Why does <h:inputText required="true"> allow blank spaces?

Solution 1:

That's normal and natural behaviour and not JSF specific. A blank space may be perfectly valid input. The required="true" only kicks in on empty inputs, not in filled inputs. In JSF you can however just create a Converter for String class to automatically trim the whitespace.

@FacesConverter(forClass=String.class)
public class StringTrimmer implements Converter {

    @Override
    public Object getAsObject(FacesContext context, UIComponent component, String value) {
        return value != null ? value.trim() : null;
    }

    @Override
    public String getAsString(FacesContext context, UIComponent component, Object value) {
        return (String) value;
    }

}

Put this class somewhere in your project. It'll be registered automatically thanks to @FacesConverter and invoked automatically for every String entry thanks to forClass=String.class.

No need to hack the JSF API/impl. This makes no sense.

Solution 2:

If you want to turn off the behavior that BalusC notes as one of the answers as standard JSF behavior, you can modify the web.xml and include the following.

<context-param>
   <param-name>javax.faces.INTERPRET_EMPTY_STRING_SUBMITTED_VALUES_AS_NULL</param-name>
   <param-value>true</param-value>
<context-param>

This will trigger the JSF framework to consider the values null which may be preferable, or an alternative to the answer from BalusC.