title: Spring AutowiredAnnotationBeanPostProcessor uses only parameter less constructor
body: <p>Below is the quote from springs documentation of AutowiredAnnotationBeanPostProcessor,</p>
  
  <blockquote>
    <p>Only one constructor (at max) of any given bean class may carry this
    annotation with the 'required' parameter set to true, indicating the
    constructor to autowire when used as a Spring bean. If multiple
    non-required constructors carry the annotation, they will be
    considered as candidates for autowiring. The constructor with the
    greatest number of dependencies that can be satisfied by matching
    beans in the Spring container will be chosen. If none of the
    candidates can be satisfied, then a default constructor (if present)
    will be used. An annotated constructor does not have to be public.</p>
  </blockquote>
  
  <p>Since I am new to Spring I just know that when we use <code>@Autowired</code> it calls parameterless constructor to inject dependency. </p>
  
  <p>How does this <code>required</code> can be used with constructor and what does this quote means?</p>