How to proceed with complex object in POST request - spring

Question

Hello SO I had 2 entities
Main entity
#Entity
#Table(name = "Events")
public class Event {
//Some fields ...
#ManyToMany(cascade = CascadeType.ALL)
#JoinTable(name = "event_eventtypes" ,
joinColumns = #JoinColumn(name = "event_id"),
inverseJoinColumns = #JoinColumn(name = "event_type_id"))
private Set<EventType> eventTypes;
//Getters and setters...
Now I have a form that is created using spring form-taglib
<form:form modelAttribute="event" method="post" action="/event/registerEvent" commandName="event">
<form:label path="name">Event display name</form:label>
<form:input path="name" type="text" cssClass="form-control" placeholder="Display name"/>
<form:label path="description" >Description</form:label>
<form:textarea path="description" cssClass="form-control"/>
<form:label path="priv" cssClass="">Make private? <span style="font-family:'Open Sans', sans-serif; font-size:11px; color: dodgerblue;">(It will be seen by your friends and people who you send invitation.)</span></form:label>
<form:checkbox path="priv" cssClass="form-check-input"/>
<form:label path="age">Age limit</form:label>
<form:select path="age">
<form:options items="${age}"/>
</form:select>
<form:hidden path="lng" id="formLang" />
<form:hidden path="lat" id="formLat"/>
<%--Question appear here--%>
<form:select path="eventTypes" items="${eventTypes}" multiple="true"/>
<input type="submit" value="Submit">
Controller
#Controller
public class EventController {
private static final Logger logger = LoggerFactory.getLogger(EventController.class);
#Autowired
private EventService eventService;
#Autowired
private UserService userService;
#Autowired
private EventTypeService eventTypeService;
#RequestMapping(path = "/event/create", method = RequestMethod.GET)
public String init(ModelMap modelMap) {
List<String> tags = eventTypeService.listEventTypes().stream().map(EventType::getName).collect(Collectors.toList());
ArrayList<Integer> ageArr = new ArrayList();
ageArr.add(0);
ageArr.add(6);
ageArr.add(12);
ageArr.add(16);
ageArr.add(18);
modelMap.addAttribute("event", new Event());
modelMap.addAttribute("age", ageArr);
modelMap.addAttribute("eventTypes", tags);
return "/event/create";
}
#RequestMapping(path = "/event/registerEvent", method = RequestMethod.POST)
public String createEvent(#ModelAttribute("event") Event event, #ModelAttribute("eventTypes1") List<String> eventTypes){
event.setDate(new Date());
event.setUser(userService.getUserByUsername(
AuthenticationService.getLoggedInUser())
);
eventService.addEvent(event);
return "redirect:/";
}
When complete form with values, click submit, get error
400 The request sent by the client was syntactically incorrect.
It's because eventTypes property is of String type. How can I send that list as another parameter in controller or what should I do it?

Answer 1

Maybe you need a DTO to include event and eventType list both.

Answer 2

When I have done this I send a DTO with a list of IDs/Strings for event types to the form and then create a new event from the DTO.
For the select statements loop round each option returned in the DTO and use a service findById to retrieve each eventType and then add this to the event model.
for (String tag : eventDTO.getEventTags()) {
EventType eventTag = eventTypeService.findById(Long.valueOf(tag));
if (eventTag != null) {
event.getEventTypes().add(eventTag );
}
}

Answer 3

Found soulution.
Just implement jsp-based form as :
<form:form modelAttribute="event" method="post" action="/event/registerEvent" commandName="event">
...
<%--There I'm not using more jsp tabs.--%>
<select multiple name="et" id="tags">
<c:forEach items="${eventTypes}" var="e">
<option value=${e}>${e}</option>
</c:forEach>
</select>
<input type="submit" value="Submit">
</form:form>
In Controller I get parameters as request.getParameterValues("et")) - that return String[] from HttpServletRequest