Categorization of messages

JSF provides for the following categories of messages, error, fatal, info, and warn.

Standardized error messages

The JSF API includes series of constants that define a set of default messages. Examples of such constants and messages are shown below.

javax.faces.component.UIInput.REQUIRED=Validation Error: Value is required.
javax.faces.component.UIInput.CONVERSION=Conversion error during model data update.
javax.faces.component.UISelectOne.INVALID=Validation Error: Value is not valid.
javax.faces.component.UISelectMany.INVALID=Validation Error: Value is not valid.

These messages could be overridden by defining them in resource bundle that is explicitly loaded on the page, rather that using the default.

It is the accumulated messages that are shown with the message components. Custom errors could be added in the backing bean using the following syntax.

FacesMessage message = new FacesMessage("Email address is required.");
facesContext.addMessage(clientId,message);

Field Errors

The field errors are handled as part of standardized error scheme. JSF would display errors for a component. The errors might appear a little unfriendly, like the following.

j_id23:j_id24:0:TxtEmail: Validation Error: Value is required

This is why it is important to attach a label component to input components involved in validations. This message could be made user friendly by attaching a label component to the input element. There are situation that this is not practical; examples are input elements in rows or grid data. The input components have ?label? attribute that could be used in such cases.

Whenever custom messages are specified, the following component attributes could be used to implement them.

• converterMessage
• validatorMessage
• requiredMessage

UIMessage and UIMessages JSF families

The messages for specific element could be displayed next to an input element. The annotation would simply denote the id of the element, as shown below.

	<tr>
		<th class="rightLabel">
			<label for="categoryName">Category Name</label>
					<font color="red">*</font></th>
		<td align="left">
			<input type="text" name="categoryName" value="">
		</td>
		<td><!-- aws:element type="messages" id="categoryName" -->
				Category Name is required.<!-- /aws:element --></td>
	</tr>
  

The messages elements represent messages for the page as well as for a single element. Whenever an id attribute is specified, the message that pertains to the identified element is specified to show.

The implementation code is shown below.

        <h:messages for="categoryName"/>
        

This messages element captures the various way platforms would provide text messages for display on the page view.

The representation in the content source is with annotations.

        <!-- aws:element type="messages" value="error" -->
        	<!-- mock presentation could be included here -->
        <!-- /aws:element -->
        

Within the annotations would be the mock representation of the messages. The value would be as recognized on the platform. For example, this could error, info, warning, debug, etc.

The position of the representation outside a form, would dictate that the message is for the page, whereas within a form, it is for the specific form.

The implementation on JSF platform is shown below.

<h:messages styleClass="error" />