I wrote a demo

public interface UserMapper extends Mapper<User>

Note that it inherits Mapper, which already has a selectByPrimaryKey method
Then I call

User u = userMapper.selectByPrimaryKey(1);

Gave me an error and cried

The error message is as follows

DEBUG - Fetching JDBC Connection from DataSource

DEBUG - JDBC Connection [jdbc:mysql://localhost:3306/test?useUnicode=true&characterEncoding=UTF-8, UserName=root@localhost , MySQL Connector Java] will not be managed by Spring

DEBUG - ==>  Preparing: SELECT id,name,age FROM User WHERE (id = ? AND name = ? AND age = ? ) 

DEBUG - Closing non transactional SqlSession [org.apache.ibatis.session.defaults.DefaultSqlSession@3b71d667]

DEBUG - Returning JDBC Connection to DataSource

DEBUG - Resolving exception from handler [public java.lang.String com.zqws.app.trade.controller.TestController.test(org.springframework.ui.Model,com.github.pagehelper.PageInfo)]: org.mybatis.spring.MyBatisSystemException: nested exception is org.apache.ibatis.exceptions.PersistenceException: 

### Error querying database.  Cause: java.lang.ClassCastException: java.lang.Integer cannot be cast to java.lang.String

### The error may exist in com/zqws/app/trade/mapper/UserMapper.java (best guess)

### The error may involve com.zqws.app.trade.mapper.UserMapper.

selectByPrimaryKey–Inline

### The error occurred while setting parameters

### SQL: SELECT id,name,age FROM User WHERE

(id = ? AND name = ? AND age = ?

 )

### Cause: java.lang.ClassCastException:

java.lang.Integer cannot be cast to java.lang.String

DEBUG - Resolving exception from handler [public java.lang.String com.zqws.app.trade.controller.TestController.test(org.springframework.ui.Model,com.github.pagehelper.PageInfo)]: org.mybatis.spring.MyBatisSystemException: nested exception is org.apache.ibatis.exceptions.PersistenceException: 

### Error querying database.  Cause: java.lang.ClassCastException: java.lang.Integer cannot be cast to java.lang.String

### The error may exist in com/zqws/app/trade/mapper/UserMapper.java (best guess)

### The error may involve com.zqws.app.trade.mapper.UserMapper.selectByPrimaryKey-Inline

### The error occurred while setting parameters

### SQL: SELECT id,name,age FROM User WHERE (id = ? AND name = ? AND age = ? )

### Cause: java.lang.ClassCastException: java.lang.Integer cannot be cast to java.lang.String

DEBUG - Resolving exception from handler [public java.lang.String com.zqws.app.trade.controller.TestController.test(org.springframework.ui.Model,com.github.pagehelper.PageInfo)]: org.mybatis.spring.MyBatisSystemException: nested exception is org.apache.ibatis.exceptions.PersistenceException: 

### Error querying database.  Cause: java.lang.ClassCastException: java.lang.Integer cannot be cast to java.lang.String

### The error may exist in com/zqws/app/trade/mapper/UserMapper.java (best guess)

### The error may involve com.zqws.app.trade.mapper.UserMapper.selectByPrimaryKey-Inline

### The error occurred while setting parameters

### SQL: SELECT id,name,age FROM User WHERE (id = ? AND name = ? AND age = ? )

### Cause: java.lang.ClassCastException: java.lang.Integer cannot be cast to java.lang.String

DEBUG - Could not complete request

org.mybatis.spring.MyBatisSystemException: nested exception is org.apache.ibatis.exceptions.PersistenceException: 

### Error querying database.  Cause: java.lang.ClassCastException: java.lang.Integer cannot be cast to java.lang.String

### The error may exist in com/zqws/app/trade/mapper/UserMapper.java (best guess)

### The error may involve com.zqws.app.trade.mapper.UserMapper.selectByPrimaryKey-Inline

### The error occurred while setting parameters

### SQL: SELECT id,name,age FROM User WHERE (id = ? AND name = ? AND age = ? )

### Cause: java.lang.ClassCastException: java.lang.Integer cannot be cast to java.lang.String

at org.mybatis.spring.MyBatisExceptionTranslator.translateExceptionIfPossible(MyBatisExceptionTranslator.java:75)

at org.mybatis.spring.SqlSessionTemplate$SqlSessionInterceptor.invoke(SqlSessionTemplate.java:371)

at com.sun.proxy.$Proxy86.selectOne(Unknown Source)

at org.mybatis.spring.SqlSessionTemplate.selectOne(SqlSessionTemplate.java:163)

at org.apache.ibatis.binding.MapperMethod.execute(MapperMethod.java:68)

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

at com.sun.proxy.$Proxy92.selectByPrimaryKey(Unknown Source)

at com.zqws.app.trade.controller.TestController.test(TestController.java:25)

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

at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)

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

at java.lang.reflect.Method.invoke(Method.java:483)

at org.springframework.web.method.support.InvocableHandlerMethod.doInvoke(InvocableHandlerMethod.java:221)

at org.springframework.web.method.support.InvocableHandlerMethod.invokeForRequest(InvocableHandlerMethod.java:137)

at org.springframework.web.servlet.mvc.method.annotation.ServletInvocableHandlerMethod.invokeAndHandle(ServletInvocableHandlerMethod.java:110)

at org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.invokeHandleMethod(RequestMappingHandlerAdapter.java:777)

at org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.handleInternal(RequestMappingHandlerAdapter.java:706)

at org.springframework.web.servlet.mvc.method.AbstractHandlerMethodAdapter.handle(AbstractHandlerMethodAdapter.java:85)

at org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:943)

at org.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:877)

at org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:966)

at org.springframework.web.servlet.FrameworkServlet.doGet(FrameworkServlet.java:857)

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

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

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.springframework.web.filter.HttpPutFormContentFilter.doFilterInternal(HttpPutFormContentFilter.java:87)

at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:107)

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

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

at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:107)

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:503)

at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:170)

at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:103)

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:421)

at org.apache.coyote.http11.AbstractHttp11Processor.process(AbstractHttp11Processor.java:1070)

at org.apache.coyote.AbstractProtocol$AbstractConnectionHandler.process(AbstractProtocol.java:611)

at org.apache.tomcat.util.net.NioEndpoint $ SocketProcessor.doRun (NioEndpoint.java: 1736 )

at org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.run(NioEndpoint.java:1695)

at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142)

at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617)

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

at java.lang.Thread.run(Thread.java:745)

Caused by: org.apache.ibatis.exceptions.PersistenceException: 

### Error querying database.  Cause: java.lang.ClassCastException: java.lang.Integer cannot be cast to java.lang.String

### The error may exist in com/zqws/app/trade/mapper/UserMapper.java (best guess)

### The error may involve com.zqws.app.trade.mapper.UserMapper.selectByPrimaryKey-Inline

### The error occurred while setting parameters

### SQL: SELECT id,name,age FROM User WHERE (id = ? AND name = ? AND age = ? )

### Cause: java.lang.ClassCastException: java.lang.Integer cannot be cast to java.lang.String

at org.apache.ibatis.exceptions.ExceptionFactory.wrapException(ExceptionFactory.java:26)

at org.apache.ibatis.session.defaults.DefaultSqlSession.selectList(DefaultSqlSession.java:111)

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

at org.apache.ibatis.session.defaults.DefaultSqlSession.selectOne(DefaultSqlSession.java:66)

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

at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)

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

at java.lang.reflect.Method.invoke(Method.java:483)

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

... 52 more

Caused by: java.lang.ClassCastException: java.lang.Integer cannot be cast to java.lang.String

at org.apache.ibatis.type.StringTypeHandler.setNonNullParameter(StringTypeHandler.java:26)

at org.apache.ibatis.type.BaseTypeHandler.setParameter (BaseTypeHandler.java: 50 )

at org.apache.ibatis.scripting.defaults.DefaultParameterHandler.setParameters(DefaultParameterHandler.java:81)

at org.apache.ibatis.executor.statement.PreparedStatementHandler.parameterize(PreparedStatementHandler.java:80)

at org.apache.ibatis.executor.statement.RoutingStatementHandler.parameterize(RoutingStatementHandler.java:61)

at org.apache.ibatis.executor.SimpleExecutor.prepareStatement(SimpleExecutor.java:74)

at org.apache.ibatis.executor.SimpleExecutor.doQuery(SimpleExecutor.java:59)

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 sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)

at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)

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

at java.lang.reflect.Method.invoke(Method.java:483)

at org.apache.ibatis.plugin.Invocation.proceed(Invocation.java:49)

at com.github.pagehelper.SqlUtil._processPage(SqlUtil.java:351)

at com.github.pagehelper.SqlUtil.processPage(SqlUtil.java:329)

at com.github.pagehelper.PageHelper.intercept(PageHelper.java:150)

at org.apache.ibatis.plugin.Plugin.invoke(Plugin.java:60)

at com.sun.proxy.$Proxy93.query(Unknown Source)

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

at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)

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

at java.lang.reflect.Method.invoke(Method.java:483)

at org.apache.ibatis.plugin.Invocation.proceed(Invocation.java:49)

at tk.mybatis.mapper.mapperhelper.MapperOnceInterceptor.intercept(MapperOnceInterceptor.java:81)

at org.apache.ibatis.plugin.Plugin.invoke(Plugin.java:60)

at com.sun.proxy.$Proxy93.query(Unknown Source)

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

... 59 more

DEBUG - Returning cached instance of singleton bean 'sqlSessionFactory'

August 01, 2015 5:02:43 PM org.apache.catalina.core.StandardWrapperValve invoke

严重: Servlet.service() for servlet [springmvc] in context with path [] threw exception [Request processing failed; nested exception is org.mybatis.spring.MyBatisSystemException: nested exception is org.apache.ibatis.exceptions.PersistenceException: 

### Error querying database.  Cause: java.lang.ClassCastException: java.lang.Integer cannot be cast to java.lang.String

### The error may exist in com/zqws/app/trade/mapper/UserMapper.java (best guess)

### The error may involve com.zqws.app.trade.mapper.UserMapper.selectByPrimaryKey-Inline

### The error occurred while setting parameters

### SQL: SELECT id,name,age FROM User WHERE (id = ? AND name = ? AND age = ? )

### Cause: java.lang.ClassCastException: java.lang.Integer cannot be cast to java.lang.String] with root cause

java.lang.ClassCastException: java.lang.Integer cannot be cast to java.lang.String

at org.apache.ibatis.type.StringTypeHandler.setNonNullParameter(StringTypeHandler.java:26)

at org.apache.ibatis.type.BaseTypeHandler.setParameter (BaseTypeHandler.java: 50 )

at org.apache.ibatis.scripting.defaults.DefaultParameterHandler.setParameters(DefaultParameterHandler.java:81)

at org.apache.ibatis.executor.statement.PreparedStatementHandler.parameterize(PreparedStatementHandler.java:80)

at org.apache.ibatis.executor.statement.RoutingStatementHandler.parameterize(RoutingStatementHandler.java:61)

at org.apache.ibatis.executor.SimpleExecutor.prepareStatement(SimpleExecutor.java:74)

at org.apache.ibatis.executor.SimpleExecutor.doQuery(SimpleExecutor.java:59)

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 sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)

at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)

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

at java.lang.reflect.Method.invoke(Method.java:483)

at org.apache.ibatis.plugin.Invocation.proceed(Invocation.java:49)

at com.github.pagehelper.SqlUtil._processPage(SqlUtil.java:351)

at com.github.pagehelper.SqlUtil.processPage(SqlUtil.java:329)

at com.github.pagehelper.PageHelper.intercept(PageHelper.java:150)

at org.apache.ibatis.plugin.Plugin.invoke(Plugin.java:60)

at com.sun.proxy.$Proxy93.query(Unknown Source)

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

at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)

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

at java.lang.reflect.Method.invoke(Method.java:483)

at org.apache.ibatis.plugin.Invocation.proceed(Invocation.java:49)

at tk.mybatis.mapper.mapperhelper.MapperOnceInterceptor.intercept(MapperOnceInterceptor.java:81)

at org.apache.ibatis.plugin.Plugin.invoke(Plugin.java:60)

at com.sun.proxy.$Proxy93.query(Unknown Source)

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

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

at org.apache.ibatis.session.defaults.DefaultSqlSession.selectOne(DefaultSqlSession.java:66)

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

at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)

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

at java.lang.reflect.Method.invoke(Method.java:483)

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

at com.sun.proxy.$Proxy86.selectOne(Unknown Source)

at org.mybatis.spring.SqlSessionTemplate.selectOne(SqlSessionTemplate.java:163)

at org.apache.ibatis.binding.MapperMethod.execute(MapperMethod.java:68)

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

at com.sun.proxy.$Proxy92.selectByPrimaryKey(Unknown Source)

at com.zqws.app.trade.controller.TestController.test(TestController.java:25)

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

at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)

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

at java.lang.reflect.Method.invoke(Method.java:483)

at org.springframework.web.method.support.InvocableHandlerMethod.doInvoke(InvocableHandlerMethod.java:221)

at org.springframework.web.method.support.InvocableHandlerMethod.invokeForRequest(InvocableHandlerMethod.java:137)

at org.springframework.web.servlet.mvc.method.annotation.ServletInvocableHandlerMethod.invokeAndHandle(ServletInvocableHandlerMethod.java:110)

at org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.invokeHandleMethod(RequestMappingHandlerAdapter.java:777)

at org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.handleInternal(RequestMappingHandlerAdapter.java:706)

at org.springframework.web.servlet.mvc.method.AbstractHandlerMethodAdapter.handle(AbstractHandlerMethodAdapter.java:85)

at org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:943)

at org.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:877)

at org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:966)

at org.springframework.web.servlet.FrameworkServlet.doGet(FrameworkServlet.java:857)

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

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

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.springframework.web.filter.HttpPutFormContentFilter.doFilterInternal(HttpPutFormContentFilter.java:87)

at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:107)

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

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

at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:107)

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:503)

at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:170)

at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:103)

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:421)

at org.apache.coyote.http11.AbstractHttp11Processor.process(AbstractHttp11Processor.java:1070)

at org.apache.coyote.AbstractProtocol$AbstractConnectionHandler.process(AbstractProtocol.java:611)

at org.apache.tomcat.util.net.NioEndpoint $ SocketProcessor.doRun (NioEndpoint.java: 1736 )

at org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.r

un (NioEndpoint.java: 1695 )

at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142)

at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617)

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

at java.lang.Thread.run(Thread.java:745)