重要的话说在前面！！！

Leave是MySQL的关键字！

Leave是MySQL的关键字！

Leave是MySQL的关键字！

今天发生了一件很诡异的Exception，具体如下：

Type 异常报告

消息 Request processing failed; nested exception is org.springframework.jdbc.BadSqlGrammarException:

描述 服务器遇到一个意外的情况，阻止它完成请求。

Exception

org.springframework.web.util.NestedServletException: Request processing failed; nested exception is org.springframework.jdbc.BadSqlGrammarException: 
### Error querying database.  Cause: com.mysql.jdbc.exceptions.jdbc4.MySQLSyntaxErrorException: You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near 'leave WHERE studentId = 1' at line 1
### The error may exist in com/kwxy/hyt/mapper/LeaveMapper.xml
### The error may involve defaultParameterMap
### The error occurred while setting parameters
### SQL: SELECT count(0) FROM leave WHERE studentId = 1
### Cause: com.mysql.jdbc.exceptions.jdbc4.MySQLSyntaxErrorException: You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near 'leave WHERE studentId = 1' at line 1
; bad SQL grammar []; nested exception is com.mysql.jdbc.exceptions.jdbc4.MySQLSyntaxErrorException: You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near 'leave WHERE studentId = 1' at line 1
	org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:978)
	org.springframework.web.servlet.FrameworkServlet.doGet(FrameworkServlet.java:857)
	javax.servlet.http.HttpServlet.service(HttpServlet.java:634)
	org.springframework.web.servlet.FrameworkServlet.service(FrameworkServlet.java:842)
	javax.servlet.http.HttpServlet.service(HttpServlet.java:741)
	org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:53)
	com.kwxy.hyt.filter.SystemContextFilter.doFilter(SystemContextFilter.java:38)
	org.springframework.web.filter.CharacterEncodingFilter.doFilterInternal(CharacterEncodingFilter.java:88)
	org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:107)

Root Cause

org.springframework.jdbc.BadSqlGrammarException: 
### Error querying database.  Cause: com.mysql.jdbc.exceptions.jdbc4.MySQLSyntaxErrorException: You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near 'leave WHERE studentId = 1' at line 1
### The error may exist in com/kwxy/hyt/mapper/LeaveMapper.xml
### The error may involve defaultParameterMap
### The error occurred while setting parameters
### SQL: SELECT count(0) FROM leave WHERE studentId = 1
### Cause: com.mysql.jdbc.exceptions.jdbc4.MySQLSyntaxErrorException: You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near 'leave WHERE studentId = 1' at line 1
; bad SQL grammar []; nested exception is com.mysql.jdbc.exceptions.jdbc4.MySQLSyntaxErrorException: You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near 'leave WHERE studentId = 1' at line 1
	org.springframework.jdbc.support.SQLErrorCodeSQLExceptionTranslator.doTranslate(SQLErrorCodeSQLExceptionTranslator.java:231)
	org.springframework.jdbc.support.AbstractFallbackSQLExceptionTranslator.translate(AbstractFallbackSQLExceptionTranslator.java:73)
	org.mybatis.spring.MyBatisExceptionTranslator.translateExceptionIfPossible(MyBatisExceptionTranslator.java:73)
	org.mybatis.spring.SqlSessionTemplate$SqlSessionInterceptor.invoke(SqlSessionTemplate.java:371)
	com.sun.proxy.$Proxy16.selectList(Unknown Source)
	org.mybatis.spring.SqlSessionTemplate.selectList(SqlSessionTemplate.java:198)
	org.apache.ibatis.binding.MapperMethod.executeForMany(MapperMethod.java:119)
	org.apache.ibatis.binding.MapperMethod.execute(MapperMethod.java:63)
	org.apache.ibatis.binding.MapperProxy.invoke(MapperProxy.java:52)
	com.sun.proxy.$Proxy21.findBySqlRerturnEntity(Unknown Source)
	com.kwxy.hyt.base.BaseServiceImpl.findBySqlRerturnEntity(BaseServiceImpl.java:280)
	com.kwxy.hyt.controller.LeaveController.myleave(LeaveController.java:177)
	java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
	java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
	java.base/jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
	java.base/java.lang.reflect.Method.invoke(Method.java:567)
	org.springframework.web.method.support.InvocableHandlerMethod.doInvoke(InvocableHandlerMethod.java:221)
	org.springframework.web.method.support.InvocableHandlerMethod.invokeForRequest(InvocableHandlerMethod.java:137)
	org.springframework.web.servlet.mvc.method.annotation.ServletInvocableHandlerMethod.invokeAndHandle(ServletInvocableHandlerMethod.java:110)
	org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.invokeHandleMethod(RequestMappingHandlerAdapter.java:777)
	org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.handleInternal(RequestMappingHandlerAdapter.java:706)
	org.springframework.web.servlet.mvc.method.AbstractHandlerMethodAdapter.handle(AbstractHandlerMethodAdapter.java:85)
	org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:943)
	org.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:877)
	org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:966)
	org.springframework.web.servlet.FrameworkServlet.doGet(FrameworkServlet.java:857)
	javax.servlet.http.HttpServlet.service(HttpServlet.java:634)
	org.springframework.web.servlet.FrameworkServlet.service(FrameworkServlet.java:842)
	javax.servlet.http.HttpServlet.service(HttpServlet.java:741)
	org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:53)
	com.kwxy.hyt.filter.SystemContextFilter.doFilter(SystemContextFilter.java:38)
	org.springframework.web.filter.CharacterEncodingFilter.doFilterInternal(CharacterEncodingFilter.java:88)
	org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:107)

可以看到异常很明确地告诉我是SQL语句异常，可是我当时还不知道具体是哪里出了问题，我就把这句SQL一遍又一遍地在Navicat上面执行，发现完全没有问题啊！

然后我以为是mybatis地xml没配置好，随即有用原先的方式演示了一遍，也完全没有问题啊！！！

但是，但是！一旦换成英文版的请假“leave”就必定出错！

然后我就这样陷入了蜜汁自信（我写的SQL一定没有错！）疯狂的找是不是因为反射或者代理出问题了导致SQL语句解析有问题...就这样我耗了七个多小时，，忽然灵机一动，，，是不是‘leave'是MySQL的关键字啊？然后搜了一下...我TM心态崩了啊！学了三四年、用了三四年SQL从来都不知道’leave'是关键字...我这辈子都不会忘记了，都不好意思说我学过数据库语言！