You'll need to copy acegi-security.jar into your WEB-INF/lib directory.
You can find the JAR in the /dist directory of any ZIP distribution.

Acegi-security.jar requires the following JARs in WEB-INF/lib:

commons-logging.jar
commons-codec.jar
commons-collections.jar
jakarta-oro.jar
spring.jar

Most of the above JARs are included with Spring. Those that are not are
definitely included in the Acegi Security "with dependencies" release ZIP.

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