在使用springboot上传文件时后报错如下

 ERROR 11136 --- [nio-8080-exec-2] o.a.c.c.C.[.[.[/].[dispatcherServlet]    : Servlet.service() for servlet [dispatcherServlet] in context with path [] threw exception [Request processing failed; nested exception is org.springframework.web.multipart.MaxUploadSizeExceededException: Maximum upload size exceeded; nested exception is java.lang.IllegalStateException: org.apache.tomcat.util.http.fileupload.impl.FileSizeLimitExceededException: The field photos exceeds its maximum permitted size of 1048576 bytes.] with root cause

org.apache.tomcat.util.http.fileupload.impl.FileSizeLimitExceededException: The field photos exceeds its maximum permitted size of 1048576 bytes.
	at org.apache.tomcat.util.http.fileupload.impl.FileItemStreamImpl$1.raiseError(FileItemStreamImpl.java:114) ~[tomcat-embed-core-9.0.52.jar:9.0.52]
	at org.apache.tomcat.util.http.fileupload.util.LimitedInputStream.checkLimit(LimitedInputStream.java:76) ~[tomcat-embed-core-9.0.52.jar:9.0.52]
	at org.apache.tomcat.util.http.fileupload.util.LimitedInputStream.read(LimitedInputStream.java:135) ~[tomcat-embed-core-9.0.52.jar:9.0.52]
	at java.io.FilterInputStream.read(FilterInputStream.java:107) ~[na:1.8.0_221]
	at org.apache.tomcat.util.http.fileupload.util.Streams.copy(Streams.java:98) ~[tomcat-embed-core-9.0.52.jar:9.0.52]
	at org.apache.tomcat.util.http.fileupload.FileUploadBase.parseRequest(FileUploadBase.java:291) ~[tomcat-embed-core-9.0.52.jar:9.0.52]
	at org.apache.catalina.connector.Request.parseParts(Request.java:2922) ~[tomcat-embed-core-9.0.52.jar:9.0.52]
	at org.apache.catalina.connector.Request.getParts(Request.java:2824) ~[tomcat-embed-core-9.0.52.jar:9.0.52]
	at org.apache.catalina.connector.RequestFacade.getParts(RequestFacade.java:1098) ~[tomcat-embed-core-9.0.52.jar:9.0.52]
	at org.springframework.web.multipart.support.StandardMultipartHttpServletRequest.parseRequest(StandardMultipartHttpServletRequest.java:95) ~[spring-web-5.3.9.jar:5.3.9]
	at org.springframework.web.multipart.support.StandardMultipartHttpServletRequest.<init>(StandardMultipartHttpServletRequest.java:88) ~[spring-web-5.3.9.jar:5.3.9]
	at org.springframework.web.multipart.support.StandardServletMultipartResolver.resolveMultipart(StandardServletMultipartResolver.java:122) ~[spring-web-5.3.9.jar:5.3.9]
	at org.springframework.web.servlet.DispatcherServlet.checkMultipart(DispatcherServlet.java:1202) ~[spring-webmvc-5.3.9.jar:5.3.9]
	at org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:1036) ~[spring-webmvc-5.3.9.jar:5.3.9]
	at org.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:963) ~[spring-webmvc-5.3.9.jar:5.3.9]
	at org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:1006) ~[spring-webmvc-5.3.9.jar:5.3.9]
	at org.springframework.web.servlet.FrameworkServlet.doPost(FrameworkServlet.java:909) ~[spring-webmvc-5.3.9.jar:5.3.9]
	at javax.servlet.http.HttpServlet.service(HttpServlet.java:681) ~[tomcat-embed-core-9.0.52.jar:4.0.FR]
	at org.springframework.web.servlet.FrameworkServlet.service(FrameworkServlet.java:883) ~[spring-webmvc-5.3.9.jar:5.3.9]
	at javax.servlet.http.HttpServlet.service(HttpServlet.java:764) ~[tomcat-embed-core-9.0.52.jar:4.0.FR]
	at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:227) ~[tomcat-embed-core-9.0.52.jar:9.0.52]
	at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:162) ~[tomcat-embed-core-9.0.52.jar:9.0.52]
	at org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:53) ~[tomcat-embed-websocket-9.0.52.jar:9.0.52]
	at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:189) ~[tomcat-embed-core-9.0.52.jar:9.0.52]
	at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:162) ~[tomcat-embed-core-9.0.52.jar:9.0.52]
	at org.springframework.web.filter.RequestContextFilter.doFilterInternal(RequestContextFilter.java:100) ~[spring-web-5.3.9.jar:5.3.9]
	at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:119) ~[spring-web-5.3.9.jar:5.3.9]
	at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:189) ~[tomcat-embed-core-9.0.52.jar:9.0.52]
	at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:162) ~[tomcat-embed-core-9.0.52.jar:9.0.52]
	at org.springframework.web.filter.FormContentFilter.doFilterInternal(FormContentFilter.java:93) ~[spring-web-5.3.9.jar:5.3.9]
	at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:119) ~[spring-web-5.3.9.jar:5.3.9]
	at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:189) ~[tomcat-embed-core-9.0.52.jar:9.0.52]
	at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:162) ~[tomcat-embed-core-9.0.52.jar:9.0.52]
	at org.springframework.web.filter.CharacterEncodingFilter.doFilterInternal(CharacterEncodingFilter.java:201) ~[spring-web-5.3.9.jar:5.3.9]
	at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:119) ~[spring-web-5.3.9.jar:5.3.9]
	at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:189) ~[tomcat-embed-core-9.0.52.jar:9.0.52]
	at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:162) ~[tomcat-embed-core-9.0.52.jar:9.0.52]
	at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:197) ~[tomcat-embed-core-9.0.52.jar:9.0.52]
	at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:97) [tomcat-embed-core-9.0.52.jar:9.0.52]
	at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:542) [tomcat-embed-core-9.0.52.jar:9.0.52]
	at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:135) [tomcat-embed-core-9.0.52.jar:9.0.52]
	at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:92) [tomcat-embed-core-9.0.52.jar:9.0.52]
	at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:78) [tomcat-embed-core-9.0.52.jar:9.0.52]
	at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:357) [tomcat-embed-core-9.0.52.jar:9.0.52]
	at org.apache.coyote.http11.Http11Processor.service(Http11Processor.java:382) [tomcat-embed-core-9.0.52.jar:9.0.52]
	at org.apache.coyote.AbstractProcessorLight.process(AbstractProcessorLight.java:65) [tomcat-embed-core-9.0.52.jar:9.0.52]
	at org.apache.coyote.AbstractProtocol$ConnectionHandler.process(AbstractProtocol.java:893) [tomcat-embed-core-9.0.52.jar:9.0.52]
	at org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.doRun(NioEndpoint.java:1726) [tomcat-embed-core-9.0.52.jar:9.0.52]
	at org.apache.tomcat.util.net.SocketProcessorBase.run(SocketProcessorBase.java:49) [tomcat-embed-core-9.0.52.jar:9.0.52]
	at org.apache.tomcat.util.threads.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1191) [tomcat-embed-core-9.0.52.jar:9.0.52]
	at org.apache.tomcat.util.threads.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:659) [tomcat-embed-core-9.0.52.jar:9.0.52]
	at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61) [tomcat-embed-core-9.0.52.jar:9.0.52]
	at java.lang.Thread.run(Thread.java:748) [na:1.8.0_221]

报错原因：

单个文件上传大小不能多于1MB

多个文件上传大小不能多于10MB

springboot底层的源码简单解析

// 这两个类我都截取了部分，感兴趣的朋友可以自己去看

// 文件上传的配置类
public class MultipartProperties {
    private boolean enabled = true;
    private String location;

    // 默认单个文件大小为1MB
    private DataSize maxFileSize = DataSize.ofMegabytes(1L);
    
    // 默认多个文件大小为10MB
    private DataSize maxRequestSize = DataSize.ofMegabytes(10L);
    
    private DataSize fileSizeThreshold = DataSize.ofBytes(0L);
    private boolean resolveLazily = false;
}

// 设置文件大小
public final class DataSize implements Comparable<DataSize>, Serializable {
	/**
	 * The pattern for parsing.
	 */
	private static final Pattern PATTERN = Pattern.compile("^([+\\-]?\\d+)([a-zA-Z]{0,2})$");

	/**
	 * Bytes per Kilobyte.
	 */
	private static final long BYTES_PER_KB = 1024;

	/**
	 * Bytes per Megabyte.
	 */
	private static final long BYTES_PER_MB = BYTES_PER_KB * 1024;

	/**
	 * Bytes per Gigabyte.
	 */
	private static final long BYTES_PER_GB = BYTES_PER_MB * 1024;

	/**
	 * Bytes per Terabyte.
	 */
	private static final long BYTES_PER_TB = BYTES_PER_GB * 1024;


	private final long bytes;


	/**
	 * Obtain a {@link DataSize} representing the specified number of megabytes.
	 * @param megabytes the number of megabytes, positive or negative
	 * @return a {@link DataSize}
	 */
	public static DataSize ofMegabytes(long megabytes) {
		return new DataSize(Math.multiplyExact(megabytes, BYTES_PER_MB));
	}
}

解决办法：在properties或者yaml配置文件里自定义配置即可修改springboot文件上传最大限制，这里我在yaml里配置

spring:
  mvc: 
  servlet:
    multipart:
      max-file-size: 10MB  		# 设置单个文件最大大小为10MB
      max-request-size: 100MB  	# 设置多个文件大小为100MB