@[TOC](springboot，mybatis报错 Servlet.service() for servlet [dispatcherServlet] in context with path 解决方案)

问题背景

我在使用mybatis-generator生成的xml文件，在进行插入mysql数据库的时候，出现以下问题，因为以下问题并看不出来是什么问题，有很多情况都会出现一样的报错，这里介绍我出现这个问题的原因，如果不是你需要的解决方案，可以看看其他别人的解决方案

2022-02-09 10:06:26.326 ERROR [http-nio-7788-exec-1] o.a.c.c.C.[.[.[.[dispatcherServlet].log(DirectJDKLog.java:175): Servlet.service() for servlet [dispatcherServlet] in context with path [] threw exception [Request processing failed; nested exception is java.lang.NullPointerException] with root cause
java.lang.NullPointerException: null
        at com.dazhen.data.api.controller.TransformController.executeIdmapping(TransformController.java:133)
        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:498)
        at org.springframework.web.method.support.InvocableHandlerMethod.doInvoke(InvocableHandlerMethod.java:190)
        at org.springframework.web.method.support.InvocableHandlerMethod.invokeForRequest(InvocableHandlerMethod.java:138)
        at org.springframework.web.servlet.mvc.method.annotation.ServletInvocableHandlerMethod.invokeAndHandle(ServletInvocableHandlerMethod.java:105)
        at org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.invokeHandlerMethod(RequestMappingHandlerAdapter.java:879)
        at org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.handleInternal(RequestMappingHandlerAdapter.java:793)
        at org.springframework.web.servlet.mvc.method.AbstractHandlerMethodAdapter.handle(AbstractHandlerMethodAdapter.java:87)
        at org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:1040)
        at org.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:943)
        at org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:1006)
        at org.springframework.web.servlet.FrameworkServlet.doPost(FrameworkServlet.java:909)
        at javax.servlet.http.HttpServlet.service(HttpServlet.java:660)
        at org.springframework.web.servlet.FrameworkServlet.service(FrameworkServlet.java:883)
        at javax.servlet.http.HttpServlet.service(HttpServlet.java:741)
        at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:231)
        at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166)
        at org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:53)
        at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193)
        at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166)
        at com.alibaba.druid.support.http.WebStatFilter.doFilter(WebStatFilter.java:124)
        at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193)

解决方案

在使用insert插入的时候，我的项目需要用到当条记录的主键，但生成的xml没有返回主键，可以使用两种方式增加返回主键

方式一

打开xml文件，原本为

  <insert id="insert" parameterType="data.api.entity.mysql.TransformRecord">

添加返回主键：useGeneratedKeys=“true” keyProperty=“recordId” ，recordId替换为你自己的主键，更改为

  <insert id="insert" parameterType="data.api.entity.mysql.TransformRecord"
          useGeneratedKeys="true" keyProperty="recordId">

方式二

原本我的generatorConfig配置文件是这样

<table tableName="transform_record">
    <property name="useActualColumnNames" value="false"/>
</table>

更改为

<table tableName="transform_record"
	enableInsert="true">
    <generatedKey column="recordId" sqlStatement="MySql" identity="true"/>
</table>

心得

• 这个问题不好找 ，我完全不知道哪里出错了，报错信息与本身错误无关

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