Wsrtjtyk

I'm new with java controllers. I'm working on Play framework and I'm trying to return an ArrayList from the controller, and it gives errors.
What is the right way to do so? My code is right below.

Another question, I would like to write the simplest page with html and javascript angular functionality which call the Play framework controller. Is there a simple platform like Play framework but for the front side?

this method:

public Result getComments(int postId) {        

    ArrayList<Comment> comments = this.commentsDic.getComments(postId);        

    return ok(comments);

}

gives the following error:

no suitable method found for ok(java.util.ArrayList<models.Comment>)

method play.mvc.Results.ok(play.twirl.api.Content) is not applicable

  (argument mismatch; java.util.ArrayList<models.Comment> cannot be converted to play.twirl.api.Content)

method play.mvc.Results.ok(java.lang.String) is not applicable

  (argument mismatch; java.util.ArrayList<models.Comment> cannot be converted to java.lang.String)

method play.mvc.Results.ok(com.fasterxml.jackson.databind.JsonNode) is not applicable

  (argument mismatch; java.util.ArrayList<models.Comment> cannot be converted to com.fasterxml.jackson.databind.JsonNode)

method play.mvc.Results.ok(byte) is not applicable

  (argument mismatch; java.util.ArrayList<models.Comment> cannot be converted to byte)

method play.mvc.Results.ok(java.io.InputStream) is not applicable

  (argument mismatch; java.util.ArrayList<models.Comment> cannot be converted to java.io.InputStream)

method play.mvc.Results.ok(java.io.File) is not applicable

  (argument mismatch; java.util.ArrayList<models.Comment> cannot be converted to java.io.File)

and this way:

    public ArrayList<Comment> getComments(int postId) {        

    ArrayList<Comment> comments = this.commentsDic.getComments(postId);        

    return comments;

}

gives this error:

Cannot use a method returning java.util.ArrayList[models.Comment] as a Handler for requests

pointing to the routes file on the marked line:

# Routes

# This file defines all application routes (Higher priority routes first)

# ~~~~



# An example controller showing a sample home page

GET     /                           controllers.HomeController.index

# An example controller showing how to use dependency injection

GET     /count                      controllers.CountController.count

# An example controller showing how to write asynchronous code

GET     /message                    controllers.AsyncController.message



****************the error points on this line:************

GET     /comments                            

controllers.CommentsController.getComments(postId: Integer)



# Map static resources from the /public folder to the /assets URL path

GET     /assets/*file                       

controllers.Assets.versioned(path="/public", file: Asset)

The full controller code:

package controllers;



import play.mvc.Controller;

import play.mvc.Result;



import services.CommentsDictionary;

import java.util.ArrayList;

import models.Comment;



import javax.inject.Inject;

import javax.inject.Singleton;



import java.util.List;





@Singleton

public class CommentsController extends Controller {



private final CommentsDictionary commentsDic;



@Inject

public CommentsController() {

   this.commentsDic = new CommentsDictionary();

}





public List<Comment> getComments(int postId) {        

    List<Comment> comments = this.commentsDic.getComments(postId);        

    return comments;

}



}

Which content type of HTTP response do you want?

If you want Json simply return

ok(play.libs.Json.toJson(comments));

If you want show page render template like this:

ok(views.html.yourTemplate.render(comments));

Some tips for further reading:

https://www.playframework.com/documentation/2.6.x/JavaActions#Results
https://www.playframework.com/documentation/2.5.8/api/java/play/mvc/Results.html