What are the meanings and functions of Jsp,action,service,dao,po in the Java Web?

JSP: Full name is Java Server Pages, the Chinese name is Java Servers page, it is a simplified servlet design, it [1] is advocated by Sun Microsystems Company, many companies involved in the establishment of a dynamic Web technology standards. JSP technology is a bit like ASP technology, it is in the traditional Web page HTML (standard Common Markup Language subset) file (*.htm,*.html) inserted Java program segment (scriptlet) and JSP tag (tag), thereby forming a JSP file, suffix named (*.jsp). Web applications developed with JSP are cross-platform and can run on Linux and other operating systems. 

The Action:action class is a bridge between user requests and business logic, and each Action acts as a business agent for the customer. is the control layer in MVC mode

The service:service layer is a new layer in the MCV three layer mode, which defines the boundaries of the application more clearly, and accesses the DAO layer through the Service layer when the data needs to be manipulated. What the service layer does is not just invoking DAO operational data, but it also contains some business logic. The design of the entire program has also become a service-oriented design. 

Dao:data Access object is a data access interface where data access: As the name implies, deals with databases. Sandwiched between business logic and database resources. is the model layer in MVC mode

Po:persistent object is persistent objects, which consist of the get and set methods of a set of properties and properties. Can be viewed as a Java object mapped to a table in the database





In the Struts+spring+hibernate system,
The calling process for an object is: Jsp-> Action-> Service->dao->hibernate.
The flow of data is Actionformbean accepts the user's data, the Action takes the data out of the Actionfrombean, encapsulates it into VO or PO,
Then call the business layer of the Bean class, complete a variety of business processing and then forward. When the business layer Bean receives the PO object, it invokes the DAO interface method for persistence. 

What are the meanings and functions of Jsp,action,service,dao,po in the Java Web?