dropdown lists with Thymeleaf and SpringBoot

Question

I have a Spring Boot 1.3 app that uses Thymeleaf on the HTML. I have page of users and when I edit them, I would like the user institution selected from a list. I have the window showing everything properly, but when I select the institution, the controller does not show the selected value.

Here is my HTML:

 <div class="form-group">
     <label class="col-md-3 control-label">Institution</label>
         <div class="col-md-5">
         <div th:if="${institutionList != null and not #lists.isEmpty(institutionList)}">
             <select>
                 <option th:each="dropDownItem : ${institutionList}"
                                 th:value="${dropDownItem.name}"
                                 th:text="${dropDownItem.name}" />
             </select>
        </div>
        <div th:if="${institutionList == null or lists.isEmpty(institutionList)}">
            <div>"No Institutions were found, please create some first"</div>
        </div>
    </div>
 </div>

And here is my controller

@Controller
@PreAuthorize("hasRole('Admin')")
@RequestMapping("/admin")
public class AdminController {
    @Transactional
    @PreAuthorize("hasRole('ADMIN')")
    @RequestMapping(value = "/addUser", method = RequestMethod.POST)
    public String checkPersonInfo(@ModelAttribute User user, Model model, Authentication authentication) {
        // user does not have the selected institution set
        customUserDetailsService.createNewUser(user);
        updateModelWithAllUsers(model);
        return "admin";
    }

    private void updateModelWithAllUsers(Model model) {
        model.addAttribute(USERLIST, customUserDetailsService.findAllUsers());
        model.addAttribute(INSTITUTION_LIST, institutionService.findAll());
        model.addAttribute("user", new User());
    }

...
}

Here is my User:

@Entity
@Table(name = "Users")
public class User implements UserDetails {
 @Id
    private String username;

    @Column(nullable = false)
    private String password;

    private boolean enabled;
    private boolean accountNonExpired;
    private boolean accountNonLocked;
    private boolean credentialsNonExpired;
    private String companyName;
    private String email;

    @ElementCollection(fetch=FetchType.EAGER)
    @CollectionTable(name="Authorities", joinColumns=@JoinColumn(name="username"))
    @Column(name="authority")
    private Set<String> roles = new HashSet<String>();

    @ManyToOne(fetch = FetchType.EAGER, cascade = CascadeType.ALL)
    @JoinColumn(name = "institutionId", nullable = false)
    private Institution institution;
... getters & setters
}

And my Institution:

@Entity
@Table(name = "Institution")
public class Institution {

    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private Long institutionId;
    private String name;

    @OneToMany(mappedBy = "institution", fetch = FetchType.EAGER)
    @Fetch(value = FetchMode.SUBSELECT)
    List<User> users = new ArrayList<User>();
    ... getters & setters
}

When the "/addUser" gets the User object from the UI, the institution is null.

EDIT I used Sergios suggestion to use select th:field="${user.institution}" as well as select th:field="*{institution}"

but that gives me an error:

org.springframework.validation.BeanPropertyBindingResult: 1 errors Field error in object 'user' on field 'institution': rejected value [com.security.Institution@3e3945d2]; codes [typeMismatch.user.institution,typeMismatch.institution,typeMismatch.com. .security.Institution,typeMismatch]; arguments [org.springframework.context.support.DefaultMessageSourceResolvable: codes [user.institution,institution]; arguments []; default message [institution]]; default message [Failed to convert property value of type 'java.lang.String' to required type 'com.security.Institution' for property 'institution'; nested exception is org.springframework.core.convert.ConversionFailedException: Failed to convert from type java.lang.String to type java.lang.Long for value 'com.security.Institution@3e3945d2'; nested exception is java.lang.NumberFormatException: For input string: "com. .security.Institution@3e3945d2"]

Not sure if I am reading this correctly, but does that mean Thymeleaf is trying to pass the Institution.name to the user.institution field?

Can anyone offer any advice on how to do this?

Answer 1

You have forgot indicate the field from where it has to take the selected value:

Example: I supousse the User class has an attribute for institution.

<div class="form-group">
 <label class="col-md-3 control-label">Institution</label>
     <div class="col-md-5">
     <div th:if="${institutionList != null and not #lists.isEmpty(institutionList)}">
         <select th:field="*{institution}">
             <option th:each="dropDownItem : ${institutionList}"
                             th:value="${dropDownItem.name}"
                             th:text="${dropDownItem.name}" />
         </select>
    </div>
    <div th:if="${institutionList == null or lists.isEmpty(institutionList)}">
        <div>"No Institutions were found, please create some first"</div>
    </div>
</div>

More info: http://www.thymeleaf.org/doc/tutorials/2.1/thymeleafspring.html#dropdownlist-selectors

EDIT: You need to indicate to your app how convert a Id of Insitution returned inside form (String type) to a Institution entity. For that you have to use a Converter.

First change the value of option to institutionId:

<div class="form-group">
 <label class="col-md-3 control-label">Institution</label>
     <div class="col-md-5">
     <div th:if="${institutionList != null and not #lists.isEmpty(institutionList)}">
         <select th:field="*{institution}">
             <option th:each="dropDownItem : ${institutionList}"
                             th:value="${dropDownItem.institutionId}"
                             th:text="${dropDownItem.name}" />
         </select>
    </div>
    <div th:if="${institutionList == null or lists.isEmpty(institutionList)}">
        <div>"No Institutions were found, please create some first"</div>
    </div>
</div>

You have to create a class that implements the Converter interface.

@Component
public class StringToInstitution implements Converter<String, Institution> {

@Autowired
private InstitutionRepository repository; //Or the class that implments the repository.

    @Override
    public Institution convert(String arg0) {
        Long id = new Long(arg0);
        return repository.findOne(id);
    }

}