我创建了一个项目，您可以在其中添加带头像和不带头像的学生。 问题是，当我添加一个没有头像的学生时，仍然有一个标签。如何删除该标签。现在我将添加一个图像和几个类。我写的一切都正确，我不知道错误可能在哪里
@Controller
public class AvatarController {
@Value("${storage.location}")
private String storageLocation;
private StudentService studentService;
@Autowired
private ServletContext servletContext;
// Constructor based Dependency Injection
@Autowired
public AvatarController(StudentService studentService) {
this.studentService = studentService;
}
@GetMapping(value = "/avatar")
public void getAvatar(HttpServletResponse response, @Param("avatar") String avatar) {
if (avatar == null || avatar.isEmpty()) {
return;
}
response.setContentType(MediaType.IMAGE_JPEG_VALUE);
try (FileInputStream input = new FileInputStream(studentService.loadAvatarByFileName(avatar))){
IOUtils.copy(input, response.getOutputStream());
} catch (IOException e) {
e.printStackTrace();
}
}
@RequestMapping(value = "/image", method = RequestMethod.GET)
public void image(@RequestParam String url, HttpServletResponse response) throws IOException {
InputStream in = new FileInputStream(url);
response.setContentType(MediaType.IMAGE_JPEG_VALUE);
IOUtils.copy(in, response.getOutputStream());
}
}
学生服务实现
@Service
@Transactional
public class StudentServiceImpl implements StudentService {
@Value("${storage.location}")
private String storageLocation;
private StudentRepository repository;
public StudentServiceImpl() {
}
@Autowired
public StudentServiceImpl(StudentRepository repository) {
super();
this.repository = repository;
}
@Override
public List<Student> getAllStudents() {
List<Student> list = new ArrayList<Student>();
repository.findAll().forEach(e -> list.add(e));
return list;
}
@Override
public Student getStudentById(Long id) {
Student student = repository.findById(id).get();
return student;
}
@Override
public boolean saveStudent(Student student) {
try {
repository.save(student);
return true;
} catch (Exception ex) {
return false;
}
}
@Override
public boolean deleteStudentById(Long id) {
try {
repository.deleteById(id);
return true;
} catch (Exception ex) {
return false;
}
}
@Override
public File loadAvatarByFileName(String filename) {
return new File(storageLocation + "/" + filename);
}
@Override
public File saveAvatarImage(MultipartFile avatarImage) throws IOException {
File newFile = File.createTempFile(
avatarImage.getName(),
"." + avatarImage.getOriginalFilename().split("\\.")[1],
new File(storageLocation));
avatarImage.transferTo(newFile);
return newFile;
}
@Override
public Student updateStudent(String name, String surname, MultipartFile avatar, Student targetStudent)
throws IOException {
if (name != null && !name.equals(targetStudent.getName())) {
targetStudent.setName(name);
}
if (surname != null && !surname.equals(targetStudent.getSurname())) {
targetStudent.setSurname(surname);
}
File newAvatar;
if (!avatar.getOriginalFilename().isEmpty()) {
if (targetStudent.getAvatar() != null) {
Files.deleteIfExists(Paths.get(storageLocation + File.separator + targetStudent.getAvatar()));
}
newAvatar = saveAvatarImage(avatar);
assert newAvatar != null;
targetStudent.setAvatar(newAvatar.getName());
}
boolean isSaved = saveStudent(targetStudent);
if (!isSaved) {
throw new IOException();
}
return targetStudent;
}
}
学生 Controller
@Controller
public class StudentController {
@Autowired
private ServletContext servletContext;
// Constructor based Dependency Injection
private StudentService studentService;
public StudentController() {
}
@Autowired
public StudentController(StudentService studentService) {
this.studentService = studentService;
}
@RequestMapping(value = "/allStudents", method = {RequestMethod.GET, RequestMethod.POST})
public ModelAndView displayAllUser() {
System.out.println("User Page Requested : All Students");
ModelAndView mv = new ModelAndView();
List<Student> studentList = studentService.getAllStudents();
mv.addObject("studentList", studentList);
mv.setViewName("allStudents");
return mv;
}
@Secured("ROLE_ADMIN")
@RequestMapping(value = "/allStudentsAdmin", method = {RequestMethod.GET, RequestMethod.POST})
public ModelAndView displayAllUsers() {
System.out.println("User Page Requested : All Students");
ModelAndView mv = new ModelAndView();
List<Student> studentList = studentService.getAllStudents();
mv.addObject("studentList", studentList);
mv.setViewName("allStudentsUser");
return mv;
}
@Secured("ROLE_USER")
@RequestMapping(value = "/allStudentsUser", method = {RequestMethod.GET, RequestMethod.POST})
public ModelAndView displayAllUsers() {
System.out.println("User Page Requested : All Students");
ModelAndView mv = new ModelAndView();
List<Student> studentList = studentService.getAllStudents();
mv.addObject("studentList", studentList);
mv.setViewName("allStudentsUser");
return mv;
}
@RequestMapping(value = "/addStudent", method = RequestMethod.GET)
public ModelAndView displayNewUserForm() {
ModelAndView mv = new ModelAndView("addStudent");
mv.addObject("headerMessage", "Add Student Details");
mv.addObject("student", new Student());
return mv;
}
@PostMapping(value = "/addStudent")
public String saveNewStudent(@RequestParam("name") @NonNull String name,
@RequestParam("surname") @NonNull String surname,
@RequestParam("avatar") MultipartFile file)
throws IOException {
Student student = new Student();
student.setSurname(surname);
student.setName(name);
if (file != null && !file.isEmpty()) {
student.setAvatar(studentService.saveAvatarImage(file).getName());
}
studentService.saveStudent(student);
return "redirect:/allStudents";
}
@GetMapping(value = "/editStudent/{id}")
public ModelAndView displayEditUserForm(@PathVariable Long id) {
ModelAndView mv = new ModelAndView("editStudent");
Student student = studentService.getStudentById(id);
mv.addObject("headerMessage", "Редактирование студента");
mv.addObject("student", student);
return mv;
}
@PostMapping(value = "/editStudent")
public String saveEditedUser(
@RequestParam("id") Long id,
@RequestParam("name") String name,
@RequestParam("surname") String surname,
@RequestParam("avatar") MultipartFile file) {
try {
studentService.updateStudent(name, surname, file, studentService.getStudentById(id));
} catch (FileSystemException ex) {
ex.printStackTrace();
} catch (IOException e) {
return "redirect:/error";
}
return "redirect:/allStudents";
}
@GetMapping(value = "/deleteStudent/{id}")
public ModelAndView deleteUserById(@PathVariable Long id) {
studentService.deleteStudentById(id);
ModelAndView mv = new ModelAndView("redirect:/allStudents");
return mv;
}
}
AllStudent JSP
<%@ page language="java" contentType="text/html; charset=UTF-8" pageEncoding="UTF-8" isELIgnored="false"%>
<%@taglib prefix="c" uri="http://java.sun.com/jsp/jstl/core"%>
<%@ taglib prefix="sec" uri="http://www.springframework.org/security/tags"%>
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
<link rel="stylesheet" href="https://maxcdn.bootstrapcdn.com/bootstrap/3.4.0/css/bootstrap.min.css">
<script src="https://ajax.googleapis.com/ajax/libs/jquery/3.3.1/jquery.min.js"></script>
<script src="https://maxcdn.bootstrapcdn.com/bootstrap/3.4.0/js/bootstrap.min.js"></script>
<link href="../css/style.css" rel="stylesheet" type="text/css">
<style><%@include file="/css/style.css"%></style>
<title>Все студенты</title>
</head>
<body>
<br>
<br>
<br>
<br>
<div class="it">
<h3>Список всех студентов</h3>
${message}
<br>
<br>
<table class="table">
<thead>
<tr>
<th scope="col">#</th>
<th scope="col">Name</th>
<th scope="col">Surname</th>
<th scope="col">Avatar</th>
</tr>
</thead>
<tbody>
<c:forEach var="student" items="${studentList}">
<tr>
<th scope="row">1</th>
<td>${student.name}</td>
<td>${student.surname}</td>
<td><c:choose>
<c:when test="${student.avatar ne null}">
<td>
<img src="${pageContext.request.contextPath}/avatar?avatar=${student.avatar}"
style="max-height: 200px; max-width: 200px;" />
</td>
</c:when>
</c:choose></td>
<td>
<sec:authorize access="hasRole('ADMIN')">
<a href="${pageContext.request.contextPath}/editStudent/${student.id}">
<button type="button" class="btn btn-primary">Edit</button>
</a>
</sec:authorize>
</td>
<td>
<sec:authorize access="hasRole('ADMIN')">
<a href="${pageContext.request.contextPath}/deleteStudent/${student.id}">
<button type="button" class="btn btn-primary">Delete</button>
</a>
</sec:authorize>
</td>
</tr>
</c:forEach>
</tbody>
</table>
</div>
</body>
</html>
最佳答案
@user404 回答可以，但需要一些更改
<c:choose>
<c:when test="${student.avatar ne null}">
<td>
<img src="${pageContext.request.contextPath}/avatar?avatar=${student.avatar}"
style="max-height: 200px; max-width: 200px;" />
</td>
</c:when>
<c:otherwise>
<td></td>
</c:otherwise>
</c:choose>
despription : When avater is null or empty then add a empty cell on our html table other wise add image with full src path
关于spring - 添加没有头像的学生，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/56783424/