Object.const_set("Connection1",Class.new(ActiveRecord::Base) do
  self.abstract_class = true
  self.establish_connection({
    :host=>"localhost", :username=>"root", :password=>"root", :database=>"db1", :encoding=>"utf8", :adapter=>"mysql2"})
end)

Object.const_set("Connection2",Class.new(ActiveRecord::Base) do
  self.abstract_class = true
  self.establish_connection({
    :host=>"localhost", :username=>"root", :password=>"root", :database=>"db2", :encoding=>"utf8", :adapter=>"mysql2"})
end)

Object.const_set("ConnectionUser1",Class.new(Connection1) do
  self.table_name = 'user'
  def self.foo
    all.count
  end
end)

Object.const_set("ConnectionUser2",Class.new(Connection2) do
  self.table_name = 'user'
  def self.foo
    all.count
  end
end)

p ConnectionUser1.foo
p ConnectionUser2.foo