Step 8: Translatable Texts

In this step we move the texts of our UI to a separate resource file.

This way, they are all in a central place and can be easily translated into other languages. This process of internationalization – in short i18n – is achieved in OpenUI5 by using a special resource model and the standard data binding syntax, but without a preceding "/" character.

Preview

^{An input field and a description displaying the value of the input field (No visual changes to last step)}

You can access the live preview by clicking on this link: 🔗 Live Preview of Step 8.

To download the solution for this step as a zip file, just choose the link here: 📥 Download Solution for Step 8.

Coding

webapp/i18n/i18n.properties (New)

The i18n file allows you to store translated texts for multiple languages, making your application accessible to a wider audience. In oder to achive this, the properties file for texts contains name-value pairs for each element. You can add any number of placeholders to the texts by enclosing them in curly brackets with corresponding numbers. These numbers indicate the sequence in which the placeholders are accessed (starting with 0).

To set up the i18n file, we navigate to the webapp folder and create a new folder named i18n. Inside this folder, we place the i18n.properties file, which serves as a storage for our translated texts. We add two name-value pairs to our properties file: The showHelloButtonText name represents the text for the button on our App view. The helloMsg name represents the greeting message we will display in the message toast. To include the appropriate recipient's name in the message, we use a placeholder with the greeting message text.

showHelloButtonText=Say Hello
helloMsg=Hello {0}

In this tutorial we'll only have one properties file. However, in real-world projects, you would have a separate file for each supported language with a suffix for the locale, for examplei18n_de.properties for German, i18n_en.properties for English, and so on. When a user runs the app, OpenUI5 will load the language file that fits best to the user's environment.

webapp/controller/App.controller.ts

In the controller, we'll create a new resource model that refers to our resource bundle file (i18n.properties) and link it to the view associated with the controller. This allows us to bind control properties in the view to translatable texts. We'll also modify the onShowHello event handler function to replace the static "Hello World" text with a dynamic greeting text.

To connect our resource bundle to our view, we instantiate a ResourceModel in the onInit function of our controller. We specify the bundleName parameter to point to our resource bundle file. Then, we use the setModel function of the view to set this resource model as a named model with the key i18n.

In the onShowHello event handler function, we first get access to the data model associated with the view. We use the getProperty method with the data path to the recipient's name as an argument to retrive the corresponding value. Next, we get the resource bundle from the resource model named i18n which we just linked to the view. We do this by using the getResourceBundle method provided by the ResourceModel module. The resource bundle has a specific getText method, which returns a locale-specific string value for a given text key. It can also accept an array of strings as a second argument. When this argument is provided, the getText method uses the sap/base/strings/formatMessage API to replace placeholders in the text with the corresponding values from the arguments array. In our case, we use the second parameter of getText to replace the helloMsg text's placeholder with the recipient's name. The resulting string is then returned by getText and passed to the show method of the message toast control.

import MessageToast from "sap/m/MessageToast";
import Controller from "sap/ui/core/mvc/Controller";
import JSONModel from "sap/ui/model/json/JSONModel";
import ResourceModel from "sap/ui/model/resource/ResourceModel";
import ResourceBundle from "sap/base/i18n/ResourceBundle";

/**
 * @name ui5.walkthrough.controller.App
 */
export default class AppController extends Controller {
   onInit(): void {
      // set data model on view
      const data = {
         recipient: {
            name: "World"
         }
      };
      const dataModel = new JSONModel(data);
      // because of "strict" mode in tsconfig.json a null check is required for this.getView()
      this.getView()?.setModel(dataModel);

      // set i18n model on view
      const i18nModel = new ResourceModel({
         bundleName: "ui5.walkthrough.i18n.i18n"
      });
      this.getView()?.setModel(i18nModel, "i18n");
   }

   onShowHello(): void {
      // read msg from i18n model
      const recipient = (this.getView()?.getModel() as JSONModel)?.getProperty("/recipient/name");
      const resourceBundle = (this.getView()?.getModel("i18n") as ResourceModel)?.getResourceBundle() as ResourceBundle;
      const msg = resourceBundle.getText("helloMsg", [recipient]);
      // show message
      MessageToast.show(msg);
   }
};

The bundle name (ui5.walkthrough.i18n.i18n) consists of the application namespace ui5.walkthrough (the application root as defined in the index.html), the folder name i18n, and finally the base file name i18n without extension. The OpenUI5 runtime calculates the correct path to the resource, to which .properties is then appended.

During runtime, OpenUI5 tries to load the correcti18n_*.properties file based on your browser settings and your locale. In our case we have only created the base i18n.properties file to make it simple. However, you can see in the network traffic of your browser’s developer tools that OpenUI5 tries to load one or more i18n_*.properties files before falling back to the default i18n.properties file.

webapp/view/App.view.xml

We now bind the text properties in our XML view to the texts in our resource bundle. We connect text property of the button control to the showHelloButtonText key in the i18n model.

To correctly reference the model, the binding path should start with the model name i18n, followed by a '>'.

A resource bundle is a flat structure, therefore the preceding slash (/) can be omitted for the path to the text.

<mvc:View controllerName="ui5.walkthrough.controller.App"
   xmlns="sap.m"
   xmlns:mvc="sap.ui.core.mvc">
   <Button
      text="{i18n>showHelloButtonText}"
      press=".onShowHello"/>
   <Input
      value="{/recipient/name}"
      description="Hello {/recipient/name}"
      valueLiveUpdate="true"
      width="60%"/>      
</mvc:View>

📝 Note:
The description text is not completely localized in this example for illustration purposes. To be on the safe side, we would have to use a similar mechanism as in the controller to use a string from the resource bundle and replace parts of it. This can be done with the sap/base/strings/formatMessage formatter.

Furthermore, i18n files only impact client-side application texts. Texts that are loaded from back-end systems can appear in all languages that are supported by the back-end system.