Annotation in spring

@ Component: Mark a common spring Bean class

@ Controller: Mark A Controller component class

@ Service: Mark a business logic component class

@ Repository: Mark a DaO component class

The Convention is to change the first letter of the bean class to lowercase, And the other parts remain unchanged.

@ Scope: Specifies the scope.

@ Resource: configure the dependency

@ Autowired: the default bytype is automatically assembled. If multiple classes of the same type appear in a class, it should be made into an array field []

@ Qualifier ("name"): precise automatic assembly