Bean overriding in tests refers to the ability to override specific beans in the
ApplicationContext
for a test class, by annotating one or more fields in the test class.
Note
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This feature is intended as a less risky alternative to the practice of registering
a bean via @Bean with the DefaultListableBeanFactory
setAllowBeanDefinitionOverriding flag set to true .
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The Spring TestContext framework provides two sets of annotations for bean overriding.
The former relies purely on Spring, while the latter set relies on the Mockito third-party library.
The three annotations mentioned above build upon the @BeanOverride
meta-annotation and
associated infrastructure, which allows one to define custom bean overriding variants.
To create custom bean override support, the following is needed:
-
An annotation meta-annotated with
@BeanOverride
that defines theBeanOverrideProcessor
to use -
A custom
BeanOverrideProcessor
implementation -
One or more concrete
OverrideMetadata
implementations provided by the processor
The Spring TestContext framework includes implementations of the following APIs that support bean overriding and are responsible for setting up the rest of the infrastructure.
-
a
BeanFactoryPostProcessor
-
a
ContextCustomizerFactory
-
a
TestExecutionListener
The spring-test
module registers implementations of the latter two
(BeanOverrideContextCustomizerFactory
and BeanOverrideTestExecutionListener
) in its
{spring-framework-code}/spring-test/src/main/resources/META-INF/spring.factories[META-INF/spring.factories
properties file].
The bean overriding infrastructure searches in test classes for any field meta-annotated
with @BeanOverride
and instantiates the corresponding BeanOverrideProcessor
which is
responsible for registering appropriate OverrideMetadata
.
The internal BeanOverrideBeanFactoryPostProcessor
then uses that information to alter
the test’s ApplicationContext
by registering and replacing bean definitions as defined
by the corresponding BeanOverrideStrategy
:
-
REPLACE_DEFINITION
: Replaces the bean definition. Throws an exception if a corresponding bean definition does not exist. -
REPLACE_OR_CREATE_DEFINITION
: Replaces the bean definition if it exists. Creates a new bean definition if a corresponding bean definition does not exist. -
WRAP_BEAN
: Retrieves the original bean instance and wraps it.
Note
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In contrast to Spring’s autowiring mechanism (for example, resolution of an Typically, the bean is selected by type by the Some |