Binding a list of form backing beans to a list of form

问题

I have a list of time entry for which i want to create a modal for in my page. Each time entry will have it's own modal. Inside of these modal, i want to put a form. Each form must point to one of the time entry backing bean.

Here is the relevant part of the endpoint attach to this page

@GetMapping("/time/{year}/{month}/{dayOfTheMonth}")
  public String show(
    ModelMap model,
    @PathVariable Integer year,
    @PathVariable Integer month,
    @PathVariable Integer dayOfTheMonth
  ){
   ....
    var editEntryForms = entries
      .stream()
      .map(EditEntryForm::new)
      .collect(Collectors.toList());

    model.addAttribute("editEntryForms", editEntryForms);


    return "timesheet/show";
  }

My form backing object

@Data
class EditEntryForm {

  public EditEntryForm(TimeEntry timeEntry){
    id = timeEntry.getId();
    description = timeEntry.getDescription();
  }

  private Long id;
  private String description;
}

And the (relevant parts of the) template

<div class="ui modal"
     th:each="editEntryForm : ${editEntryForms}"
     th:id="${'edit-entry-modal-'+editEntryForm.id}">
  <div class="header">
    Edit time entry
  </div>
  <div class="content">
    <form class="ui form"
          th:object="${editEntryForm}"
          th:classappend="${#fields.hasErrors('*')} ? error"
          th:id="${'edit-entry-form'+ editEntryForm.id}"
          th:action="@{/time/{year}/{month}/{day}/{entryId}(year=${year}, month=${month}, day=${dayOfTheMonth}, entryId=${editEntryForm.id})}"
          method="POST">
...
    </form>
  </div>
  <div class="actions">
   <button class="ui approve primary button" form="add-entry-form">Update entry</button>
   <div class="ui cancel button">Cancel</div>
   <div class="ui right floated basic button">
     Delete
   </div>
 </div>

</div>

The form is visible in the resulting page, with the correct id (as requested by th:id="${'edit-entry-modal-'+editEntryForm.id}"), so i assume the that my binding is correct.

But the template evaluation can't be completed, I have the following error


org.thymeleaf.exceptions.TemplateInputException: An error happened during template parsing (template: "class path resource [templates/timesheet/show.html]")
        at 
...
    Caused by: java.lang.IllegalStateException: Neither BindingResult nor plain target object for bean name 'editEntryForm' available as request attribute
...
2020-05-15 09:19:47.449 ERROR 10251 --- [nio-9090-exec-2] o.a.c.c.C.[.[.[/].[dispatcherServlet]    : Servlet.service() for servlet [dispatcherServlet] in context with path [] threw exception [Request processing failed; nested exception is org.thymeleaf.exceptions.TemplateInputException: An error happened during template parsing (template: "class path resource [templates/timesheet/show.html]")] with root cause
...
java.lang.IllegalStateException: Neither BindingResult nor plain target object for bean name 'editEntryForm' available as request attribute
        at org.springframework.web.servlet.support.BindStatus.<init>(BindStatus.java:153) ~[spring-webmvc-5.2.6.RELEASE.jar:5.2.6.RELEASE]
        at

Do you see something I'm doing wrong, or maybe it's a limitation of Thymleaf that I'm not aware of.

回答1:

Try using a plain Java Array, for iterating through in Thymeleaf in your th:each. Maybe try something like a .toArray() on editEntryForms since that should be of type List<>. Then delete your th:object in form. Now you should be able to access the contents of all the items in the Array, like you normally would in Thymeleaf. Also throw a look at my updated Answer to my question https://stackoverflow.com/a/59703725/10112957

来源：https://stackoverflow.com/questions/61820680/binding-a-list-of-form-backing-beans-to-a-list-of-form

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java

Spring

spring-boot

spring-mvc

thymeleaf