自动读写分离

场景：

1. 在纯的读写分离环境，写操作全部是 master，读操作全部是 slave。
2. 不想通过注解配置完成以上功能。

答：在 mybatis 环境下可以基于 mybatis 插件结合本数据源完成以上功能。

手动注入插件。

@Bean
public MasterSlaveAutoRoutingPlugin masterSlaveAutoRoutingPlugin(){
    return new MasterSlaveAutoRoutingPlugin();
}

默认主库名称 master,从库名称 slave。

暂不支持更多，源码简单可参考重写。

@Intercepts({@Signature(type = Executor.class, method = "query", args = {MappedStatement.class, Object.class, RowBounds.class, ResultHandler.class}),
        @Signature(type = Executor.class, method = "update", args = {MappedStatement.class, Object.class})})
@Slf4j
public class MasterSlaveAutoRoutingPlugin implements Interceptor {

    private static final String MASTER = "master";

    private static final String SLAVE = "slave";

    @Override
    public Object intercept(Invocation invocation) throws Throwable {
        Object[] args = invocation.getArgs();
        MappedStatement ms = (MappedStatement) args[0];
        try {
            DynamicDataSourceContextHolder.push(SqlCommandType.SELECT == ms.getSqlCommandType() ? SLAVE : MASTER);
            return invocation.proceed();
        } finally {
            DynamicDataSourceContextHolder.clear();
        }
    }

    @Override
    public Object plugin(Object target) {
        return target instanceof Executor ? Plugin.wrap(target, this) : target;
    }

    @Override
    public void setProperties(Properties properties) {
    }
}