一、网上的一般做法

网上搜出来的教程，基本都是只上传文件的，但对于如何把数据和文件一起上传，那能找到的资料就很少了，不过不管是单独传文件，还是文件带数据，原理都一样，都是模拟浏览器行为，构造请求头和请求参数上传，对于带文件的，需要指定contentType，然后通过流的方式进行上传。

这种方法，不是很方便，因为既要带文件，又要带数据，尤其如果数据是跟文件相关的时候，不好处理，Java中数据的接收方法如下:

c#中的发送数据如下：

1.完整的c#代码如下：

using System;
using System.Collections.Generic;
using System.Diagnostics;
using System.IO;
using System.Net;
using System.Text;
using NUnit.Framework;
using System.Drawing;
namespace TestProject1
{  /// <summary>
    /// 实现文件和参数一起提交
    /// </summary>
    public static class FormUpload
    {
        /// <summary>
        /// 字符编码格式
        /// </summary>
        private static readonly Encoding encoding = Encoding.UTF8;
        private const string DefaultUserAgent = "Mozilla/4.0 (compatible; MSIE 6.0; Windows NT 5.2; SV1; .NET CLR 1.1.4322; .NET CLR 2.0.50727)";

        public static String ImageFile2Base64(String imageFile)
        {
            
            Image image = Image.FromFile(imageFile);
            MemoryStream ms = new MemoryStream();
            image.Save(ms, image.RawFormat);
            byte[] byteArray = ms.ToArray();
            ms.Close();
            return Convert.ToBase64String(byteArray);
        }
        
        
        
        /// <summary>
        /// 上传图像和参数
        /// </summary>
        /// <param name="url">上传地址</param>
        /// <param name="image">图像byte数组</param>
        /// <param name="imageName">图像名称，带扩展名</param>
        /// <param name="data">参数</param>
        /// <returns>响应内容</returns>
        public static string UploadImageAndData(string url,byte[] image,string imageName,string data)
        {
            Dictionary<string, object> dic = new Dictionary<string, object>();
            //dic.Add("file", new FormUpload.FileParameter(image, imageName));
            dic.Add("file", new FormUpload.FileParameter(image, imageName));
            
            //可以封装跟文件相关的其他属性，这里是最舒服的
            dic.Add("info", data);
            dic.Add("文件相关的业务参数", "1");
            
            
            try
            {
                HttpWebResponse r = FormUpload.MultipartFormDataPost(url, DefaultUserAgent, dic);
                Stream instream = r.GetResponseStream();
                StreamReader sr = new StreamReader(instream, Encoding.UTF8);
                //返回结果网页(html)代码 
                string retValue = sr.ReadToEnd();
                r.Close();
                sr.Close();
                return retValue;
            }
            catch (Exception e)
            {
                Debug.WriteLine("文件传输异常： " + e.Message);
                throw e;
            }
        }

        public static HttpWebResponse MultipartFormDataPost(string postUrl, string userAgent, Dictionary<string, object> postParameters)
        {
            //分割标记
            string formDataBoundary = String.Format("----------{0:N}", Guid.NewGuid());
            //内容类型
            string contentType = "multipart/form-data; boundary=" + formDataBoundary;
            byte[] formData = GetMultipartFormData(postParameters, formDataBoundary);
            return PostForm(postUrl, userAgent, contentType, formData);
        }

        private static HttpWebResponse PostForm(string postUrl, string userAgent, string contentType, byte[] formData)
        {
            HttpWebRequest request = WebRequest.Create(postUrl) as HttpWebRequest;
            if (request == null)
            {
                throw new NullReferenceException("request is not a http request");
            }
            // Set up the request properties. 
            request.Method = "POST";
            request.ContentType = contentType;
            //request.ContentType = "application/json;charset=utf-8";
           // request.UserAgent = userAgent;
           // request.CookieContainer = new CookieContainer();
            request.ContentLength = formData.Length;
            //request.Timeout = 1000*60;
            //request.Headers.Add("Seq","1");
            //request.Headers.Add("Authorization", "d10CdKTSbGPqdhrk9HcPvAnknuDp7d2WnsFDrWFA");
            //request.Headers.Add("Cha-Code","1501042092");
            
            // You could add authentication here as well if needed: 
            // request.PreAuthenticate = true; 
            // request.AuthenticationLevel = System.Net.Security.AuthenticationLevel.MutualAuthRequested; 
            // request.Headers.Add("Authorization", "Basic " + Convert.ToBase64String(System.Text.Encoding.Default.GetBytes("username" + ":" + "password"))); 
            // Send the form data to the request. 
            using (Stream requestStream = request.GetRequestStream())
            {
                requestStream.Write(formData, 0, formData.Length);
                requestStream.Close();
            }
            return request.GetResponse() as HttpWebResponse;
        }

        private static byte[] GetMultipartFormData(Dictionary<string, object> postParameters, string boundary)
        {
            Stream formDataStream = new System.IO.MemoryStream();
            bool needsCLRF = false;
            foreach (var param in postParameters)
            {
                // Thanks to feedback from commenters, add a CRLF to allow multiple parameters to be added. 
                // Skip it on the first parameter, add it to subsequent parameters. 
                if (needsCLRF)
                {
                    formDataStream.Write(encoding.GetBytes("\r\n"), 0, encoding.GetByteCount("\r\n"));
                }
                needsCLRF = true;
                if (param.Value is FileParameter)
                {
                    FileParameter fileToUpload = (FileParameter)param.Value;
                    // Add just the first part of this param, since we will write the file data directly to the Stream 
                    string header = string.Format("--{0}\r\nContent-Disposition: form-data; name=\"{1}\"; filename=\"{2}\";\r\nContent-Type: {3}\r\n\r\n", boundary, param.Key, fileToUpload.FileName ?? param.Key, fileToUpload.ContentType ?? "application/octet-stream");
                    formDataStream.Write(encoding.GetBytes(header), 0, encoding.GetByteCount(header));
                    // Write the file data directly to the Stream, rather than serializing it to a string. 
                    formDataStream.Write(fileToUpload.File, 0, fileToUpload.File.Length);
                }
                else
                {
                    string postData = string.Format("--{0}\r\nContent-Disposition: form-data; name=\"{1}\"\r\n\r\n{2}", boundary, param.Key, param.Value);
                    formDataStream.Write(encoding.GetBytes(postData), 0, encoding.GetByteCount(postData));
                }
            }
            // Add the end of the request. Start with a newline 
            string footer = "\r\n--" + boundary + "--\r\n";
            formDataStream.Write(encoding.GetBytes(footer), 0, encoding.GetByteCount(footer));
            // Dump the Stream into a byte[] 
            formDataStream.Position = 0;
            byte[] formData = new byte[formDataStream.Length];
            formDataStream.Read(formData, 0, formData.Length); formDataStream.Close();
            return formData;
        }

        /// <summary>
        /// 文件参数对象
        /// </summary>
        public class FileParameter
        {
            /// <summary>
            /// 文件二进制数组
            /// </summary>
            public byte[] File { get; set; }
            /// <summary>
            /// 文件名称，带扩展名，例如：aaa.jpg
            /// </summary>
            public string FileName { get; set; }

            /// <summary>
            /// 内容类型，默认application/octet-stream
            /// </summary>
            public string ContentType { get; set; }
            public FileParameter(byte[] file)
                : this(file, null)
            {
            }
            public FileParameter(byte[] file, string filename)
                : this(file, filename, null)
            {
            }
            public FileParameter(byte[] file, string filename, string contenttype)
            {
                File = file;
                FileName = filename;
                ContentType = contenttype;
            }
        }
        
        
        class Programss
        {
            [Test]
            public void Test1()
            {
                
                
                string retValue = UploadFiles();
                Console.WriteLine(retValue);
                Console.Read();
        
            }

            static string UploadFiles()
            {
                string url= "http://ip:port/路径";
                //string url = "http:.......";
                string imageName = Guid.NewGuid().ToString("N") + ".jpg";
                byte[] image = File.ReadAllBytes("D:\\1.jpg");
                string data = "提交参数";
                return FormUpload.UploadImageAndData(url,image, imageName, data);
            }
        }
    }
}

2.Java端接收代码：

//接收实体类
@Data
public class ReportImgVO {

	/** 文件*/
	private MultipartFile file;

	/** 文件名称*/
	private String fileName;

	private String info;

	/** 业务字段*/
	private Integer sampleNo;
}

//mvc接收的方法
@RequestMapping("/file")
@ResponseBody
public Map<String,Object> file(ReportImgVO reportImgVO){
	Map<String, Object> map =new HashMap<>();		
	System.out.println(reportImgVO.getFile());		
	return map;
}

二、更优的选择

上面的方法完全可以实现我的需求，也已经做出来了，但存在的问题是c#端的代码比较复杂，因为文件需要通过流的方式进行上传，后面的一位大神朋友帅翔（坐标上海）的提示下，文件既然是上传后放到oss的，那为何不直接把文件在c#就转换成base64的字符串呢？这样就不需要处理流的问题了。上传就是一个普通的对象。

优化后的方法来了：

using System.Drawing;

//省略中间部分。。。

//文件转base64
public static String ImageFile2Base64(String imageFile)
{            
     Image image = Image.FromFile(imageFile);
     MemoryStream ms = new MemoryStream();
     image.Save(ms, image.RawFormat);
     byte[] byteArray = ms.ToArray();
     ms.Close();
     return "data:image/png;base64,"+Convert.ToBase64String(byteArray);
}

注意，转完还不行，需要给这个字符串加上一个头，标识这是一个图片，在这个字符串最前面加上

"data:image/png;base64,"，注意，直接拷贝我的代码，逗号不要丢了。

剩余的c#代码就简单了，把跟流相关的都去掉，就是个普通的数据上传，再不需要考虑文件的问题。

Java端的实体类变成：

@Data
public class ReportImgVO extends BaseEntity {

	/** 文件，变成了字符串*/
	private String file;
	
	/** 文件名称*/
	private String fileName;

	private String info;

	/** 样本号*/
	private Integer sampleNo;
}

这样就简单多了，其他没啥太多变化，c#我也不熟，只能看得懂，会改。