Put model values into translated texts

Use these models when a label, a link text or an attribute must show a translated text, possibly with values from your data in it. Both look up the text when the component renders, through the same search as <wicket:message>, so they follow a change of language. Where the texts live is covered in Translate component texts.

Show a translated text

ResourceModel returns the text for a key:

add(new Label("title", new ResourceModel("orders.title")));

Give a default for when no bundle has the key:

add(new Label("title", new ResourceModel("orders.title", "Your orders")));

The model uses the component it is assigned to for the lookup, so the bundles of that component and its parents are searched.

Insert properties of an object

StringResourceModel takes a model of an object as well. ${...} expressions in the text are property expressions on that object, as in a PropertyModel:

Order.java

public class Order implements Serializable {
    private String number;
    private LocalDate orderDate;
    private Status status;
    // getters and setters
}

OrderPanel.properties

order.summary=Order ${number} of ${orderDate}

OrderPanel.java

add(new Label("summary", new StringResourceModel("order.summary", this, orderModel)));

Values are converted to text with the converters of the component and its locale, so ${orderDate} shows as a date in the user’s format.

The second argument is the component whose bundles are searched. Pass null, or use the constructor without it, to use the component the model is assigned to.

Choose the key from the data

The key may contain property expressions too. This picks one text per status of the order:

add(new Label("status",
    new StringResourceModel("order.status.${status}", this, orderModel)));

order.status.ACCEPTED=Your payment for order ${number} was accepted.
order.status.SHIPPED=Order ${number} is on its way.
order.status.DELIVERED=Order ${number} was delivered.

Pass parameters with MessageFormat

setParameters passes values for {0}, {1} and so on, formatted by java.text.MessageFormat in the locale of the component. A parameter that is a model is replaced by its object each time the text is rendered. Here delayModel is an IModel<Integer> with the number of days:

add(new Label("delay", new StringResourceModel("order.delay", this)
    .setParameters(orderModel.map(Order::getNumber), delayModel)));

order.delay=Order {0} is delayed by {1,choice,1#one day|1<{1,number,integer} days}.

The choice format picks a text by number, which handles singular and plural. You do not need to double single quotes in these texts: Wicket escapes quotes outside {...} before it calls MessageFormat, so Don't worry stays as it is.

Property expressions and parameters can be combined. Wicket applies the parameters first, then the ${...} expressions on the model object.

Use a default text

setDefaultValue takes a string or a model, used when no bundle has the key:

new StringResourceModel("order.note", this, orderModel)
    .setDefaultValue("No note for order ${number}");

Use the text as an attribute

Both models fit everywhere a model of a string fits, such as an attribute:

link.add(AttributeModifier.replace("title", new ResourceModel("order.details.tooltip")));