Dynamic checkbox from list with Thymeleaf - checkbox

Question

I try to save the values from dynamically created checkboxes:
<div>
<ul>
<li th:each="item, stat : *{users}">
<input type="checkbox" th:field="*{users[__${stat.index}__]}" th:value="${item}" />
<label th:text="${item}"></label>
</li>
</ul>
</div>
The controller provides the String items as follwing:
public List<String> getUsers() {
return users;
}
And the setter for the Strings is:
public void setUsers(final String[] users) {
for (final String string : users) {
System.out.println(string);
}
}
The values are correct shown in the html page. But when i click save button, and the setter is called, the values are empty. What can i do, where is the problem?
Any help would appreciate.

Answer 1

Please check out section about handlin multi-value checkboxes in Tutorial: Thymeleaf + Spring.
You should provide some model attribute (of type List<String>) containing all users possible to select. Let's call it selectableUsers.
Then it can collaborate with your form-backing bean (that one containing users) in a following manner:
<div>
<ul>
<li th:each="item : ${selectableUsers}">
<input type="checkbox" th:field="*{users}" th:value="${item}" />
<label th:for="${#ids.prev('users')}" th:text="${item}"></label>
</li>
</ul>
</div>
Note I think that getter and setter for a field should handle the same type, but they don't (getter returns List<String> however setter consumes String[])

Answer 2

What you are trying to do looks logical, but it does not work that way.
If you did not get it resolved you can do this instead:
In relevant method of your controller you can add list of titles for your checkboxes:
List<String> allUsers = Arrays.asList("abc","xyz"); // OR generate list dynamically
model.addAttribute("selectableUsers", allUsers);
Or add it to ModelAndView if that is what you are using.
Change your html to what was suggested by #Jakub Ch.
Change your getter and setter methods as follows:
private String users;
...
public String getUsers() {
return this.users;
}
public void setUsers(String users) {
this.users = users;
}
Then 'users' field will contain comma separated String values or their id numbers ( depending on how you set it up) indicating selected checkboxes. Then you can convert String values to array using code like below or if id numbers are stored get String values from your ArrayList.
public List<String> getStrings() {
return Arrays.asList(strings.split(","));
}
Hope it helps.