| Log4Web FAQ | ||||||||||||||||||||||||
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This section describes the frequently asked questions for the Log4Web components application.
1. Which web servers and application servers is Log4Web compatible with ? Any server that supports Java Servlet 2.3 and JSP 1.2 should be able to host the Log4Web application. Therefore, Tomcat version 3.x is not suitable, but Tomcat version 4.x should be. The application has been tested successfully on Tomcat version 4.01 and 4.04. However, problems have been found with Tomcat version 4.03 which prevent it from hosting Log4Web. The best advice is to download the evaluation version of Log4Web and test it in your target server. The following table summarises the compatibility of various Tomcat versions.
Servlet Container Compatible ? Tomcat 3.x No Tomcat 4.0.1 Yes Tomcat 4.0.3 No Tomcat 4.0.4-b1 Yes Tomcat 4.0.4-b2 Yes 2. Which web browsers is Log4Web compatible with ? Any web browser that supports cascading style sheets should be able to display the web pages generated by Log4Web correctly. The application has been tested on Netscape Navigator version 4.7 and 6.x. Any version 4.0 or later should be suitable. Likewise for Internet Explorer, versions later than 4.0 should be able to display the pages correctly, although most of the browser versions have slight differences in the way that they choose to display the pages. 3. Can I use Log4Web with my own logging package ? Yes, provided that the logging package can generate XML output files conforming to the same DTD (Document Type Definition) as used by the Log4J package. The DTD document can be found on the Log4J website. 4. Which versions of Log4J is Log4Web compatible with ? Log4Web remains compatible with newer versions of Log4J, provided that the Log4J development team do not alter the DTD that is used to set the output format of the XML messages file. Unfortunately, this format has been changed several times in the past, leading to compatibility issues between Log4Web and Log4J versions. It is to be hoped that the Log4J output is now stabilised. Log4Web provides a configuration switch to support the different Log4J versions. The following table summarises the Log4J versions that are supported by the various Log4Web versions.
Log4Web Version Compatible With Log4J Versions Default Log4J Compatibility 1.0 1.1 1.1 1.1 1.1 to 1.2.3 1.1 1.2 1.1 upwards 1.2.4 upwards 5. How can I use Log4Web with JDK 1.4 ? With the release of JDK 1.4, Sun has bundled in the XML parser and transformation classes with the JRE. However, from time to time, new versions of the XML parsers are released. It is a mistake to assume that all applications will use the same version of these parser classes. Log4Web uses a different version of the parser classes than the one included in the JDK 1.4 release. The Jar files containing the classes that Log4Web uses, are included as part of the Log4Web web application. However, these classes will never be loaded because the JVM has already loaded a set of default classes when the JVM is booted up. This will cause an exception to be thrown when the Log4Web application is used within a servlet container running with JDK 1.4. This has caused a number of bug reports to be filed against JDK 1.4, and it is to be hoped that JDK 1.4.1 will fix this problem. However, it is possible to workaround the problem by using the Endorsed Standards Override Mechanism. In short, this means that a directory $JRE_HOME/lib/endorsed must be created, where $JRE_HOME is the location of the JRE 1.4 installation. Then, the Jar files crimson.jar, xalan.jar, and jaxp.jar should be copied into this directory. These Jar files can be found in the Log4Web.war file. When this has been done, Log4Web should work fine using JDK 1.4. |