public void setAuthorizer(Authorizer authorizer) {
        if (authorizer == null) {
            String msg = "Authorizer argument cannot be null.";
            throw new IllegalArgumentException(msg);
        }
        this.authorizer = authorizer;
    }
Sets the underlying <tt>Authorizer</tt> instance to which this <tt>SecurityManager</tt> implementation will
delegate all of its authorization calls.

@param authorizer the <tt>Authorizer</tt> this <tt>SecurityManager</tt> should wrap and delegate all of its
                  authorization calls to.
core/src/main/java/org/apache/shiro/mgt/AuthorizingSecurityManager.java