Springmvc upload file MultipartFile to File Notes

Business scenario: When the ssm framework uploads files to the application server, it needs to be transferred to the dedicated file server and return the url for other operations.

Business difficulty: MultipartFile to File type

Solution code:

/**
     * Convert MultipartFile to File
     *
     * @param multfile original file type
     * @return File
     * @throws IOException
     */
    private File multipartToFile(MultipartFile multfile) throws IOException {
    	CommonsMultipartFile cf = (CommonsMultipartFile)multfile;
		//This myfile is MultipartFile
		DiskFileItem fi = (DiskFileItem) cf.getFileItem();
		File file = fi.getStoreLocation();
		//Create a temporary file manually
		if(file.length() < CommonConstants.MIN_FILE_SIZE){
			File tmpFile = new File(System.getProperty("java.io.tmpdir") + System.getProperty("file.separator") +
					file.getName());
			multfile.transferTo(tmpFile);
	        return tmpFile;
		}
        return file;
    }

Note: If the upload file size is less than 2048, no temporary file will be generated

<bean id="multipartResolver" class="org.springframework.web.multipart.commons.CommonsMultipartResolver">
		<property name="defaultEncoding" value="UTF-8" />
		<property name="maxUploadSize" value="10240000" />
		<!-- Set the maximum value that is allowed to be written to memory during file upload, in bytes, the default is 10240 -->
        <!-- But after experiments, if the upload file size is smaller than this parameter, no temporary file will be generated, so it is changed to 2048 -->
        <property name="maxInMemorySize" value="2048" />  
	</bean>

Solver : fage