Bridging legacy APIs Often, some of the components you depend on rely on a logging API other than SLF4J. You may also assume that these components will not switch to SLF4J in the immediate future. To deal with such circumstances, SLF4J ships with several bridging modules which redirect calls made to log4j 1.x, JCL and java.util.logging APIs to behave as if they were made to the SLF4J API instead.