springboot结合mysql主从来实现读写分离的方法示例

1.实现的功能

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。

2.代码实现

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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我要扼住命运的咽喉。