无法将类型 [java.lang.String] 的值转换为属性所需的类型 [org.springframework.web.multipart.MultipartFile]

Question

我正在保存来自 jsp 的图像文件并在控制器中重命名它

问题是同一段代码在控制器的一部分工作，而在控制器的另一部分不工作

这里是 jsp 两种情况下相同的代码：-

<div class="form-group ">
                                <label for="photo">Photo:</label>
                                <form:input type="file" class="filestyle" path="studentPhoto"
                                    id="studentPhoto" placeholder="Upload Photo"
                                    required="required" />
                            </div>

这是按预期工作的控制器部分：-

@RequestMapping(value = "/student", params = "add", method = RequestMethod.POST)
    public String postAddStudent(@ModelAttribute @Valid Student student,
            BindingResult result, Model model) throws IOException {

        if (result.hasErrors()) {
            System.out.println(result.getAllErrors().toString());

            model.addAttribute("examination_names", ExaminationName.values());

            ArrayList<Role> roles = new ArrayList<Role>();
            roles.add(Role.STUDENT);
            model.addAttribute("roles", roles);

            return "student/add";
        } else {

            System.out.println("Inside postAddStudent");
            System.out.println(student);
            student = studentService.save(student);

            String PROFILE_UPLOAD_LOCATION = servletContext.getRealPath("/")
                    + File.separator + "resources" + File.separator
                    + "student_images" + File.separator;

            BufferedImage photo = ImageIO.read(new ByteArrayInputStream(student
                    .getStudentPhoto().getBytes()));
            File destination = new File(PROFILE_UPLOAD_LOCATION
                    + student.getId() + "_photo" + ".jpg");
            ImageIO.write(photo, "jpg", destination);

            return "redirect:student?id=" + student.getId();

        }

    }

下面是控制器的一部分，它不工作并说错误：-

Failed to convert property value of type java.lang.String to required type org.springframework.web.multipart.MultipartFile for property studentPhoto; nested exception is java.lang.IllegalStateException: Cannot convert value of type [java.lang.String] to required type [org.springframework.web.multipart.MultipartFile] for property studentPhoto: no matching editors or conversion strategy found

控制器代码

@RequestMapping(value = "/examForm", params = "edit", method = RequestMethod.POST)
public String postEditExamForm(@ModelAttribute @Valid Student student,
        BindingResult result, Model model) throws IOException {

    String PROFILE_UPLOAD_LOCATION = servletContext.getRealPath("/")
            + File.separator + "resources" + File.separator
            + "student_images" + File.separator;

    if (result.hasErrors()) {
        model.addAttribute("flags", Flag.values());
        return "examForm/edit";

    } else {

        Student updatedStudent = studentService.findOne(student.getId());

        updatedStudent.setDisqualifiedDescription(student
                .getDisqualifiedDescription());
        student = studentService.update(updatedStudent);


        BufferedImage photo = ImageIO.read(new ByteArrayInputStream(student
                .getStudentPhoto().getBytes()));
        File destination = new File(PROFILE_UPLOAD_LOCATION
                + student.getId() + "_photo" + ".jpg");
        ImageIO.write(photo, "jpg", destination);


        return "redirect:examForm?id=" + updatedStudent.getId();

    }

}

Answer 1

您的 <form:form...> 标签中缺少 enctype="multipart/form-data"。

由于您的表单没有 enctype="multipart/form-data" spring 将 <form:input type="file".. 视为 String 并在无法将 String 转换为 [= 时抛出错误16=] for studentPhoto MultipartFile in Student class.

这是完整的 source code。

无法将类型 [java.lang.String] 的值转换为 属性 所需的类型 [org.springframework.web.multipart.MultipartFile]

Cannot convert value of type [java.lang.String] to required type [org.springframework.web.multipart.MultipartFile] for property

java

spring

jsp

file-handling

无法将类型 [java.lang.String] 的值转换为属性所需的类型 [org.springframework.web.multipart.MultipartFile]