无法将类型的值转换为所需类型的属性

我正在从jsp保存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个部分工作，而不在控制器的另一部分工作

这里是jsp代码，在两种情况下都是相同的： –

 Photo: 
  

以下是控制器按预期工作的部分： –

 @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 roles = new ArrayList(); 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(); } } 

以下是控制器无法正常工作的部分，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 

ControllerCode

 @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

您在标记中缺少enctype="multipart/form-data" 。

由于你的表单没有enctype="multipart/form-data" spring正在使用作为String并且当它无法将String转换为MultipartFile为了Student类中MultipartFile类型的studentPhoto而抛出错误。

这是完整的源代码 。