Use DatePicker in Wicket 1.3/1.4

In Wicket 1.3/1.4, DatePicker is replaced by an YUI implementation. Add wicket-datetime-1.4-m3.jar and you can find DatePicker class. However, if you just add wicket-datetime-1.4-m3.jar, you'll get tihs exception:

......
Root cause:

java.lang.ClassNotFoundException: org.joda.time.ReadWritableInstant
at org.apache.catalina.loader.WebappClassLoader.loadClass(WebappClassLoader.java:1363)
at org.apache.catalina.loader.WebappClassLoader.loadClass(WebappClassLoader.java:1209)
at java.lang.ClassLoader.loadClassInternal(ClassLoader.java:336)
......

In order to fix this, just add joda-time-1.4.jar in your classpath :)