一、错误提示：

10:35:20.872 [main] WARN  o.s.b.w.s.c.AnnotationConfigServletWebServerApplicationContext - [refresh,559] - Exception encountered during context initialization - cancelling refresh attempt: org.springframework.context.ApplicationContextException: Unable to start web server; nested exception is org.springframework.boot.web.server.WebServerException: Unable to create tempDir. java.io.tmpdir is set to C:\Users\ADMINI~1\AppData\Local\Temp\2\
10:35:20.904 [main] ERROR o.s.b.SpringApplication - [reportFailure,826] - Application run failed
org.springframework.context.ApplicationContextException: Unable to start web server; nested exception is org.springframework.boot.web.server.WebServerException: Unable to create tempDir. java.io.tmpdir is set to C:\Users\ADMINI~1\AppData\Local\Temp\2\
        at org.springframework.boot.web.servlet.context.ServletWebServerApplicationContext.onRefresh(ServletWebServerApplicationContext.java:156)
        at org.springframework.context.support.AbstractApplicationContext.refresh(AbstractApplicationContext.java:545)
        at org.springframework.boot.web.servlet.context.ServletWebServerApplicationContext.refresh(ServletWebServerApplicationContext.java:141)
        at org.springframework.boot.SpringApplication.refresh(SpringApplication.java:747)
        at org.springframework.boot.SpringApplication.refreshContext(SpringApplication.java:405)
        at org.springframework.boot.SpringApplication.run(SpringApplication.java:315)
        at org.springframework.boot.SpringApplication.run(SpringApplication.java:1226)
        at org.springframework.boot.SpringApplication.run(SpringApplication.java:1215)
        at com.ruoyi.RuoYiApplication.main(RuoYiApplication.java:18)
        at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
        at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source)
        at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)
        at java.lang.reflect.Method.invoke(Unknown Source)
        at org.springframework.boot.loader.MainMethodRunner.run(MainMethodRunner.java:48)
        at org.springframework.boot.loader.Launcher.launch(Launcher.java:87)
        at org.springframework.boot.loader.Launcher.launch(Launcher.java:50)
        at org.springframework.boot.loader.JarLauncher.main(JarLauncher.java:51)
Caused by: org.springframework.boot.web.server.WebServerException: Unable to create tempDir. java.io.tmpdir is set to C:\Users\ADMINI~1\AppData\Local\Temp\2\
        at org.springframework.boot.web.server.AbstractConfigurableWebServerFactory.createTempDir(AbstractConfigurableWebServerFactory.java:179)
        at org.springframework.boot.web.embedded.tomcat.TomcatServletWebServerFactory.getWebServer(TomcatServletWebServerFactory.java:180)
        at org.springframework.boot.web.servlet.context.ServletWebServerApplicationContext.createWebServer(ServletWebServerApplicationContext.java:180)
        at org.springframework.boot.web.servlet.context.ServletWebServerApplicationContext.onRefresh(ServletWebServerApplicationContext.java:153)
        ... 16 common frames omitted

二、原因：

项目启动时会创建一个临时目录存放数据

三、解决方法1

既然没有目录，创建一个类重新指定目录

@Configuration(proxyBeanMethods = false)
public class MultipartConfig {

    /**
     * 文件上传临时路径
     */
    @Bean
    MultipartConfigElement multipartConfigElement() {
        MultipartConfigFactory factory = new MultipartConfigFactory();
        // C:/Users/xxx/.ruoyi/file/tmp
        String location = System.getProperty("user.home") + "/.ruoyi/file/tmp";
        File tmpFile = new File(location);
        if (!tmpFile.exists()) {
            tmpFile.mkdirs();
        }
        factory.setLocation(location);
        return factory.createMultipartConfig();
    }
}

四、解决方法2

错误中提示路径被设置为：

 is set to C:\Users\ADMINI~1\AppData\Local\Temp\2\

直接创建以下目录就好了

注：目录中的 ADMINI~1 其实就是 Administrator 文件夹，我这里是少了提示路径中的 2 文件夹

其它解决方法：

1. 重新指定临时文件位置  java -Djava.io.tempdir=D:/tmpdir -jar -my_project.jar

2. 手动创建指定文件夹