AutowiredAnnotationBeanPostProcessor tolerates annotated no-arg constructors

Issue: SPR-15005

Author: jhoeller

spring-beans/src/main/java/org/springframework/beans/factory/annotation/AutowiredAnnotationBeanPostProcessor.java

@@ -305,10 +305,6 @@ public void doWith(Method method) throws IllegalArgumentException, IllegalAccess
 										". Found constructor with 'required' Autowired annotation already: " +
 										requiredConstructor);
 							}
-							if (candidate.getParameterCount() == 0) {
-								throw new IllegalStateException(
-										"Autowired annotation requires at least one argument: " + candidate);
-							}
 							boolean required = determineRequiredStatus(ann);
 							if (required) {
 								if (!candidates.isEmpty()) {

spring-beans/src/test/java/org/springframework/beans/factory/annotation/AutowiredAnnotationBeanPostProcessorTests.java

@@ -2184,6 +2184,15 @@ public void testSingleConstructorWithProvidedArgument() {
 		assertNotNull(bf.getBean(ProvidedArgumentBean.class));
 	}
 
+	@Test
+	public void testAnnotatedDefaultConstructor() {
+		DefaultListableBeanFactory bf = new DefaultListableBeanFactory();
+		bf.addBeanPostProcessor(new AutowiredAnnotationBeanPostProcessor());
+		bf.registerBeanDefinition("annotatedBean", new RootBeanDefinition(AnnotatedDefaultConstructorBean.class));
+
+		assertNotNull(bf.getBean("annotatedBean"));
+	}
+
 
 	public static class ResourceInjectionBean {
 
@@ -3411,7 +3420,14 @@ public static Set<TestBean> testBeanSet() {
 			tbs.add(new TestBean("tb2"));
 			return tbs;
 		}
+	}
+
+
+	public static class AnnotatedDefaultConstructorBean {
 
+		@Autowired
+		public AnnotatedDefaultConstructorBean() {
+		}
 	}
 
 }

spring-beans/src/test/java/org/springframework/beans/factory/annotation/InjectAnnotationBeanPostProcessorTests.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2014 the original author or authors.
+ * Copyright 2002-2016 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -742,6 +742,15 @@ public void testProviderOfOptionalMethodInjectionWithBeanNotAvailable() {
 		bf.destroySingletons();
 	}
 
+	@Test
+	public void testAnnotatedDefaultConstructor() {
+		DefaultListableBeanFactory bf = new DefaultListableBeanFactory();
+		bf.addBeanPostProcessor(new AutowiredAnnotationBeanPostProcessor());
+		bf.registerBeanDefinition("annotatedBean", new RootBeanDefinition(AnnotatedDefaultConstructorBean.class));
+
+		assertNotNull(bf.getBean("annotatedBean"));
+	}
+
 
 	public static class ResourceInjectionBean {
 
@@ -750,7 +759,6 @@ public static class ResourceInjectionBean {
 
 		private TestBean testBean2;
 
-
 		@Inject
 		public void setTestBean2(TestBean testBean2) {
 			if (this.testBean2 != null) {
@@ -819,7 +827,6 @@ public BeanFactory getBeanFactory() {
 
 
 	public static class TypedExtendedResourceInjectionBean extends ExtendedResourceInjectionBean<NestedTestBean> {
-
 	}
 
 
@@ -1087,7 +1094,6 @@ public static class MapFieldInjectionBean {
 		@Inject
 		private Map<String, TestBean> testBeanMap;
 
-
 		public Map<String, TestBean> getTestBeanMap() {
 			return this.testBeanMap;
 		}
@@ -1346,4 +1352,12 @@ public Optional<TestBean> getTestBean() {
 		}
 	}
 
+
+	public static class AnnotatedDefaultConstructorBean {
+
+		@Inject
+		public AnnotatedDefaultConstructorBean() {
+		}
+	}
+
 }