Java Can'；t在Spring上保存/打开文件

我构建了一个页面，允许用户上传文件，但保存文件的功能无法在文件系统上打开文件，下面是代码：

@RequestMapping(value="/upload", method=RequestMethod.POST)
public @ResponseBody String handleFileUpload(@RequestParam("file") MultipartFile file){
    String name="dsotm.png";
    FileSystemResource res;
    res=new FileSystemResource(name);
    if (!file.isEmpty()) {
        System.out.println("file is not empty");
        try {
            byte[] bytes = file.getBytes();
            System.out.println(bytes[1]);
            BufferedOutputStream stream =
                    new BufferedOutputStream(new FileOutputStream(res.getFile()));
            stream.write(bytes);
            stream.close();
            return "You successfully uploaded " + name + "!";
        } catch (Exception e) {
            e.printStackTrace();
            return "You failed to upload " + name + " => " + e.getMessage();

        }
    } else {
        return "You failed to upload " + name + " because the file was empty.";
    }
}

这是stacktrace：

java.io.FileNotFoundException: dsotm.png (Accesso negato)
at java.io.FileOutputStream.open(Native Method)
at java.io.FileOutputStream.<init>(Unknown Source)
at java.io.FileOutputStream.<init>(Unknown Source)
at it.unibo.ai.fratup.controller.HomeController.handleFileUpload(HomeController.java:108)
at it.unibo.ai.fratup.controller.HomeController$$FastClassByCGLIB$$98be424b.invoke(<generated>)
at org.springframework.cglib.proxy.MethodProxy.invoke(MethodProxy.java:204)
at org.springframework.aop.framework.CglibAopProxy$CglibMethodInvocation.invokeJoinpoint(CglibAopProxy.java:698)
at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:150)
at org.springframework.aop.framework.adapter.MethodBeforeAdviceInterceptor.invoke(MethodBeforeAdviceInterceptor.java:51)
at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:172)
at org.springframework.aop.interceptor.ExposeInvocationInterceptor.invoke(ExposeInvocationInterceptor.java:91)
at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:172)
at org.springframework.aop.framework.CglibAopProxy$DynamicAdvisedInterceptor.intercept(CglibAopProxy.java:631)
at it.unibo.ai.fratup.controller.HomeController$$EnhancerByCGLIB$$3690e43c.handleFileUpload(<generated>)
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.invoke(InvocableHandlerMethod.java:219)
at org.springframework.web.method.support.InvocableHandlerMethod.invokeForRequest(InvocableHandlerMethod.java:132)
at org.springframework.web.servlet.mvc.method.annotation.ServletInvocableHandlerMethod.invokeAndHandle(ServletInvocableHandlerMethod.java:104)
at org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.invokeHandleMethod(RequestMappingHandlerAdapter.java:745)
at org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.handleInternal(RequestMappingHandlerAdapter.java:686)
at org.springframework.web.servlet.mvc.method.AbstractHandlerMethodAdapter.handle(AbstractHandlerMethodAdapter.java:80)
at org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:925)
at org.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:856)
at org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:936)
at org.springframework.web.servlet.FrameworkServlet.doPost(FrameworkServlet.java:838)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:648)
at org.springframework.web.servlet.FrameworkServlet.service(FrameworkServlet.java:812)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:729)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:291)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)
at org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:52)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:239)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)
at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:330)
at org.springframework.security.web.access.intercept.FilterSecurityInterceptor.invoke(FilterSecurityInterceptor.java:118)
at org.springframework.security.web.access.intercept.FilterSecurityInterceptor.doFilter(FilterSecurityInterceptor.java:84)
at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:342)
at org.springframework.security.web.access.ExceptionTranslationFilter.doFilter(ExceptionTranslationFilter.java:113)
at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:342)
at org.springframework.security.web.session.SessionManagementFilter.doFilter(SessionManagementFilter.java:103)
at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:342)
at org.springframework.security.web.authentication.AnonymousAuthenticationFilter.doFilter(AnonymousAuthenticationFilter.java:113)
at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:342)
at org.springframework.security.web.servletapi.SecurityContextHolderAwareRequestFilter.doFilter(SecurityContextHolderAwareRequestFilter.java:154)
at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:342)
at org.springframework.security.web.savedrequest.RequestCacheAwareFilter.doFilter(RequestCacheAwareFilter.java:45)
at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:342)
at org.springframework.security.web.authentication.AbstractAuthenticationProcessingFilter.doFilter(AbstractAuthenticationProcessingFilter.java:199)
at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:342)
at org.springframework.security.web.authentication.logout.LogoutFilter.doFilter(LogoutFilter.java:110)
at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:342)
at org.springframework.security.web.header.HeaderWriterFilter.doFilterInternal(HeaderWriterFilter.java:57)
at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:107)
at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:342)
at org.springframework.security.web.context.SecurityContextPersistenceFilter.doFilter(SecurityContextPersistenceFilter.java:87)
at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:342)
at org.springframework.security.web.context.request.async.WebAsyncManagerIntegrationFilter.doFilterInternal(WebAsyncManagerIntegrationFilter.java:50)
at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:107)
at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:342)
at org.springframework.security.web.FilterChainProxy.doFilterInternal(FilterChainProxy.java:192)
at org.springframework.security.web.FilterChainProxy.doFilter(FilterChainProxy.java:160)
at org.springframework.web.filter.DelegatingFilterProxy.invokeDelegate(DelegatingFilterProxy.java:343)
at org.springframework.web.filter.DelegatingFilterProxy.doFilter(DelegatingFilterProxy.java:260)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:239)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)
at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:219)
at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:106)
at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:502)
at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:142)
at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:79)
at org.apache.catalina.valves.AbstractAccessLogValve.invoke(AbstractAccessLogValve.java:610)
at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:88)
at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:518)
at org.apache.coyote.http11.AbstractHttp11Processor.process(AbstractHttp11Processor.java:1091)
at org.apache.coyote.AbstractProtocol$AbstractConnectionHandler.process(AbstractProtocol.java:668)
at org.apache.coyote.http11.Http11NioProtocol$Http11ConnectionHandler.process(Http11NioProtocol.java:223)
at org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.doRun(NioEndpoint.java:1517)
at org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.run(NioEndpoint.java:1474)
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)

java.io.FileNotFoundException:dsotm.png（Accesso否定）
在java.io.FileOutputStream.open（本机方法）
位于java.io.FileOutputStream。（未知源）
位于java.io.FileOutputStream。（未知源）
at it.unibo.ai.fratup.controller.HomeController.handleFileUpload（HomeController.java:108）
在it.unibo.ai.fratup.controller.HomeController$$FastClassByCGLIB$$98be424b.invoke（）中
位于org.springframework.cglib.proxy.MethodProxy.invoke（MethodProxy.java:204）
位于org.springframework.aop.framework.CglibAopProxy$CglibMethodInvocation.invokeJoinpoint（CglibAopProxy.java:698）
在org.springframework.aop.framework.ReflectiveMethodInvocation.procedue（ReflectiveMethodInvocation.java:150）上
位于org.springframework.aop.framework.adapter.MethodBeforeAdviceInterceptor.invoke（MethodBeforeAdviceInterceptor.java:51）
位于org.springframework.aop.framework.ReflectiveMethodInvocation.procedue（ReflectiveMethodInvocation.java:172）
位于org.springframework.aop.interceptor.ExposeInvocationInterceptor.invoke（ExposeInvocationInterceptor.java:91）
位于org.springframework.aop.framework.ReflectiveMethodInvocation.procedue（ReflectiveMethodInvocation.java:172）
位于org.springframework.aop.framework.CglibAopProxy$DynamicAdvisedInterceptor.intercept（CglibAopProxy.java:631）
在it.unibo.ai.fratup.controller.HomeController$$enhancerbyglib$$3690e43c.handleFileUpload（）上
在sun.reflect.NativeMethodAccessorImpl.invoke0（本机方法）处
位于sun.reflect.NativeMethodAccessorImpl.invoke（未知源）
在sun.reflect.DelegatingMethodAccessorImpl.invoke处（未知源）
位于java.lang.reflect.Method.invoke（未知源）
位于org.springframework.web.method.support.InvocableHandlerMethod.invoke（InvocableHandlerMethod.java:219）
位于org.springframework.web.method.support.InvocableHandlerMethod.invokeForRequest（InvocableHandlerMethod.java:132）
位于org.springframework.web.servlet.mvc.method.annotation.ServletInvocableHandlerMethod.invokeAndHandle（ServletInvocableHandlerMethod.java:104）
位于org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.invokeHandleMethod（RequestMappingHandlerAdapter.java:745）
位于org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.handleInternal（RequestMappingHandlerAdapter.java:686）
位于org.springframework.web.servlet.mvc.method.AbstractHandlerMethodAdapter.handle（AbstractHandlerMethodAdapter.java:80）
位于org.springframework.web.servlet.DispatcherServlet.doDispatch（DispatcherServlet.java:925）
位于org.springframework.web.servlet.DispatcherServlet.doService（DispatcherServlet.java:856）
位于org.springframework.web.servlet.FrameworkServlet.processRequest（FrameworkServlet.java:936）
位于org.springframework.web.servlet.FrameworkServlet.doPost（FrameworkServlet.java:838）
位于javax.servlet.http.HttpServlet.service（HttpServlet.java:648）
位于org.springframework.web.servlet.FrameworkServlet.service（FrameworkServlet.java:812）
位于javax.servlet.http.HttpServlet.service（HttpServlet.java:729）
位于org.apache.catalina.core.ApplicationFilterChain.internalDoFilter（ApplicationFilterChain.java:291）
位于org.apache.catalina.core.ApplicationFilterChain.doFilter（ApplicationFilterChain.java:206）
位于org.apache.tomcat.websocket.server.WsFilter.doFilter（WsFilter.java:52）
位于org.apache.catalina.core.ApplicationFilterChain.internalDoFilter（ApplicationFilterChain.java:239）
位于org.apache.catalina.core.ApplicationFilterChain.doFilter（ApplicationFilterChain.java:206）
位于org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter（FilterChainProxy.java:330）
位于org.springframework.security.web.access.intercept.FilterSecurityInterceptor.invoke（FilterSecurityInterceptor.java:118）
位于org.springframework.security.web.access.intercept.FilterSecurityInterceptor.doFilter（FilterSecurityInterceptor.java:84）
位于org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter（FilterChainProxy.java:342）
位于org.springframework.security.web.access.ExceptionTranslationFilter.doFilter（ExceptionTranslationFilter.java:113）
位于org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter（FilterChainProxy.java:342）
位于org.springframework.security.web.session.SessionManagementFilter.doFilter（SessionManagementFilter.java:103）
位于org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter（FilterChainProxy.java:342）
位于org.springframework.security.web.authentication.AnonymousAuthenticationFilter.doFilter（AnonymousAuthenticationFilter.java:113）
位于org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter（FilterChainProxy.java:342）
位于org.springframework.security.web.servletapi.SecurityContextHolderAwareRequestFilter.doFilter（SecurityContextHolderAwareRequestFilter.java:154）
位于org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter（FilterChainProxy.java:342）
位于org.springframework.security.web.savedrequest.RequestCacheAwarRefilter.doFilter（RequestCacheAwarRefilter.java:45）
位于org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter（FilterChainProxy.java:342）
位于org.springframework.security.web.authentication.AbstractAuthenticationProcessingFilter.doFilter（AbstractAuthenticationProcessingFilter.java:199）
位于org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter（FilterChainProxy.java:342）
位于org.springframework.security.web.authentication.logout.LogoutFilter.doFilter（LogoutFilter.java:110）
位于org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter（FilterChainProxy.java:342）
位于org.springframework.security.web.header.HeaderWriterFilter.doFilterInternal（HeaderWriterFilter.java:57）
位于org.springframework.web.filter.OncePerRequestFilter.doFilter（OncePerRequestFilter.java:107）
在org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter（FilterChainProxy.j
FileSystemResource res;
    res=new FileSystemResource(name);

 BufferedOutputStream stream =
                new BufferedOutputStream(new FileOutputStream(new File(name)));