Thymeleaf dropdown selection

Question

I am using Thymeleaf for one of my java projects. Now, what I am trying to achieve, is when i choose something else from the drop down, and not a default value which is "ALL", and then press submit button [POST], to get the details about the chosen item. I would like to keep that chose item displaying in the drop down, after the submission. And what it does now, it returns back to default value. If I add to the provided code below attribute selected, then it selects all items from the list, which is not acceptable as well, as it end up always displaying the last item of the list.

<div class="controls">
    <select class="form-control" name="example" id="example">
        <option value="0">ALL</option>
        <option th:each="user : ${allUsers}" th:value="${user.id}" th:text="${user.name}">
        </option>
    </select>
</div>

my controller to get the list, I kept it as simple as possible:

@ModelAttribute("allUsers")
public List<User> allUsers() {
    List<User> userList= repo.findAll();
    return userList;
}

also I would like to note, that my object is:

<form class="form-search" action="#" method="post"
      th:action="@{/combinedsearch}"
      th:object="${combinedreport}">

So the idea to use something like this doesn't work

<select th:field="*{user}">, as my object doesn't actually have User as a field.

Any ideas? Help?

Solution 1

Basically what I did is in a combinedReport controller, I have extracted that user_ID, which I receive after HTML form submission, then I used it to whatever I need to do in back end, and then I send that user_id back to front end, simply by adding it to a model as an attribute:

model.addAttribute("lastselected", userId);

Then I have created custom logic method in a User's object:

public boolean isSelected(Integer userId){
        if (userId != null) {
            return userId.equals(id);
        }
        return false;
    } 

and then I have modified my code in my thymeleaf template to:

<select class="form-control" name="example" id="example">
     <option value="0">ALL</option>
     <option th:each="user : ${allUsers}"
             th:value="${user.id}"
             th:selected="${user.isSelected(lastselected)}"
             th:text="${user.name}">
     </option>
</select>

and baaaam! it works like a charm !

Solution 2

There's no need to implement that method in the backend, just use the SPEL expression eq

<select class="form-control" name="example" id="example">
 <option value="0">ALL</option>
 <option th:each="user : ${allUsers}"
         th:value="${user.id}"
         th:selected="${lastselected eq user.id}"
         th:text="${user.name}">
 </option>

PS: when looping through an ENUM remember to call .name() so you will compare the string value.

Comments

[jacobcs]

I had a form with a select field too and thymeleaf changes the name attribute if I use the th:field which at my back end throws an error. So I used something similar to your solution as a work around, so that I have the desired name attribute than the one assigned by thymeleaf from the object name.