[英]Sping MVC, Thymeleaf, POST request, how to pass list of objects to controller
A "teacher" can have several assigned "subjects" to teach:一个“老师”可以有几个指定的“科目”来教:
public class Teacher {
private int id;
private String firstName;
private String lastName;
...
private List<Subject> subjects;
}
In HTML view user can select one ore more subjects for the teacher and send POST request:在 HTML 视图中,用户可以为教师选择一门或多门科目并发送 POST 请求:
<select class="form-control" id="subjects" name="subjects" size="5" multiple required>
<option th:each="subject: ${allSubjects}"
th:value="${subject.id}"
th:text="${subject.name}"
th:selected="${teacher.subjects.contains(subject)}">
</option>
</select>
Controller to process this request:处理此请求的控制器:
@PostMapping("/update")
public String update(@ModelAttribute("teacher") Teacher teacher) {
logger.debug("Received update data: {}", teacher);
teacherService.update(teacher);
return "redirect:/teachers";
}
Here is the POST request that is being passed:这是正在传递的 POST 请求:
I expect Spring to take subject.id`s and inject them into teacher as list of subjects.我希望 Spring 将 subject.id`s 作为主题列表注入到老师中。 But I get exception:但我得到了例外:
BindException
org.springframework.validation.BeanPropertyBindingResult:
1 errors Field error in object 'teacher' on field 'subjects': rejected value [2,4]; codes [typeMismatch.teacher.subjects,typeMismatch.subjects,typeMismatch.java.util.List,typeMismatch];
arguments [org.springframework.context.support.DefaultMessageSourceResolvable: codes [teacher.subjects,subjects];
arguments []; default message [subjects]]; default message [Failed to convert property value of type 'java.lang.String[]' to required type 'java.util.List' for property 'subjects'; nested exception is java.lang.IllegalStateException: Cannot convert value of type 'java.lang.String' to required type 'ua.com.foxminded.university.model.Subject' for property 'subjects[0]': no matching editors or conversion strategy found]
I carefully read first 50 google results for my question, code should work, but it doesn't.我仔细阅读了我的问题的前 50 个谷歌结果,代码应该可以工作,但它没有。 I must be missing something.我肯定错过了什么。
First of all wrong annotation - u dont use @ModelAttribute
inside of the post but rather @RequestBody
which is implicit in spring controllers for post.首先是错误的注释 - 你不要在帖子内部使用@ModelAttribute
,而是在帖子的弹簧控制器中隐含的@RequestBody
。
Other than that what you are sending is not a teacher entity but rather teacherDTO which wont have all the fields (collections) that teacher entity that you showed has.除此之外,您发送的不是老师实体,而是老师DTO,它不会包含您展示的老师实体所具有的所有字段(集合)。 That means you should be receiving a different class (TeacherDTO) and then convert it correctly to teacher entity which you then update in the database这意味着您应该接收不同的类(TeacherDTO),然后将其正确转换为教师实体,然后在数据库中更新
i suppose this is an update form, so it take an object teacher as an input.我想这是一个更新表格,所以它需要一个对象老师作为输入。 try this尝试这个
<form th:object="${teacher}" method="post">
<select class="form-control" th:field="*{subjects}" id="subjects" name="subjects" size="5" multiple required>
<option th:each="subject: ${allSubjects}"
th:value="${subject.id}"
th:text="${subject.name}"
th:selected="*{subjects.contains(subject)}">
</option>
</select>
</form>
Finally I found the solution while working on another part of my project.最后,我在处理项目的另一部分时找到了解决方案。 I tried to pass Lecture object to controller, Lecture contains List of student groups.我试图将 Lecture 对象传递给控制器,Lecture 包含学生组列表。 Each group has 2 fields: id and name.每个组有 2 个字段:id 和 name。 First we implement a formatter首先我们实现一个格式化程序
public class GroupFormatter implements Formatter<Group> {
@Override
public Group parse(String text, Locale locale) throws ParseException {
Group group=new Group();
if (text != null) {
String[] parts = text.split(",");
group.setId(Integer.parseInt(parts[0]));
if(parts.length>1) {
group.setName(parts[1]);
}
}
return group;
}
@Override
public String print(Group group, Locale locale) {
return group.toString();
}
}
Register formatter in MVCConfig在 MVCConfig 中注册格式化程序
@Override
public void addFormatters(FormatterRegistry registry) {
GroupFormatter groupFormatter=new GroupFormatter();
registry.addFormatter(groupFormatter);
}
And we get the correct format from POST request:我们从 POST 请求中得到正确的格式:
groups=[4:VM-08, 5:QWE-123]
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