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About JSP tags

A JavaServer Page (JSP) tag is a Java class that encapsulates functionality, like conditional logic, or database access, that can be used from a JSP. The use of tags makes it easy to interface with business logic in a transparent way. It also keeps the JSPs manageable and easy to read. Instead of writing a lot of inline Java code, a simple call to a tag can be made. Only when the .jsp is run does the tag get substituted with the corresponding code, completely transparent to both the JSP developer and the users.

JSP 1.1 supports custom tag libraries.This means that you can write your own sets of tags and call them in your JSPs. To use these custom tag libraries, the corresponding Java classes need to be placed in a location where the JSP container can execute them and the Tag Library Descriptor (or .tld) file needs to be edited. The .tld file defines tag names, tag attributes and class file locations. Furthermore, a taglib directive needs to be issued in the JSP before calls to the custom tags are made.

Here is an example of the use of a custom JSP tag:

<%@ taglib uri="/WEB-INF/lib/reports_tld.jar" prefix="test" %>
<HTML>
<BODY>
	<P>Hello The time is
	<test:curTime/>
	</P>
</BODY>
</HTML>

In the preceding example, the first line of the JSP specifies the custom tag library definition file and defines a prefix that is to be used for the custom tags. This is also refered to as the taglib directive. In this case the prefix is test. Inside the HTML body, the custom tag test:curTime is then called. When the JSP is requested from the server, the JSP container will see that tags with prefix test are to be handled according to the specified .tld file. The Java class that corresponds with the function that is being called for will in this case generate the current time as output, which will in turn be added to the existing HTML and the combined result will be seen by the end user.

What is important is that the internal workings of the Java class that contains the custom tag's functionality is not all coded inside the JSP. Instead, they are simple tags that any Web developer can easily use.

About custom JSP tags in Oracle Reports

By default, the custom JSP tags defined by Oracle Reports use the rw prefix. You may, however, choose any prefix.

The <rw:report> and <rw:objects> tags, respectively, delimit and define the report block. Inside these tags, other custom tags define the content and the look and feel of the report data.

A comprehensive example of the use of most of the Oracle Reports custom JSP tags is shown in the <rw:report> tag description.

Usage notes

See also

Oracle Reports JSP tags

About JavaServer Pages and servlets