<!-- MyBatis依賴 -->
<dependency>
    <groupId>org.mybatis.spring.boot</groupId>
    <artifactId>mybatis-spring-boot-starter</artifactId>
    <version>2.2.0</version>
</dependency>

<!-- 數(shù)據(jù)庫(kù)連接池依賴（這里以HikariCP為例） -->
<dependency>
    <groupId>com.zaxxer</groupId>
    <artifactId>HikariCP</artifactId>
</dependency>

# 主庫(kù)
spring.datasource.master.url=jdbc:mysql://master-host:3306/master_db
spring.datasource.master.username=root
spring.datasource.master.password=root
# 從庫(kù)
spring.datasource.slave.url=jdbc:mysql://slave-host:3306/slave_db
spring.datasource.slave.username=root
spring.datasource.slave.password=root

import org.springframework.jdbc.datasource.lookup.AbstractRoutingDataSource;

public class RoutingDataSource extends AbstractRoutingDataSource {

    @Override
    protected Object determineCurrentLookupKey() {
        return DataSourceContextHolder.getDataSourceType();
    }
}

import org.springframework.beans.factory.annotation.Qualifier;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import org.springframework.jdbc.datasource.DataSourceTransactionManager;
import org.springframework.transaction.PlatformTransactionManager;

import javax.sql.DataSource;
import java.util.HashMap;
import java.util.Map;

@Configuration
public class DataSourceConfig {

    @Bean(name = "masterDataSource")
    @ConfigurationProperties(prefix = "spring.datasource.master")
    public DataSource masterDataSource() {
        return DataSourceBuilder.create().build();
    }

    @Bean(name = "slaveDataSource")
    @ConfigurationProperties(prefix = "spring.datasource.slave")
    public DataSource slaveDataSource() {
        return DataSourceBuilder.create().build();
    }

    @Bean(name = "routingDataSource")
    public RoutingDataSource routingDataSource(
            @Qualifier("masterDataSource") DataSource masterDataSource,
            @Qualifier("slaveDataSource") DataSource slaveDataSource) {
        RoutingDataSource routingDataSource = new RoutingDataSource();
        Map<Object, Object> targetDataSources = new HashMap<>();
        targetDataSources.put(DataSourceType.MASTER, masterDataSource);
        targetDataSources.put(DataSourceType.SLAVE, slaveDataSource);
        routingDataSource.setTargetDataSources(targetDataSources);
        routingDataSource.setDefaultTargetDataSource(masterDataSource);
        return routingDataSource;
    }

    @Bean
    public PlatformTransactionManager transactionManager(DataSource routingDataSource) {
        return new DataSourceTransactionManager(routingDataSource);
    }
}

public class DataSourceContextHolder {

    private static final ThreadLocal<DataSourceType> contextHolder = new ThreadLocal<>();

    public static void setDataSourceType(DataSourceType dataSourceType) {
        contextHolder.set(dataSourceType);
    }

    public static DataSourceType getDataSourceType() {
        return contextHolder.get();
    }

    public static void clearDataSourceType() {
        contextHolder.remove();
    }
}

@Aspect
@Component
public class DataSourceAspect {

    @Before("@annotation(master)")
    public void setMasterDataSource(JoinPoint joinPoint, Master master) {
        DataSource

ContextHolder.setDataSourceType(DataSourceType.MASTER);
    }

    @Before("@annotation(slave)")
    public void setSlaveDataSource(JoinPoint joinPoint, Slave slave) {
        DataSourceContextHolder.setDataSourceType(DataSourceType.SLAVE);
    }

    @After("@annotation(master) || @annotation(slave)")
    public void clearDataSourceType(JoinPoint joinPoint, Master master, Slave slave) {
        DataSourceContextHolder.clearDataSourceType();
    }
}

@Service
public class UserService {

    @Autowired
    private UserMapper userMapper;

    @Master
    public User getUserById(int userId) {
        return userMapper.selectById(userId);
    }

    @Slave
    public List<User> listAllUsers() {
        return userMapper.selectAll();
    }

    @Master
    public void saveUser(User user) {
        userMapper.insert(user);
    }
}