Apache Tomcat

When updating from one Apache Tomcat branch to a newer one, please make sure the JVM that is installed on your system supports at least the required Java version. It is also possible that older versions of Tomcat may not be compatible with newer JVMs.

The Apache Tomcat configuration sometimes needs to be adjusted when upgrading, and the lists below compile all changes which may cause backwards compatibility problems.

Java 5 required

Apache Tomcat 6.0.x requires Java 5, unlike Apache Tomcat 5.5.x which could use a compatibility package to run on JRE 1.4.

Modified directory structure

Apache Tomcat 5.5.x used, by default, a directory structure including common, shared and server. Apache Tomcat 6.0.x merges these repositories into a single lib folder. The conf/catalina.properties file can be used to modify the directory structure. In addition, all of the default web applications are located in the webapps folder. When using a shared webhosting environment, it is recommended that usage of context.xml inside a WAR is forbidden (using the deployXML attribute of the Host element).

Modified classloading

As a result of the modification of the directory structure, the common, shared and server classloaders have been merged into one. The lib folder accepts both exploded class hierarchies and JARs. This behavior and structure can be modified using the conf/catalina.properties file.

Logging API package renaming

Commons-logging was package renamed to org.apache.juli.logging so that application logging can be as independent as possible from the container, while still having the possibility of being unified. This change is transparent when using java.logging, but requires compilation of the extra components when using log4j for Tomcat's logging. See the logging and extras documentation for more details.

SSLEnabled attribute on Connector

For all SSL enabled connectors, the SSLEnabled flag must be set to true to enable encryption. Tomcat no longer relies on using the protocol and other parameters to determine if the transport should be encrypted, to give maximum flexibility in proxied scenarios.

Clustering configuration changes

Clustering configuration was refactored. See the clustering documentation for more details.