簡單多數據源配置
在一個普通Spring + Mybatis項目中,如果使用了多數據源,可以通過在dao層注入不同的SqlSessionTemplate來實現與不同數據庫交互的目的。單個SqlSessionTemplate注入容器的過程如下:
<!-- 配置數據源 -->
<bean id="dataSource" class="com.alibaba.druid.pool.DruidDataSource">
<property name="driverClassName" value="${jdbc.driver}"/>
<property name="url" value="${jdbc.url}"/>
<property name="username" value="${jdbc.username}"/>
<property name="password" value="${jdbc.password}"/>
</bean>
<!-- 註冊sqlSessionFactory -->
<bean id="sqlSessionFactory" class="org.mybatis.spring.SqlSessionFactoryBean">
<property name="dataSource" ref="dataSource"/>
<property name="configLocation" value="classpath:config/mybatis-config.xml"/>
<property name="typeAliasesPackage" value="com.wch.base.domain"/>
<property name="mapperLocations" value="classpath:mapper/*.xml"/>
</bean>
<!-- 配置dao接口掃描,配置sqlSessionTemplate -->
<context:component-scan base-package="com.wch.base.mapper"/>
<bean id="sqlSessionTemplate" class="org.mybatis.spring.SqlSessionTemplate">
<constructor-arg ref="sqlSessionFactory"/>
</bean>
如果項目需要連接多個數據源,從DataSource、SqlSessionFactory、SqlSessionTemplate都需要配置多次,難於維護和管理。
AbstractRoutingDataSource
AbstractRoutingDataSource是spring-jdbc包提供的一個了AbstractDataSource的抽象類,它實現了DataSource接口的用於獲取數據庫連接的方法。
@Override
public Connection getConnection() throws SQLException {
return determineTargetDataSource().getConnection();
}
@Override
public Connection getConnection(String username, String password) throws SQLException {
return determineTargetDataSource().getConnection(username, password);
}
protected DataSource determineTargetDataSource() {
Assert.notNull(this.resolvedDataSources, "DataSource router not initialized");
// 獲取指定數據源關鍵字
Object lookupKey = determineCurrentLookupKey();
DataSource dataSource = this.resolvedDataSources.get(lookupKey);
if (dataSource == null && (this.lenientFallback || lookupKey == null)) {
dataSource = this.resolvedDefaultDataSource;
}
if (dataSource == null) {
throw new IllegalStateException("Cannot determine target DataSource for lookup key [" + lookupKey + "]");
}
return dataSource;
}
public void setTargetDataSources(Map<Object, Object> targetDataSources) {
this.targetDataSources = targetDataSources;
}
AbstractRoutingDataSource的內部維護了一個名爲targetDataSources的Map,並提供的setter方法用於設置數據源關鍵字與數據源的關係,實現類被要求實現其determineCurrentLookupKey()方法,由此方法的返回值決定具體從哪個數據源中獲取連接。
數據源動態切換
AbstractRoutingDataSource提供了程序運行時動態切換數據源的方法,在dao類或方法上標註需要訪問數據源的關鍵字,路由到指定數據源,獲取連接。
數據源切換方法
維護一個static變量datasourceContext用於記錄每個線程需要使用的數據源關鍵字。並提供切換、讀取、清除數據源配置信息的方法。
@Slf4j
public class DataSourceContextHolder {
private static ThreadLocal<String> datasourceContext = new ThreadLocal<>();
public static void switchDataSource(String datasource) {
log.debug("switchDataSource: {}", datasource);
datasourceContext.set(datasource);
}
public static String getDataSource() {
return datasourceContext.get();
}
public static void clear() {
datasourceContext.remove();
}
}
實現AbstractRoutingDataSource
public class RoutingDataSource extends AbstractRoutingDataSource {
@Override
protected Object determineCurrentLookupKey() {
return DataSourceContextHolder.getDataSource();
}
}
配置數據源信息
# master datasource
ds.financial.master.driverClassName=com.mysql.jdbc.Driver
ds.financial.master.url=jdbc:mysql://127.0.0.1:3306/financial?useUnicode=true&characterEncoding=utf8&useSSL=true
ds.financial.master.username=root
ds.financial.master.password=
ds.financial.master.type=com.alibaba.druid.pool.DruidDataSource
# slave datasource
ds.financial.slave.driverClassName=com.mysql.jdbc.Driver
ds.financial.slave.url=jdbc:mysql://127.0.0.1:3306/financial_slave?useUnicode=true&characterEncoding=utf8&useSSL=true
ds.financial.slave.username=root
ds.financial.slave.password=
ds.financial.slave.type=com.alibaba.druid.pool.DruidDataSource
注入數據源
@Configuration
public class DataSourceConfig {
@Bean
@Primary
@ConfigurationProperties(prefix = "ds.financial.master")
public DataSource financialMasterDataSource() {
return DataSourceBuilder.create().build();
}
@Bean
@ConfigurationProperties(prefix = "ds.financial.slave")
public DataSource financialSlaveDataSource() {
return DataSourceBuilder.create().build();
}
@Bean(name = "routingDataSource")
public RoutingDataSource routingDataSource() {
Map<Object, Object> dataSourceMap = new HashMap<>();
dataSourceMap.put("financial-master", financialMasterDataSource());
dataSourceMap.put("financial-slave", financialSlaveDataSource());
RoutingDataSource routingDataSource = new RoutingDataSource();
routingDataSource.setTargetDataSources(dataSourceMap);
routingDataSource.setDefaultTargetDataSource(financialMasterDataSource());
return routingDataSource;
}
}
Mybatis配置
@Configuration
public class MyBatisConfig {
@Resource(name = "routingDataSource")
private RoutingDataSource routingDataSource;
/**
* routingDataSource sqlSessionFactory
*
* @return
*/
@Bean
public SqlSessionFactory sqlSessionFactory() throws Exception {
SqlSessionFactoryBean sqlSessionFactoryBean = new SqlSessionFactoryBean();
sqlSessionFactoryBean.setDataSource(routingDataSource);
sqlSessionFactoryBean.setMapperLocations(new PathMatchingResourcePatternResolver().getResources("classpath:mapper/**/*.xml"));
sqlSessionFactoryBean.setTypeAliasesPackage("com.wch.financial.domain");
return sqlSessionFactoryBean.getObject();
}
/**
* 註冊 sqlSessionTemplate
*
* @param sqlSessionFactory
* @return
*/
@Bean
public SqlSessionTemplate financialMasterSqlSessionTemplate(SqlSessionFactory sqlSessionFactory) {
return new SqlSessionTemplate(sqlSessionFactory);
}
}
關鍵字標記生命週期管理
當一個線程執行某個dao方法時讀取此方法配置的數據源關鍵字並寫入datasourceContext,在此方法執行完成後清除datasourceContext中的標記。此生命週期使用aop實現。
標記註解
用於dao類或方法上。
@Target({ElementType.TYPE, ElementType.METHOD})
@Retention(RetentionPolicy.RUNTIME)
public @interface DataSource {
String name() default "";
}
標記註解的方法的切面處理
@Aspect
@Component
public class HandleDatasourceAspect {
@Pointcut("@annotation(com.wch.financial.config.DataSource)")
public void pointcut() {
}
@Before("pointcut()")
public void beforeExecute(JoinPoint joinPoint) {
Method method = ((MethodSignature) joinPoint.getSignature()).getMethod();
DataSource annotation = method.getAnnotation(DataSource.class);
if (null == annotation) {
annotation = joinPoint.getTarget().getClass().getAnnotation(DataSource.class);
}
if (null != annotation) {
// 切換數據源
DataSourceContextHolder.switchDataSource(annotation.name());
}
}
@After("pointcut()")
public void afterExecute() {
DataSourceContextHolder.clear();
}
}
使用
在dao實現類的類或方法上標註@DataSource註解。
@Repository
public class ProductDaoImpl implements ProductDao {
@Resource
private SqlSessionTemplate sst;
@Override
@DataSource(name = "financial-slave")
public List<Product> selectProduct() {
return sst.selectList("financial.product.selectProduct");
}
}