一个很奇怪的42000的错误，折腾了我一晚上。。。。

我的系统是Spring + SpringMVC + MyBatis结构， 数据库的mapper以及model等文件都是用MyBatisGenerator自动生成的，一切都很快就完成了。 我的表结构module如下：

 mysql> desc module;

 +----------+---------------+------+-----+---------+----------------+

 | Field    | Type          | Null | Key | Default | Extra          |

 +----------+---------------+------+-----+---------+----------------+

 | id       | int(11)       | NO   | PRI | NULL    | auto_increment |

 | name     | varchar(128)  | YES  |     | NULL    |                |

 | type     | varchar(128)  | NO   |     | NULL    |                |

 | usage    | varchar(1024) | YES  |     | NULL    |                |

 | ctime    | datetime      | NO   |     | NULL    |                |

 | mtime    | datetime      | NO   |     | NULL    |                |

 | operator | varchar(64)   | NO   |     | NULL    |                |

 | moduleid | varchar(128)  | NO   |     | NULL    |                |

 | context  | longblob      | YES  |     | NULL    |                |

 +----------+---------------+------+-----+---------+----------------+

 9 rows in set (0.02 sec)

请注意上面的红色字段！

我在Eclipse里面调试的时候，遇到下面的错误：

 [2016-05-13 08:47:44] [DEBUG] [http-bio-8080-exec-9] [org.mybatis.spring.transaction.SpringManagedTransaction.openConnection(SpringManagedTransaction.java:88)] - JDBC Connection [com.alibaba.druid.proxy.jdbc.ConnectionProxyImpl@722f0164] will be managed by Spring

   [2016-05-13 08:47:44] [DEBUG] [http-bio-8080-exec-9] [org.apache.ibatis.logging.jdbc.BaseJdbcLogger.debug(BaseJdbcLogger.java:139)] - ==>  Preparing: select id, type, name, usage, ctime, mtime, operator, moduleid , context from module where 1=1 limit ?, ?

   [2016-05-13 08:47:44] [DEBUG] [http-bio-8080-exec-9] [org.apache.ibatis.logging.jdbc.BaseJdbcLogger.debug(BaseJdbcLogger.java:139)] - ==> Parameters: 0(Integer), 10(Integer)

   [2016-05-13 08:47:44] [ INFO] [http-bio-8080-exec-9] [org.springframework.beans.factory.xml.XmlBeanDefinitionReader.loadBeanDefinitions(XmlBeanDefinitionReader.java:316)] - Loading XML bean definitions from class path resource [org/springframework/jdbc/support/sql-error-codes.xml]

   [2016-05-13 08:47:44] [ INFO] [http-bio-8080-exec-9] [org.springframework.jdbc.support.SQLErrorCodesFactory.<init>(SQLErrorCodesFactory.java:126)] - SQLErrorCodes loaded: [DB2, Derby, H2, HSQL, Informix, MS-SQL, MySQL, Oracle, PostgreSQL, Sybase]

   [2016-05-13 08:47:44] [DEBUG] [http-bio-8080-exec-9] [org.mybatis.spring.SqlSessionUtils.closeSqlSession(SqlSessionUtils.java:168)] - Releasing transactional SqlSession [org.apache.ibatis.session.defaults.DefaultSqlSession@5783249]

   [2016-05-13 08:47:44] [DEBUG] [http-bio-8080-exec-9] [org.mybatis.spring.SqlSessionUtils$SqlSessionSynchronization.afterCompletion(SqlSessionUtils.java:301)] - Transaction synchronization closing SqlSession [org.apache.ibatis.session.defaults.DefaultSqlSession@5783249]

   五月 13, 2016 8:48:16 上午 org.apache.catalina.core.StandardWrapperValve invoke

 严重: Servlet.service() for servlet [spring] in context with path [/NewTKCMS] threw exception [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 'usage, ctime, mtime, operator, moduleid

     ,

     context

     from' at line 3

 ### The error may exist in file [E:\2016\workwps\.metadata\.plugins\org.eclipse.wst.server.core\tmp0\wtpwebapps\NewTKCMS\WEB-INF\classes\com\tk\cms\module\dao\mapper\ModuleMapper.xml]

 ### The error may involve com.tk.cms.module.dao.ModuleMapper.queryList-Inline

 ### The error occurred while setting parameters

 ### SQL: select            id, type, name, usage, ctime, mtime, operator, moduleid         ,           context         from module where 1=1                                                                                                      limit ?, ?

 ### 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 'usage, ctime, mtime, operator, moduleid

     ,

     context

     from' at line 3

 ; 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 'usage, ctime, mtime, operator, moduleid

     ,

     context

     from' at line 3] with root 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 'usage, ctime, mtime, operator, moduleid

     ,

     context

     from' at line 3

     at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method)

     at sun.reflect.NativeConstructorAccessorImpl.newInstance(NativeConstructorAccessorImpl.java:57)

     at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:45)

     at java.lang.reflect.Constructor.newInstance(Constructor.java:526)

     at com.mysql.jdbc.Util.handleNewInstance(Util.java:406)

     at com.mysql.jdbc.Util.getInstance(Util.java:381)

     at com.mysql.jdbc.SQLError.createSQLException(SQLError.java:1030)

     at com.mysql.jdbc.SQLError.createSQLException(SQLError.java:956)

     at com.mysql.jdbc.MysqlIO.checkErrorPacket(MysqlIO.java:3515)

     at com.mysql.jdbc.MysqlIO.checkErrorPacket(MysqlIO.java:3447)

     at com.mysql.jdbc.MysqlIO.sendCommand(MysqlIO.java:1951)

     at com.mysql.jdbc.MysqlIO.sqlQueryDirect(MysqlIO.java:2101)

     at com.mysql.jdbc.ConnectionImpl.execSQL(ConnectionImpl.java:2554)

     at com.mysql.jdbc.PreparedStatement.executeInternal(PreparedStatement.java:1761)

     at com.mysql.jdbc.PreparedStatement.execute(PreparedStatement.java:1021)

     at com.alibaba.druid.filter.FilterChainImpl.preparedStatement_execute(FilterChainImpl.java:2931)

     at com.alibaba.druid.filter.FilterEventAdapter.preparedStatement_execute(FilterEventAdapter.java:440)

     at com.alibaba.druid.filter.FilterChainImpl.preparedStatement_execute(FilterChainImpl.java:2929)

     at com.alibaba.druid.proxy.jdbc.PreparedStatementProxyImpl.execute(PreparedStatementProxyImpl.java:118)

     at com.alibaba.druid.pool.DruidPooledPreparedStatement.execute(DruidPooledPreparedStatement.java:493)

     at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)

     at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57)

     at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)

     at java.lang.reflect.Method.invoke(Method.java:606)

     at org.apache.ibatis.logging.jdbc.PreparedStatementLogger.invoke(PreparedStatementLogger.java:62)

     at com.sun.proxy.$Proxy33.execute(Unknown Source)

     at org.apache.ibatis.executor.statement.PreparedStatementHandler.query(PreparedStatementHandler.java:59)

     at org.apache.ibatis.executor.statement.RoutingStatementHandler.query(RoutingStatementHandler.java:73)

     at org.apache.ibatis.executor.SimpleExecutor.doQuery(SimpleExecutor.java:60)

     at org.apache.ibatis.executor.BaseExecutor.queryFromDatabase(BaseExecutor.java:267)

     at org.apache.ibatis.executor.BaseExecutor.query(BaseExecutor.java:137)

     at org.apache.ibatis.executor.CachingExecutor.query(CachingExecutor.java:96)

     at org.apache.ibatis.executor.CachingExecutor.query(CachingExecutor.java:77)

     at org.apache.ibatis.session.defaults.DefaultSqlSession.selectList(DefaultSqlSession.java:108)

     at org.apache.ibatis.session.defaults.DefaultSqlSession.selectList(DefaultSqlSession.java:102)

     at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)

     at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57)

     at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)

     at java.lang.reflect.Method.invoke(Method.java:606)

     at org.mybatis.spring.SqlSessionTemplate$SqlSessionInterceptor.invoke(SqlSessionTemplate.java:358)

     at com.sun.proxy.$Proxy8.selectList(Unknown Source)

     at org.mybatis.spring.SqlSessionTemplate.selectList(SqlSessionTemplate.java:198)

     at org.apache.ibatis.binding.MapperMethod.executeForMany(MapperMethod.java:119)

     at org.apache.ibatis.binding.MapperMethod.execute(MapperMethod.java:63)

     at org.apache.ibatis.binding.MapperProxy.invoke(MapperProxy.java:52)

     at com.sun.proxy.$Proxy25.queryList(Unknown Source)

     at com.tk.cms.module.service.impl.ModuleService.queryList(ModuleService.java:87)

     at com.tk.cms.module.service.impl.ModuleService$$FastClassBySpringCGLIB$$835fbc07.invoke(<generated>)

     at org.springframework.cglib.proxy.MethodProxy.invoke(MethodProxy.java:204)

     at org.springframework.aop.framework.CglibAopProxy$CglibMethodInvocation.invokeJoinpoint(CglibAopProxy.java:700)

     at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:150)

     at com.alibaba.druid.support.spring.stat.DruidStatInterceptor.invoke(DruidStatInterceptor.java:73)

     at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:172)

     at org.springframework.transaction.interceptor.TransactionInterceptor$1.proceedWithInvocation(TransactionInterceptor.java:96)

     at org.springframework.transaction.interceptor.TransactionAspectSupport.invokeWithinTransaction(TransactionAspectSupport.java:260)

     at org.springframework.transaction.interceptor.TransactionInterceptor.invoke(TransactionInterceptor.java:94)

     at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:172)

     at org.springframework.aop.interceptor.ExposeInvocationInterceptor.invoke(ExposeInvocationInterceptor.java:91)

     at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:172)

     at org.springframework.aop.framework.CglibAopProxy$DynamicAdvisedInterceptor.intercept(CglibAopProxy.java:633)

     at com.tk.cms.module.service.impl.ModuleService$$EnhancerBySpringCGLIB$$828018db.queryList(<generated>)

     at com.tk.cms.module.controller.ModuleController.moduleElementList(ModuleController.java:186)

     at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)

     at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57)

     at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)

     at java.lang.reflect.Method.invoke(Method.java:606)

     at org.springframework.web.method.support.InvocableHandlerMethod.invoke(InvocableHandlerMethod.java:215)

     at org.springframework.web.method.support.InvocableHandlerMethod.invokeForRequest(InvocableHandlerMethod.java:132)

     at org.springframework.web.servlet.mvc.method.annotation.ServletInvocableHandlerMethod.invokeAndHandle(ServletInvocableHandlerMethod.java:104)

     at org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.invokeHandleMethod(RequestMappingHandlerAdapter.java:743)

     at org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.handleInternal(RequestMappingHandlerAdapter.java:672)

     at org.springframework.web.servlet.mvc.method.AbstractHandlerMethodAdapter.handle(AbstractHandlerMethodAdapter.java:82)

     at org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:933)

     at org.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:867)

     at org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:951)

     at org.springframework.web.servlet.FrameworkServlet.doGet(FrameworkServlet.java:842)

     at javax.servlet.http.HttpServlet.service(HttpServlet.java:620)

     at org.springframework.web.servlet.FrameworkServlet.service(FrameworkServlet.java:827)

     at javax.servlet.http.HttpServlet.service(HttpServlet.java:727)

     at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:303)

     at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:208)

     at org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:52)

     at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:241)

     at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:208)

     at org.apache.shiro.web.servlet.AbstractShiroFilter.executeChain(AbstractShiroFilter.java:449)

     at org.apache.shiro.web.servlet.AbstractShiroFilter$1.call(AbstractShiroFilter.java:365)

     at org.apache.shiro.subject.support.SubjectCallable.doCall(SubjectCallable.java:90)

     at org.apache.shiro.subject.support.SubjectCallable.call(SubjectCallable.java:83)

     at org.apache.shiro.subject.support.DelegatingSubject.execute(DelegatingSubject.java:383)

     at org.apache.shiro.web.servlet.AbstractShiroFilter.doFilterInternal(AbstractShiroFilter.java:362)

     at org.apache.shiro.web.servlet.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:125)

     at org.springframework.web.filter.DelegatingFilterProxy.invokeDelegate(DelegatingFilterProxy.java:343)

     at org.springframework.web.filter.DelegatingFilterProxy.doFilter(DelegatingFilterProxy.java:260)

     at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:241)

     at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:208)

     at org.springframework.web.filter.CharacterEncodingFilter.doFilterInternal(CharacterEncodingFilter.java:88)

     at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:106)

     at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:241)

     at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:208)

     at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:220)

     at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:122)

     at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:501)

     at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:171)

     at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:102)

     at org.apache.catalina.valves.AccessLogValve.invoke(AccessLogValve.java:950)

     at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:116)

     at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:408)

     at org.apache.coyote.http11.AbstractHttp11Processor.process(AbstractHttp11Processor.java:1040)

     at org.apache.coyote.AbstractProtocol$AbstractConnectionHandler.process(AbstractProtocol.java:607)

     at org.apache.tomcat.util.net.JIoEndpoint$SocketProcessor.run(JIoEndpoint.java:316)

     at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1145)

     at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:615)

     at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61)

     at java.lang.Thread.run(Thread.java:744)

下面的这个日志是核心的错误信息，于是乎，我就在MySQL下面直接用命令执行，因为怀疑是MyBatis生成的查询有错误！

 ### The error may involve com.tk.cms.module.dao.ModuleMapper.queryList-Inline

 ### The error occurred while setting parameters

 ### SQL: select            id, type, name, usage, ctime, mtime, operator, moduleid         ,           context         from module where 1=1                                                                                                      limit ?, ?

 ### 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 'usage, ctime, mtime, operator, moduleid

     ,

     context

     from' at line 3

 ; 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 'usage, ctime, mtime, operator, moduleid

     ,

     context

     from' at line 3] with root 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 'usage, ctime, mtime, operator, moduleid

     ,

     context

     from' at line 3

直接MySQL查询，得到下面的错误：

 mysql> select id, type, name, usage, ctime, mtime, operator, moduleid, context from module;

 ERROR 1064 (42000): 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 'usage, ctime, mtime, operator, moduleid, context from module' at line 1

为什么我会怀疑是这个关键字usage在作怪呢？其实还是上面的错误日志有点提示作用，于是乎，我就专门针对这个字段做了查询：

 mysql> select usage from module;

 ERROR 1064 (42000): 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 'usage from module' at line 1

那我再试试其他的呢？如下：

 mysql> select id, type, name, ctime, mtime, operator, moduleid, context from module;

 Empty set (0.00 sec)

是不是很神奇呢?这个查询就可以通过。。。。

后来，我将这个usage改成了其他的字段，比如usedStatus。如下：

 mysql> desc module;

 +------------+---------------+------+-----+---------+----------------+

 | Field      | Type          | Null | Key | Default | Extra          |

 +------------+---------------+------+-----+---------+----------------+

 | id         | int(11)       | NO   | PRI | NULL    | auto_increment |

 | name       | varchar(128)  | YES  |     | NULL    |                |

 | type       | varchar(128)  | NO   |     | NULL    |                |

 | usedStatus | varchar(1024) | YES  |     | NULL    |                |

 | ctime      | datetime      | NO   |     | NULL    |                |

 | mtime      | datetime      | NO   |     | NULL    |                |

 | operator   | varchar(64)   | NO   |     | NULL    |                |

 | moduleid   | varchar(128)  | NO   |     | NULL    |                |

 | context    | longblob      | YES  |     | NULL    |                |

 +------------+---------------+------+-----+---------+----------------+

 9 rows in set (0.02 sec)

再次查询：

 mysql> select id, type, name, usedStatus, ctime, mtime, operator, moduleid, context from module;

 Empty set (0.00 sec)

这次不报错误了。。。。

是不是可以总结一下：数据库表字段定义的时候，要避开MySQL系统的关键字？？？？

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