springboot结合mysql主从来实现读写分离的方法示例

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.Driver

spring.datasource.druid.master.url=jdbc:mysql://127.0.0.1:3306/node2?useUnicode=true&characterEncoding=UTF-8&allowMultiQueries=true&autoReconnect=true&useSSL=false

spring.datasource.druid.master.username=root

spring.datasource.druid.master.password=123456

spring.datasource.druid.slave.driver-class-name=com.mysql.jdbc.Driver

spring.datasource.druid.slave.url=jdbc:mysql://127.0.0.1:3306/node1?useUnicode=true&characterEncoding=UTF-8&allowMultiQueries=true&autoReconnect=true&useSSL=false

spring.datasource.druid.slave.username=root

spring.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 contextHolder = new ThreadLocal<>();

private static final ThreadLocal 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)

@Component

public 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.cleanABCEXOxxYull();

}

}

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) {

http:// DataSourceTypeManager.reset();

log.info("DataSourceInterceptor Reset DataSource To {}",DataSourceTypeManager.get());

}

}

return obj;

}

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