转载自 Spring Boot 集成 Mybatis 实现双数据源
这里用到了Spring Boot + Mybatis + DynamicDataSource配置动态双数据源，可以动态切换数据源实现数据库的读写分离。
添加依赖
加入Mybatis启动器，这里添加了Druid连接池、Oracle数据库驱动为例。
<dependency><groupId>org.mybatis.spring.boot</groupId><artifactId>mybatis-spring-boot-starter</artifactId>
</dependency><dependency><groupId>com.alibaba</groupId><artifactId>druid</artifactId>
</dependency><dependency><groupId>com.oracle</groupId><artifactId>ojdbc6</artifactId>
</dependency>添加启动类
@EnableMybatis
@EnableTransactionManagement
@SpringBootApplication(exclude = { DataSourceAutoConfiguration.class })
public class Application {public static void main(String[] args) {SpringApplication.run(ServiceApplication.class, args);}}@EnableTransactionManagement：开启事务支持。
@EnableMybatis：开启Mybatis功能
@Target(ElementType.TYPE)
@Retention(RetentionPolicy.RUNTIME)
@Documented
@Import(MybatisConfig.class)
public @interface EnableMybatis {}Mybatis配置类
@Configuration
@MapperScan(basePackages = DSConfig.BASE_PACKAGES)
public class MybatisConfig implements DSConfig {@Primary@Beanpublic DynamicDataSource dynamicDataSource(@Qualifier(DB_MASTER) DataSource master,@Qualifier(DB_SLAVE) DataSource slave) {Map<Object, Object> dsMap = new HashMap<>();dsMap.put(DB_MASTER, master);dsMap.put(DB_MASTER, slave);DynamicDataSource dynamicDataSource = new DynamicDataSource();dynamicDataSource.setDefaultTargetDataSource(master);dynamicDataSource.setTargetDataSources(dsMap);return dynamicDataSource;}@Beanpublic PlatformTransactionManager transactionManager(DynamicDataSource dynamicDataSource) {return new DataSourceTransactionManager(dynamicDataSource);}@Beanpublic SqlSessionFactory sqlSessionFactory(DynamicDataSource dynamicDataSource)throws Exception {SqlSessionFactoryBean sessionFactory = new SqlSessionFactoryBean();sessionFactory.setDataSource(dynamicDataSource);sessionFactory.setMapperLocations(((ResourcePatternResolver) new PathMatchingResourcePatternResolver()).getResources(DSConfig.MAPPER_LOCATIONS));return sessionFactory.getObject();}}DSConfig常量类：
public interface DSConfig {String DS_PREFIX = "spring.datasource";String DS_ACTIVE = "active";String DB_MASTER = "db-master";String DB_SLAVE = "db-slave";String DRUID = "druid";String DRUID_MONITOR_USERNAME = "spring.druid.username";String DRUID_MONITOR_PASSWORD = "spring.druid.password";String DRUID_MONITOR_URL = "/druid/*";String DRUID_FILTER_EXCLUSIONS = "*.js,*.gif,*.jpg,*.png,*.css,*.ico,/druid/*";String DRUID_FILTER_URL = "/*";String BASE_PACKAGES = "com.example.**.mapper";String MAPPER_LOCATIONS = "mapper/**/*.xml";}连接池配置类
Druid连接池的自动配置类：
@Configuration
@Import({ PropertiesConfig.class })
@ConditionalOnClass(DruidDataSource.class)
@ConditionalOnProperty(prefix = DSConfig.DS_PREFIX, value = DSConfig.DS_ACTIVE, havingValue = DSConfig.DRUID)
public class DruidAutoConfig implements DSConfig {private Logger logger = LoggerUtils.getLogger(this);@Bean(name = DB_MASTER, initMethod = "init", destroyMethod = "close")public DataSource dataSourceMaster(DruidMasterProperties masterProperties) throws SQLException {logger.debug("master properties: {}", masterProperties.toString());DruidDataSource dds = new DruidDataSource();dds.setDriverClassName(masterProperties.getDriverClassName());dds.setUrl(masterProperties.getUrl());dds.setUsername(masterProperties.getUsername());dds.setPassword(masterProperties.getPassword());dds.setInitialSize(masterProperties.getInitialSize());dds.setMinIdle(masterProperties.getMinIdle());dds.setMaxActive(masterProperties.getMaxActive());dds.setMaxWait(masterProperties.getMaxWait());dds.setTimeBetweenEvictionRunsMillis(masterProperties.getTimeBetweenEvictionRunsMillis());dds.setMinEvictableIdleTimeMillis(masterProperties.getMinEvictableIdleTimeMillis());dds.setValidationQuery(masterProperties.getValidationQuery());dds.setTestOnBorrow(masterProperties.isTestOnBorrow());dds.setTestWhileIdle(masterProperties.isTestWhileIdle());dds.setTestOnReturn(masterProperties.isTestOnReturn());dds.setPoolPreparedStatements(masterProperties.isPoolPreparedStatements());dds.setMaxPoolPreparedStatementPerConnectionSize(masterProperties.getMaxPoolPreparedStatementPerConnectionSize());dds.setFilters(masterProperties.getFilters());return dds;}@Bean(name = DB_SLAVE, initMethod = "init", destroyMethod = "close")public DataSource dataSourceSlave(DruidSlaveProperties slaveProperties) throws SQLException {logger.debug("slave properties: {}", slaveProperties.toString());DruidDataSource dds = new DruidDataSource();dds.setDriverClassName(slaveProperties.getDriverClassName());dds.setUrl(slaveProperties.getUrl());dds.setUsername(slaveProperties.getUsername());dds.setPassword(slaveProperties.getPassword());dds.setInitialSize(slaveProperties.getInitialSize());dds.setMinIdle(slaveProperties.getMinIdle());dds.setMaxActive(slaveProperties.getMaxActive());dds.setMaxWait(slaveProperties.getMaxWait());dds.setTimeBetweenEvictionRunsMillis(slaveProperties.getTimeBetweenEvictionRunsMillis());dds.setMinEvictableIdleTimeMillis(slaveProperties.getMinEvictableIdleTimeMillis());dds.setValidationQuery(slaveProperties.getValidationQuery());dds.setTestOnBorrow(slaveProperties.isTestOnBorrow());dds.setTestWhileIdle(slaveProperties.isTestWhileIdle());dds.setTestOnReturn(slaveProperties.isTestOnReturn());dds.setPoolPreparedStatements(slaveProperties.isPoolPreparedStatements());dds.setMaxPoolPreparedStatementPerConnectionSize(slaveProperties.getMaxPoolPreparedStatementPerConnectionSize());dds.setFilters(slaveProperties.getFilters());return dds;}@Beanpublic ServletRegistrationBean druidServletRegistrationBean(EnvConfig env) {String username = env.getStringValue(DSConfig.DRUID_MONITOR_USERNAME);String password = env.getStringValue(DSConfig.DRUID_MONITOR_PASSWORD);return new ServletRegistrationBean(new DruidStatViewServlet(username, password),DSConfig.DRUID_MONITOR_URL);}@Beanpublic FilterRegistrationBean druidFilterRegistrationBean() {WebStatFilter wsf = new WebStatFilter();FilterRegistrationBean filterRegistrationBean = new FilterRegistrationBean();filterRegistrationBean.setFilter(wsf);filterRegistrationBean.setUrlPatterns(Arrays.asList(DSConfig.DRUID_FILTER_URL));filterRegistrationBean.setInitParameters(Collections.singletonMap("exclusions", DSConfig.DRUID_FILTER_EXCLUSIONS));return filterRegistrationBean;}}根据类路径下有DruidDataSource这个类即有Druid这个jar包和配置文件中spring.datasource.active=druid才开启对Druid连接池的自动配置。
导入的配置文件：
@Configuration
@ComponentScan(basePackages = "com.example.common.config.properties")
public class PropertiesConfig {}DruidMasterProperties、DruidSlaveProperties属性文件读取的配置省略。
连接池监控配置类：
public class DruidStatViewServlet extends StatViewServlet {private static final long serialVersionUID = 1L;private String username;private String password;@Overridepublic String getInitParameter(String name) {if ("loginUsername".equals(name)) {return username;}if ("loginPassword".equals(name)) {return password;}return super.getInitParameter(name);}public DruidStatViewServlet(String username, String password) {super();this.username = username;this.password = password;}public String getUsername() {return username;}public String getPassword() {return password;}}在META-INF/spring.factories中加入Druid自动配置映射：
org.springframework.boot.autoconfigure.EnableAutoConfiguration=\
com.example.common.config.ds.DruidAutoConfig切换数据源
切换数据源注解：
@Target(ElementType.METHOD)
@Retention(RetentionPolicy.RUNTIME)
@Documented
public @interface DS {String value() default DSConfig.DB_MASTER;
}动态数据源类：
public class DynamicDataSource extends AbstractRoutingDataSource {private final Logger logger = LoggerUtils.getLogger(this);@Overrideprotected Object determineCurrentLookupKey() {logger.debug("当前数据源为{}", DataSourceContextHolder.getDS());return DataSourceContextHolder.getDS();}}动态数据源AOP实现类：
@Aspect
@Component
public class DynamicDataSourceAspect {@Before("@annotation(DS)")public void beforeSwitchDS(JoinPoint point) {Class<?> className = point.getTarget().getClass();String methodName = point.getSignature().getName();Class<?>[] argClass = ((MethodSignature) point.getSignature()).getParameterTypes();String dataSource = DataSourceContextHolder.DEFAULT_DS;try {Method method = className.getMethod(methodName, argClass);if (method.isAnnotationPresent(DS.class)) {DS annotation = method.getAnnotation(DS.class);dataSource = annotation.value();}} catch (Exception e) {e.printStackTrace();}DataSourceContextHolder.setDS(dataSource);}@After("@annotation(DS)")public void afterSwitchDS(JoinPoint point) {DataSourceContextHolder.clearDS();}}绑定当前线程数据源类：
public class DataSourceContextHolder {public static final String DEFAULT_DS = DSConfig.DB_MASTER;private static final ThreadLocal<String> DS_HOLDER = new ThreadLocal<>();public static void setDS(String dbType) {DS_HOLDER.set(dbType);}public static String getDS() {return (DS_HOLDER.get());}public static void clearDS() {DS_HOLDER.remove();}
}
)
