Parameterizing Error Messages

• The ActionError constructor in our example takes the property name global.error.login.requiredfield as its first parameter
• The value of this property is the string representing an HTML list item:

       <li>The {0} is required for login</li>   

• The list item takes an argument, specified by "{0}"
• The value of the argument is found in the second parameter to the ActionError constructor
• In our example, the value is the label of the field that the user failed to fill in
• If the user did not provide the user name, the string returned in the ActionError will be:

       <li>The User Name is required for login</li>