JSF messages

Detail or Summary
showDetail="true" => "javax.faces.component.UIInput.REQUIRED_detail"
showSummary="true" => "javax.faces.component.UIInput.REQUIRED"
For example

<h:message for="lastName" errorClass="errorClass"
       showSummary="true" showDetail="false"/>

Default, showDetail="true", showSummary="false".

Look up Convention

<h:inputText ... required="true" ..."/>
javax.faces.component.UIInput.REQUIRED

This is message for converter.
javax.faces.converter.IntegerConverter.INTEGER

This is message for validator
javax.faces.validator.LengthValidator.MINIMUM

Message for custom converter

public class xxxConverter implements Converter {

public Object getAsObject(FacesContext facesContext, UIComponent component,
String value) {
  //validation
   if ( ... ) {
      throw new ConverterException(new FacesMessage(
FacesMessage.SEVERITY_ERROR, "summary message", "detail message"));
      }
   ...
   }
...

Message for custom validator

public class xxxValidator implements Validator {
public void validate(FacesContext context,
                     UIComponent component,
                     Object obj)
        throws ValidatorException {
    //validation
    if(...)
        throw new ValidatorException(new FacesMessage(
             FacesMessage.SEVERITY_ERROR,
             "summary message", "detail message"));
    }...
}
}