springboot结合mysql主从来实现读写分离的方法示例

基于springboot框架，application.yml配置多个数据源，使用AOP以及AbstractRootingDataSource、ThreadLocal来实现多数据源切换，以实现读写分离。mysql的主从数据库需要进行设置数据之间的同步。

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

写一个DataSourceConfig.java来注入两个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(); }

写一个enum来标识有哪些数据源

public enum DBTypeEnum { MASTER, SLAVE;}

然后写一个ThreadLocal本地线程的管理类,用于设置当前线程是那一个数据源

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('切换到master数据源'); } public static void slave() {set(DBTypeEnum.SLAVE);logger.info('切换到slave数据源'); } public static void cleanAll() {contextHolder.remove(); }

然后写一个DynamicDataSource继承AbstractRootingDataSource,重写它的determineCurrentLookupKey方法。

public class DynamicDataSource extends AbstractRoutingDataSource { private Logger logger = LogManager.getLogger(DynamicDataSource.class); @Override protected Object determineCurrentLookupKey() {logger.info('此时数据源为{}', DBContextHolder.get());return DBContextHolder.get(); }}

最后写一个AOP来实现数据源切换

@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：这里只是使用了偷懒的方法，对于service里面的select、get、find前缀的方法都使用从库，对于insert、update和delete方法都使用主库。

可以使用注解如下来进行优化:

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

使用此注解来放入到service方法上，

@DataSource(DBTypeEnum.SLAVE)

然后AOP方法修改为：

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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