@Resource injection points support @Lazy as well

Issue: SPR-12654

spring-context/src/main/java/org/springframework/context/annotation/CommonAnnotationBeanPostProcessor.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2014 the original author or authors.
+ * Copyright 2002-2015 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.
@@ -44,6 +44,8 @@ import javax.xml.ws.Service;
 import javax.xml.ws.WebServiceClient;
 import javax.xml.ws.WebServiceRef;
 
+import org.springframework.aop.TargetSource;
+import org.springframework.aop.framework.ProxyFactory;
 import org.springframework.beans.BeanUtils;
 import org.springframework.beans.BeansException;
 import org.springframework.beans.PropertyValues;
@@ -414,6 +416,44 @@ public class CommonAnnotationBeanPostProcessor extends InitDestroyAnnotationBean
 		return new InjectionMetadata(clazz, elements);
 	}
 
+	/**
+	 * Obtain a lazily resolving resource proxy for the given name and type,
+	 * delegating to {@link #getResource} on demand once a method call comes in.
+	 * @param element the descriptor for the annotated field/method
+	 * @param requestingBeanName the name of the requesting bean
+	 * @return the resource object (never {@code null})
+	 * @since 4.2
+	 * @see #getResource
+	 * @see Lazy
+	 */
+	protected Object buildLazyResourceProxy(final LookupElement element, final String requestingBeanName) {
+		TargetSource ts = new TargetSource() {
+			@Override
+			public Class<?> getTargetClass() {
+				return element.lookupType;
+			}
+			@Override
+			public boolean isStatic() {
+				return false;
+			}
+			@Override
+			public Object getTarget() {
+				return getResource(element, requestingBeanName);
+			}
+			@Override
+			public void releaseTarget(Object target) {
+			}
+		};
+		ProxyFactory pf = new ProxyFactory();
+		pf.setTargetSource(ts);
+		if (element.lookupType.isInterface()) {
+			pf.addInterface(element.lookupType);
+		}
+		ClassLoader classLoader = (this.beanFactory instanceof ConfigurableBeanFactory ?
+				((ConfigurableBeanFactory) this.beanFactory).getBeanClassLoader() : null);
+		return pf.getProxy(classLoader);
+	}
+
 	/**
 	 * Obtain the resource object for the given name and type.
 	 * @param element the descriptor for the annotated field/method
@@ -527,6 +567,8 @@ public class CommonAnnotationBeanPostProcessor extends InitDestroyAnnotationBean
 	 */
 	private class ResourceElement extends LookupElement {
 
+		private final boolean lazyLookup;
+
 		public ResourceElement(Member member, AnnotatedElement ae, PropertyDescriptor pd) {
 			super(member, pd);
 			Resource resource = ae.getAnnotation(Resource.class);
@@ -552,11 +594,14 @@ public class CommonAnnotationBeanPostProcessor extends InitDestroyAnnotationBean
 			this.name = resourceName;
 			this.lookupType = resourceType;
 			this.mappedName = resource.mappedName();
+			Lazy lazy = ae.getAnnotation(Lazy.class);
+			this.lazyLookup = (lazy != null && lazy.value());
 		}
 
 		@Override
 		protected Object getResourceToInject(Object target, String requestingBeanName) {
-			return getResource(this, requestingBeanName);
+			return (this.lazyLookup ? buildLazyResourceProxy(this, requestingBeanName) :
+					getResource(this, requestingBeanName));
 		}
 	}
 

spring-context/src/test/java/org/springframework/context/annotation/CommonAnnotationBeanPostProcessorTests.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2014 the original author or authors.
+ * Copyright 2002-2015 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.
@@ -437,6 +437,60 @@ public class CommonAnnotationBeanPostProcessorTests {
 		assertTrue(bean.destroy2Called);
 	}
 
+	@Test
+	public void testLazyResolutionWithResourceField() {
+		DefaultListableBeanFactory bf = new DefaultListableBeanFactory();
+		CommonAnnotationBeanPostProcessor bpp = new CommonAnnotationBeanPostProcessor();
+		bpp.setBeanFactory(bf);
+		bf.addBeanPostProcessor(bpp);
+
+		bf.registerBeanDefinition("annotatedBean", new RootBeanDefinition(LazyResourceFieldInjectionBean.class));
+		bf.registerBeanDefinition("testBean", new RootBeanDefinition(TestBean.class));
+
+		LazyResourceFieldInjectionBean bean = (LazyResourceFieldInjectionBean) bf.getBean("annotatedBean");
+		assertFalse(bf.containsSingleton("testBean"));
+		bean.testBean.setName("notLazyAnymore");
+		assertTrue(bf.containsSingleton("testBean"));
+		TestBean tb = (TestBean) bf.getBean("testBean");
+		assertEquals("notLazyAnymore", tb.getName());
+	}
+
+	@Test
+	public void testLazyResolutionWithResourceMethod() {
+		DefaultListableBeanFactory bf = new DefaultListableBeanFactory();
+		CommonAnnotationBeanPostProcessor bpp = new CommonAnnotationBeanPostProcessor();
+		bpp.setBeanFactory(bf);
+		bf.addBeanPostProcessor(bpp);
+
+		bf.registerBeanDefinition("annotatedBean", new RootBeanDefinition(LazyResourceMethodInjectionBean.class));
+		bf.registerBeanDefinition("testBean", new RootBeanDefinition(TestBean.class));
+
+		LazyResourceMethodInjectionBean bean = (LazyResourceMethodInjectionBean) bf.getBean("annotatedBean");
+		assertFalse(bf.containsSingleton("testBean"));
+		bean.testBean.setName("notLazyAnymore");
+		assertTrue(bf.containsSingleton("testBean"));
+		TestBean tb = (TestBean) bf.getBean("testBean");
+		assertEquals("notLazyAnymore", tb.getName());
+	}
+
+	@Test
+	public void testLazyResolutionWithCglibProxy() {
+		DefaultListableBeanFactory bf = new DefaultListableBeanFactory();
+		CommonAnnotationBeanPostProcessor bpp = new CommonAnnotationBeanPostProcessor();
+		bpp.setBeanFactory(bf);
+		bf.addBeanPostProcessor(bpp);
+
+		bf.registerBeanDefinition("annotatedBean", new RootBeanDefinition(LazyResourceCglibInjectionBean.class));
+		bf.registerBeanDefinition("testBean", new RootBeanDefinition(TestBean.class));
+
+		LazyResourceCglibInjectionBean bean = (LazyResourceCglibInjectionBean) bf.getBean("annotatedBean");
+		assertFalse(bf.containsSingleton("testBean"));
+		bean.testBean.setName("notLazyAnymore");
+		assertTrue(bf.containsSingleton("testBean"));
+		TestBean tb = (TestBean) bf.getBean("testBean");
+		assertEquals("notLazyAnymore", tb.getName());
+	}
+
 
 	public static class AnnotatedInitDestroyBean {
 
@@ -716,6 +770,35 @@ public class CommonAnnotationBeanPostProcessorTests {
 	}
 
 
+	private static class LazyResourceFieldInjectionBean {
+
+		@Resource @Lazy
+		private ITestBean testBean;
+	}
+
+
+	private static class LazyResourceMethodInjectionBean {
+
+		private ITestBean testBean;
+
+		@Resource @Lazy
+		public void setTestBean(ITestBean testBean) {
+			this.testBean = testBean;
+		}
+	}
+
+
+	private static class LazyResourceCglibInjectionBean {
+
+		private TestBean testBean;
+
+		@Resource @Lazy
+		public void setTestBean(TestBean testBean) {
+			this.testBean = testBean;
+		}
+	}
+
+
 	@SuppressWarnings("unused")
 	private static class NullFactory {