1.当上传时未配置上传内容大小，会报错【org.apache.tomcat.util.http.fileupload.FileUploadBase$SizeLimitExceededException】。

此时，可以在启动类中配置以下代码。

　　 @Bean    public MultipartConfigElement multipartConfigElement() {        MultipartConfigFactory factory = new MultipartConfigFactory();        factory.setMaxFileSize("10240KB");//单个数据大小         factory.setMaxRequestSize("102400KB");//总上传数据大小        return factory.createMultipartConfig();    }

2.当上传文件为MultipartFile时，实现按行写，核心代码。

MultipartFile file = null;BufferedReader bufferedReader = new BufferedReader(new InputStreamReader(file.getInputStream()));        FileWriter fileWriter = new FileWriter((targetFile));        BufferedWriter writer = new BufferedWriter(fileWriter);        String str;        int total = 0;        HashSet
     
       set = new HashSet<>();        while ((str = bufferedReader.readLine()) != null) {            if (set.add(str)) {                writer.write(str);                writer.write(",");//                writer.newLine();            }            total++;        }        writer.flush();        writer.close();        bufferedReader.close();