuartzScheduler : Quartz Scheduler v.2.3.0 created.
2018-12-07 11:49:05.570 INFO 5154 --- [ main] org.quartz.simpl.RAMJobStore : RAMJobStore initialized.
2018-12-07 11:49:05.571 INFO 5154 --- [ main] org.quartz.core.QuartzScheduler : Scheduler meta-data: Quartz Scheduler (v2.3.0) 'quartzScheduler' with instanceId 'NON_CLUSTERED'
Scheduler class: 'org.quartz.core.QuartzScheduler' - running locally.
NOT STARTED.
Currently in standby mode.
Number of jobs executed: 0
Using thread pool 'org.quartz.simpl.SimpleThreadPool' - with 10 threads.
Using job-store 'org.quartz.simpl.RAMJobStore' - which does not support persistence. and is not clustered.

2018-12-07 11:49:05.571 INFO 5154 --- [ main] org.quartz.impl.StdSchedulerFactory : Quartz scheduler 'quartzScheduler' initialized from an externally provided properties instance.
2018-12-07 11:49:05.571 INFO 5154 --- [ main] org.quartz.impl.StdSchedulerFactory : Quartz scheduler version: 2.3.0
2018-12-07 11:49:05.571 INFO 5154 --- [ main] org.quartz.core.QuartzScheduler : JobFactory set to: org.springframework.scheduling.quartz.SpringBeanJobFactory@769a58e5
2018-12-07 11:49:05.780 WARN 5154 --- [ main] reactor.netty.tcp.TcpResources : [http] resources will use the default LoopResources: DefaultLoopResources {prefix=reactor-http, daemon=true, selectCount=4, workerCount=4}
2018-12-07 11:49:05.780 WARN 5154 --- [ main] reactor.netty.tcp.TcpResources : [http] resources will use the default ConnectionProvider: PooledConnectionProvider {name=http, poolFactory=reactor.netty.resources.ConnectionProvider$$Lambda$284/1788545647@10667848}
2018-12-07 11:49:06.061 INFO 5154 --- [ main] o.s.s.quartz.SchedulerFactoryBean : Starting Quartz Scheduler now
2018-12-07 11:49:06.062 INFO 5154 --- [ main] org.quartz.core.QuartzScheduler : Scheduler quartzScheduler_$_NON_CLUSTERED started.
2018-12-07 11:49:06.079 INFO 5154 --- [ main] bj.MyBatisApp : Started MyBatisApp in 4.645 seconds (JVM running for 6.354)
2018-12-07 11:49:06.084 DEBUG 5154 --- [ main] o.s.jdbc.core.JdbcTemplate : Executing SQL query [SELECT DATABASE()]
2018-12-07 11:49:06.105 DEBUG 5154 --- [ main] o.s.jdbc.core.JdbcTemplate : Executing SQL statement [DROP SCHEMA IF EXISTS one]
2018-12-07 11:49:06.115 DEBUG 5154 --- [ main] o.s.jdbc.core.JdbcTemplate : Executing SQL statement [CREATE SCHEMA one]
2018-12-07 11:49:06.117 DEBUG 5154 --- [ main] o.s.jdbc.core.JdbcTemplate : Executing SQL statement [USE one]
2018-12-07 11:49:06.119 DEBUG 5154 --- [ main] o.s.jdbc.core.JdbcTemplate : Executing SQL statement [CREATE TABLE user(id INT AUTO_INCREMENT PRIMARY KEY, name VARCHAR(32) CHARSET 'utf8')]
2018-12-07 11:49:06.153 DEBUG 5154 --- [ main] o.s.jdbc.core.JdbcTemplate : Executing SQL statement [INSERT INTO user(name) VALUES ('人民的儿子')]
2018-12-07 11:49:06.157 DEBUG 5154 --- [ main] o.s.jdbc.core.JdbcTemplate : Executing SQL statement [INSERT INTO user(name) VALUES ('人民的孙子')]
2018-12-07 11:49:06.161 DEBUG 5154 --- [ main] o.s.jdbc.core.JdbcTemplate : Executing SQL statement [INSERT INTO user(name) VALUES ('人民的曾孙子')]
2018-12-07 11:49:06.164 DEBUG 5154 --- [ main] o.s.jdbc.core.JdbcTemplate : Executing SQL statement [DROP SCHEMA IF EXISTS two]
2018-12-07 11:49:06.174 DEBUG 5154 --- [ main] o.s.jdbc.core.JdbcTemplate : Executing SQL statement [CREATE SCHEMA two]
2018-12-07 11:49:06.176 DEBUG 5154 --- [ main] o.s.jdbc.core.JdbcTemplate : Executing SQL statement [USE two]
2018-12-07 11:49:06.178 DEBUG 5154 --- [ main] o.s.jdbc.core.JdbcTemplate : Executing SQL statement [CREATE TABLE user(id INT AUTO_INCREMENT PRIMARY KEY, name VARCHAR(32) CHARSET 'utf8')]
2018-12-07 11:49:06.226 DEBUG 5154 --- [ main] o.s.jdbc.core.JdbcTemplate : Executing SQL statement [INSERT INTO user(name) VALUES ('人民的爹')]
2018-12-07 11:49:06.231 DEBUG 5154 --- [ main] o.s.jdbc.core.JdbcTemplate : Executing SQL statement [INSERT INTO user(name) VALUES ('人民的爷')]
2018-12-07 11:49:06.235 DEBUG 5154 --- [ main] o.s.jdbc.core.JdbcTemplate : Executing SQL statement [INSERT INTO user(name) VALUES ('人民的太爷')]
2018-12-07 11:49:06.243 DEBUG 5154 --- [ main] o.s.jdbc.core.JdbcTemplate : Executing SQL statement [INSERT INTO user(name) VALUES ('人民的老太爷')]
2018-12-07 11:49:06.246 DEBUG 5154 --- [ main] o.s.jdbc.core.JdbcTemplate : Executing SQL statement [USE one]
Users:
2018-12-07 11:49:06.271 DEBUG 5154 --- [ main] bj.MyBatisApp$UserMapper.selectAll : ==> Preparing: SELECT * FROM user
2018-12-07 11:49:06.297 DEBUG 5154 --- [ main] bj.MyBatisApp$UserMapper.selectAll : ==> Parameters:
2018-12-07 11:49:06.314 DEBUG 5154 --- [ main] bj.MyBatisApp$UserMapper.selectAll : <== Total: 3
{name=人民的儿子, id=1}
{name=人民的孙子, id=2}
{name=人民的曾孙子, id=3}
Secondary users:
2018-12-07 11:49:06.318 INFO 5154 --- [ main] com.zaxxer.hikari.HikariDataSource : HikariPool-2 - Starting...
2018-12-07 11:49:06.324 INFO 5154 --- [ main] com.zaxxer.hikari.HikariDataSource : HikariPool-2 - Start completed.
2018-12-07 11:49:06.325 DEBUG 5154 --- [ main] b.M.selectAll : ==> Preparing: SELECT * FROM user
2018-12-07 11:49:06.325 DEBUG 5154 --- [ main] b.M.selectAll : ==> Parameters:
2018-12-07 11:49:06.328 DEBUG 5154 --- [ main] b.M.selectAll : <== Total: 4
{name=人民的爹, id=1}
{name=人民的爷, id=2}
{name=人民的太爷, id=3}
{name=人民的老太爷, id=4}

总结

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