Hi again,
After a while on french forums, someone gave me a hint to resolve my problem. In fact, I did not really resolve it but changed completely to something similar. I post here for the case someone searching for the same answer falls on my topic.
Here is the configuration of the WEB-INF/web.xml file (security part only) :
<security-constraint>
<display-name>Security constraint for Currency Manager</display-name>
<web-resource-collection>
<web-resource-name>Protected area</web-resource-name>
<url-pattern>/servlet/CurrencyConverter</url-pattern>
</web-resource-collection>
<auth-constraint>
<role-name>admin</role-name>
</auth-constraint>
</security-constraint>
<login-config>
<auth-method>FORM</auth-method>
<realm-name>CurrencyManager</realm-name>
<form-login-config>
<form-login-page>/login.jsp</form-login-page>
<form-error-page>/loginerror.jsp</form-error-page>
</form-login-config>
</login-config>
<security-role>
<role-name>admin</role-name>
</security-role>
Here is the WEB-INF/jboss-web.xml file I placed
<jboss-web>
<security-domain>java:/jaas/currencysecurity</security-domain>
</jboss-web>
Here is where it becomes really different, I did change the server\default\conf\login-config.xml file of my JBoss config. Just add a new application-policy with this configuration and I worked perfectly well for me.
<application-policy name="currencysecurity">
<authentication>
<login-module code="org.jboss.security.auth.spi.DatabaseServerLoginModule"
flag="required">
<module-option name="dsJndiName">java:/DefaultDS</module-option>
<module-option name="principalsQuery">
select user_pass from users where user_name=?
</module-option>
<module-option name="rolesQuery">
select role_name,'Roles' from user_roles where user_name=?
</module-option>
</login-module>
</authentication>
</application-policy>
Hope this will help someone some day ;)
Cya soon for new questions !