Persist radio checked value in Thymeleaf Spring

Question

When searching, if we select a given field to search within and submit, our choice is forgotten. How could someone modify the view template to keep the previous search field selected when displaying results?

I have read many other SO questions and the thymeleaf documentation here but have not found a suitable answer yet.

One can hard code a string (like employer) with the following:

search.html snippet

<span th:each="column : ${columns}">
  <input
    type="radio"
    name="searchType"
    th:id="${column.key}"
    th:value="${column.key}"
    th:checked="${column.key == 'employer'}"/>

    <label th:for="${column.key}" th:text="${column.value}"></label>
 </span>

SearchController.html snippet

@RequestMapping(value = "")
public String search(Model model) {
    model.addAttribute("columns", columnChoices);
    return "search";
}

How can I persist the user selected radio value upon POST in Thymeleaf Spring? (and default to the first, value on the GET)

Answer 1

http://www.thymeleaf.org/doc/tutorials/3.0/thymeleafspring.html#creating-a-form

Command object.

public class Search {
    // default "employer"
    private String type = "employer";

    public String getType() {
        return type;
    }

    public void setType(String type) {
        this.type = type;
    }
}

Controller

@GetMapping
public String search(Model model) {
    model.addAttribute("columns", columnChoices);
    model.addAttribute("search", new Search());
    return "search";
}

@PostMapping
public String search(@ModelAttribute Search search) {
    // Search's attributes match form selections.
}

With search as your command object, a radio buttons should look like this:

<form th:object="${search}">
    <th:block th:each="column: ${columns}">
        <input type="radio" th:value="${column.key}" th:id="${column.key}" th:field="*{type}" />
        <label th:for="${column.key}" th:text="${column.value}" />
    </th:block>
</form>