Concatenate strings from an object in th:each with Thymeleaf

Question

I have a service rest (with javaEe, Spring and thymeleaf) who sends me an object book with this shape:

 public class BookDto   {
  @JsonProperty("id")
  private Long id;

  @JsonProperty("isbn")
  private String isbn;

  @JsonProperty("title")
  private String title;

  @JsonProperty("authors")
  @Valid
  private List<BooksAuthors> authors;
...

I need to extract the authors name from the list of BooksAuthors object which looks like that:

public class BooksAuthors   {
  @JsonProperty("firstName")
  private String firstName;

  @JsonProperty("lastName")
  private String lastName;
...

I would like to display in a table the informations about the authors, but i don't know how to do it with Thymeleaf. I think it will be a th:each to parse the authors, inside a th:each to parse the books, but i can't make it work. The result i would like would be

                <table class="table">
                    <thead>
                    <tr>
                        <th scope="col">Titre</th>
                        <th scope="col">Auteur</th>
                        <th scope="col">isbn</th>
                        <th scope="col">Exemplaires disponibles</th>
                    </tr>
                    </thead>
                    <tbody>
                    <tr th:each="book:${books}">
                        <td th:text="${book.getTitle()}"></td>
                        <td>Author1, Author2</td>
                        <td th:text="${book.getIsbn()}"></td>
                        <td>Pas implémenté</td>
                    </tr>
                    </tbody>
                </table>

I manage to have a result. I tried to create a var and concatenate it but i still have to remove the last ','. And more important, it looks very clumsy to me.

<td>
    <span th:each="author:${book.getAuthors()}"
          th:with="authorName=${author.getFirstName()} + ' ' + ${author.getLastName()} + ', '"
          th:text="${authorName}">
    </span>
</td>

I'm wondering if there is a nicer and simpler solution for that? Or should i do it in my business layer and not in thymeleaf? Thanks a lot !

Answer 1

I guess you can use iteration status object for this:

https://www.thymeleaf.org/doc/tutorials/2.1/usingthymeleaf.html#keeping-iteration-status

to make something like this:

<span th:each="author, iterStat:${book.getAuthors()}"
              th:with="authorName=${author.getFirstName()} + ' ' + ${author.getLastName() + ${iterStat.count != iterStat.size ? ',' : ''}}"
              th:text="${authorName}">
</span>