如何从前端服务器发送文件到后端服务器（上传），前端服务器正在接受客户端浏览器的post请求（表单数据->文件输入）？

Question

我试图构建一个前端和后端分离的系统，并通过基于用户令牌的授权rest调用进行交互。前端和后端应用程序都构建在SpringBoot上。Thymeleaf用作呈现html页面的模板引擎。

<form id="doctorDetailsId" enctype="multipart/form-data">
<input name="firstName" placeholder="first name"/>
Profile pic: <input name="photo" type="file"/>
<input name="username" placeholder="user name"/>
<input name="password" placeholder="password"/>
<button type="submit">Submit</button>
</form>

  $("#doctorDetailsId").ajaxForm({
    url: '/doctor/add',
    type: 'post',
    processData: false,
    success: function (data) {
        console.log("Added Doctor! data = " + JSON.stringify(data))
    }
})

@RequestMapping(value = URLConstants.DOCTOR + "/add", method = RequestMethod.POST)
@ResponseBody
public Map<String, Object> addDoctor(MultipartHttpServletRequest request, HttpServletResponse response) throws Exception {
    String token = (String) request.getSession().getAttribute("token");
    String role = (String)       request.getSession().getAttribute("userRole");
    if (token != null && !token.isEmpty()) {
        if (role.equals(UserRole.ADMIN.getDescription())) {
            String username = request.getParameter("username");
            String password = request.getParameter("password");
            String firstName = request.getParameter("firstName");
            MultipartFile multipartFile1 = request.getFile("photo");
//          Part file =   request.getPart("photo");
            DoctorCO doctorCO = new DoctorCO(firstName, multipartFile1);
            .
            .
            .
            String url = backendServerUrl + ":" + backendServerPort + BackApis.ADD_DOCTOR;
            //RequestResponseDTO requestResponseDTO = HttpUtils.postData(url,
                    token, RequestMethod.POST.toString(), doctorCO);
            RequestResponseDTO requestResponseDTO = HttpUtils.postDataWithoutJsonSerialising(url,
                    token, RequestMethod.POST.toString(), doctorCO);
            DoctorDto doctorDto = objectMapper.convertValue(requestResponseDTO.getData(), DoctorDto.class);
            .
            .
            return doctorDto;
        } else {
            return null;
        }
    }
    return null;
}

public String toJson(Object o) {
    ObjectMapper mapper = new ObjectMapper();
    mapper.setVisibility(PropertyAccessor.FIELD, JsonAutoDetect.Visibility.ANY);
    if (o == null) {
        return null;
    }
    try {
        return mapper.writeValueAsString(o);
    } catch (Exception e) {
        logger.error(JacksonUtils.class.getSimpleName(), e);
        throw new RuntimeException(e);
    }
}

public static byte[] serialize(Object obj) throws IOException {
    ByteArrayOutputStream out = new ByteArrayOutputStream();
    ObjectOutputStream os = new ObjectOutputStream(out);
    os.writeObject(obj);
    return out.toByteArray();
}

java.io.NotSerializableException: org.apache.catalina.core.ApplicationPart

当我尝试使用toJson方法时，另一个异常与stackOverflow错误（无限递归）有关

*** java.lang.instrument ASSERTION FAILED ***: "!errorOutstanding" with message transform method call failed at JPLISAgent.c line: 844
*** java.lang.instrument ASSERTION FAILED ***: "!errorOutstanding" with message transform method call failed at JPLISAgent.c line: 844
*** java.lang.instrument ASSERTION FAILED ***: "!errorOutstanding" with message transform method call failed at JPLISAgent.c line: 844
*** java.lang.instrument ASSERTION FAILED ***: "!errorOutstanding" with message transform method call failed at JPLISAgent.c line: 844
2016-12-21 20:23:11.493 ERROR 25797 --- [nio-8082-exec-1] com.src.main.utils.JacksonUtils          : JacksonUtils

com.fasterxml.jackson.databind.JsonMappingException: Infinite recursion (StackOverflowError) (through reference chain: java.io.FileOutputStream["fd"]->java.io.FileDescriptor["parent"]->java.io.FileOutputStream["fd"]->java.io.FileDescriptor["parent"]->java.io.FileOutputStream["fd"]->java.io.FileDescriptor["parent"]->java.io.FileOutputStream["fd"]->java.io.FileDescriptor["parent"]->java.io.FileOutputStream["fd"]->java.io.FileDescriptor["parent"]->java.io.FileOutputStream["fd"]->java.io.FileDescriptor["parent"]->java.io.FileOutputStream["fd"]->java.io.FileDescriptor["parent"]->java.io.FileOutputStream["fd"]->java.io.FileDescriptor["parent"]->java.io.FileOutputStream["fd"]->java.io.FileDescriptor["parent"]->java.io.FileOutputStream["fd"]->java.io.FileDescriptor["parent"]->java.io.FileOutputStream["fd"]->java.io.FileDescriptor["parent"]->java.io.FileOutputStream["fd"]->java.io.FileDescriptor["parent"]->java.io.FileOutputStream["fd"]->java.io.FileDescriptor["parent"]->java.io.FileOutputStream["fd"]->java.io.FileDescriptor["parent"]->java.io.FileOutputStream["fd"]->java.io.FileDescriptor["parent"]->java.io.FileOutputStream["fd"]->java.io.FileDescriptor["parent"]->java.io.FileOutputStream["fd"]->java.io.FileDescriptor["parent"]->java.io.FileOutputStream["fd"]->java.io.FileDescriptor["parent"]->java.io.FileOutputStream["fd"]->java.io.FileDescriptor["parent"]->java.io.FileOutputStream["fd"]->java.io.FileDescriptor["parent"]->java.io.FileOutputStream["fd"]->java.io.FileDescriptor["parent"]->java.io.FileOutputStream["fd"]->java.io.FileDescriptor["parent"]->java.io.FileOutputStream["fd"]->java.io.FileDescriptor["parent"]->java.io.FileOutputStream["fd"]->java.io.FileDescriptor["parent"]->java.io.FileOutputStream["fd"]->java.io.FileDescriptor["parent"]->java.io.FileOutputStream["fd"]->java.io.FileDescriptor["parent"]->java.io.FileOutputStream["fd"]->java.io.FileDescriptor["parent"]->java.io.FileOutputStream["fd"]->java.io.FileDescriptor["parent"]->java.io.FileOutputStream["fd"]->java.io.FileDescriptor["parent"]->java.io.FileOutputStream["fd"]->java.io.FileDescriptor["parent"]->java.io.FileOutputStream["fd"]->java.io.FileDescriptor["parent"]->java.io.FileOutputStream["fd"]->java.io.FileDescriptor["parent"]->java.io.FileOutputStream["fd"]->java.io.FileDescriptor["parent"]->java.io.FileOutputStream["fd"]->java.io.FileDescriptor["parent"]->java.io.FileOutputStream["fd"]->java.io.FileDescriptor["parent"]->java.io.FileOutputStream["fd"]->java.io.FileDescriptor["parent"]->java.io.FileOutputStream["fd"]->java.io.FileDescriptor["parent"]->java.io.FileOutputStream["fd"]->java.io.FileDescriptor["parent"]->java.io.FileOutputStream["fd"]->java.io.FileDescriptor["parent"]->java.io.FileOutputStream["fd"]->java.io.FileDescriptor["parent"]->java.io.FileOutputStream["fd"]->java.io.FileDescriptor["parent"]->java.io.FileOutputStream["fd"]->java.io.FileDescriptor["parent"]->java.io.FileOutputStream["fd"]->java.io.FileDescriptor["parent"]->java.io.FileOutputStream["fd"]->java.io.FileDescriptor["parent"]->java.io.FileOutputStream["fd"]->java.io.FileDescriptor["parent"]->java.io.FileOutputStream["fd"]->java.io.FileDescriptor["parent"]->java.io.FileOutputStream["fd"]->java.io.FileDescriptor["parent"]->java.io.FileOutputStream["fd"]->java.io.FileDescriptor["parent"]->java.io.FileOutputStream["fd"]->java.io.FileDescriptor["parent"]->java.io.FileOutputStream["fd"]->java.io.FileDescriptor["parent"]-.....>java.io.FileDescriptor["parent"]->java.io.FileOutputStream["fd"]->java.io.FileDescriptor["parent"]->java.io.FileOutputStream["fd"]->java.io.FileDescriptor["parent"]->java.io.FileOutputStream["fd"]->java.io.FileDescriptor["parent"]->java.io.FileOutputStream["fd"]->java.io.FileDescriptor["parent"]->java.io.FileOutputStream["fd"]->java.io.FileDescriptor["parent"]->java.io.FileOutputStream["fd"]->java.io.FileDescriptor["parent"]->java.io.FileOutputStream["fd"]->java.io.FileDescriptor["parent"]->java.io.FileOutputStream["fd"]->java.io.FileDescriptor["parent"]->java.io.FileOutputStream["fd"]->java.io.FileDescriptor["parent"]->java.io.FileOutputStream["fd"]->java.io.FileDescriptor["parent"])
at com.fasterxml.jackson.databind.ser.std.BeanSerializerBase.serializeFields(BeanSerializerBase.java:706) ~[jackson-databind-2.8.1.jar:2.8.1]
at com.fasterxml.jackson.databind.ser.BeanSerializer.serialize(BeanSerializer.java:155) ~[jackson-databind-2.8.1.jar:2.8.1]
at com.fasterxml.jackson.databind.ser.BeanPropertyWriter.serializeAsField(BeanPropertyWriter.java:693) ~[jackson-databind-2.8.1.jar:2.8.1]
at com.fasterxml.jackson.databind.ser.std.BeanSerializerBase.serializeFields(BeanSerializerBase.java:690) ~[jackson-databind-2.8.1.jar:2.8.1]
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我一直在寻找一个解决方案，以序列化文件从前端服务器到后端服务器相当长的时间。请让我知道这里出了什么问题，或者如果有人有更好的解决方案以这种方式上传文件，请让我知道。如果需要，我很乐意提供更多的细节。

Answer 1

我试图避免序列化Part或MultipartFile对象。我将MultipartFile对象转换为File对象。序列化没有出现任何类似的错误。

MultipartFile multipartFile1 = request.getFile("photo");
File imageFile = jacksonUtils.getFileOfMultipartFile(multipartFile1);

（以下片段取自此处）

public File getFileOfMultipartFile(MultipartFile multipartFile) throws IOException {
    File convFile = new File(multipartFile.getOriginalFilename());
    convFile.createNewFile();
    FileOutputStream fos = new FileOutputStream(convFile);
    fos.write(multipartFile.getBytes());
    fos.close();
    return convFile;
}