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The following UML class diagram depicts the structure of the little example.
The class HashTools contains two simple methods w.r.t. hashing. isAlreadyHashed detects whether a value has already been hashed with a known message digest algorithm. applyHashAlgorithm applies a hash algorithm to a sequence of bytes. See the source code and the unit tests of this class for details, it has not that much todo with the interceptor stuff.
The central class is PasswordHashInterceptor. Every interceptor has to implement the Interceptor interface from package org.apache.directory.server.core.interceptor. PasswordHashInterceptor does so by extended the convenience class BaseInterceptor from the same package.
Using the interceptor
Embedded mode
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