遇到这种错误怎么解决？
### Error querying database. Cause: java.lang.UnsupportedOperationException
### The error may exist in file [D:\demo\target\classes\mapper\UserMapper.xml]
### The error may involve rongji.user.mapper.UserDao.selectById
### The error occurred while handling results
### SQL: select * from tbl_user where id = ?
### Cause: java.lang.UnsupportedOperationException] with root cause
java.lang.UnsupportedOperationException: null
at org.apache.ibatis.reflection.wrapper.CollectionWrapper.findProperty(CollectionWrapper.java:48) ~[mybatis-3.4.6.jar:3.4.6]
at org.apache.ibatis.reflection.MetaObject.findProperty(MetaObject.java:85) ~[mybatis-3.4.6.jar:3.4.6]
at org.apache.ibatis.executor.resultset.DefaultResultSetHandler.createAutomaticMappings(DefaultResultSetHandler.java:492) ~[mybatis-3.4.6.jar:3.4.6]
at org.apache.ibatis.executor.resultset.DefaultResultSetHandler.applyAutomaticMappings(DefaultResultSetHandler.java:516) ~[mybatis-3.4.6.jar:3.4.6]
at org.apache.ibatis.executor.resultset.DefaultResultSetHandler.getRowValue(DefaultResultSetHandler.java:401) ~[mybatis-3.4.6.jar:3.4.6]
at org.apache.ibatis.executor.resultset.DefaultResultSetHandler.handleRowValuesForSimpleResultMap(DefaultResultSetHandler.java:355) ~[mybatis-3.4.6.jar:3.4.6]
at org.apache.ibatis.executor.resultset.DefaultResultSetHandler.handleRowValues(DefaultResultSetHandler.java:330) ~[mybatis-3.4.6.jar:3.4.6]
at org.apache.ibatis.executor.resultset.DefaultResultSetHandler.handleResultSet(DefaultResultSetHandler.java:303) ~[mybatis-3.4.6.jar:3.4.6]
at org.apache.ibatis.executor.resultset.DefaultResultSetHandler.handleResultSets(DefaultResultSetHandler.java:196) ~[mybatis-3.4.6.jar:3.4.6]
at org.apache.ibatis.executor.statement.PreparedStatementHandler.query(PreparedStatementHandler.java:64) ~[mybatis-3.4.6.jar:3.4.6]
at org.apache.ibatis.executor.statement.RoutingStatementHandler.query(RoutingStatementHandler.java:79) ~[mybatis-3.4.6.jar:3.4.6]
at org.apache.ibatis.executor.SimpleExecutor.doQuery(SimpleExecutor.java:63) ~[mybatis-3.4.6.jar:3.4.6]
at org.apache.ibatis.executor.BaseExecutor.queryFromDatabase(BaseExecutor.java:326) ~[mybatis-3.4.6.jar:3.4.6]
at org.apache.ibatis.executor.BaseExecutor.query(BaseExecutor.java:156) ~[mybatis-3.4.6.jar:3.4.6]
at org.apache.ibatis.executor.CachingExecutor.query(CachingExecutor.java:109) ~[mybatis-3.4.6.jar:3.4.6]
at org.apache.ibatis.executor.CachingExecutor.query(CachingExecutor.java:83) ~[mybatis-3.4.6.jar:3.4.6]
at org.apache.ibatis.session.defaults.DefaultSqlSession.selectList(DefaultSqlSession.java:148) ~[mybatis-3.4.6.jar:3.4.6]
at org.apache.ibatis.session.defaults.DefaultSqlSession.selectList(DefaultSqlSession.java:141) ~[mybatis-3.4.6.jar:3.4.6]
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) ~[na:1.8.0_25]
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62) ~[na:1.8.0_25]
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) ~[na:1.8.0_25]
at java.lang.reflect.Method.invoke(Method.java:483) ~[na:1.8.0_25]
at org.mybatis.spring.SqlSessionTemplate$SqlSessionInterceptor.invoke(SqlSessionTemplate.java:433) ~[mybatis-spring-1.3.2.jar:1.3.2]
at com.sun.proxy.$Proxy61.selectList(Unknown Source) ~[na:na]
at org.mybatis.spring.SqlSessionTemplate.selectList(SqlSessionTemplate.java:230) ~[mybatis-spring-1.3.2.jar:1.3.2]
at org.apache.ibatis.binding.MapperMethod.executeForMany(MapperMethod.java:139) ~[mybatis-3.4.6.jar:3.4.6]
at org.apache.ibatis.binding.MapperMethod.execute(MapperMethod.java:76) ~[mybatis-3.4.6.jar:3.4.6]
at org.apache.ibatis.binding.MapperProxy.invoke(MapperProxy.java:59) ~[mybatis-3.4.6.jar:3.4.6]
at com.sun.proxy.$Proxy62.selectById(Unknown Source) ~[na:na]
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) ~[na:1.8.0_25]
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62) ~[na:1.8.0_25]
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) ~[na:1.8.0_25]
at java.lang.reflect.Method.invoke(Method.java:483) ~[na:1.8.0_25]
at org.springframework.aop.support.AopUtils.invokeJoinpointUsingReflection(AopUtils.java:344) ~[spring-aop-5.3.13.jar:5.3.13]
at org.springframework.aop.framework.ReflectiveMethodInvocation.invokeJoinpoint(ReflectiveMethodInvocation.java:198) ~[spring-aop-5.3.13.jar:5.3.13]
at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:163) ~[spring-aop-5.3.13.jar:5.3.13]
at org.springframework.dao.support.PersistenceExceptionTranslationInterceptor.invoke(PersistenceExceptionTranslationInterceptor.java:137) ~[spring-tx-5.3.13.jar:5.3.13]
at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:186) ~[spring-aop-5.3.13.jar:5.3.13]
at org.springframework.aop.framework.JdkDynamicAopProxy.invoke(JdkDynamicAopProxy.java:215) ~[spring-aop-5.3.13.jar:5.3.13]
at com.sun.proxy.$Proxy63.selectById(Unknown Source) ~[na:na]
at rongji.user.service.impl.UserServiceImpl.selectById(UserServiceImpl.java:42) ~[classes/:na]
at rongji.user.controller.UserController.update(UserController.java:65) ~[classes/:na]
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) ~[na:1.8.0_25]
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62) ~[na:1.8.0_25]
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) ~[na:1.8.0_25]
at java.lang.reflect.Method.invoke(Method.java:483) ~[na:1.8.0_25]
at org.springframework.web.method.support.InvocableHandlerMethod.doInvoke(InvocableHandlerMethod.java:205) ~[spring-web-5.3.13.jar:5.3.13]
at org.springframework.web.method.support.InvocableHandlerMethod.invokeForRequest(InvocableHandlerMethod.java:150) ~[spring-web-5.3.13.jar:5.3.13]
at org.springframework.web.servlet.mvc.method.annotation.ServletInvocableHandlerMethod.invokeAndHandle(ServletInvocableHandlerMethod.java:117) ~[spring-webmvc-5.3.13.jar:5.3.13]
at org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.invokeHandlerMethod(RequestMappingHandlerAdapter.java:895) ~[spring-webmvc-5.3.13.jar:5.3.13]
at org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.handleInternal(RequestMappingHandlerAdapter.java:808) ~[spring-webmvc-5.3.13.jar:5.3.13]
at org.springframework.web.servlet.mvc.method.AbstractHandlerMethodAdapter.handle(AbstractHandlerMethodAdapter.java:87) ~[spring-webmvc-5.3.13.jar:5.3.13]
at org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:1067) ~[spring-webmvc-5.3.13.jar:5.3.13]
at org.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:963) ~[spring-webmvc-5.3.13.jar:5.3.13]
at org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:1006) ~[spring-webmvc-5.3.13.jar:5.3.13]
at org.springframework.web.servlet.FrameworkServlet.doGet(FrameworkServlet.java:898) ~[spring-webmvc-5.3.13.jar:5.3.13]
at javax.servlet.http.HttpServlet.service(HttpServlet.java:655) ~[tomcat-embed-core-9.0.55.jar:4.0.FR]
at org.springframework.web.servlet.FrameworkServlet.service(FrameworkServlet.java:883) ~[spring-webmvc-5.3.13.jar:5.3.13]
at javax.servlet.http.HttpServlet.service(HttpServlet.java:764) ~[tomcat-embed-core-9.0.55.jar:4.0.FR]
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:227) ~[tomcat-embed-core-9.0.55.jar:9.0.55]
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:162) ~[tomcat-embed-core-9.0.55.jar:9.0.55]
at org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:53) ~[tomcat-embed-websocket-9.0.55.jar:9.0.55]
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:189) ~[tomcat-embed-core-9.0.55.jar:9.0.55]
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:162) ~[tomcat-embed-core-9.0.55.jar:9.0.55]
at org.springframework.web.filter.RequestContextFilter.doFilterInternal(RequestContextFilter.java:100) ~[spring-web-5.3.13.jar:5.3.13]
at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:119) ~[spring-web-5.3.13.jar:5.3.13]
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:189) ~[tomcat-embed-core-9.0.55.jar:9.0.55]
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:162) ~[tomcat-embed-core-9.0.55.jar:9.0.55]
at org.springframework.web.filter.FormContentFilter.doFilterInternal(FormContentFilter.java:93) ~[spring-web-5.3.13.jar:5.3.13]
at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:119) ~[spring-web-5.3.13.jar:5.3.13]
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:189) ~[tomcat-embed-core-9.0.55.jar:9.0.55]
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:162) ~[tomcat-embed-core-9.0.55.jar:9.0.55]
at org.springframework.web.filter.CharacterEncodingFilter.doFilterInternal(CharacterEncodingFilter.java:201) ~[spring-web-5.3.13.jar:5.3.13]
at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:119) ~[spring-web-5.3.13.jar:5.3.13]
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:189) ~[tomcat-embed-core-9.0.55.jar:9.0.55]
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:162) ~[tomcat-embed-core-9.0.55.jar:9.0.55]
at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:197) ~[tomcat-embed-core-9.0.55.jar:9.0.55]
at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:97) [tomcat-embed-core-9.0.55.jar:9.0.55]
at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:540) [tomcat-embed-core-9.0.55.jar:9.0.55]
at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:135) [tomcat-embed-core-9.0.55.jar:9.0.55]
at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:92) [tomcat-embed-core-9.0.55.jar:9.0.55]
at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:78) [tomcat-embed-core-9.0.55.jar:9.0.55]
at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:357) [tomcat-embed-core-9.0.55.jar:9.0.55]
at org.apache.coyote.http11.Http11Processor.service(Http11Processor.java:382) [tomcat-embed-core-9.0.55.jar:9.0.55]
at org.apache.coyote.AbstractProcessorLight.process(AbstractProcessorLight.java:65) [tomcat-embed-core-9.0.55.jar:9.0.55]
at org.apache.coyote.AbstractProtocol$ConnectionHandler.process(AbstractProtocol.java:895) [tomcat-embed-core-9.0.55.jar:9.0.55]
at org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.doRun(NioEndpoint.java:1722) [tomcat-embed-core-9.0.55.jar:9.0.55]
at org.apache.tomcat.util.net.SocketProcessorBase.run(SocketProcessorBase.java:49) [tomcat-embed-core-9.0.55.jar:9.0.55]
at org.apache.tomcat.util.threads.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1191) [tomcat-embed-core-9.0.55.jar:9.0.55]
at org.apache.tomcat.util.threads.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:659) [tomcat-embed-core-9.0.55.jar:9.0.55]
at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61) [tomcat-embed-core-9.0.55.jar:9.0.55]
at java.lang.Thread.run(Thread.java:745) [na:1.8.0_25]
遇到上边这种报错，一般都是写SQL语句时，返回类型写错了！
错误示例：
修改后：
这样就解决了！总结：查询数据时，一定要确定好返回数据的类型，细心一点，下次就不会再出错咯！