Simple way to use parameterised UI messages in Wicket?

Question

Wicket has a flexible internationalisation system that supports parameterising UI messages in many ways. There are examples e.g. in StringResourceModel javadocs, such as this:

WeatherStation ws = new WeatherStation();
add(new Label("weatherMessage", new StringResourceModel(
    "weather.${currentStatus}", this, new Model<String>(ws)));

But I want something really simple, and couldn't find a good example of that.

Consider this kind of UI message in a .properties file:

msg=Value is {0}

Specifically, I wouldn't want to create a model object (with getters for the values to be replaced; like WeatherStation in the above example) only for this purpose. That's just overkill if I already have the values in local variables, and there is otherwise no need for such object.

Here's a stupid "brute force" way to replace the {0} with the right value:

String value = ... // contains the dynamic value to use
add(new Label("message", getString("msg").replaceAll("\\{0\\}", value)));

Is there a clean, more Wicket-y way to do this (that isn't awfully much longer than the above)?

Answer 1

In case you have a Model in your Component which holds an object with values you want to access from your placeholders as substitutions, you can write:

new StringResourceModel("salutation.text", getModel());

Let's imagine getModel()'s return type is IModel<User> and User contains fields like firstName and lastName. In this case you can easily access firstName and lastName fields inside your property string:

salutation.text=Hej ${firstName} ${lastName}, have a nice day!

Further information you can find here: https://ci.apache.org/projects/wicket/apidocs/8.x/org/apache/wicket/model/StringResourceModel.html#StringResourceModel-java.lang.String-org.apache.wicket.model.IModel-

Answer 2

Take a look at Example 4 in the StringResourceModel javadoc - you can pass a null model and explicit parameters:

add(new Label("message",
         new StringResourceModel(
             "msg", this, null, value)));

msg=Value is {0}

Answer 3

I think the most consistent WICKETY way could be accomplished by improving Jonik's answer with MessageFormat:

.properties:

msg=Saving record {0} with value {1}

.java:

add(new Label("label", MessageFormat.format(getString("msg"),obj1,obj2)));
//or
info(MessageFormat.format(getString("msg"),obj1,obj2));

Why I like it:

• Clean, simple solution
• Uses plain Java and nothing else
• You can replace as many values as you want
• Work with labels, info(), validation, etc.
• It's not completely wickety but it is consistent with wicket so you may reuse these properties with StringResourceModel.

Notes:

if you want to use Models you simply need to create a simple model that override toString function of the model like this:

abstract class MyModel extends AbstractReadOnlyModel{
    @Override
    public String toString()
    {
        if(getObject()==null)return "";
        return getObject().toString();
    }
}

and pass it as MessageFormat argument.

I don't know why Wicket does not support Model in feedback message. but if it was supported there was no reason to use these solutions and you could use StringResourceModel everywhere.