解决ajax发送Formdata数据包含文件和text数据，spring后台无法通过MultipartFile拿到文件

一开始直接使用ajax发送Formdata数据，spring后台multipartfile无法接受到文件。

经查阅很多资料，发现给我的页面加一个<form>表单，其他都不需要修改，后台即可拿到文件。

<!DOCTYPE html>
<html>

	<head>
		<meta charset="UTF-8">
		<title>加密与解密</title>
		<link rel="stylesheet" href="css/bootstrap.min.css" />
		<link rel="stylesheet" href="css/encrypt.css" />
		<script type="text/javascript" src="js/encrypt.js" ></script>
		<script type="text/javascript" src="js/jquery.min.js" ></script>
	</head>

	<body>
	    <form class="inpform" id="uploadForm" enctype="multipart/form-data">
		<div class="col-lg-6">
			<div class="input-group input-center">
				<input id="t1" type="text" class="form-control" placeholder="请选择需要加密的文件">
				<span class="input-group-btn">
					<input type="file" id="file" name="mpfile" onchange="getFilePath()" style="filter:alpha(opacity=0);opacity:0;width: 0;height: 0;"/>   
        			<button id="bj1" class="btn btn-default" type="button" onclick="selectFile();">请选择</button>
      			</span>
			</div>
			<div class="input-group input-center">
				<input id="t2" name="key" type="password" class="form-control" placeholder="请选输入密钥（或随机生成）">
				<span class="input-group-btn">
        			<button id="bj2" class="btn btn-default" type="button" onclick="KeyRandom()">随机生成</button>
      			</span>
			</div>
			<div class="radio"> 
                <label class="radio-inline">
                    <input type="radio" name="optionsRadiosinline" id="optionsRadios1" value="1" checked> 加密
                </label>
                <label class="radio-inline">
                        <input type="radio" name="optionsRadiosinline" id="optionsRadios2"  value="2"> 解密
                </label>
            </div>
            <div class="radio"> 
                <label class="radio-inline">
                    <input type="radio" name="optionsRadiosinline2" id="optionsRadios3" value="3" checked> ECB模式
                </label>
                <label class="radio-inline">
                        <input type="radio" name="optionsRadiosinline2" id="optionsRadios4"  value="4"> CBC模式
                </label>
            </div>
            <div class="radio"> 
                <label class="radio-inline">
                    <input type="radio" name="optionsRadiosinline3" id="optionsRadios5" value="5" checked> 操作后上传
                </label>
                <label class="radio-inline">
                    <input type="radio" name="optionsRadiosinline3" id="optionsRadios6"  value="6"> 操作后下载
                </label>
            </div>
			<div class="button">
                <button id="btn1" type="button" class="btn btn-primary" onclick="Save()">上传</button>
            </div>
            <div class="button">
                <span>请先上传文件再下载！</span>
            </div>
            <div class="button">
                <button id="btn2" type="button" class="btn btn-primary" onclick="DownLoad()">下载</button>
            </div>
		</div>
		  </form>
	</body>

</html>

spring后台：

package com.cczu.sm.controller;


import java.io.File;
import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.IOException;
import java.util.ArrayList;


import javax.servlet.ServletOutputStream;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;


import org.apache.commons.io.FileUtils;
import org.bouncycastle.util.encoders.Hex;
import org.springframework.http.HttpHeaders;
import org.springframework.http.HttpStatus;
import org.springframework.http.MediaType;
import org.springframework.http.ResponseEntity;
import org.springframework.stereotype.Controller;
import org.springframework.web.bind.annotation.RequestBody;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.ResponseBody;
import org.springframework.web.multipart.MultipartFile;


import com.cczu.sm.entity.SM3Digest;
import com.cczu.sm.entity.SM4;
import com.cczu.sm.entity.SM4Utils;
import com.cczu.sm.entity.SM4_Context;
import com.cczu.sm.entity.Util;


@Controller
public class SmController {
    @RequestMapping("/sm")
    @ResponseBody
    public void getFile(String optionsRadiosinline3,
            String optionsRadiosinline2, String optionsRadiosinline,
            String key, MultipartFile mpfile) throws Exception {
        String filename = mpfile.getOriginalFilename();
        String mykey = key;
        String myoption = optionsRadiosinline;
        System.out.println("密钥：" + mykey + "\n" + "文件名:" + filename + "\n"
                + "功能选择：" + myoption);


        byte[] input = mpfile.getBytes();


        //SM3杂凑密钥
        byte[] md = new byte[32];
        byte[] msg1 = mykey.getBytes();
        SM3Digest sm3 = new SM3Digest();
        sm3.update(msg1, 0, msg1.length);
        sm3.doFinal(md, 0);
        String s = new String(Hex.encode(md)).substring(0, 16).toUpperCase();
        //        System.out.println("杂凑密钥：" + s);


        //SM4加密
        //optionsRadiosinline等于1加密，等于2解密
        //optionsRadiosinline2等于3ECB模式，等于4CBC模式
        if (optionsRadiosinline.equals("1")) {
            //SM4设置加密密钥
            SM4 s4 = new SM4();
            SM4_Context ctx = new SM4_Context();
            ctx.isPadding = true;
            ctx.mode = SM4.SM4_ENCRYPT;
            byte[] keyBytes = s.getBytes();
            s4.sm4_setkey_enc(ctx, keyBytes);
            if (optionsRadiosinline2.equals("3")) {
                //ECB模式
                String path = "";
                //等于5上传保存服务器，等于6上传操作后下载
                if (optionsRadiosinline3.equals("5")) {
                    path = "F:\\MyEclipse 9Workspaces\\sm\\smfile\\";
                } else {
                    path = "F:\\MyEclipse 9Workspaces\\sm\\smfiledown\\";
                }
                File file = new File(path + filename + ".encecb");
                if (file.exists()) {
                    file.delete();
                    file.createNewFile();
                }
                FileOutputStream out = new FileOutputStream(file);
                out.write(s4.sm4_crypt_ecb(ctx, input), 0,
                    s4.sm4_crypt_ecb(ctx, input).length);
                out.close();
            } else {
                //CBC模式
                String path = "";
                if (optionsRadiosinline3.equals("5")) {
                    path = "F:\\MyEclipse 9Workspaces\\sm\\smfile\\";
                } else {
                    path = "F:\\MyEclipse 9Workspaces\\sm\\smfiledown\\";
                }
                File file = new File(path + filename + ".enccbc");
                FileOutputStream out = new FileOutputStream(file);
                out.write(s4.sm4_crypt_cbc(ctx, keyBytes, input), 0,
                    s4.sm4_crypt_cbc(ctx, keyBytes, input).length);
                out.close();
            }
        } else {
            //解密操作
            //SM4设置加密密钥
            SM4 s4 = new SM4();
            SM4_Context ctx = new SM4_Context();
            ctx.isPadding = true;
            ctx.mode = SM4.SM4_DECRYPT;
            byte[] keyBytes = s.getBytes();
            s4.sm4_setkey_dec(ctx, keyBytes);
            if (optionsRadiosinline2.equals("3")) {
                //ECB模式
                String path = "";
                //等于5上传保存服务器，等于6上传操作后下载
                if (optionsRadiosinline3.equals("5")) {
                    path = "F:\\MyEclipse 9Workspaces\\sm\\smfile\\";
                } else {
                    path = "F:\\MyEclipse 9Workspaces\\sm\\smfiledown\\";
                }
                File file = new File(path
                        + filename.substring(0, filename.lastIndexOf(".")));
                if (file.exists()) {
                    file.delete();
                    file.createNewFile();
                }
                FileOutputStream out = new FileOutputStream(file);
                out.write(s4.sm4_crypt_ecb(ctx, input), 0,
                    s4.sm4_crypt_ecb(ctx, input).length);
                out.close();
            } else {
                //CBC模式
                String path = "";
                if (optionsRadiosinline3.equals("5")) {
                    path = "F:\\MyEclipse 9Workspaces\\sm\\smfile\\";
                } else {
                    path = "F:\\MyEclipse 9Workspaces\\sm\\smfiledown\\";
                }
                File file = new File(path
                        + filename.substring(0, filename.lastIndexOf(".")));
                FileOutputStream out = new FileOutputStream(file);
                out.write(s4.sm4_crypt_cbc(ctx, keyBytes, input), 0,
                    s4.sm4_crypt_cbc(ctx, keyBytes, input).length);
                out.close();
            }
        }


    }


   

}