@Autowired annotation required attribute

stay @Autowired In the annotations , There is one required attribute , The default is true

@Target({
    ElementType.CONSTRUCTOR, ElementType.METHOD, ElementType.PARAMETER, ElementType.FIELD, ElementType.ANNOTATION_TYPE})
@Retention(RetentionPolicy.RUNTIME)
@Documented
public @interface Autowired {
    

	/** * Declares whether the annotated dependency is required. * <p>Defaults to {@code true}. */
	boolean required() default true;

}

Conclusion ：

• When required The attribute is true When , Inject SpringBean When , The bean There must be , Otherwise, the injection will fail , Initiate error reporting
• When required The attribute is false When , Inject SpringBean When , If bean There is , Just inject ; If it doesn't exist , Just ignore skip , No error will be reported during startup , But not directly