java.io.FileNotFoundException: class path resource [] cannot be resolved to URL because it does not
最近在做文件上传的时候出现了一个错误，代码在IntelliJ IDEA开发环境里正常运行，但是一旦将工程打包成jar包运行，就提示如下错误：
This application has no explicit mapping for /error, so you are seeing this as a fallback.
Sun Nov 03 12:11:58 CST 2019
There was an unexpected error (type=Internal Server Error, status=500).
class path resource [] cannot be resolved to URL because it does not exist
java.io.FileNotFoundException: class path resource [] cannot be resolved to URL because it does not exist
at org.springframework.util.ResourceUtils.getURL(ResourceUtils.java:137)
at cn.edu.lzy.tzb.controller.UploadController.uploadImg(UploadController.java:49)
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.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:104)
at org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.invokeHandlerMethod(RequestMappingHandlerAdapter.java:892)
at org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.handleInternal(RequestMappingHandlerAdapter.java:797)
at org.springframework.web.servlet.mvc.method.AbstractHandlerMethodAdapter.handle(AbstractHandlerMethodAdapter.java:87)
at org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:1039)
at org.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:942)
at org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:1005)
at org.springframework.web.servlet.FrameworkServlet.doPost(FrameworkServlet.java:908)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:660)
at org.springframework.web.servlet.FrameworkServlet.service(FrameworkServlet.java:882)
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 org.springframework.web.filter.RequestContextFilter.doFilterInternal(RequestContextFilter.java:99)
at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:118)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166)
at org.springframework.web.filter.FormContentFilter.doFilterInternal(FormContentFilter.java:92)
at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:118)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166)
at org.springframework.web.filter.HiddenHttpMethodFilter.doFilterInternal(HiddenHttpMethodFilter.java:93)
at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:118)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166)
at org.springframework.web.filter.CharacterEncodingFilter.doFilterInternal(CharacterEncodingFilter.java:200)
at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:118)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166)
at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:202)
at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:96)
at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:526)
at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:139)
at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:92)
at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:74)
at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:343)
at org.apache.coyote.http11.Http11Processor.service(Http11Processor.java:408)
at org.apache.coyote.AbstractProcessorLight.process(AbstractProcessorLight.java:66)
at org.apache.coyote.AbstractProtocol$ConnectionHandler.process(AbstractProtocol.java:860)
at org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.doRun(NioEndpoint.java:1587)
at org.apache.tomcat.util.net.SocketProcessorBase.run(SocketProcessorBase.java:49)
at java.util.concurrent.ThreadPoolExecutor.runWorker(Unknown Source)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(Unknown Source)
at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61)
at java.lang.Thread.run(Unknown Source)
这个原因就是找不到文件夹路径，经过几天的各种百度，终于解决了。解决办法如下：
第一步：
原来是这样写的
File path = new File(ResourceUtils.getURL("classpath:").getPath());
System.out.println(path.toString());
if(!path.exists()) {
path = new File("");
}
File upload = new File(path.getAbsolutePath(),"static/upload/");
if(!upload.exists()) {
upload.mkdirs();
}
String uploadPath = upload + "//";
file = new File(uploadPath + newFileName);
multipartFile.transferTo(file);
修改过后 我在getURL的classpath后面加了个通配符*
File path = new File(ResourceUtils.getURL("classpath*:").getPath());
System.out.println(path.toString());
if(!path.exists()) {
path = new File("");
}
File upload = new File(path.getAbsolutePath(),"static/upload/");
if(!upload.exists()) {
upload.mkdirs();
}
String uploadPath = upload + "//";
file = new File(uploadPath + newFileName);
multipartFile.transferTo(file);
第二步：修改pom.xml文件 在build标签中添加如下代码
<resources>
<resource>
<directory>srcdirectory>
<includes>
<include>**/*.xmlinclude>
<include>**/*.propertiesinclude>
includes>
<filtering>falsefiltering>
resource>
resources>
第三步：修改yaml配置文件，添加如下代码
spring:
#设置静态资源路径，多个以逗号分隔
resources:
static-locations:=classpath:/META-INF/resources/,classpath:/resources/,
classpath:/static/,classpath:/public/,file:static/
最后提示一下
新建的目录位置：
如果是开发环境：则会在项目目录下的 target\classes下创建目录；
如果是打成jar包后运行，则会在jar包的同级目录下创建目录。