Java SpringBoot Postgres remove rows

Help me please to remove the row in Postgres by clicking the Del button.
Maybe to link id in DB and id on the HTML page, but how?
Maybe I need to parse the HTML page and pass String id?
Any ideas will help me.

here is my database schema:

<table class="tmc">
<thead>
<tr>
    <th>ID</th><th>TMC</th><th>SN</th><th>Owner</th>
</tr>
</thead>
<tbody>
{{#messages}}
<tr>
    <td>{{id}}</td>
    <td><span>{{text}}</span></td>
    <td><i>{{sn}}</i></td>
    <td><i>{{owner}}</i></td>
    <th><form action="/remove" method="post">
        <input type="submit" value="Del"/>
        <input type="hidden" name="_csrf" value="{{_csrf.token}}" />
    </form>
    </th>
</tr>
{{/messages}}
</tbody>

</table>

@Entity
@Table(name = "message")
public class Message {
@Id
@GeneratedValue(strategy=GenerationType.AUTO)
private Integer id;
private String text;
private String sn;
private String owner;

public Message() {
}

public Message(String text, String sn, String owner) {
    this.text = text;
    this.sn = sn;
    this.owner = owner;
}

Rows are forming in database by:

@PostMapping("/main")
public String add (
        @RequestParam String owner,
        @RequestParam String text,
        @RequestParam String sn, Map<String, Object> model) {
    Message message = new Message (text, sn, owner);
    if (text != null && !text.isEmpty() & sn != null && !sn.isEmpty() & owner != null && 
!owner.isEmpty()) {
        if (!text.matches("^[0-9].*$")) {
            messageRepo2.save(message);
            Iterable<Message> messages = messageRepo2.findAll();
            model.put("messages", messages);
        } else
            model.put("error", "ТМЦ не должно начинаться с цифры");
        Iterable<Message> messages = messageRepo2.findAll();
        model.put("messages", messages);
    } else {
        model.put("error", "Заполните все поля!");
        Iterable<Message> messages = messageRepo2.findAll();
        model.put("messages", messages);
    }
    return "main";
}

There are two issues with your html code:

1. it would be to let the form element outside the table
2. need to use <input type="hidden" name="xxx" value="{{xxx}}" /> in order to let it can pass parameter to your controller method

<form action="/remove" method="post">
	<input type="hidden" name="_csrf" value="{{_csrf.token}}" />
	<table class="tmc">
	<thead>
	<tr>
		<th>ID</th><th>TMC</th><th>SN</th><th>Owner</th>
	</tr>
	</thead>
	<tbody>
	{{#messages}}
	<tr>
		<td>{{id}} <input type="hidden" name="id" value="{{id}}" /></td>
		<td><span>{{text}}</span></td>
		<td><i>{{sn}}</i> 	<input type="hidden" name="sn" value="{{sn}}" /></td>
		<td><i>{{owner}}</i> <input type="hidden" name="owner" value="{{owner}}" /></td>
		<td><input type="submit" value="Del"/></td>
		</th>
	</tr>
	{{/messages}}
	</tbody>
	</table>
</form>

<thead>
<tr>
    <th>ID ТМЦ</th><th>Наименование ТМЦ</th><th>Серийный номер ТМЦ</th><th>За кем числится</th>
</tr>
</thead>
<tbody>
{{#messages}}
<tr>
    <td>{{id}}</td>
    <td><span>{{text}}</span></td>
    <td><i>{{sn}}</i></td>
    <td><i>{{owner}}</i></td>
    <td>
    <form action="/remove" method="post" name="remove">
        <input type="submit" value="Удалить"/>
        <input type="hidden" name="_csrf" value="{{_csrf.token}}" />
        <input type="hidden" name="sn" value="{{sn}}"/>
    </form>
    </td>
</tr>
{{/messages}}
</tbody>

</table>

import com.example.webapp.domain.Message;
import org.springframework.data.repository.CrudRepository;
import org.springframework.transaction.annotation.Transactional;
import java.util.List;
@Transactional
   public interface MessageDel extends CrudRepository<Message, Long>{
   List<Message> deleteBySn (String sn);
}

@PostMapping("/remove")
public String remove (@RequestParam String sn, Map<String, Object> model) {
    Message messagedel = new Message (sn);
    messageDel.deleteBySn(sn);
    model.put("messages", messagedel);
    return "redirect:/main";
}