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Revise documentation for autowiring with annotated constructors

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Closes gh-24711
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Juergen Hoeller
2020-03-23 18:01:30 +01:00
parent 10d47d4d21
commit bb1699a9d3
1 changed files with 9 additions and 8 deletions
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17
src/docs/asciidoc/core/core-beans.adoc
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@@ -5085,21 +5085,22 @@ without an `@Autowired` annotation.
====
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
bean. As a consequence, if the `required` attribute is left at its default value `true`,
only a single constructor may be annotated with `@Autowired`. If multiple constructors
declare the annotation, they will all have to declare `required=false` in order to be
considered as candidates for autowiring (analogous to `autowire=constructor` in XML).
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.
single constructor to begin with, it will always be used, even if not annotated. Note that
an annotated constructor does not have to be public.
The `required` attribute of `@Autowired` is recommended over the deprecated `@Required`
annotation on setter methods. Setting the `required` attribute to `false` indicates that
the property is not required for autowiring purposes, and 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, and if no value is defined, a
corresponding exception is raised.
property to be set by any means supported by the container, and if no value is defined,
a corresponding exception is raised.
====
Alternatively, you can express the non-required nature of a particular dependency