diff --git a/zul/src/org/zkoss/zul/Textbox.java b/zul/src/org/zkoss/zul/Textbox.java
index ab5ebb4..1570d92 100644
--- a/zul/src/org/zkoss/zul/Textbox.java
+++ b/zul/src/org/zkoss/zul/Textbox.java
@@ -29,6 +29,12 @@
  * @author tomyeh
  */
 public class Textbox extends InputElement {
+	public static final String TEXT = "text";
+	public static final String PASSWORD = "password";
+	public static final String TEL = "tel";
+	public static final String EMAIL = "email";
+	public static final String URL = "url";
+	
 	private AuxInfo _auxinf;
 
 	public Textbox() {
@@ -80,11 +86,15 @@
 	/** Sets the type.
 	 * @param type the type. Acceptable values are "text" and "password".
 	 * Unlike XUL, "timed" is redundant because it is enabled as long as
-	 * onChanging is added. Since 6.5.0 type also support tel, email and url.
+	 * onChanging is added. Since 6.5.0 type also support "tel", "email" and "url".
+	 * <p>
+	 * If you set the type from a richlet, you can use {@link Textbox#TEXT},
+	 * {@link Textbox#PASSWORD}, {@link Textbox#TEL}, {@link Textbox#EMAIL}
+	 * or {@link Textbox#URL} constants instead of hard-coded strings.
 	 */
 	public void setType(String type) throws WrongValueException {
-		if (!TEXT.equals(type) && !"password".equals(type) &&
-				!"tel".equals(type) && !"email".equals(type) && !"url".equals(type))
+		if (!TEXT.equals(type) && !PASSWORD.equals(type) &&
+				!TEL.equals(type) && !EMAIL.equals(type) && !URL.equals(type))
 			throw new WrongValueException("Illegal type: "+type);
 
 		if (!type.equals(_auxinf != null ? _auxinf.type: TEXT)) {
@@ -173,7 +183,6 @@
 		return _zclass != null ? _zclass: "z-textbox";
 	}
 
-	private static final String TEXT = "text";
 	private AuxInfo initAuxInfo() {
 		if (_auxinf == null)
 			_auxinf = new AuxInfo();