基于springboot框架，application.yml配置多個數據源，使用AOP以及AbstractRootingDataSource、ThreadLocal來實現多數據源切換，以實現讀寫分離。mysql的主從數據庫需要進行設置數據之間的同步。

application.properties中的配置

spring.datasource.druid.master.driver-class-name=com.mysql.jdbc.Driverspring.datasource.druid.master.url=jdbc:mysql://127.0.0.1:3306/node2?useUnicode=true&characterEncoding=UTF-8&allowMultiQueries=true&autoReconnect=true&useSSL=falsespring.datasource.druid.master.username=rootspring.datasource.druid.master.password=123456 spring.datasource.druid.slave.driver-class-name=com.mysql.jdbc.Driverspring.datasource.druid.slave.url=jdbc:mysql://127.0.0.1:3306/node1?useUnicode=true&characterEncoding=UTF-8&allowMultiQueries=true&autoReconnect=true&useSSL=falsespring.datasource.druid.slave.username=rootspring.datasource.druid.slave.password=123456

寫一個DataSourceConfig.java來注入兩個bean

@Bean @ConfigurationProperties('spring.datasource.druid.master') public DataSource masterDataSource() {logger.info('select master data source');return DruidDataSourceBuilder.create().build(); } @Bean @ConfigurationProperties('spring.datasource.druid.slave') public DataSource slaveDataSource() {logger.info('select slave data source');return DruidDataSourceBuilder.create().build(); }

寫一個enum來標識有哪些數據源

public enum DBTypeEnum { MASTER, SLAVE;}

然后寫一個ThreadLocal本地線程的管理類,用于設置當前線程是那一個數據源

private static final ThreadLocal<DBTypeEnum> contextHolder = new ThreadLocal<>(); private static final ThreadLocal<DBTypeEnum> contextHolder2 = ThreadLocal.withInitial(() -> DBTypeEnum.MASTER); public static void set(DBTypeEnum dbType) {contextHolder.set(dbType); } public static DBTypeEnum get() {return contextHolder.get(); } public static void master() {set(DBTypeEnum.MASTER);logger.info('切換到master數據源'); } public static void slave() {set(DBTypeEnum.SLAVE);logger.info('切換到slave數據源'); } public static void cleanAll() {contextHolder.remove(); }

然后寫一個DynamicDataSource繼承AbstractRootingDataSource,重寫它的determineCurrentLookupKey方法。

public class DynamicDataSource extends AbstractRoutingDataSource { private Logger logger = LogManager.getLogger(DynamicDataSource.class); @Override protected Object determineCurrentLookupKey() {logger.info('此時數據源為{}', DBContextHolder.get());return DBContextHolder.get(); }}

最后寫一個AOP來實現數據源切換

@Aspect@Order(1)@Componentpublic class DataSourceAop { private Logger logger = LogManager.getLogger(DataSourceAop.class); @Pointcut('(execution(* com.springboot.demo.service..*.select*(..)) ' + '|| execution(* com.springboot.demo.service..*.find*(..)) ' + '|| execution(* com.springboot.demo.service..*.get*(..)))') public void readPointcut() {logger.info('read only operate ,into slave db'); } @Pointcut('execution(* com.springboot.demo.service..*.insert*(..)) ' + '|| execution(* com.springboot.demo.service..*.update*(..)) ' + '|| execution(* com.springboot.demo.service..*.delete*(..)) ') public void writePointcut() {logger.info('read or write operate ,into master db'); } @Before('readPointcut()') public void read() {logger.info('read operate');DBContextHolder.slave(); } @Before('writePointcut()') public void write() {logger.info('write operate');DBContextHolder.master(); } @After('writePointcut(),readPointcut()') public void clean() {logger.info('dataSource cleanAll');DBContextHolder.cleanAll(); }}

注意：這里只是使用了偷懶的方法，對于service里面的select、get、find前綴的方法都使用從庫，對于insert、update和delete方法都使用主庫。

可以使用注解如下來進行優化:

@Retention(RetentionPolicy.RUNTIME)@Target(ElementType.METHOD)public @interface DataSource { @AliasFor('dataSource') DBTypeEnum value() default DBTypeEnum.MASTER; DBTypeEnum dataSource() default DBTypeEnum.MASTER;}

使用此注解來放入到service方法上，

@DataSource(DBTypeEnum.SLAVE)

然后AOP方法修改為：

private static final String POINT = 'execution (* com.springboot.demo.service.*.*(..))'; @Around(POINT) public Object dataSourceAround(ProceedingJoinPoint joinPoint) throws Throwable {Object[] args = joinPoint.getArgs();Object obj;Object target = joinPoint.getTarget();String methodName = joinPoint.getSignature().getName();Class clazz = target.getClass();Class<?>[] parameterTypes = ((MethodSignature) joinPoint.getSignature()).getMethod().getParameterTypes();boolean isDynamicDataSourceMethod = false;try { Method method = clazz.getMethod(methodName, parameterTypes); DataSources currentDataSource = null; if (method != null && method.isAnnotationPresent(DataSource.class)) {isDynamicDataSourceMethod = true;currentDataSource = method.getAnnotation(DataSource.class).value();DataSourceTypeManager.set(currentDataSource);log.info('DataSourceInterceptor Switch DataSource To {}',currentDataSource); } obj = joinPoint.proceed(args); if (isDynamicDataSourceMethod) {log.info('DataSourceInterceptor DataSource {} proceed',currentDataSource); }} finally { if (isDynamicDataSourceMethod) {DataSourceTypeManager.reset();log.info('DataSourceInterceptor Reset DataSource To {}',DataSourceTypeManager.get()); }}return obj; }

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