JSP taglib中uri和tagdir有什么区别

Question

I am cofused between tagdir and uri used in taglib directive. What is the real difference between using tagdir and uri ?

Examples :

<%@ taglib uri="http://java.sun.com/jsp/jstl/core" prefix="notMyTags" %>

<%@ taglib uri="/WEB-INF/struts-html.tld" prefix="otherTags" %>

<%@ taglib tagdir="/WEB-INF/tags" prefix="myTags" %>

to the best of my understanding:

1) I can access non-custom tags from the uri referencing them by the provided prefix (eg: if the uri defines the tag hello , in the page where taglib-uri is pasted, I can access it as <notMyTags:hello> or <otherTags:hello> ).

2) I can access custom tags defined within the path specified in tagdir referencing them by their .tag filenames because each custom tag corresponds to a .tag file (eg: if hello.tag is a file in the tagDir specified path, in the page where taglib is pasted, I can access it as <myTags:hello> )

Answer 1

The two directive are used for two different concepts of custom JSP tags.

1) You use uri to reference a tag library , which is usually delivered in a jar and/or defined in a .tld file. These can be written in Java (implementing one of the `javax.servlet.jsp.tagext.JspTag' subinterfaces) or as plain JSP tagfiles.

2) You use tagdir to reference JSP tagfiles within /WEB-INF/tags (or subdirectories thereof). Those can not be Java classes.

See the J2EE tutorial at Orcale's website for more information regarding JSP tagfiles: http://docs.oracle.com/javaee/1.4/tutorial/doc/JSPTags5.html