Dropwizard update View from POST method

Question

I am trying to validate a form in my POST method which registers new users. In the case that errors arise such as a username that is already used, I want my View, which is retrieved from my GET method to be updated with the error. I am using Dropwizard Views and Freemarker. My code thus far:

 public class SignUpView extends View {

    List<String> errors;

    public SignUpView() {
        super("signup.ftl");
        errors = new ArrayList<>();

    }

    public SignUpView(List<String> errors) {
        super("signup.ftl");
        this.errors = errors;

    }

}

signup.ftl:

<#-- @ftlvariable name="" type="com.tm.resources.views.SignUpView" -->
<#include "include/head.html">
<#include "include/header.html">

<br><br><br>

<form action="/signup" method="post">
  <div class="container">
    <h1>Sign Up</h1>
    <p>Please fill in this form to create an account.</p>
    <hr>
    <#if errors?has_content>
        <ul class="errorMessages">
             <#list errors as error>
                 <li>${error}</li>
             </#list>
        </ul>
    </#if>    
    <label><b>Full name</b></label>
    <input type="text" placeholder="full name" name="full_name" required>

    <label><b>Email</b></label>
    <input type="email" placeholder="Enter Email" name="email" required>

    <label><b>Password</b></label>
    <input type="password" placeholder="Enter Password" name="psw" required>

    <label><b>Repeat Password</b></label>
    <input type="password" placeholder="Repeat Password" name="psw-repeat" required>

    <label>
      <input type="checkbox" checked="checked" style="margin-bottom:15px"> Remember me
    </label>

    <p>By creating an account you agree to our <a href="#" style="color:dodgerblue">Terms & Privacy</a>.</p>

    <div class="clearfix">
      <button type="button" class="cancelbtn btn-form">Cancel</button>
      <button type="submit" class="signupbtn btn-form">Sign Up</button>
    </div>
  </div>
</form>


<#include "include/footer.html">

And my resource class:

@Path("/signup")
@Produces(MediaType.TEXT_HTML)
public class SignUpResource {

    // UserService
    private UserService userService;

    public SignUpResource(UserService userService) {
        this.userService = userService;
    }

    @GET
    public SignUpView getView() {

            return new SignUpView();
    }

    @POST
    @Consumes(MediaType.APPLICATION_FORM_URLENCODED)
    @Timed
    @UnitOfWork
    public Response registerUserInfo(@FormParam("full_name") String name, 
            @FormParam("email") String email,
            @FormParam("psw") String pwd,
            @FormParam("psw-repeat") String pwdRepeat){

        String responseString = "Successfully added user details, name: "+
                name+" and pwd: "+pwd;

        try {
            userService.addUser(name,email, pwd);
        } catch (ShowAbleException e) {
            // if adding triggered an error it must be displayed on the page
            List<String> errors = new ArrayList<String>();
            errors.add(e.getMessage());

            // HOW to go back to GET method with errors?? Or just display them?
        }

        try {
            //return Response.created(new URI("/")).entity(response).build();
            return Response.seeOther(new URI("/")).build(); // redirect back to homepage...
        } catch (URISyntaxException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
            throw new RuntimeException(e.getMessage(), e);
        }
    } 
}

I have came across this page which gives some guidance, but I failed to replicate it as the source is not fully provided and it does not use Dropwizard's Views functionality. I also considered adding parameters to my GET method and redirect from the POST method, but this seems like overkill to me?

Any help will be appreciated.

Answer 1

I managed to solve this by coming across this thread which indicated that one can send a new View as a response. So if errors are encountered, a new View is created in a Response with the updated errors. Code below:

 try {
            userService.addUser(name,email, pwd);
        } catch (ShowAbleException e) {
            // if adding triggered an error it must be displayed on the page
            List<String> errors = new ArrayList<String>();
            errors.add(e.getMessage());

            return Response.ok(new SignUpView(errors)).build();
        }

        try {
            //return Response.created(new URI("/")).entity(response).build();
            return Response.seeOther(new URI("/")).build(); // redirect back to homepage...
        } catch (URISyntaxException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
            throw new RuntimeException(e.getMessage(), e);
        }

I also picked up that my SignUpView class requires a getErrors method for the errors list to be accessible to the Freemarker file. So I added:

public List<String> getErrors() {
    return errors;
}