项目场景：

程序启动时报错：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 ./tmp

原文：

2023-08-18 11:09:51.416     ERROR 20894 --- [           main]     o.s.boot.SpringApplication               : 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 ./tmp
	at org.springframework.boot.web.servlet.context.ServletWebServerApplicationContext.onRefresh(ServletWebServerApplicationContext.java:161) ~[spring-boot-2.3.12.RELEASE.jar!/:2.3.12.RELEASE]
	at org.springframework.context.support.AbstractApplicationContext.refresh(AbstractApplicationContext.java:545) ~[spring-context-5.2.15.RELEASE.jar!/:5.2.15.RELEASE]
	at org.springframework.boot.web.servlet.context.ServletWebServerApplicationContext.refresh(ServletWebServerApplicationContext.java:143) ~[spring-boot-2.3.12.RELEASE.jar!/:2.3.12.RELEASE]
	at org.springframework.boot.SpringApplication.refresh(SpringApplication.java:755) [spring-boot-2.3.12.RELEASE.jar!/:2.3.12.RELEASE]
	at org.springframework.boot.SpringApplication.refresh(SpringApplication.java:747) [spring-boot-2.3.12.RELEASE.jar!/:2.3.12.RELEASE]
	at org.springframework.boot.SpringApplication.refreshContext(SpringApplication.java:402) [spring-boot-2.3.12.RELEASE.jar!/:2.3.12.RELEASE]
	at org.springframework.boot.SpringApplication.run(SpringApplication.java:312) [spring-boot-2.3.12.RELEASE.jar!/:2.3.12.RELEASE]
	at org.springframework.boot.SpringApplication.run(SpringApplication.java:1247) [spring-boot-2.3.12.RELEASE.jar!/:2.3.12.RELEASE]
	at org.springframework.boot.SpringApplication.run(SpringApplication.java:1236) [spring-boot-2.3.12.RELEASE.jar!/:2.3.12.RELEASE]
	at cn.tongdun.atreus.loan.AppMain.main(AppMain.java:23) [classes!/:na]
	at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) ~[na:1.8.0_333]
	at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62) ~[na:1.8.0_333]
	at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) ~[na:1.8.0_333]
	at java.lang.reflect.Method.invoke(Method.java:498) ~[na:1.8.0_333]
	at org.springframework.boot.loader.MainMethodRunner.run(MainMethodRunner.java:48) [atreus-loan.jar:na]
	at org.springframework.boot.loader.Launcher.launch(Launcher.java:87) [atreus-loan.jar:na]
	at org.springframework.boot.loader.Launcher.launch(Launcher.java:51) [atreus-loan.jar:na]
	at org.springframework.boot.loader.PropertiesLauncher.main(PropertiesLauncher.java:597) [atreus-loan.jar:na]
Caused by: org.springframework.boot.web.server.WebServerException: Unable to create tempDir. java.io.tmpdir is set to ./tmp
	at org.springframework.boot.web.server.AbstractConfigurableWebServerFactory.createTempDir(AbstractConfigurableWebServerFactory.java:195) ~[spring-boot-2.3.12.RELEASE.jar!/:2.3.12.RELEASE]
	at org.springframework.boot.web.embedded.tomcat.TomcatServletWebServerFactory.getWebServer(TomcatServletWebServerFactory.java:180) ~[spring-boot-2.3.12.RELEASE.jar!/:2.3.12.RELEASE]
	at org.springframework.boot.web.servlet.context.ServletWebServerApplicationContext.createWebServer(ServletWebServerApplicationContext.java:178) ~[spring-boot-2.3.12.RELEASE.jar!/:2.3.12.RELEASE]
	at org.springframework.boot.web.servlet.context.ServletWebServerApplicationContext.onRefresh(ServletWebServerApplicationContext.java:158) ~[spring-boot-2.3.12.RELEASE.jar!/:2.3.12.RELEASE]
	... 17 common frames omitted
Caused by: java.nio.file.NoSuchFileException: ./tmp/tomcat.8094.5929425290742081680
	at sun.nio.fs.UnixException.translateToIOException(UnixException.java:86) ~[na:1.8.0_333]
	at sun.nio.fs.UnixException.rethrowAsIOException(UnixException.java:102) ~[na:1.8.0_333]
	at sun.nio.fs.UnixException.rethrowAsIOException(UnixException.java:107) ~[na:1.8.0_333]
	at sun.nio.fs.UnixFileSystemProvider.createDirectory(UnixFileSystemProvider.java:384) ~[na:1.8.0_333]
	at java.nio.file.Files.createDirectory(Files.java:674) ~[na:1.8.0_333]
	at java.nio.file.TempFileHelper.create(TempFileHelper.java:136) ~[na:1.8.0_333]
	at java.nio.file.TempFileHelper.createTempDirectory(TempFileHelper.java:173) ~[na:1.8.0_333]
	at java.nio.file.Files.createTempDirectory(Files.java:991) ~[na:1.8.0_333]
	at org.springframework.boot.web.server.AbstractConfigurableWebServerFactory.createTempDir(AbstractConfigurableWebServerFactory.java:189) ~[spring-boot-2.3.12.RELEASE.jar!/:2.3.12.RELEASE]
	... 20 common frames omitted

问题描述：

应用程序在启动时遇到了问题。

错误信息表明应用程序无法启动Web服务器，具体的错误是 org.springframework.boot.web.server.WebServerException: Unable to create tempDir. java.io.tmpdir is set to ./tmp。

原因分析：

这个错误意味着应用程序无法创建临时目录（tempDir），因为系统属性 java.io.tmpdir 被设置为 ./tmp。然后出现了 java.nio.file.NoSuchFileException 异常，报告找不到 ./tmp/tomcat.8094.5929425290742081680 这个目录。

可能存在以下两种原因：