记录一个报错！！！

在学习 mybatis-plus 遇到一个报错：

2021-09-03 21:24:59.735 DEBUG 23620 --- [nio-8999-exec-1] c.i.s.mapper.OrderMapper.update          : ==>  Preparing: update `order` set uid = ?,total = ?,date = ? where id=? 
2021-09-03 21:24:59.765 ERROR 23620 --- [nio-8999-exec-1] o.a.c.c.C.[.[.[/].[dispatcherServlet]    : Servlet.service() for servlet [dispatcherServlet] in context with path [] threw exception [Request processing failed; nested exception is org.mybatis.spring.MyBatisSystemException: nested exception is org.apache.ibatis.binding.BindingException: Parameter 'uid' not found. Available parameters are [ew, param1, et, param2]] with root cause

org.apache.ibatis.binding.BindingException: Parameter 'uid' not found. Available parameters are [ew, param1, et, param2]
	at org.apache.ibatis.binding.MapperMethod$ParamMap.get(MapperMethod.java:212) ~[mybatis-3.5.1.jar:3.5.1]
	at org.apache.ibatis.reflection.wrapper.MapWrapper.get(MapWrapper.java:45) ~[mybatis-3.5.1.jar:3.5.1]
	at org.apache.ibatis.reflection.MetaObject.getValue(MetaObject.java:122) ~[mybatis-3.5.1.jar:3.5.1]
	at com.baomidou.mybatisplus.core.MybatisDefaultParameterHandler.setParameters(MybatisDefaultParameterHandler.java:219) ~[mybatis-plus-core-3.1.1.jar:3.1.1]
	at org.apache.ibatis.executor.statement.PreparedStatementHandler.parameterize(PreparedStatementHandler.java:94) ~[mybatis-3.5.1.jar:3.5.1]
	at org.apache.ibatis.executor.statement.RoutingStatementHandler.parameterize(RoutingStatementHandler.java:64) ~[mybatis-3.5.1.jar:3.5.1]
	at com.baomidou.mybatisplus.core.executor.MybatisSimpleExecutor.prepareStatement(MybatisSimpleExecutor.java:99) ~[mybatis-plus-core-3.1.1.jar:3.1.1]
	at com.baomidou.mybatisplus.core.executor.MybatisSimpleExecutor.doUpdate(MybatisSimpleExecutor.java:53) ~[mybatis-plus-core-3.1.1.jar:3.1.1]
	at org.apache.ibatis.executor.BaseExecutor.update(BaseExecutor.java:117) ~[mybatis-3.5.1.jar:3.5.1]
	at org.apache.ibatis.executor.CachingExecutor.update(CachingExecutor.java:76) ~[mybatis-3.5.1.jar:3.5.1]
	at org.apache.ibatis.session.defaults.DefaultSqlSession.update(DefaultSqlSession.java:197) ~[mybatis-3.5.1.jar:3.5.1]
	at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) ~[na:1.8.0_77]
	at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62) ~[na:1.8.0_77]
	at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) ~[na:1.8.0_77]
	at java.lang.reflect.Method.invoke(Method.java:498) ~[na:1.8.0_77]
	at org.mybatis.spring.SqlSessionTemplate$SqlSessionInterceptor.invoke(SqlSessionTemplate.java:433) ~[mybatis-spring-2.0.1.jar:2.0.1]
	at com.sun.proxy.$Proxy60.update(Unknown Source) ~[na:na]
	at org.mybatis.spring.SqlSessionTemplate.update(SqlSessionTemplate.java:294) ~[mybatis-spring-2.0.1.jar:2.0.1]
	at com.baomidou.mybatisplus.core.override.MybatisMapperMethod.execute(MybatisMapperMethod.java:63) ~[mybatis-plus-core-3.1.1.jar:3.1.1]
	at com.baomidou.mybatisplus.core.override.MybatisMapperProxy.invoke(MybatisMapperProxy.java:62) ~[mybatis-plus-core-3.1.1.jar:3.1.1]
	at com.sun.proxy.$Proxy61.update(Unknown Source) ~[na:na]
	at com.itlong.spring_boot.service.Impl.OrderServiceImpl.update3(OrderServiceImpl.java:87) ~[classes/:na]
	at com.itlong.spring_boot.controller.orderController.update_3(orderController.java:90) ~[classes/:na]
	at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) ~[na:1.8.0_77]
	at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62) ~[na:1.8.0_77]
	at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) ~[na:1.8.0_77]
	at java.lang.reflect.Method.invoke(Method.java:498) ~[na:1.8.0_77]
	at org.springframework.web.method.support.InvocableHandlerMethod.doInvoke(InvocableHandlerMethod.java:197) ~[spring-web-5.3.9.jar:5.3.9]
	at org.springframework.web.method.support.InvocableHandlerMethod.invokeForRequest(InvocableHandlerMethod.java:141) ~[spring-web-5.3.9.jar:5.3.9]
	at org.springframework.web.servlet.mvc.method.annotation.ServletInvocableHandlerMethod.invokeAndHandle(ServletInvocableHandlerMethod.java:106) ~[spring-webmvc-5.3.9.jar:5.3.9]
	at org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.invokeHandlerMethod(RequestMappingHandlerAdapter.java:895) ~[spring-webmvc-5.3.9.jar:5.3.9]
	at org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.handleInternal(RequestMappingHandlerAdapter.java:808) ~[spring-webmvc-5.3.9.jar:5.3.9]
	at org.springframework.web.servlet.mvc.method.AbstractHandlerMethodAdapter.handle(AbstractHandlerMethodAdapter.java:87) ~[spring-webmvc-5.3.9.jar:5.3.9]
	at org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:1064) ~[spring-webmvc-5.3.9.jar:5.3.9]
	at org.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:963) ~[spring-webmvc-5.3.9.jar:5.3.9]
	at org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:1006) ~[spring-webmvc-5.3.9.jar:5.3.9]
	at org.springframework.web.servlet.FrameworkServlet.doGet(FrameworkServlet.java:898) ~[spring-webmvc-5.3.9.jar:5.3.9]
	at javax.servlet.http.HttpServlet.service(HttpServlet.java:655) ~[tomcat-embed-core-9.0.52.jar:4.0.FR]
	at org.springframework.web.servlet.FrameworkServlet.service(FrameworkServlet.java:883) ~[spring-webmvc-5.3.9.jar:5.3.9]
	at javax.servlet.http.HttpServlet.service(HttpServlet.java:764) ~[tomcat-embed-core-9.0.52.jar:4.0.FR]
	at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:227) ~[tomcat-embed-core-9.0.52.jar:9.0.52]
	at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:162) ~[tomcat-embed-core-9.0.52.jar:9.0.52]
	at org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:53) ~[tomcat-embed-websocket-9.0.52.jar:9.0.52]
	at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:189) ~[tomcat-embed-core-9.0.52.jar:9.0.52]
	at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:162) ~[tomcat-embed-core-9.0.52.jar:9.0.52]
	at org.springframework.web.filter.RequestContextFilter.doFilterInternal(RequestContextFilter.java:100) ~[spring-web-5.3.9.jar:5.3.9]
	at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:119) ~[spring-web-5.3.9.jar:5.3.9]
	at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:189) ~[tomcat-embed-core-9.0.52.jar:9.0.52]
	at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:162) ~[tomcat-embed-core-9.0.52.jar:9.0.52]
	at org.springframework.web.filter.FormContentFilter.doFilterInternal(FormContentFilter.java:93) ~[spring-web-5.3.9.jar:5.3.9]
	at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:119) ~[spring-web-5.3.9.jar:5.3.9]
	at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:189) ~[tomcat-embed-core-9.0.52.jar:9.0.52]
	at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:162) ~[tomcat-embed-core-9.0.52.jar:9.0.52]
	at org.springframework.web.filter.CharacterEncodingFilter.doFilterInternal(CharacterEncodingFilter.java:201) ~[spring-web-5.3.9.jar:5.3.9]
	at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:119) ~[spring-web-5.3.9.jar:5.3.9]
	at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:189) ~[tomcat-embed-core-9.0.52.jar:9.0.52]
	at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:162) ~[tomcat-embed-core-9.0.52.jar:9.0.52]
	at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:197) ~[tomcat-embed-core-9.0.52.jar:9.0.52]
	at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:97) [tomcat-embed-core-9.0.52.jar:9.0.52]
	at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:542) [tomcat-embed-core-9.0.52.jar:9.0.52]
	at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:135) [tomcat-embed-core-9.0.52.jar:9.0.52]
	at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:92) [tomcat-embed-core-9.0.52.jar:9.0.52]
	at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:78) [tomcat-embed-core-9.0.52.jar:9.0.52]
	at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:357) [tomcat-embed-core-9.0.52.jar:9.0.52]
	at org.apache.coyote.http11.Http11Processor.service(Http11Processor.java:382) [tomcat-embed-core-9.0.52.jar:9.0.52]
	at org.apache.coyote.AbstractProcessorLight.process(AbstractProcessorLight.java:65) [tomcat-embed-core-9.0.52.jar:9.0.52]
	at org.apache.coyote.AbstractProtocol$ConnectionHandler.process(AbstractProtocol.java:893) [tomcat-embed-core-9.0.52.jar:9.0.52]
	at org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.doRun(NioEndpoint.java:1726) [tomcat-embed-core-9.0.52.jar:9.0.52]
	at org.apache.tomcat.util.net.SocketProcessorBase.run(SocketProcessorBase.java:49) [tomcat-embed-core-9.0.52.jar:9.0.52]
	at org.apache.tomcat.util.threads.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1191) [tomcat-embed-core-9.0.52.jar:9.0.52]
	at org.apache.tomcat.util.threads.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:659) [tomcat-embed-core-9.0.52.jar:9.0.52]
	at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61) [tomcat-embed-core-9.0.52.jar:9.0.52]
	at java.lang.Thread.run(Thread.java:745) [na:1.8.0_77]

在翻遍各大论坛，试过 N 个解决办法之后，最后终于解决了。

造成问题的原因：mybatis-plus 的 BaseMapper 中提供某些方法和自己定义的 mapper 映射文件中某个映射语句的 id 重复。

 public String update3(Order order) {
    UpdateWrapper<Order> wrapper = new UpdateWrapper<>();
      wrapper.eq("id",1);
      int i = this.orderMapper.update(order,wrapper);
      if (i == 1) {
          return "修改成功";
      }
      return "修改失败";
  }

调用了 BaseMapper 的 update 方法，而这个方法有使用 UpdateWrapper 条件构造器。而在自定义的 xml 中也有一个 id为 update 的映射语句：

在使用 Mybatis-Plus 是有三个地方可以生成SQL语句，第一个是 XML 映射文件中，第二个是继承 BaseMapper 类之后可以调用方法，第三个是实体类继承 Model 类。使用这三个方法生成SQL语句时，需要注意避免映射语句的 id 重复。