ConditionalOnSingleCandidate class

Registers a bean only when exactly one bean of a type can be injected where that type is asked for.

ConditionalOnBean is satisfied by several beans of a type, but a bean that takes one of them as a constructor parameter would then fail with an ambiguity. This condition checks that the injection works: there is one candidate, or one @Primary() among several, or one that is not @Fallback(). Beans with autowireCandidate: false or defaultCandidate: false do not count; beans of parent contexts do. Like ConditionalOnBean, it only sees beans registered before it.

// Safe to inject a DataSource here: there is exactly one to choose.
@Bean()
@ConditionalOnSingleCandidate(DataSource)
Migrations migrations(DataSource source) => Migrations(source);

Spring (Java): @ConditionalOnSingleCandidate(DataSource.class).

Implemented types

• ConfigurationCondition

Constructors

ConditionalOnSingleCandidate(Type type)

Requires that a single bean of type can be injected.

const

Properties

configurationPhase → ConfigurationPhase

Decided when the bean definitions are registered, after every earlier configuration class, so that it sees their beans (Spring Boot's OnBeanCondition is a REGISTER_BEAN ConfigurationCondition).

no setter, override

hashCode → int

The hash code for this object.

no setter, inherited

runtimeType → Type

A representation of the runtime type of the object.

no setter, inherited

type → Type

The type that must have a single injectable bean.

final

Methods

matches(ConditionContext context) → bool

Whether the annotated bean should be registered; context gives access to the configuration and the definitions registered so far.

override

noSuchMethod(Invocation invocation) → dynamic

Invoked when a nonexistent method or property is accessed.

inherited

toString() → String

A string representation of this object.

override

Operators

operator ==(Object other) → bool

The equality operator.

inherited