How to decode stored passwords

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Hi, i'm trying to implement a function that permit to login in jetspeed 
"as a user".
I've tried to decode users password using the "PasswordEncodingService", 
but trying to enable it i retrieve an error in jetspeed log:

"Error creating bean with name 'PortalServices' defined in 
ServletContext resource [/WEB-INF/assembly/jetspeed-services.xml]: 
Cannot resolve reference to bean 
'org.apache.jetspeed.security.PasswordEncodingService' while setting 
constructor argument with key [TypedStringValue: value 
[PasswordEncodingService], target type [null]]; nested exception is 
org.springframework.beans.factory.NoSuchBeanDefinitionException: No bean 
named 'org.apache.jetspeed.security.PasswordEncodingService' is defined"

How can i enable the api PasswordEncodingService?

Best regards,
Giacomo Morri

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