Programming Jakarta Struts

Jakarta Commons Logging

The Commons Logging package is an open source Logging library that allows developers to use a common logging API, while maintaining the freedom to use many different third-party logging implementations. The Commons Logging API insulates the application and protects it from becoming coupled to a specific logging implementation. The API provides a small set of Java classes and interfaces that an application imports and relies upon but that has no implicit dependencies on any one logging product.

The Logging library allows developers to declaratively configure the logging implementation; the library will dynamically discover which implementation is being used. An application that uses the Commons Logging API does not have to be modified when the logging implementation is changed. This is the greatest benefit of such a package.

The Commons Logging package supports several logging implementations out of the box:

• log4j (http://jakarta.apache.org/log4j)

• JDK 1.4 Logging

• LogKit (http://jakarta.apache.org/avalon/logkit)

• SimpleLog (writes log messages to stdout and stderr)

• NoOpLog (log messages are ignored)

Tip

The Commons Logging package includes only the SimpleLog and NoOpLog implementations; it does not contain the other third-party logging implementations. You will need to download those separately.

Another powerful feature of the Commons Logging package is that it is completely extensible. If you are using a logging package that is not yet supported, you ...