Spring MVC [entry]

MVC Design Overview

In the early Java Web development in the unified display layer, the control layer, data layer operation of all to the JSP or JavaBean to handle, we call Model1:

Drawbacks arise:
Serious coupling between the JSP and Java Bean, Java code and HTML code are also coupled together
It requires developers not only to master Java, but also a superb front-end level
Front and rear interdependence, need to wait for the backend to complete the front-end, back-end is also dependent on the completion of the front end, in order to effectively test
Code reuse is difficult

Because of the above drawbacks, so in this way it was soon replaced by the Servlet + JSP + Java Bean, early MVC model (Model2) such as the following figure:

First, the user's request will reach the Servlet, then calls the appropriate Java Bean, upon request, and all the displayed results to the JSP to complete, so we called MVC pattern mode.

M represents the model (Model)
What model is it? It is the data model, that is, dao, bean
V represents the view (View)
what view is it? That is, pages, JSP, used to display the data model
C represents the controller (controller)
What controllers? The controller's role is to different data (Model), show that such a role in the different views (View), Servlet plays.

Let's write about our first Spring MVC program:

Further reading: Web development model

Spring MVC architecture

To solve the persistence layer has been good database transaction untreated programming, but also in order to meet the strong rise of NoSQL, Spring MVC gives the program:

传统的模型层被拆分为了业务层(Service)和数据访问层（DAO,Data Access Object）。 在 Service 下可以通过 Spring 的声明式事务操作数据访问层，而在业务层上还允许我们访问 NoSQL ，这样就能够满足异军突起的 NoSQL 的使用了，它可以大大提高互联网系统的性能。