文件上传
上传到服务器的磁盘路径
@RestController
public class UpDownloadController{@RequestMapping("uploadFile")public String uploadFile(MultipartFile file) throws IOException {// 要保存到服务器的路径(根据实际需要修改)String remorePath = "/home/test";String fileName = file.getOriginalFilename();String filePath = remorePath+"/"+fileName;file.transferTo(new File(filePath));// 返回前端的文件访问地址（一般是http请求的地址，不要直接返回remorePath这样的磁盘路径）return remorePath; }
}
文件上传，前端需设置请求头为：multipart/form-data。
MultipartFile常用方法说明
String getName()：获取文件对应的表单参数名称
String getOriginalFilename()：获取文件的名称
InputStream getInputStream()：获取文件的输入流。我们的示例是上传到服务器的磁盘，很多项目可能是上传到文件服务器等。可通过该输入流将文件数据对接到文件服务器的对应接口上。
byte[] getBytes()：获取文件的数据
void transferTo(File dest)：将文件输出到定义的 dest 文件
带其他参数的文件上传
@RequestMapping("uploadFile")public String uploadFile(Param param,MultipartFile file) throws IOException {log.error("文件上传参数：{}",param);// 要保存到服务器的路径(根据实际需要修改)String remorePath = "/home/test";String fileName = file.getOriginalFilename();String filePath = remorePath+"/"+fileName;file.transferTo(new File(filePath));// 返回前端的文件访问地址（一般是http请求的地址，不要直接返回remorePath这样的磁盘路径）return remorePath;}
其他参数的获取和普通的Controller获取一样。
文件下载
@RequestMapping("downloadFile/{param1}/{param2}")public void downloadFile(@PathVariable Long param1, @PathVariable Long param2,String filePath, HttpServletResponse response) throws IOException {File f = new File("C:\\work\\test\\2022_11_01\\720513e0d488.txt");log.error("param1：{},param2：{},filePath：{}",param1,param2,filePath);// 下载为中文的文件名称String fileName = new String("测试下载".getBytes("UTF-8"),"ISO-8859-1") + ".txt";response.setContentType("application/force-download");// 设置强制下载不打开response.addHeader("Content-Disposition", "attachment;fileName=" + fileName);FileUtils.copyFile(f,response.getOutputStream());response.getOutputStream().close();}
注：fileName 如果直接使用汉字字符串，下载后文件名称变成了下划线。通过示例中的方式转换即可。
支持文件上传下载的配置说明
如果在 Spring MVC 下，需要配置 一个名称为 multipartResolver 的 MultipartResolver 类型的bean来支持文件上传。Spring-web包为其提供了两个实现CommonsMultipartResolver、StandardServletMultipartResolver
| 类名 | 说明 |
|---|---|
| CommonsMultipartResolver | 基于 Commons FileUpload 上仅适用于POST请求，但接受任何多部分/内容类型。 |
| StandardServletMultipartResolver | 使用Servlet容器的多部分解析器，可能会使应用程序暴露于容器实现的差异。 |
如果要使用 CommonsMultipartResolver 需要引入 Commons FileUpload 依赖包。
spring boot 下，默认是可以不用什么配置，就支持文件的上传和下载的。我们来看看spring boot 的相关自动配置代码
@Bean(name = "multipartResolver")@ConditionalOnMissingBean(MultipartResolver.class)public StandardServletMultipartResolver multipartResolver() {StandardServletMultipartResolver multipartResolver = new StandardServletMultipartResolver();multipartResolver.setResolveLazily(this.multipartProperties.isResolveLazily());return multipartResolver;}
说明Spring Boot 默认是使用的 StandardServletMultipartResolver。但其使用了条件注解，我们可以在我们的应用中使用 CommonsMultipartResolver 将其替换掉。
限制上传文件的大小
Spring Boot 自动配置中还有个类我们需要了解 MultipartProperties，文件上传的配置。其在application.properties 文件中的配置前缀为 spring.servlet.multipart
- location：指定上载文件的存储目录。如果未指定，将使用临时目录。
- max-file-size ：指定上传文件允许的最大大小。默认值为1MB（意味着我们上传文件的默认最大大小为1MB）
- max-request-size：指定多部分/表单数据请求允许的最大大小。默认值为10MB。
- file-size-threshold ：文件大小阈值指定文件将写入磁盘的大小阈值。默认值为0。
- resolve-lazily：是否在文件或参数访问时延迟解析多部分请求
配置示例
# 上传文件的表单数据最大大小
spring.servlet.multipart.max-request-size= 20MB
# 上传文件的最大大小
spring.servlet.multipart.max-file-size= 5MB
常见问题解析
MaxUploadSizeExceededException 异常 @ControllerAdvice 标注的 ExceptionHandler 无法解析的问题
org.springframework.web.multipart.MaxUploadSizeExceededException: Maximum upload size exceeded; nested exception is java.lang.IllegalStateException: org.apache.tomcat.util.http.fileupload.impl.SizeLimitExceededException: the request was rejected because its size (336958720) exceeds the configured maximum (20971520)at org.springframework.web.multipart.support.StandardMultipartHttpServletRequest.handleParseFailure(StandardMultipartHttpServletRequest.java:122)at org.springframework.web.multipart.support.StandardMultipartHttpServletRequest.parseRequest(StandardMultipartHttpServletRequest.java:115)at org.springframework.web.multipart.support.StandardMultipartHttpServletRequest.initializeMultipart(StandardMultipartHttpServletRequest.java:129)at org.springframework.web.multipart.support.AbstractMultipartHttpServletRequest.getMultipartFiles(AbstractMultipartHttpServletRequest.java:141)at org.springframework.web.multipart.support.AbstractMultipartHttpServletRequest.getFile(AbstractMultipartHttpServletRequest.java:88)at org.springframework.web.multipart.support.MultipartResolutionDelegate.resolveMultipartArgument(MultipartResolutionDelegate.java:108)at org.springframework.web.method.annotation.RequestParamMethodArgumentResolver.resolveName(RequestParamMethodArgumentResolver.java:166)at org.springframework.web.method.annotation.AbstractNamedValueMethodArgumentResolver.resolveArgument(AbstractNamedValueMethodArgumentResolver.java:108)at org.springframework.web.method.support.HandlerMethodArgumentResolverComposite.resolveArgument(HandlerMethodArgumentResolverComposite.java:122)at org.springframework.web.method.support.InvocableHandlerMethod.getMethodArgumentValues(InvocableHandlerMethod.java:179)at org.springframework.web.method.support.InvocableHandlerMethod.invokeForRequest(InvocableHandlerMethod.java:146)at org.springframework.web.servlet.mvc.method.annotation.ServletInvocableHandlerMethod.invokeAndHandle(ServletInvocableHandlerMethod.java:117)at org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.invokeHandlerMethod(RequestMappingHandlerAdapter.java:895)at org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.handleInternal(RequestMappingHandlerAdapter.java:808)at org.springframework.web.servlet.mvc.method.AbstractHandlerMethodAdapter.handle(AbstractHandlerMethodAdapter.java:87)at org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:1067)at org.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:963)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:681)at org.springframework.web.servlet.FrameworkServlet.service(FrameworkServlet.java:883)at javax.servlet.http.HttpServlet.service(HttpServlet.java:764)at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:227)at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:162)at org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:53)at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:189)at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:162)at org.apache.shiro.web.servlet.ProxiedFilterChain.doFilter(ProxiedFilterChain.java:61)at org.apache.shiro.web.servlet.AdviceFilter.executeChain(AdviceFilter.java:108)at org.apache.shiro.web.servlet.AdviceFilter.doFilterInternal(AdviceFilter.java:137)at org.apache.shiro.web.servlet.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:125)at org.apache.shiro.web.servlet.ProxiedFilterChain.doFilter(ProxiedFilterChain.java:66)at org.apache.shiro.web.servlet.AdviceFilter.executeChain(AdviceFilter.java:108)at org.apache.shiro.web.servlet.AdviceFilter.doFilterInternal(AdviceFilter.java:137)at org.apache.shiro.web.servlet.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:125)at org.apache.shiro.web.servlet.ProxiedFilterChain.doFilter(ProxiedFilterChain.java:66)at org.apache.shiro.web.servlet.AbstractShiroFilter.executeChain(AbstractShiroFilter.java:450)at org.apache.shiro.web.servlet.AbstractShiroFilter$1.call(AbstractShiroFilter.java:365)at org.apache.shiro.subject.support.SubjectCallable.doCall(SubjectCallable.java:90)at org.apache.shiro.subject.support.SubjectCallable.call(SubjectCallable.java:83)at org.apache.shiro.subject.support.DelegatingSubject.execute(DelegatingSubject.java:387)at org.apache.shiro.web.servlet.AbstractShiroFilter.doFilterInternal(AbstractShiroFilter.java:362)at org.apache.shiro.web.servlet.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:125)at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:189)at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:162)at com.yyoo.mybase.base.filter.CorsFilter.doFilter(CorsFilter.java:58)at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:189)at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:162)at com.yyoo.mybase.base.filter.xss.XssFilter.doFilter(XssFilter.java:75)at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:189)at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:162)at org.springframework.web.filter.RequestContextFilter.doFilterInternal(RequestContextFilter.java:100)at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:117)at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:189)at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:162)at org.springframework.web.filter.FormContentFilter.doFilterInternal(FormContentFilter.java:93)at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:117)at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:189)at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:162)at org.springframework.session.web.http.SessionRepositoryFilter.doFilterInternal(SessionRepositoryFilter.java:142)at org.springframework.session.web.http.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:82)at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:189)at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:162)at org.springframework.web.filter.CharacterEncodingFilter.doFilterInternal(CharacterEncodingFilter.java:201)at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:117)at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:189)at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:162)at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:197)at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:97)at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:540)at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:135)at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:92)at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:78)at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:357)at org.apache.coyote.http11.Http11Processor.service(Http11Processor.java:382)at org.apache.coyote.AbstractProcessorLight.process(AbstractProcessorLight.java:65)at org.apache.coyote.AbstractProtocol$ConnectionHandler.process(AbstractProtocol.java:895)at org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.doRun(NioEndpoint.java:1732)at org.apache.tomcat.util.net.SocketProcessorBase.run(SocketProcessorBase.java:49)at org.apache.tomcat.util.threads.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1191)at org.apache.tomcat.util.threads.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:659)at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61)at java.lang.Thread.run(Thread.java:748)
Caused by: java.lang.IllegalStateException: org.apache.tomcat.util.http.fileupload.impl.SizeLimitExceededException: the request was rejected because its size (336958720) exceeds the configured maximum (20971520)at org.apache.catalina.connector.Request.parseParts(Request.java:2974)at org.apache.catalina.connector.Request.getParts(Request.java:2834)at org.apache.catalina.connector.RequestFacade.getParts(RequestFacade.java:1098)at javax.servlet.http.HttpServletRequestWrapper.getParts(HttpServletRequestWrapper.java:361)at javax.servlet.http.HttpServletRequestWrapper.getParts(HttpServletRequestWrapper.java:361)at javax.servlet.http.HttpServletRequestWrapper.getParts(HttpServletRequestWrapper.java:361)at org.springframework.web.multipart.support.StandardMultipartHttpServletRequest.parseRequest(StandardMultipartHttpServletRequest.java:95)... 81 common frames omitted
Caused by: org.apache.tomcat.util.http.fileupload.impl.SizeLimitExceededException: the request was rejected because its size (336958720) exceeds the configured maximum (20971520)at org.apache.tomcat.util.http.fileupload.impl.FileItemIteratorImpl.init(FileItemIteratorImpl.java:161)at org.apache.tomcat.util.http.fileupload.impl.FileItemIteratorImpl.getMultiPartStream(FileItemIteratorImpl.java:205)at org.apache.tomcat.util.http.fileupload.impl.FileItemIteratorImpl.findNextItem(FileItemIteratorImpl.java:224)at org.apache.tomcat.util.http.fileupload.impl.FileItemIteratorImpl.<init>(FileItemIteratorImpl.java:142)at org.apache.tomcat.util.http.fileupload.FileUploadBase.getItemIterator(FileUploadBase.java:252)at org.apache.tomcat.util.http.fileupload.FileUploadBase.parseRequest(FileUploadBase.java:276)at org.apache.catalina.connector.Request.parseParts(Request.java:2932)... 87 common frames omitted
由于我们Spring Boot 默认使用了容器的文件上传支持，所以此处的错误是 tomcat 容器报的，此处修改办法有两个。
1. 修改配置文件
# 上传文件的表单数据最大大小
spring.servlet.multipart.max-request-size= 20MB
# 上传文件的最大大小
spring.servlet.multipart.max-file-size= 5MB
# 设置tomcat的允许大小为-1，不限制
server.tomcat.max-swallow-size = -1
# 是否在文件或参数访问时延迟解析多部分请求
spring.servlet.multipart.resolve-lazily=true
2. 使用 CommonsMultipartResolver
- 添加依赖
<dependency><groupId>commons-fileupload</groupId><artifactId>commons-fileupload</artifactId><version>1.4</version>
</dependency>
- 配置 CommonsMultipartResolver
