Module com.github.robtimus.junit.support

Package com.github.robtimus.junit.support.extension

Class InjectingExtension

java.lang.Object

com.github.robtimus.junit.support.extension.InjectingExtension

All Implemented Interfaces:

BeforeAllCallback, BeforeEachCallback, Extension, ParameterResolver

Direct Known Subclasses:

AnnotationBasedInjectingExtension

public abstract class InjectingExtension
extends Object
implements BeforeAllCallback, BeforeEachCallback, ParameterResolver

An abstract base class for JUnit extensions that can inject values in fields and/or parameters.

Author:

Rob Spoor

Since:

2.0

Constructor Summary

Constructors

Modifier	Constructor	Description
protected	InjectingExtension(Predicate<Field> fieldPredicate, MethodHandles.Lookup lookup)	Creates a new extension.

Method Summary

Modifier and Type	Method	Description
void	beforeAll(ExtensionContext context)
void	beforeEach(ExtensionContext context)
Object	resolveParameter(ParameterContext parameterContext, ExtensionContext extensionContext)
protected abstract Object	resolveValue(InjectionTarget target, ExtensionContext context)	Resolves the value to inject.
boolean	supportsParameter(ParameterContext parameterContext, ExtensionContext extensionContext)
protected abstract Optional<JUnitException>	validateTarget(InjectionTarget target, ExtensionContext context)	Validates that a target is valid for injecting.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Detail

InjectingExtension

protected InjectingExtension(Predicate<Field> fieldPredicate,
                             MethodHandles.Lookup lookup)

Creates a new extension.

Concrete sub classes should call MethodHandles.lookup() and pass the result to this constructor. This prevents extensions piggy-backing on access granted to this class' module.

Parameters:

fieldPredicate - A predicate that determines which fields are eligible for injection.

lookup - The object to use for looking up the objects that are necessary for setting field values.

Throws:

NullPointerException - If the given predicate or lookup is null.

Method Detail

beforeAll

public final void beforeAll(ExtensionContext context)
                     throws Exception

Specified by:

beforeAll in interface BeforeAllCallback

Throws:

Exception

beforeEach

public final void beforeEach(ExtensionContext context)
                      throws Exception

Specified by:

beforeEach in interface BeforeEachCallback

Throws:

Exception

supportsParameter

public final boolean supportsParameter(ParameterContext parameterContext,
                                       ExtensionContext extensionContext)

Specified by:

supportsParameter in interface ParameterResolver

validateTarget

protected abstract Optional<JUnitException> validateTarget(InjectionTarget target,
                                                           ExtensionContext context)

Validates that a target is valid for injecting.

If this method returns a non-empty Optional for parameter injection, supportsParameter(ParameterContext, ExtensionContext) will return false, and JUnit will fail if no other extension supports the parameter.

If this method returns a non-empty Optional for field injection, the exception is thrown. This situation may or may not be prevented using the field predicate used to create this extension. In some cases the predicate may not test all aspects that are used to inject a value into fields; if that's the case, throwing an error may be an appropriate action.

Parameters:

target - The target to validate; never null.

context - The current extension context; never null.

Returns:

Optional.empty() if the given target is valid for injecting, or an Optional describing an exception that indicates why the target is invalid otherwise. In that case, the exception should have been created using InjectionTarget.createException(String) or InjectionTarget.createException(String, Throwable).

resolveParameter

public final Object resolveParameter(ParameterContext parameterContext,
                                     ExtensionContext extensionContext)

Specified by:

resolveParameter in interface ParameterResolver

resolveValue

protected abstract Object resolveValue(InjectionTarget target,
                                       ExtensionContext context)
                                throws Exception

Resolves the value to inject.

When this method is called for parameter injection, supportsParameter(ParameterContext, ExtensionContext) will have returned true, which means that validateTarget(InjectionTarget, ExtensionContext) will have returned an empty Optional.

When this method is called for field injection, validateTarget(InjectionTarget, ExtensionContext) will have been called and verified to have returned an empty Optional.

Parameters:

target - The target to inject the value in; never null.

context - The current extension context; never null.

Returns:

The value to inject; possibly null.

Throws:

Exception - If the value could not be resolved.