springboot2.x上传文件抛出错误的问题

错误：

org.apache.tomcat.util.http.fileupload.FileUploadBase$FileSizeLimitExceededException: The field front exceeds its maximum permitted size of 1048576 bytes.
	at org.apache.tomcat.util.http.fileupload.FileUploadBase$FileItemIteratorImpl$FileItemStreamImpl$1.raiseError(FileUploadBase.java:633) ~[tomcat-embed-core-9.0.22.jar:9.0.22]
	at org.apache.tomcat.util.http.fileupload.util.LimitedInputStream.checkLimit(LimitedInputStream.java:76) ~[tomcat-embed-core-9.0.22.jar:9.0.22]
	at org.apache.tomcat.util.http.fileupload.util.LimitedInputStream.read(LimitedInputStream.java:135) ~[tomcat-embed-core-9.0.22.jar:9.0.22]
	at java.io.FilterInputStream.read(FilterInputStream.java:107) ~[na:1.8.0_171]
	at org.apache.tomcat.util.http.fileupload.util.Streams.copy(Streams.java:98) ~[tomcat-embed-core-9.0.22.jar:9.0.22]
	at org.apache.tomcat.util.http.fileupload.FileUploadBase.parseRequest(FileUploadBase.java:294) ~[tomcat-embed-core-9.0.22.jar:9.0.22]
	at org.apache.catalina.connector.Request.parseParts(Request.java:2881) ~[tomcat-embed-core-9.0.22.jar:9.0.22]
	at org.apache.catalina.connector.Request.parseParameters(Request.java:3214) ~[tomcat-embed-core-9.0.22.jar:9.0.22]
	at org.apache.catalina.connector.Request.getParameter(Request.java:1116) ~[tomcat-embed-core-9.0.22.jar:9.0.22]
	at org.apache.catalina.connector.RequestFacade.getParameter(RequestFacade.java:381) ~[tomcat-embed-core-9.0.22.jar:9.0.22]
	at org.springframework.web.filter.HiddenHttpMethodFilter.doFilterInternal(HiddenHttpMethodFilter.java:84) ~[spring-web-5.1.9.RELEASE.jar:5.1.9.RELEASE]
	at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:118) ~[spring-web-5.1.9.RELEASE.jar:5.1.9.RELEASE]
	at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193) ~[tomcat-embed-core-9.0.22.jar:9.0.22]
	at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166) ~[tomcat-embed-core-9.0.22.jar:9.0.22]
	at org.springframework.web.filter.CharacterEncodingFilter.doFilterInternal(CharacterEncodingFilter.java:200) ~[spring-web-5.1.9.RELEASE.jar:5.1.9.RELEASE]
	at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:118) ~[spring-web-5.1.9.RELEASE.jar:5.1.9.RELEASE]
	at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193) ~[tomcat-embed-core-9.0.22.jar:9.0.22]
	at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166) ~[tomcat-embed-core-9.0.22.jar:9.0.22]
	at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:202) ~[tomcat-embed-core-9.0.22.jar:9.0.22]
	at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:96) [tomcat-embed-core-9.0.22.jar:9.0.22]
	at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:490) [tomcat-embed-core-9.0.22.jar:9.0.22]
	at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:139) [tomcat-embed-core-9.0.22.jar:9.0.22]
	at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:92) [tomcat-embed-core-9.0.22.jar:9.0.22]
	at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:74) [tomcat-embed-core-9.0.22.jar:9.0.22]
	at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:343) [tomcat-embed-core-9.0.22.jar:9.0.22]
	at org.apache.coyote.http11.Http11Processor.service(Http11Processor.java:408) [tomcat-embed-core-9.0.22.jar:9.0.22]
	at org.apache.coyote.AbstractProcessorLight.process(AbstractProcessorLight.java:66) [tomcat-embed-core-9.0.22.jar:9.0.22]
	at org.apache.coyote.AbstractProtocol$ConnectionHandler.process(AbstractProtocol.java:853) [tomcat-embed-core-9.0.22.jar:9.0.22]
	at org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.doRun(NioEndpoint.java:1587) [tomcat-embed-core-9.0.22.jar:9.0.22]
	at org.apache.tomcat.util.net.SocketProcessorBase.run(SocketProcessorBase.java:49) [tomcat-embed-core-9.0.22.jar:9.0.22]
	at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149) [na:1.8.0_171]
	at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624) [na:1.8.0_171]
	at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61) [tomcat-embed-core-9.0.22.jar:9.0.22]
	at java.lang.Thread.run(Thread.java:748) [na:1.8.0_171]

原因：springboot默认只支持10MB以下大小的文件上传（记不太清了，反正不大）

解决办法一：
spring boot1.5的时候可以直接在properties/yml中添加配置（以下给出的方式是yml文件）：

 http:
    multipart:
      max-file-size: 20mb
      max-request-size: 20mb

而springboot2.x之后不在提倡这种配置方式，所以就给抛弃了，可以使用这种方式代替：

 servlet:
    multipart:
      max-file-size: 50MB
      max-request-size: 50MB

解决办法二：
在启动类下或者创建一个配置类，使用注解的方式利用MultpartConfigFactory多部件配置工厂设置参数，然后创建MultipartConfigElement对象注入容器中替换springboot的默认配置（配置类不要忽略了@Configuration注解）：

@MapperScan("com.rx.mapper")
@Configuration
@SpringBootApplication
public class DiscernIdentityApplication {

    /**
     *
     * @param args
     */
    public static void main(String[] args) {
        SpringApplication.run(DiscernIdentityApplication.class, args);
    }

    @Bean
    private static MultipartConfigElement multipartConfigElement(){
        MultipartConfigFactory configFactory = new MultipartConfigFactory();
        configFactory.setMaxFileSize("50MB");
        configFactory.setMaxRequestSize("50MB");
        return configFactory.createMultipartConfig();
    }

}