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Servlet Filters

by Daniel H. Steinberg
ONJava Newsletter for 11/25/2003


ApacheCon was a lot of fun. The highlight for me was seeing the work of the Geronimo team. There has been plenty of news about them in blogs and articles, but the short story as reported by OpenEJB guy David Blevins: "First, the Apache Software Foundation will license the TCK from Sun to test and officially release Geronimo as a certified J2EE 1.4 application server. Secondly, the critical EJB 2.1 container functionality will be provided by OpenEJB."

Here on ONJava, Jayson Falkner writes about Two Servlet Filters Every Web Application Should Have. He reviews the mechanism of Servlet filters and then presents "A caching filter that optimizes the time it takes to send back a response from your web server, and a compression filter that optimizes the size of the content you send from your web server to a user via the Internet." The article lets you know both how you should apply these filters as well as when. When it comes to compression Jayson advises "For general use, only apply a compression filter to any resources in the web application that are text-producing, namely all JSP and HTML pages."

Also this week, Gunjan Doshi presents his Best Practices for Exception Handling. Exceptions seem to be on everyone's mind again with a great deal of disagreement on how or if they should be used. In recent Artima interviews, C# architect Anders Hejlsberg explains why he decided not to put checked exceptions in his language, while James Gosling explains that "In Java you can ignore exceptions, but you have to willfully do it. You can't accidentally say, 'I don't care.' You have to explicitly say, 'I don't care.'" Doshi begins with the question, "What action can the client code take when the exception occurs?" His rules of thumb are helpful in deciding when and how to throw and catch exceptions.

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This week's java.net pointer features Budi Kurniawan's first installment in his series on Easy Custom Tags with Tag Files. Budi explains some of the differences in JSP 2.0 in terms of how you deal with custom tag libraries. One enhancement simplifies the tag handler life cycle, with tag files making it easier to write tag extensions. The new tag files look a lot like JSP pages. Budi argues that this makes it easier for non-Java programmers to create these tag files. I worry that it is just a way of moving the problem for which tags were created in the first place out of JSP pages and into tag files. There is still code being embedded in these tag files.

Till next week,

Daniel H Steinberg, editor
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