在查閱測試環境業務日誌中的ERROR級別的日誌時，發現了有一個Mybatis相關的異常錯誤org.apache.ibatis.exceptions.TooManyResultsException: Expected one result (or null) to be returned by selectOne(), but found: 13。

一、分析:詳細堆棧信息打印如下

2018-09-30 17:30:17.548 ERROR 14146 --- [DubboServerHandler-172.16.44.184:20882-thread-136] [c.a.dubbo.rpc.filter.ExceptionFilter    :85] :  [DUBBO] Got unchecked and undeclared exception which called by 172.16.44.184. service: net.lingyejun.mall.product.facade.ProductDetailService, method: getSkuLiveStatusInfo, exception: org.mybatis.spring.MyBatisSystemException: nested exception is org.apache.ibatis.exceptions.TooManyResultsException: Expected one result (or null) to be returned by selectOne(), but found: 13, dubbo version: 2.6.2, current host: ip
org.mybatis.spring.MyBatisSystemException: nested exception is org.apache.ibatis.exceptions.TooManyResultsException: Expected one result (or null) to be returned by selectOne(), but found: 13
        at org.mybatis.spring.MyBatisExceptionTranslator.translateExceptionIfPossible(MyBatisExceptionTranslator.java:77)
        at org.mybatis.spring.SqlSessionTemplate$SqlSessionInterceptor.invoke(SqlSessionTemplate.java:446)
        at com.sun.proxy.$Proxy78.selectOne(Unknown Source)
        at org.mybatis.spring.SqlSessionTemplate.selectOne(SqlSessionTemplate.java:166)
        at org.apache.ibatis.binding.MapperMethod.execute(MapperMethod.java:82)
        at org.apache.ibatis.binding.MapperProxy.invoke(MapperProxy.java:59)
        at com.sun.proxy.$Proxy84.selectOneByExample(Unknown Source)
        at net.lingyejun.mall.product.impl.ProductSkuServiceImpl.getSkuInfoById(ProductSkuServiceImpl.java:95)
        at sun.reflect.GeneratedMethodAccessor138.invoke(Unknown Source)
        at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
        at java.lang.reflect.Method.invoke(Method.java:498)
        at org.springframework.aop.support.AopUtils.invokeJoinpointUsingReflection(AopUtils.java:343)
        at org.springframework.aop.framework.ReflectiveMethodInvocation.invokeJoinpoint(ReflectiveMethodInvocation.java:197)
        at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:163)
        at org.springframework.transaction.interceptor.TransactionAspectSupport.invokeWithinTransaction(TransactionAspectSupport.java:294)
        at org.springframework.transaction.interceptor.TransactionInterceptor.invoke(TransactionInterceptor.java:98)
        at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:185)
        at org.springframework.aop.framework.JdkDynamicAopProxy.invoke(JdkDynamicAopProxy.java:212)
        at com.sun.proxy.$Proxy95.getSkuInfoById(Unknown Source)
        at net.lingyejun.mall.product.impl.ProductDetailServiceImpl.getSkuLiveStatusInfo(ProductDetailServiceImpl.java:122)
        at sun.reflect.GeneratedMethodAccessor178.invoke(Unknown Source)
        at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
        at java.lang.reflect.Method.invoke(Method.java:498)
        at org.springframework.aop.support.AopUtils.invokeJoinpointUsingReflection(AopUtils.java:343)
        at org.springframework.aop.framework.ReflectiveMethodInvocation.invokeJoinpoint(ReflectiveMethodInvocation.java:197)
        at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:163)
        at org.springframework.transaction.interceptor.TransactionAspectSupport.invokeWithinTransaction(TransactionAspectSupport.java:294)
        at org.springframework.transaction.interceptor.TransactionInterceptor.invoke(TransactionInterceptor.java:98)
        at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:185)
        at org.springframework.aop.framework.JdkDynamicAopProxy.invoke(JdkDynamicAopProxy.java:212)
        at com.sun.proxy.$Proxy98.getSkuLiveStatusInfo(Unknown Source)
        at com.alibaba.dubbo.common.bytecode.Wrapper2.invokeMethod(Wrapper2.java)
        at com.alibaba.dubbo.rpc.proxy.javassist.JavassistProxyFactory$1.doInvoke(JavassistProxyFactory.java:47)
        at com.alibaba.dubbo.rpc.proxy.AbstractProxyInvoker.invoke(AbstractProxyInvoker.java:76)
        at com.alibaba.dubbo.config.invoker.DelegateProviderMetaDataInvoker.invoke(DelegateProviderMetaDataInvoker.java:52)
        at com.alibaba.dubbo.rpc.protocol.InvokerWrapper.invoke(InvokerWrapper.java:56)
        at com.alibaba.dubbo.validation.filter.ValidationFilter.invoke(ValidationFilter.java:58)
        at com.alibaba.dubbo.rpc.protocol.ProtocolFilterWrapper$1.invoke(ProtocolFilterWrapper.java:72)
        at com.alibaba.dubbo.rpc.filter.ExceptionFilter.invoke(ExceptionFilter.java:62)
        at com.alibaba.dubbo.rpc.protocol.ProtocolFilterWrapper$1.invoke(ProtocolFilterWrapper.java:72)
        at com.alibaba.dubbo.monitor.support.MonitorFilter.invoke(MonitorFilter.java:75)
        at com.alibaba.dubbo.rpc.protocol.ProtocolFilterWrapper$1.invoke(ProtocolFilterWrapper.java:72)
        at com.alibaba.dubbo.rpc.filter.TimeoutFilter.invoke(TimeoutFilter.java:42)
        at com.alibaba.dubbo.rpc.protocol.ProtocolFilterWrapper$1.invoke(ProtocolFilterWrapper.java:72)
        at com.alibaba.dubbo.rpc.filter.AccessLogFilter.invoke(AccessLogFilter.java:155)
        at com.alibaba.dubbo.rpc.protocol.ProtocolFilterWrapper$1.invoke(ProtocolFilterWrapper.java:72)
		at com.alibaba.dubbo.rpc.protocol.dubbo.DubboProtocol$1.reply(DubboProtocol.java:103)
        at com.alibaba.dubbo.remoting.exchange.support.header.HeaderExchangeHandler.handleRequest(HeaderExchangeHandler.java:96)
        at com.alibaba.dubbo.remoting.exchange.support.header.HeaderExchangeHandler.received(HeaderExchangeHandler.java:172)
        at com.alibaba.dubbo.remoting.transport.DecodeHandler.received(DecodeHandler.java:51)
        at com.alibaba.dubbo.remoting.transport.dispatcher.ChannelEventRunnable.run(ChannelEventRunnable.java:80)
        at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149)
        at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624)
        at java.lang.Thread.run(Thread.java:748)
		Caused by: org.apache.ibatis.exceptions.TooManyResultsException: Expected one result (or null) to be returned by selectOne(), but found: 13
        at org.apache.ibatis.session.defaults.DefaultSqlSession.selectOne(DefaultSqlSession.java:81)
        at sun.reflect.GeneratedMethodAccessor183.invoke(Unknown Source)
        at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
        at java.lang.reflect.Method.invoke(Method.java:498)
        at org.mybatis.spring.SqlSessionTemplate$SqlSessionInterceptor.invoke(SqlSessionTemplate.java:433)
        ... 62 common frames omitted　　

二、根源:條件為Null則會忽略

檢查數據庫查詢那裏的代碼後發現並無異樣，但是這個堆棧信息又將錯誤非常明晰地指出，一定是Mybatis的SelectOne查詢sql，查出了多條記錄，但是在數據庫表中skuId和status對應的是唯一一條記錄。難不成？有些條件沒有生效，執行sql時將skuId這一查詢條件去掉後發現查詢出來的的確是13條記錄。

Example example = new Example(ProductSku.class);
// 設置查詢條件
Example.Criteria criteria = example.createCriteria();
criteria.andEqualTo("skuId", skuId);
criteria.andEqualTo("status", ProductConst.DataStatus.NORMAL);
ProductSku productSku = productSkuMapper.selectOneByExample(example);

　沒錯，當Mybatis的Criteria中的查詢條件為Null時，則會忽略掉這個查詢條件。即，skuId為空Null的時候就沒有帶skuId這個條件，直接是where status = 0;所以查處了多條，像這樣的查詢條件要在最外層做判空處理。

org.apache.ibatis.exceptions.TooManyResultsException