The application framework based on MVC pattern struts (1)

1.struts Development Steps

• The introduction of struts's jar package;
• The core functions of struts are introduced in Web. XML, and the Struts core filter is configured.
• Development action, generally inherited from Actionsupport, the business method must return a string type, the method cannot have parameters;
• Configure the action in Src/struts.xml;

2.struts Execution Process

Server Startup

• Load the project's web. xml;
• Create a struts core filter object and execute its init () method, reading Struts-default.xml, Struts-plugin.xml, and struts.xml configuration files sequentially;

Access

• The user accesses the action, and the server creates an action instance based on the access URL to find the corresponding action class;
• Execute Struts Interceptor;
• Each subsequent visit creates an instance of the action and then executes the interceptor;

3.struts-default.xml detailed

• The bean node develops the node type that struts creates at run time;

• Specifies the Struts-default package that the package in the user-written struts.xml must inherit from.

These include:

• The result type of the jump

Dispathcer: Default Value

Redirect: redirect

Redirectaction: Redirect to Action resource

Stream: used when downloading files

• 32 interceptors are defined, and for convenience of reference, the Interceptor can be referenced by means of a stack definition;
• The default execution of interceptors (8), executed sequentially;
• Action of the default value type;

4. Interceptor vs Filter

Interceptors and filters play a role in intercepting resources.

Filter:

Intercept all resources: JSP, servlet, CSS, JS and so on;

Can be used in all servlet projects;

Interceptors:

Only action requests can be intercepted;

Is the concept of struts and can only be used in struts projects;

The application framework based on MVC pattern struts (1)