Juergen Hoeller
7 years ago
5 changed files with 371 additions and 298 deletions
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/* |
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* Copyright 2002-2019 the original author or authors. |
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* |
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* Licensed under the Apache License, Version 2.0 (the "License"); |
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* you may not use this file except in compliance with the License. |
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* You may obtain a copy of the License at |
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* |
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* http://www.apache.org/licenses/LICENSE-2.0
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* |
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* Unless required by applicable law or agreed to in writing, software |
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* distributed under the License is distributed on an "AS IS" BASIS, |
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. |
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* See the License for the specific language governing permissions and |
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* limitations under the License. |
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*/ |
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package org.springframework.beans.factory.annotation; |
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import java.lang.annotation.Annotation; |
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import java.lang.reflect.AnnotatedElement; |
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import java.lang.reflect.Constructor; |
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import java.lang.reflect.Executable; |
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import java.lang.reflect.Parameter; |
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import org.springframework.beans.BeansException; |
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import org.springframework.beans.factory.config.AutowireCapableBeanFactory; |
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import org.springframework.beans.factory.config.DependencyDescriptor; |
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import org.springframework.core.MethodParameter; |
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import org.springframework.core.annotation.AnnotatedElementUtils; |
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import org.springframework.core.annotation.SynthesizingMethodParameter; |
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import org.springframework.lang.Nullable; |
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import org.springframework.util.Assert; |
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import org.springframework.util.ClassUtils; |
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/** |
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* Public delegate for resolving autowirable parameters on externally managed |
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* constructors and methods. |
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* |
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* @author Sam Brannen |
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* @author Juergen Hoeller |
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* @since 5.2 |
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* @see #isAutowirable |
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* @see #resolveDependency |
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*/ |
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public final class ParameterResolutionDelegate { |
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private static final AnnotatedElement EMPTY_ANNOTATED_ELEMENT = new AnnotatedElement() { |
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@Override |
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@Nullable |
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public <T extends Annotation> T getAnnotation(Class<T> annotationClass) { |
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return null; |
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} |
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@Override |
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public Annotation[] getAnnotations() { |
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return new Annotation[0]; |
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} |
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@Override |
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public Annotation[] getDeclaredAnnotations() { |
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return new Annotation[0]; |
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} |
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}; |
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private ParameterResolutionDelegate() { |
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} |
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/** |
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* Determine if the supplied {@link Parameter} can <em>potentially</em> be |
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* autowired from an {@link AutowireCapableBeanFactory}. |
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* <p>Returns {@code true} if the supplied parameter is annotated or |
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* meta-annotated with {@link Autowired @Autowired}, |
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* {@link Qualifier @Qualifier}, or {@link Value @Value}. |
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* <p>Note that {@link #resolveDependency} may still be able to resolve the |
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* dependency for the supplied parameter even if this method returns {@code false}. |
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* @param parameter the parameter whose dependency should be autowired |
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* (must not be {@code null}) |
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* @param parameterIndex the index of the parameter in the constructor or method |
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* that declares the parameter |
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* @see #resolveDependency |
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*/ |
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public static boolean isAutowirable(Parameter parameter, int parameterIndex) { |
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Assert.notNull(parameter, "Parameter must not be null"); |
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AnnotatedElement annotatedParameter = getEffectiveAnnotatedParameter(parameter, parameterIndex); |
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return (AnnotatedElementUtils.hasAnnotation(annotatedParameter, Autowired.class) || |
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AnnotatedElementUtils.hasAnnotation(annotatedParameter, Qualifier.class) || |
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AnnotatedElementUtils.hasAnnotation(annotatedParameter, Value.class)); |
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} |
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/** |
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* Resolve the dependency for the supplied {@link Parameter} from the |
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* supplied {@link AutowireCapableBeanFactory}. |
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* <p>Provides comprehensive autowiring support for individual method parameters |
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* on par with Spring's dependency injection facilities for autowired fields and |
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* methods, including support for {@link Autowired @Autowired}, |
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* {@link Qualifier @Qualifier}, and {@link Value @Value} with support for property |
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* placeholders and SpEL expressions in {@code @Value} declarations. |
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* <p>The dependency is required unless the parameter is annotated or meta-annotated |
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* with {@link Autowired @Autowired} with the {@link Autowired#required required} |
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* flag set to {@code false}. |
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* <p>If an explicit <em>qualifier</em> is not declared, the name of the parameter |
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* will be used as the qualifier for resolving ambiguities. |
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* @param parameter the parameter whose dependency should be resolved (must not be |
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* {@code null}) |
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* @param parameterIndex the index of the parameter in the constructor or method |
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* that declares the parameter |
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* @param containingClass the concrete class that contains the parameter; this may |
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* differ from the class that declares the parameter in that it may be a subclass |
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* thereof, potentially substituting type variables (must not be {@code null}) |
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* @param beanFactory the {@code AutowireCapableBeanFactory} from which to resolve |
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* the dependency (must not be {@code null}) |
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* @return the resolved object, or {@code null} if none found |
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* @throws BeansException if dependency resolution failed |
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* @see #isAutowirable |
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* @see Autowired#required |
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* @see SynthesizingMethodParameter#forExecutable(Executable, int) |
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* @see AutowireCapableBeanFactory#resolveDependency(DependencyDescriptor, String) |
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*/ |
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@Nullable |
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public static Object resolveDependency( |
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Parameter parameter, int parameterIndex, Class<?> containingClass, AutowireCapableBeanFactory beanFactory) |
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throws BeansException { |
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Assert.notNull(parameter, "Parameter must not be null"); |
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Assert.notNull(containingClass, "Containing class must not be null"); |
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Assert.notNull(beanFactory, "AutowireCapableBeanFactory must not be null"); |
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AnnotatedElement annotatedParameter = getEffectiveAnnotatedParameter(parameter, parameterIndex); |
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Autowired autowired = AnnotatedElementUtils.findMergedAnnotation(annotatedParameter, Autowired.class); |
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boolean required = (autowired == null || autowired.required()); |
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MethodParameter methodParameter = SynthesizingMethodParameter.forExecutable( |
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parameter.getDeclaringExecutable(), parameterIndex); |
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DependencyDescriptor descriptor = new DependencyDescriptor(methodParameter, required); |
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descriptor.setContainingClass(containingClass); |
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return beanFactory.resolveDependency(descriptor, null); |
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} |
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/** |
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* Due to a bug in {@code javac} on JDK versions prior to JDK 9, looking up |
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* annotations directly on a {@link Parameter} will fail for inner class
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* constructors. |
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* <h4>Bug in javac in JDK < 9</h4> |
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* <p>The parameter annotations array in the compiled byte code excludes an entry |
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* for the implicit <em>enclosing instance</em> parameter for an inner class
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* constructor. |
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* <h4>Workaround</h4> |
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* <p>This method provides a workaround for this off-by-one error by allowing the |
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* caller to access annotations on the preceding {@link Parameter} object (i.e., |
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* {@code index - 1}). If the supplied {@code index} is zero, this method returns |
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* an empty {@code AnnotatedElement}. |
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* <h4>WARNING</h4> |
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* <p>The {@code AnnotatedElement} returned by this method should never be cast and |
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* treated as a {@code Parameter} since the metadata (e.g., {@link Parameter#getName()}, |
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* {@link Parameter#getType()}, etc.) will not match those for the declared parameter |
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* at the given index in an inner class constructor. |
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* @return the supplied {@code parameter} or the <em>effective</em> {@code Parameter} |
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* if the aforementioned bug is in effect |
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*/ |
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private static AnnotatedElement getEffectiveAnnotatedParameter(Parameter parameter, int index) { |
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Executable executable = parameter.getDeclaringExecutable(); |
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if (executable instanceof Constructor && ClassUtils.isInnerClass(executable.getDeclaringClass()) && |
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executable.getParameterAnnotations().length == executable.getParameterCount() - 1) { |
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// Bug in javac in JDK <9: annotation array excludes enclosing instance parameter
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// for inner classes, so access it with the actual parameter index lowered by 1
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return (index == 0 ? EMPTY_ANNOTATED_ELEMENT : executable.getParameters()[index - 1]); |
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} |
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return parameter; |
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} |
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} |
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@ -0,0 +1,171 @@ |
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/* |
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* Copyright 2002-2019 the original author or authors. |
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* |
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* Licensed under the Apache License, Version 2.0 (the "License"); |
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* you may not use this file except in compliance with the License. |
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* You may obtain a copy of the License at |
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* |
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* http://www.apache.org/licenses/LICENSE-2.0
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* |
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* Unless required by applicable law or agreed to in writing, software |
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* distributed under the License is distributed on an "AS IS" BASIS, |
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. |
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* See the License for the specific language governing permissions and |
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* limitations under the License. |
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*/ |
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package org.springframework.beans.factory.annotation; |
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import java.lang.reflect.Constructor; |
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import java.lang.reflect.Executable; |
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import java.lang.reflect.Method; |
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import java.lang.reflect.Parameter; |
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import org.junit.Rule; |
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import org.junit.Test; |
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import org.junit.rules.ExpectedException; |
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import org.springframework.beans.factory.config.AutowireCapableBeanFactory; |
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import org.springframework.beans.factory.config.DependencyDescriptor; |
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import org.springframework.util.ClassUtils; |
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import static org.junit.Assert.*; |
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import static org.mockito.Mockito.*; |
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/** |
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* Unit tests for {@link ParameterResolutionDelegate}. |
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* |
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* @author Sam Brannen |
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* @author Juergen Hoeller |
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* @author Loïc Ledoyen |
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*/ |
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public class ParameterResolutionTests { |
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@Rule |
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public final ExpectedException exception = ExpectedException.none(); |
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@Test |
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public void isAutowirablePreconditions() { |
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exception.expect(IllegalArgumentException.class); |
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exception.expectMessage("Parameter must not be null"); |
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ParameterResolutionDelegate.isAutowirable(null, 0); |
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} |
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@Test |
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public void annotatedParametersInMethodAreCandidatesForAutowiring() throws Exception { |
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Method method = getClass().getDeclaredMethod("autowirableMethod", String.class, String.class, String.class, String.class); |
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assertAutowirableParameters(method); |
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} |
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@Test |
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public void annotatedParametersInTopLevelClassConstructorAreCandidatesForAutowiring() throws Exception { |
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Constructor<?> constructor = AutowirableClass.class.getConstructor(String.class, String.class, String.class, String.class); |
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assertAutowirableParameters(constructor); |
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} |
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@Test |
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public void annotatedParametersInInnerClassConstructorAreCandidatesForAutowiring() throws Exception { |
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Class<?> innerClass = AutowirableClass.InnerAutowirableClass.class; |
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assertTrue(ClassUtils.isInnerClass(innerClass)); |
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Constructor<?> constructor = innerClass.getConstructor(AutowirableClass.class, String.class, String.class); |
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assertAutowirableParameters(constructor); |
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} |
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private void assertAutowirableParameters(Executable executable) { |
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int startIndex = (executable instanceof Constructor) |
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&& ClassUtils.isInnerClass(executable.getDeclaringClass()) ? 1 : 0; |
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Parameter[] parameters = executable.getParameters(); |
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for (int parameterIndex = startIndex; parameterIndex < parameters.length; parameterIndex++) { |
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Parameter parameter = parameters[parameterIndex]; |
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assertTrue("Parameter " + parameter + " must be autowirable", |
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ParameterResolutionDelegate.isAutowirable(parameter, parameterIndex)); |
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} |
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} |
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@Test |
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public void nonAnnotatedParametersInTopLevelClassConstructorAreNotCandidatesForAutowiring() throws Exception { |
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Constructor<?> notAutowirableConstructor = AutowirableClass.class.getConstructor(String.class); |
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Parameter[] parameters = notAutowirableConstructor.getParameters(); |
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for (int parameterIndex = 0; parameterIndex < parameters.length; parameterIndex++) { |
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Parameter parameter = parameters[parameterIndex]; |
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assertFalse("Parameter " + parameter + " must not be autowirable", |
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ParameterResolutionDelegate.isAutowirable(parameter, parameterIndex)); |
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} |
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} |
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@Test |
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public void resolveDependencyPreconditionsForParameter() { |
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exception.expect(IllegalArgumentException.class); |
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exception.expectMessage("Parameter must not be null"); |
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ParameterResolutionDelegate.resolveDependency(null, 0, null, mock(AutowireCapableBeanFactory.class)); |
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} |
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@Test |
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public void resolveDependencyPreconditionsForContainingClass() throws Exception { |
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exception.expect(IllegalArgumentException.class); |
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exception.expectMessage("Containing class must not be null"); |
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ParameterResolutionDelegate.resolveDependency(getParameter(), 0, null, null); |
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} |
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@Test |
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public void resolveDependencyPreconditionsForBeanFactory() throws Exception { |
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exception.expect(IllegalArgumentException.class); |
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exception.expectMessage("AutowireCapableBeanFactory must not be null"); |
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ParameterResolutionDelegate.resolveDependency(getParameter(), 0, getClass(), null); |
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} |
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private Parameter getParameter() throws NoSuchMethodException { |
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Method method = getClass().getDeclaredMethod("autowirableMethod", String.class, String.class, String.class, String.class); |
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return method.getParameters()[0]; |
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} |
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@Test |
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public void resolveDependencyForAnnotatedParametersInTopLevelClassConstructor() throws Exception { |
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Constructor<?> constructor = AutowirableClass.class.getConstructor(String.class, String.class, String.class, String.class); |
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AutowireCapableBeanFactory beanFactory = mock(AutowireCapableBeanFactory.class); |
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// Configure the mocked BeanFactory to return the DependencyDescriptor for convenience and
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// to avoid using an ArgumentCaptor.
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when(beanFactory.resolveDependency(any(), isNull())).thenAnswer(invocation -> invocation.getArgument(0)); |
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Parameter[] parameters = constructor.getParameters(); |
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for (int parameterIndex = 0; parameterIndex < parameters.length; parameterIndex++) { |
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Parameter parameter = parameters[parameterIndex]; |
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DependencyDescriptor intermediateDependencyDescriptor = (DependencyDescriptor) ParameterResolutionDelegate.resolveDependency( |
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parameter, parameterIndex, AutowirableClass.class, beanFactory); |
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assertEquals(constructor, intermediateDependencyDescriptor.getAnnotatedElement()); |
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assertEquals(parameter, intermediateDependencyDescriptor.getMethodParameter().getParameter()); |
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} |
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} |
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void autowirableMethod( |
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@Autowired String firstParameter, |
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@Qualifier("someQualifier") String secondParameter, |
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@Value("${someValue}") String thirdParameter, |
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@Autowired(required = false) String fourthParameter) { |
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} |
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public static class AutowirableClass { |
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public AutowirableClass(@Autowired String firstParameter, |
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@Qualifier("someQualifier") String secondParameter, |
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@Value("${someValue}") String thirdParameter, |
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@Autowired(required = false) String fourthParameter) { |
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} |
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public AutowirableClass(String notAutowirableParameter) { |
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} |
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public class InnerAutowirableClass { |
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public InnerAutowirableClass(@Autowired String firstParameter, |
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@Qualifier("someQualifier") String secondParameter) { |
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} |
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} |
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} |
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} |
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