CODEWITHSUNDEEP
javagwt
Michael
Michael

Reputation: 35341

GWT: Accessing i18n messages in server code

I have an interface that extends the com.google.gwt.i18n.client.Messages class, which I use for retrieving i18n messages in my GWT application. It looks like this:

public interface MyMessages extends com.google.gwt.i18n.client.Messages {
  @DefaultMessage("Hello world")
  @Key("message1")
  String message1();

  @DefaultMessage("Hello again")
  @Key("message2")
  String message2();

  //...
}

Normally, I create an instance of it using GWT.create() like so:

private MyMessages messages = GWT.create(MyMessages.class);

However, this does not work with server-side code, only client-side code (it throws an error saying that GWT.create() is only usable in client-side code).

The answer to a similar question points to a separate library that you can download which will let you access the i18n messages on the server, but I don't want to download any extra libraries (this seems like a simple problem, there must be a simple solution).

In summary: How can I access my i18n messages in server-side code? Thanks.

Upvotes: 7

Views: 5250

Answers (5)

carlossierra
carlossierra

Reputation: 4707

Following vanje's answer, and considering the encoding used for the properties files (which can be troublesome as ResourceBundle uses by default "ISO-8859-1", here is the solution I came up with:

import java.io.UnsupportedEncodingException;
import java.util.Locale;
import java.util.ResourceBundle;

public class MyResourceBundle {

    // feature variables
    private ResourceBundle bundle;
    private String fileEncoding;

    public MyResourceBundle(Locale locale, String fileEncoding){
        this.bundle = ResourceBundle.getBundle("com.app.Bundle", locale);
        this.fileEncoding = fileEncoding;
    }

    public MyResourceBundle(Locale locale){
        this(locale, "UTF-8");
    }

    public String getString(String key){
        String value = bundle.getString(key); 
        try {
            return new String(value.getBytes("ISO-8859-1"), fileEncoding);
        } catch (UnsupportedEncodingException e) {
            return value;
        }
    }
}

The way to use this would be very similar than the regular ResourceBundle usage:

private MyResourceBundle labels = new MyResourceBundle("es", "UTF-8");
String label = labels.getString(key)

Or you can use the alternate constructor which uses UTF-8 by default:

private MyResourceBundle labels = new MyResourceBundle("es");

Upvotes: 0

hjbolide
hjbolide

Reputation: 391

GWT.create() can only be used in client-side code.

The good thing to do is that you provide your own I18NProvider class/interface, from which then you can extend to server side I18N factory and client side I18N factory read the same resource bundle.

After that you can simply use it all over your system, unify your code. Hope that helps.

Upvotes: 0

beastieboy
beastieboy

Reputation: 91

There's a great library for GWT internationalization gwt-dmesg. It allows you to 'share' .properties files between clent and server. However, project looks to be abandoned by author and you must recompile it manually for use with GWT versio >= 2.1.0.

Upvotes: 1

Renato
Renato

Reputation: 13690

I agree with Michael.. I was having this problem of trying to "localize" messages generated on the server.... but I decided to instead just throw an Exception on the server (because it is an error message which should only happen exceptionally) which contains the message code, which the client code can then look up and show the correct localized message to the user.

Upvotes: 4

vanje
vanje

Reputation: 10383

On the server side you can use the standard Java localization tools like ResourceBundle. Look here for a tutorial how to use it.

// Create a ResourceBundle out of your property files
ResourceBundle labels =
  ResourceBundle.getBundle("LabelsBundle", currentLocale);

// Get localized value
String value = labels.getString(key);

The GWT specific way of creating an interface out of your property files and providing implementations via deferred binding can not be used on sever side Java.

If you are fearless and willing to spend the time, you can implement a code generation step to read your property files and generate implementation classes for your message interface. That's exactly what the Google GWT compiler does behind the scene.

Upvotes: 8

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