SpringBoot基于AbstractRoutingDataSource实现多数据源动态切换

目录一、场景二、原理三、代码示例

一、场景

在生产业务中，有一些任务执行了耗时较长的查询操作，在实时性要求不高的时候，我们希望将这些查询sql分离出来，去从库查询，以减少应用对主数据库的压力。

一种方案是在配置文件中配置多个数据源，然后通过配TVVNgSPOx置类来获取数据源以及mapper相关的扫描配置，不同的数据源配置不佟的mapper扫描位置，然后需要哪一个数据源就注入哪一个mapper接口即可，这种方法比较简单。特征是通过mapper扫描位置区分数据源。

第二种方案是配置一个默认使用的数据源，然后定义多个其他的数据源，使用aop形成注解式选择数据源。此种方案实现的核心是对AbstractRoutingDhttp://ataSource 类的继承。这是本文的重点。

二、原理

AbstractRoutingDataSource的多数据源动态切换的核心逻辑是：在程序运行时，把数据源数据源通过 AbstractRoutingDataSource 动态织入到程序中，灵活的进行数据源切换。基于AbstractRoutingDataSource的多数据源动态切换，可以实现读写分离。逻辑如下：

/**

* Retrieve the current target DataSource. Determines the

* {@link #determineCurrentLookupKey() current lookup key}, performs

* a lookup in the {@link #setTargetDataSources targetDataSources} map,

* falls back to the specified

* {@link #setDefaultTargetDataSource default target DataSource} if necessary.

* @see #determineCurrentLookupKey()

*/

protected DataSource determineTargetDataSource() {

Assert.notNull(this.resolvedDataSources, "DataSource router not initialized");

Object lookupKey = determineCurrentLookupKey();

DataSource dataSource = this.resolvedDataSources.get(lookupKey);

if (dataSource == null &&ampTVVNgSPOx; (this.lenientFallback || lookupKey == null)) {

dataSource = this.resolvedDefaultDataSource;

}

if (dataSource == null) {

throw new IllegalStateException("Cannot determine target DataSource for lookup key [" + lookupKey + "]");

}

return dataSource;

}

/**

* Determine the current lookup key. This will typically be

* implemented to check a thread-bound transaction context.

*

Allows for arbitrary keys. The returned key needs

* to match the stored lookup key type, as resolved by the

* {@link #resolveSpecifiedLookupKey} method.

*/

@Nullable

protected abstract Object determineCurrentLookupKey();

通过实现抽象方法determineCurrentLookupKey指定需要切换的数据源

三、代码示例

示例中主要依赖

com.alibaba.druid;tk.mybatis

定义一个类用于关联数据源。通过 TheadLocal 来保存每个线程选择哪个数据源的标志(key)

@Slf4j

public class DynamicDataSourceContextHolder {

private static final ThreadLocal contextHolder = new ThreadLocal();

public static List dataSourceIds = new ArrayList();

public static void setDataSourceType(String dataSourceType) {

log.info("设置当前数据源为{}",dataSourceType);

contextHolder.set(dataSourceType);

}

public static String getDataSourceType() {

return contextHolder.get() ;

}

public static void clearDataSourceType() {

contextHolder.remove();

}

public static boolean containsDataSource(String dataSourceId){

log.info("list = {},dataId={}", jsON.toJSON(dataSourceIds),dataSourceId);

return dataSourceIds.contains(dataSourceId);

}

}

继承

AbstractRoutingDataSource

public class DynamicDataSource extends AbstractRoutingDataSource {

@Override

protected Object determineCurrentLookupKey() {

return DynamicDataSourceContextHolder.getDataSourceType();

}

}

配置主数据库master 与从数据库slave（略）。数据源配置可以从简

@Configuration

@tk.mybatis.spring.annotation.MapperScan(value = {"com.server.dal.dao"})

@ConditionalOnProperty(name = "java.druid.datasource.master.url")

public class JavaDruidDataSourceConfiguration {

private static final Logger logger = LoggerFactory.getLogger(JavaDruidDataSourceConfiguration.class);

@Resource

private JavaDruidDataSourceProperties druidDataSourceProperties;

@Primary

@Bean(name = "masterDataSource", initMethod = "init", destroyMethod = "close")

@ConditionalOnMissingBean(name = "masterDataSource")

public DruidDataSource javaReadDruidDataSource() {

DruidDataSource result = new DruidDataSource();

try {

// result.setName(druidDataSourceProperties.getName());

result.setUrl(druidDataSourceProperties.getUrl());

result.setUsername(druidDataSourceProperties.getUsername());

result.setPassword(druidDataSourceProperties.getPassword());

result.setConnectionProperties(

"config.decrypt=false;config.decrypt.key=" + druidDataSourceProperties.getPwdPublicKey());

result.setFilters("config");

result.setMaxActive(druidDataSourceProperties.getMaxActive());

result.setInitialSize(druidDataSourceProperties.getInitialSize());

result.setMaxWait(druidDataSourceProperties.getMaxWait());

result.setMinIdle(druidDataSourceProperties.getMinIdle());

result.setTimeBetweenEvictionRunsMillis(druidDataSourceProperties.getTimeBetweenEvictionRunsMillis());

result.setMinEvictableIdleTimeMillis(druidDataSourceProperties.getMinEvictableIdleTimeMillis());

result.setValidationQuery(druidDataSourceProperties.getValidationQuery());

result.setTestWhileIdle(druidDataSourceProperties.isTestWhileIdle());

result.setTestOnBorrow(druidDataSourceProperties.isTestOnBorrow());

result.setTestOnReturn(druidDataSourceProperties.isTestOnReturn());

result.setPoolPreparedStatements(druidDataSourceProperties.isPoolPreparedStatements());

result.setMaxOpenPreparedStatements(druidDataSourceProperties.getMaxOpenPreparedStatements());

if (druidDataSourceProperties.isEnableMonitor()) {

StatFilter filter = new StatFilter();

filter.setLogSlowSql(druidDataSourceProperties.isLogSlowSql());

filter.setMergeSql(druidDataSourceProperties.isMergeSql());

filter.setSlowSqlMillis(druidDataSourceProperties.getSlowSqlMillis());

List list = new ArrayList<>();

list.add(filter);

result.setProxyFilters(list);

}

} catch (Exception e) {

logger.error("数据源加载失败:", e);

} finally {

result.close();

}

return result;

}

}

注意主从数据库的bean name

配置DynamicDataSource

targetDataSources 存放数据源的k-v对defaultTargetDataSource 存放默认数据源

配置事务管理器和SqlSessionFactoryBean

@Configuration

public class DynamicDataSourceConfig {

private static final String MAPPER_LOCATION = "classpath*:sqlmap/dao/*Mapper.xml";

@Bean(name = "dynamicDataSource")

public DynamicDataSource dynamicDataSource(@Qualifier("masterDataSource") DruidDataSource masterDataSource,

@Qualifier("slaveDataSource") DruidDataSource slaveDataSource) {

Map

DynamicDataSourceContextHolder.dataSourceIds.add("masterDataSource");

targetDataSource.put("masterDataSource", masterDataSource);

DynamicDataSourceContextHolder.dataSourceIds.add("slaveDataSource");

targetDataSource.put("slaveDataSource", slaveDataSource);

DynamicDataSource dataSource = new DynamicDataSource();

dataSource.setTargetDataSources(targetDataSource);

dataSource.setDefaultTargetDataSource(masterDataSource);

return dataSource;

}

@Primary

@Bean(name = "javaTransactionManager")

@ConditionalOnMissingBean(name = "javaTransactionManager")

public DataSourceTransactionManager transactionManager(@Qualifier("dynamicDataSource") DynamicDataSource druidDataSource) {

return new DataSourceTransactionManager(druidDataSource);

}

@Bean(name = "sqlSessionFactoryBean")

public SqlSessionFactoryBean myGetSqlSessionFactory(@Qualifier("dynamicDataSource") DynamicDataSource dataSource) {

SqlSessionFactoryBean sqlSessionFactoryBean = new SqlSessionFactoryBean();

ResourcePatternResolver resolver = new PathMatchingResourcePatternResolver();

try {

sqlSessionFactoryBean.setMapperLocations(resolver.getResources(MAPPER_LOCATION));

} catch (IOException e) {

e.printStackTrace();

}

sqlSessionFactoryBean.setDataSource(dataSource);

return sqlSessionFactoryBean;

}

}

定义一个注解用于指定数据源

@Target({ ElementType.METHOD, ElementType.TYPE })

@Retention(RetentionPolicy.RUNTIME)

@Documented

public @interface TargetDataSource {

String value();

}

切面的业务逻辑。注意指定order，以确保在开启事务之前执行 。

@Aspect

@Slf4j

@Order(-1)

@Component

public class DataSourceAop {

@Before("@annotation(targetDataSource)")

public void changeDataSource(JoinPoint point, TargetDataSource targetDataSource) {

String dsId = targetDataSource.value();

if (!DynamicDataSourceContextHolder.containsDataSource(dsId)) {

log.error("数据源[{}]不存在，使用默认数据源 > {}" + targetDataSource.value() + point.getSignature());

} else {

log.info("UseDataSource : {} > {}" + targetDataSource.value() + point.getSignature());

DynamicDataSourceContextHolder.setDataSourceType(targetDataSource.value());

}

}

@After("@annotation(targetDataSource)")

public void restoreDataSource(JoinPoint point, TargetDataSource targetDataSource) {

log.info("RevertDataSource : {} > {}"+targetDataSource.value()+point.getSignature());

DynamicDataSourceContextHolder.clearDataSourceType();

}

}

以上略去了pom.xml和application.yml

使用示例

@Resource

private ShopBillDOMapper shopBillDOMapper;

//使用默认数据源

public ShopBillBO queryTestData(Integer id){

return shopBillDOMapper.getByShopBillId(id);

}

//切换到指定的数据源

@TargetDataSource("slaveDataSource")

public ShopBill queryTestData2(Integer id){

return shopBillDOMapper.getByShopBillId(id);

}

如果返回不同的结果就成功了！

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