My problem solving record 1: the @component annotation is used on the class. If you want to use the methods in this class, you can't directly new, but should use @autowired for injection, otherwise an

I haven't used it for a long time springboot,spring Some annotations of are not clear about how to use , Therefore, the current problem appears

Use Springbooot Creating a thread pool , And use thread pool , Created a util class , It is found that other methods cannot be used directly new Methods , Later, I found that I put this util Class is used. @Component, Can't be used directly new One way （ Such as xxxUtils p = new xxxUtils()）, Instead, it should be used in the methods that use the tool class @Autowired This goes to injection bean

class @Component annotation , Want to use the methods in this class , You can't just new, Instead, use # @Autowired For injection , Otherwise, an error will be reported （ Such as null pointer exception, etc ）

@Component

Is a meta-annotation , Other class annotations can be annotated , The function is to tell spring The current class is a Bean object , And then let spring Automatically create and manage this class

1. Appoint bean The name of , Default to class name initial lowercase ：@Component
2. Appoint bean The name of ,@Component(“university1”)

@Autowired

Indicates whether a property needs dependency injection , Can be used in attribute 、 In the ordinary way 、 In terms of construction method . In the annotations required Property default is true, If no object can be injected into attributes , Then an exception will be reported ;

1. Add to an attribute ,spring Meeting from ioc Found in the container bean Objects are injected into attributes , If you find more than one of this type Bean object , Then, according to the name of the attribute, select from multiple Bean Confirm one of the objects ;
2. Written in set() On the way , stay spring According to the parameter type of the method ioc Found this type of Bean Object is injected into the row parameters of the method , And automatically reflect and call the method ( By @Autowired The method of decoration must be implemented ), So it is generally used in set In the method 、 No need for ordinary methods ;
3. Used in construction methods ： Formal parameters according to the construction method 、 The name of the parameter , from ioc Found this type of Bean object , Inject into the formal parameters of the construction method , And execute the method ;