mcDropdown是一个独特的UI控件，它能够让用户在一个复杂分级的树形下拉选项中进行选择。-mcDropdown is a unique UI controls, it allows the user to choose in a complex hierarchical tree drop-down options.

用servlet+jsp+zTree控件实现树形展示，其中数据库表的设计非常好，不是平常的父子关系，而是用左右关系来描述父子关系。(Servlet+jsp+zTree control to achieve tree display, in which the database table design is very good, not an ordinary father son relationship, but to describe the relationship between fa