mybatis plus 查询数据库字段名自动添加下划线-编程知识

问题

mybatis plus 查询数据库字段名自动添加下划线

详细问题

笔者使用mybatis plus 查询数据库，执行查询语句报错。详细报错信息

2024-03-08 11:08:33.156 ERROR 4816 --- [nio-9090-exec-9] o.a.c.c.C.[.[.[/].[dispatcherServlet]    : Servlet.service() for servlet [dispatcherServlet] in context with path [] threw exception [Request processing failed; nested exception is org.springframework.jdbc.BadSqlGrammarException: 
### Error querying database.  Cause: java.sql.SQLSyntaxErrorException: Unknown column 'a_l_l_s_k_y_s_f_c_s_w_d_w_n' in 'field list'
### The error may exist in com/qingge/springboot/mapper/AgriculturalMapper.java (best guess)
### The error may involve defaultParameterMap
### The error occurred while setting parameters
### SQL: SELECT id,year,doy,a_l_l_s_k_y_s_f_c_s_w_d_w_n,g_w_e_t_r_o_o_t,latitude,longitude,w_s2_m,sunshine_time FROM agricultural WHERE id=?
### Cause: java.sql.SQLSyntaxErrorException: Unknown column 'a_l_l_s_k_y_s_f_c_s_w_d_w_n' in 'field list'
; bad SQL grammar []; nested exception is java.sql.SQLSyntaxErrorException: Unknown column 'a_l_l_s_k_y_s_f_c_s_w_d_w_n' in 'field list'] with root causejava.sql.SQLSyntaxErrorException: Unknown column 'a_l_l_s_k_y_s_f_c_s_w_d_w_n' in 'field list'at com.mysql.cj.jdbc.exceptions.SQLError.createSQLException(SQLError.java:120) ~[mysql-connector-java-8.0.28.jar:8.0.28]at com.mysql.cj.jdbc.exceptions.SQLExceptionsMapping.translateException(SQLExceptionsMapping.java:122) ~[mysql-connector-java-8.0.28.jar:8.0.28]at com.mysql.cj.jdbc.ClientPreparedStatement.executeInternal(ClientPreparedStatement.java:953) ~[mysql-connector-java-8.0.28.jar:8.0.28]at com.mysql.cj.jdbc.ClientPreparedStatement.execute(ClientPreparedStatement.java:371) ~[mysql-connector-java-8.0.28.jar:8.0.28]at com.zaxxer.hikari.pool.ProxyPreparedStatement.execute(ProxyPreparedStatement.java:44) ~[HikariCP-4.0.3.jar:na]at com.zaxxer.hikari.pool.HikariProxyPreparedStatement.execute(HikariProxyPreparedStatement.java) ~[HikariCP-4.0.3.jar:na]at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke0(Native Method) ~[na:na]at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62) ~[na:na]at java.base/jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) ~[na:na]at java.base/java.lang.reflect.Method.invoke(Method.java:566) ~[na:na]at org.apache.ibatis.logging.jdbc.PreparedStatementLogger.invoke(PreparedStatementLogger.java:59) ~[mybatis-3.5.9.jar:3.5.9]at com.sun.proxy.$Proxy135.execute(Unknown Source) ~[na:na]at org.apache.ibatis.executor.statement.PreparedStatementHandler.query(PreparedStatementHandler.java:64) ~[mybatis-3.5.9.jar:3.5.9]at org.apache.ibatis.executor.statement.RoutingStatementHandler.query(RoutingStatementHandler.java:79) ~[mybatis-3.5.9.jar:3.5.9]at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke0(Native Method) ~[na:na]at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62) ~[na:na]at java.base/jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) ~[na:na]at java.base/java.lang.reflect.Method.invoke(Method.java:566) ~[na:na]at org.apache.ibatis.plugin.Plugin.invoke(Plugin.java:64) ~[mybatis-3.5.9.jar:3.5.9]at com.sun.proxy.$Proxy133.query(Unknown Source) ~[na:na]at org.apache.ibatis.executor.SimpleExecutor.doQuery(SimpleExecutor.java:63) ~[mybatis-3.5.9.jar:3.5.9]at org.apache.ibatis.executor.BaseExecutor.queryFromDatabase(BaseExecutor.java:325) ~[mybatis-3.5.9.jar:3.5.9]at org.apache.ibatis.executor.BaseExecutor.query(BaseExecutor.java:156) ~[mybatis-3.5.9.jar:3.5.9]at org.apache.ibatis.executor.CachingExecutor.query(CachingExecutor.java:109) ~[mybatis-3.5.9.jar:3.5.9]at com.baomidou.mybatisplus.extension.plugins.MybatisPlusInterceptor.intercept(MybatisPlusInterceptor.java:81) ~[mybatis-plus-extension-3.5.1.jar:3.5.1]at org.apache.ibatis.plugin.Plugin.invoke(Plugin.java:62) ~[mybatis-3.5.9.jar:3.5.9]at com.sun.proxy.$Proxy131.query(Unknown Source) ~[na:na]at org.apache.ibatis.session.defaults.DefaultSqlSession.selectList(DefaultSqlSession.java:151) ~[mybatis-3.5.9.jar:3.5.9]at org.apache.ibatis.session.defaults.DefaultSqlSession.selectList(DefaultSqlSession.java:145) ~[mybatis-3.5.9.jar:3.5.9]at org.apache.ibatis.session.defaults.DefaultSqlSession.selectList(DefaultSqlSession.java:140) ~[mybatis-3.5.9.jar:3.5.9]at org.apache.ibatis.session.defaults.DefaultSqlSession.selectOne(DefaultSqlSession.java:76) ~[mybatis-3.5.9.jar:3.5.9]at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke0(Native Method) ~[na:na]at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62) ~[na:na]at java.base/jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) ~[na:na]at java.base/java.lang.reflect.Method.invoke(Method.java:566) ~[na:na]at org.mybatis.spring.SqlSessionTemplate$SqlSessionInterceptor.invoke(SqlSessionTemplate.java:427) ~[mybatis-spring-2.0.6.jar:2.0.6]at com.sun.proxy.$Proxy86.selectOne(Unknown Source) ~[na:na]at org.mybatis.spring.SqlSessionTemplate.selectOne(SqlSessionTemplate.java:160) ~[mybatis-spring-2.0.6.jar:2.0.6]at com.baomidou.mybatisplus.core.override.MybatisMapperMethod.execute(MybatisMapperMethod.java:89) ~[mybatis-plus-core-3.5.1.jar:3.5.1]at com.baomidou.mybatisplus.core.override.MybatisMapperProxy$PlainMethodInvoker.invoke(MybatisMapperProxy.java:148) ~[mybatis-plus-core-3.5.1.jar:3.5.1]at com.baomidou.mybatisplus.core.override.MybatisMapperProxy.invoke(MybatisMapperProxy.java:89) ~[mybatis-plus-core-3.5.1.jar:3.5.1]at com.sun.proxy.$Proxy87.selectById(Unknown Source) ~[na:na]at com.baomidou.mybatisplus.extension.service.IService.getById(IService.java:292) ~[mybatis-plus-extension-3.5.1.jar:3.5.1]at com.baomidou.mybatisplus.extension.service.impl.ServiceImpl.saveOrUpdate(ServiceImpl.java:165) ~[mybatis-plus-extension-3.5.1.jar:3.5.1]at com.baomidou.mybatisplus.extension.service.impl.ServiceImpl$$FastClassBySpringCGLIB$$76535273.invoke(<generated>) ~[mybatis-plus-extension-3.5.1.jar:3.5.1]at org.springframework.cglib.proxy.MethodProxy.invoke(MethodProxy.java:218) ~[spring-core-5.3.15.jar:5.3.15]at org.springframework.aop.framework.CglibAopProxy$CglibMethodInvocation.invokeJoinpoint(CglibAopProxy.java:783) ~[spring-aop-5.3.15.jar:5.3.15]at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:163) ~[spring-aop-5.3.15.jar:5.3.15]at org.springframework.aop.framework.CglibAopProxy$CglibMethodInvocation.proceed(CglibAopProxy.java:753) ~[spring-aop-5.3.15.jar:5.3.15]at org.springframework.transaction.interceptor.TransactionInterceptor$1.proceedWithInvocation(TransactionInterceptor.java:123) ~[spring-tx-5.3.15.jar:5.3.15]at org.springframework.transaction.interceptor.TransactionAspectSupport.invokeWithinTransaction(TransactionAspectSupport.java:388) ~[spring-tx-5.3.15.jar:5.3.15]at org.springframework.transaction.interceptor.TransactionInterceptor.invoke(TransactionInterceptor.java:119) ~[spring-tx-5.3.15.jar:5.3.15]at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:186) ~[spring-aop-5.3.15.jar:5.3.15]at org.springframework.aop.framework.CglibAopProxy$CglibMethodInvocation.proceed(CglibAopProxy.java:753) ~[spring-aop-5.3.15.jar:5.3.15]at org.springframework.aop.framework.CglibAopProxy$DynamicAdvisedInterceptor.intercept(CglibAopProxy.java:698) ~[spring-aop-5.3.15.jar:5.3.15]at com.qingge.springboot.service.impl.AgriculturalServiceImpl$$EnhancerBySpringCGLIB$$6b4ea3a6.saveOrUpdate(<generated>) ~[classes/:na]at com.qingge.springboot.controller.AgriculturalController.save(AgriculturalController.java:76) ~[classes/:na]at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke0(Native Method) ~[na:na]at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62) ~[na:na]at java.base/jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) ~[na:na]at java.base/java.lang.reflect.Method.invoke(Method.java:566) ~[na:na]at org.springframework.web.method.support.InvocableHandlerMethod.doInvoke(InvocableHandlerMethod.java:205) ~[spring-web-5.3.15.jar:5.3.15]at org.springframework.web.method.support.InvocableHandlerMethod.invokeForRequest(InvocableHandlerMethod.java:150) ~[spring-web-5.3.15.jar:5.3.15]at org.springframework.web.servlet.mvc.method.annotation.ServletInvocableHandlerMethod.invokeAndHandle(ServletInvocableHandlerMethod.java:117) ~[spring-webmvc-5.3.15.jar:5.3.15]at org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.invokeHandlerMethod(RequestMappingHandlerAdapter.java:895) ~[spring-webmvc-5.3.15.jar:5.3.15]at org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.handleInternal(RequestMappingHandlerAdapter.java:808) ~[spring-webmvc-5.3.15.jar:5.3.15]at org.springframework.web.servlet.mvc.method.AbstractHandlerMethodAdapter.handle(AbstractHandlerMethodAdapter.java:87) ~[spring-webmvc-5.3.15.jar:5.3.15]at org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:1067) ~[spring-webmvc-5.3.15.jar:5.3.15]at org.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:963) ~[spring-webmvc-5.3.15.jar:5.3.15]at org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:1006) ~[spring-webmvc-5.3.15.jar:5.3.15]at org.springframework.web.servlet.FrameworkServlet.doPost(FrameworkServlet.java:909) ~[spring-webmvc-5.3.15.jar:5.3.15]at javax.servlet.http.HttpServlet.service(HttpServlet.java:681) ~[tomcat-embed-core-9.0.56.jar:4.0.FR]at org.springframework.web.servlet.FrameworkServlet.service(FrameworkServlet.java:883) ~[spring-webmvc-5.3.15.jar:5.3.15]at javax.servlet.http.HttpServlet.service(HttpServlet.java:764) ~[tomcat-embed-core-9.0.56.jar:4.0.FR]at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:227) ~[tomcat-embed-core-9.0.56.jar:9.0.56]at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:162) ~[tomcat-embed-core-9.0.56.jar:9.0.56]at org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:53) ~[tomcat-embed-websocket-9.0.56.jar:9.0.56]at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:189) ~[tomcat-embed-core-9.0.56.jar:9.0.56]at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:162) ~[tomcat-embed-core-9.0.56.jar:9.0.56]at org.springframework.web.filter.CorsFilter.doFilterInternal(CorsFilter.java:91) ~[spring-web-5.3.15.jar:5.3.15]at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:117) ~[spring-web-5.3.15.jar:5.3.15]at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:189) ~[tomcat-embed-core-9.0.56.jar:9.0.56]at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:162) ~[tomcat-embed-core-9.0.56.jar:9.0.56]at org.springframework.web.filter.RequestContextFilter.doFilterInternal(RequestContextFilter.java:100) ~[spring-web-5.3.15.jar:5.3.15]at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:117) ~[spring-web-5.3.15.jar:5.3.15]at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:189) ~[tomcat-embed-core-9.0.56.jar:9.0.56]at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:162) ~[tomcat-embed-core-9.0.56.jar:9.0.56]at org.springframework.web.filter.FormContentFilter.doFilterInternal(FormContentFilter.java:93) ~[spring-web-5.3.15.jar:5.3.15]at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:117) ~[spring-web-5.3.15.jar:5.3.15]at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:189) ~[tomcat-embed-core-9.0.56.jar:9.0.56]at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:162) ~[tomcat-embed-core-9.0.56.jar:9.0.56]at org.springframework.web.filter.CharacterEncodingFilter.doFilterInternal(CharacterEncodingFilter.java:201) ~[spring-web-5.3.15.jar:5.3.15]at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:117) ~[spring-web-5.3.15.jar:5.3.15]at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:189) ~[tomcat-embed-core-9.0.56.jar:9.0.56]at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:162) ~[tomcat-embed-core-9.0.56.jar:9.0.56]at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:197) ~[tomcat-embed-core-9.0.56.jar:9.0.56]at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:97) ~[tomcat-embed-core-9.0.56.jar:9.0.56]at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:540) ~[tomcat-embed-core-9.0.56.jar:9.0.56]at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:135) ~[tomcat-embed-core-9.0.56.jar:9.0.56]at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:92) ~[tomcat-embed-core-9.0.56.jar:9.0.56]at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:78) ~[tomcat-embed-core-9.0.56.jar:9.0.56]at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:357) ~[tomcat-embed-core-9.0.56.jar:9.0.56]at org.apache.coyote.http11.Http11Processor.service(Http11Processor.java:382) ~[tomcat-embed-core-9.0.56.jar:9.0.56]at org.apache.coyote.AbstractProcessorLight.process(AbstractProcessorLight.java:65) ~[tomcat-embed-core-9.0.56.jar:9.0.56]at org.apache.coyote.AbstractProtocol$ConnectionHandler.process(AbstractProtocol.java:895) ~[tomcat-embed-core-9.0.56.jar:9.0.56]at org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.doRun(NioEndpoint.java:1732) ~[tomcat-embed-core-9.0.56.jar:9.0.56]at org.apache.tomcat.util.net.SocketProcessorBase.run(SocketProcessorBase.java:49) ~[tomcat-embed-core-9.0.56.jar:9.0.56]at org.apache.tomcat.util.threads.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1191) ~[tomcat-embed-core-9.0.56.jar:9.0.56]at org.apache.tomcat.util.threads.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:659) ~[tomcat-embed-core-9.0.56.jar:9.0.56]at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61) ~[tomcat-embed-core-9.0.56.jar:9.0.56]at java.base/java.lang.Thread.run(Thread.java:834) ~[na:na]

解决方案

若使用application.yml作为配置文件
在application.yml中添加如下配置

mybatis-plus:configuration:map-underscore-to-camel-case: false

若使用application.properties作为配置文件
在application.properties中添加如下配置

mybatis-plus.configuration.map-underscore-to-camel-case=false

产生原因

问题产生的原因是MyBatis Plus默认的命名策略，它将驼峰命名的Java实体类属性名转换为数据库下划线命名的字段名。这样，在进行数据库查询时，MyBatis Plus会使用自动转换后的字段名，但如果数据库中的字段名与自动转换后的字段名不一致，就会导致查询失败，出现类似“未知列”（Unknown column）的错误。

解决原因

为了解决这个问题，可以禁用MyBatis Plus的命名转换功能，让它直接使用Java实体类属性名与数据库字段名一致的情况。具体操作是在应用的配置文件中将mybatis-plus.configuration.map-underscore-to-camel-case设置为false。这样设置后，MyBatis Plus将会直接使用映射或查询中指定的数据库字段名，而不进行自动的驼峰命名转换。