A brief introduction to spring annotations

The core components of spring MVC

Dispatcher servlet - C > controller, request entry handermapping - controller, request dispatch controller - controller, request processing flow modelandview - model, encapsulate business processing results and views, viewresolver - view, view display processor

Processing flow

The browser sends a request to spotting, and the request is sent to the front-end controller dispatcherservlet for processing.

The controller finds the corresponding controller component through handermapping to process the request.

Execute the method processing request agreed by the controller component. The agreed method calls the model component to complete the business processing. The agreed method can return a modelandview object, which encapsulates the business processing result data and view name information.

After receiving the ModelAndView, the controller calls the ViewResolver component to locate View (JSP) and transmit the information to generate the response interface result.

Annotation configuration has many advantages over XML configuration:

It can make full use of java reflection mechanism to obtain class structure information, which can effectively reduce the work of configuration. For example, when configuring ORM mapping with JPA annotation, we do not need to specify the attribute name, type and other information of Po. If the relationship table fields are consistent with the Po attribute name and type, you do not even need to write task attribute mapping information - because these information can be obtained through java reflection mechanism.

Comments and Java code are located in one file, while XML configuration adopts an independent configuration file. Most configuration information will not be adjusted after program development. If the configuration information and Java code are put together, it will help to enhance the cohesion of the program. When using an independent XML configuration file, programmers often need to switch between the program file and the configuration file when writing a function. This incoherence in thinking will reduce the development efficiency.

Controller component

The controller component is responsible for performing specific business processing. When writing, it needs to implement the controller interface and agreed methods.

Modelandview component

A modelandview object will be returned in the controller contract component, which encapsulates the business processing result model data and view information.

The modelandview constructor is as follows:

-ModelAndView(StringviewName)

-ModelAndView(StringviewName,Mapmodel)

Where VIEWNAME is the name of the JSP page, and the data of the model is stored in the attribute of the request

Handermapping component

Through the handermapping component, the dispatcher servlet controller can map HTTP requests to the controller component.

-Simpleuserhandlermapping maintains an HTTP request and controller mapping relationship (map), and calls controller according to the list correspondence

Simpleuserhandlermapping using

The hellocontroller in the simpleuserhandlermapping tag above corresponds to the component with ID hellocontroller in the bean tag below.

RequestMappingHandlerMapping ResquestMappingHandlerAdapter

Use the @ resquestmapping annotation on the controller class and method to specify the corresponding client HTTP request.

Viewresolver component

All controller components return a modelandview instance, which encapsulates the view name. The view in spring is identified by its name, and the view parser viewresolver parses the view by its name.

The packaging of servlets and JSPS by internalresourceviewresolver. Examples:

For example, the view name Hello can be mapped to / WEB-INF / Hello. Through the above configuration jsp

Controller annotation

We generally use the @ controller annotation to declare the controller component, which makes it more flexible. We don't need to implement the controller interface as before.

A prerequisite for using the above annotation is to enable annotation scanning:

The base package contains the package of the controller component.

Resquestmapping annotation

Resquestmapping indicates which request this class or method corresponds to.

If requestmapping needs to be used, two bean components, requestmappinghandlermapping (before class definition) and requestmappingadapter (before method definition), need to be defined in the XML configuration file of spring. For example (it needs to be defined in sping3.1 version):

spring3. Version 2 does not need to be defined

summary

The above is a brief introduction to the notes on spring in this article. I hope it will be helpful to you. Interested friends can continue to refer to other related topics on this site. If there are deficiencies, please leave a message to point out. Thank you for your support!