Taglibs : Java Glossary

*.tld files

Java Code to Implement a Custom Tag

You must write getters and setters for each parameter, and aSimpleTagSupport.doTag orTagSupport.doStartTag method to generate the HTML from the parameter values.

Navigating

Oddly, TagSupport has a completely different way of finding associated information. TagSupport has a protected field called pageContext. From there you can find the other control objects such as: JspWriter with getOut where you write the expanded HTML, Servlet with getPage, ServletRequest with getRequest, ServletResponse with getResponse, ServletConfig with getServletConfig and ServletContext with getServletContext.

Most of the navigation in convoluted, but straightforward. Getting the URL (Uniform Resource Locator) of the page you are generating is trickier:

Including

• <%@ include file="filename" %> : works at translation time. Included text may contain tags that are parsed at translate time.
• <jsp:include page="some.jsp" %> : works at request time (runtime). some.jsp may contain tags, which are parsed on first use of some.jsp.
• <c:import url="http://any.place.com/at/all" > : works at request time too, but takes URLs which is more flexible.
• Your code to implement tags has Java at its disposal to find and include text. However, unless you compose *.jsp files on the fly, you won’t be able to parse included tags at requst time.

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