Only one constructor (at max) of any given bean class may declare this annotation - * with the 'required' parameter set to {@code true}, indicating the constructor - * to autowire when used as a Spring bean. If multiple non-required constructors - * declare 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 primary/default constructor (if present) will be used. - * If a class only declares a single constructor to begin with, it will always be used, - * even if not annotated. An annotated constructor does not have to be public. + *
Only one constructor of any given bean class may declare this annotation with + * the 'required' attribute set to {@code true}, indicating the constructor + * to autowire when used as a Spring bean. Furthermore, if the 'required' attribute + * is set to {@code true}, only a single constructor may be annotated with + * {@code @Autowired}. If multiple non-required constructors declare 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 primary/default constructor (if present) will be used. If a class only + * declares a single constructor to begin with, it will always be used, even if not + * annotated. An annotated constructor does not have to be public. * *
Fields are injected right after construction of a bean, before any config methods diff --git a/src/docs/asciidoc/core/core-beans.adoc b/src/docs/asciidoc/core/core-beans.adoc index 54b2731b98..3795be1b55 100644 --- a/src/docs/asciidoc/core/core-beans.adoc +++ b/src/docs/asciidoc/core/core-beans.adoc @@ -4538,15 +4538,19 @@ e.g. declared as a single public constructor without an `@Autowired` annotation. [NOTE] ==== -Only one annotated constructor per class can be marked as required, but multiple -non-required constructors can be annotated. In that case, each is considered among -the candidates and Spring uses the greediest constructor whose dependencies can be -satisfied -- that is, the constructor that has the largest number of arguments. -The constructor resolution algorithm is the same as for non-annotated classes with -overloaded constructors, just narrowing the candidates to annotated constructors. +Only one constructor of any given bean class may declare `@Autowired` with the `required` +attribute set to `true`, indicating _the_ constructor to autowire when used as a Spring +bean. Furthermore, if the `required` attribute is set to `true`, only a single +constructor may be annotated with `@Autowired`. If multiple _non-required_ constructors +declare 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 primary/default constructor (if present) will be used. If a class only declares a +single constructor to begin with, it will always be used, even if not annotated. An +annotated constructor does not have to be public. -The 'required' attribute of `@Autowired` is recommended over the `@Required` annotation -on setter methods. The 'required' attribute indicates that the property is not required +The `required` attribute of `@Autowired` is recommended over the `@Required` annotation +on setter methods. The `required` attribute indicates that the property is not required for autowiring purposes. The property is ignored if it cannot be autowired. `@Required`, on the other hand, is stronger in that it enforces the property to be set by any means supported by the container. If no value is defined, a corresponding exception is raised.