JavaSercer Pages 16.10 Packaging and Installing a Tag
JavaSercer Pages 16.10 Packaging and Installing a Tag Library During development, you may want to let the tag library classes and the TLD file reside as-is in the filesystem, since it makes it easy to change the TLD and modify and recompile the classes. Just make sure the class files are stored in a directory that’s part of the classpath for the JSP container, such as the WEBINF/ classes directory for the web application. The TLD must also be in a directory where the JSP container can find it. The recommended location is the WEB-INF/tlds directory. To identify the library with the TLD stored in this location, use a taglib directive in the JSP pages like this: <%@ taglib uri="/WEB-INF/tlds/orataglib_1_0.tld" prefix="ora" %> Here the uri attribute refers directly to the TLD file’s location. When you’re done with the development, you may want to package all tag handler classes, TagExtraInfo classes, beans used by the tag handler classes, and the TLD in a JAR file. This makes it easier to install the library in an application. The TLD must be saved as /META-INF/taglib.tld within the JAR file. To create the JAR file, first arrange the files in a directory with a structure like this: META-INF/ taglib.tld com/ ora/ jsp/ tags/ generic/ EncodeHTMLTag.class … util/ StringFormat.class … The structure for the class files must match the package names for your classes. Here a few of the classes in the tag library for this java blog are shown as an example. With the file structure in place, use the jar command to create the JAR file: jar cvf orataglib_1_0.jar META-INF com This command creates a JAR file named orataglib_1_0.jar containing the files in the META-INF and com directories. Use any JAR filename that makes sense for your own tag library. Including the version number for the library is also a good idea, since it lets the users know which version of the library they are using. You can now use the packaged tag library in any application. Just copy the JAR file to the application’s WEBINF/ lib directory and use a taglib directive like this in the JSP pages: <%@ taglib uri="/WEB-INF/lib/orataglib_1_0.jar" prefix="ora" %> Note that the uri attribute now refers to the JAR file instead of the TLD file. A JSP 1.1 container is supposed to be able to find the TLD file in the JAR file, but this is a fairly recent clarification of the specification. If the JSP container you use doesn’t support this notation yet, you have to extract the TLD file from the JAR file, save it somewhere else, for instance in WEB-INF/tlds, and let the uri attribute refer to the TLD file instead. Instead of letting the taglib directive point directly to the TLD or JAR file, you can specify a symbolic name as the uri attribute value, and provide a mapping between this name and the real location in the WEBINF/ web.xml file for the application: <%@ taglib uri="/orataglib" prefix="ora" %> page 233
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