def self.establish_connection(spec = nil)
case spec
when nil
raise AdapterNotSpecified unless defined? RAILS_ENV
establish_connection(RAILS_ENV)
when ConnectionSpecification
clear_active_connection_name
@active_connection_name = name
@@defined_connections[name] = spec
when Symbol, String
if configuration = configurations[spec.to_s]
establish_connection(configuration)
else
raise AdapterNotSpecified, "#{spec} database is not configured"
end
else
spec = spec.symbolize_keys
unless spec.key?(:adapter) then raise AdapterNotSpecified, "database configuration does not specify adapter" end
adapter_method = "#{spec[:adapter]}_connection"
unless respond_to?(adapter_method) then raise AdapterNotFound, "database configuration specifies nonexistent #{spec[:adapter]} adapter" end
remove_connection
establish_connection(ConnectionSpecification.new(spec, adapter_method))
end
end