Merge branch '5.2.x'

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

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2015 the original author or authors.
+ * Copyright 2002-2020 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.
@@ -41,12 +41,11 @@ import java.lang.annotation.Target;
  * regular constructors: i.e. lookup methods cannot get replaced on beans returned
  * from factory methods where we cannot dynamically provide a subclass for them.
  *
- * <p><b>Concrete limitations in typical Spring configuration scenarios:</b>
- * When used with component scanning or any other mechanism that filters out abstract
- * beans, provide stub implementations of your lookup methods to be able to declare
- * them as concrete classes. And please remember that lookup methods won't work on
- * beans returned from {@code @Bean} methods in configuration classes; you'll have
- * to resort to {@code @Inject Provider<TargetBean>} or the like instead.
+ * <p><b>Recommendations for typical Spring configuration scenarios:</b>
+ * When a concrete class may be needed in certain scenarios, consider providing stub
+ * implementations of your lookup methods. And please remember that lookup methods
+ * won't work on beans returned from {@code @Bean} methods in configuration classes;
+ * you'll have to resort to {@code @Inject Provider<TargetBean>} or the like instead.
  *
  * @author Juergen Hoeller
  * @since 4.1

spring-context/src/main/java/org/springframework/context/expression/StandardBeanExpressionResolver.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2018 the original author or authors.
+ * Copyright 2002-2020 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.
@@ -41,8 +41,13 @@ import org.springframework.util.StringUtils;
  * {@link org.springframework.beans.factory.config.BeanExpressionResolver}
  * interface, parsing and evaluating Spring EL using Spring's expression module.
  *
+ * <p>All beans in the containing {@code BeanFactory} are made available as
+ * predefined variables with their common bean name, including standard context
+ * beans such as "environment", "systemProperties" and "systemEnvironment".
+ *
  * @author Juergen Hoeller
  * @since 3.0
+ * @see BeanExpressionContext#getBeanFactory()
  * @see org.springframework.expression.ExpressionParser
  * @see org.springframework.expression.spel.standard.SpelExpressionParser
  * @see org.springframework.expression.spel.support.StandardEvaluationContext

spring-context/src/main/java/org/springframework/context/support/AbstractRefreshableApplicationContext.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2018 the original author or authors.
+ * Copyright 2002-2020 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.
@@ -72,10 +72,7 @@ public abstract class AbstractRefreshableApplicationContext extends AbstractAppl
 
 	/** Bean factory for this context. */
 	@Nullable
-	private DefaultListableBeanFactory beanFactory;
-
-	/** Synchronization monitor for the internal BeanFactory. */
-	private final Object beanFactoryMonitor = new Object();
+	private volatile DefaultListableBeanFactory beanFactory;
 
 
 	/**
@@ -131,10 +128,8 @@ public abstract class AbstractRefreshableApplicationContext extends AbstractAppl
 			beanFactory.setSerializationId(getId());
 			customizeBeanFactory(beanFactory);
 			loadBeanDefinitions(beanFactory);
-			synchronized (this.beanFactoryMonitor) {
 			this.beanFactory = beanFactory;
 		}
-		}
 		catch (IOException ex) {
 			throw new ApplicationContextException("I/O error parsing bean definition source for " + getDisplayName(), ex);
 		}
@@ -142,43 +137,38 @@ public abstract class AbstractRefreshableApplicationContext extends AbstractAppl
 
 	@Override
 	protected void cancelRefresh(BeansException ex) {
-		synchronized (this.beanFactoryMonitor) {
-			if (this.beanFactory != null) {
-				this.beanFactory.setSerializationId(null);
-			}
+		DefaultListableBeanFactory beanFactory = this.beanFactory;
+		if (beanFactory != null) {
+			beanFactory.setSerializationId(null);
 		}
 		super.cancelRefresh(ex);
 	}
 
 	@Override
 	protected final void closeBeanFactory() {
-		synchronized (this.beanFactoryMonitor) {
-			if (this.beanFactory != null) {
-				this.beanFactory.setSerializationId(null);
+		DefaultListableBeanFactory beanFactory = this.beanFactory;
+		if (beanFactory != null) {
+			beanFactory.setSerializationId(null);
 			this.beanFactory = null;
 		}
 	}
-	}
 
 	/**
 	 * Determine whether this context currently holds a bean factory,
 	 * i.e. has been refreshed at least once and not been closed yet.
 	 */
 	protected final boolean hasBeanFactory() {
-		synchronized (this.beanFactoryMonitor) {
 		return (this.beanFactory != null);
 	}
-	}
 
 	@Override
 	public final ConfigurableListableBeanFactory getBeanFactory() {
-		synchronized (this.beanFactoryMonitor) {
-			if (this.beanFactory == null) {
+		DefaultListableBeanFactory beanFactory = this.beanFactory;
+		if (beanFactory == null) {
 			throw new IllegalStateException("BeanFactory not initialized or already closed - " +
 					"call 'refresh' before accessing beans via the ApplicationContext");
 		}
-			return this.beanFactory;
-		}
+		return beanFactory;
 	}
 
 	/**

spring-messaging/src/main/java/org/springframework/messaging/support/AbstractMessageChannel.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2019 the original author or authors.
+ * Copyright 2002-2020 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.
@@ -87,17 +87,20 @@ public abstract class AbstractMessageChannel implements MessageChannel, Intercep
 
 	@Override
 	public void setInterceptors(List<ChannelInterceptor> interceptors) {
+		Assert.noNullElements(interceptors, "'interceptors' must not contain null elements");
 		this.interceptors.clear();
 		this.interceptors.addAll(interceptors);
 	}
 
 	@Override
 	public void addInterceptor(ChannelInterceptor interceptor) {
+		Assert.notNull(interceptor, "'interceptor' must not be null");
 		this.interceptors.add(interceptor);
 	}
 
 	@Override
 	public void addInterceptor(int index, ChannelInterceptor interceptor) {
+		Assert.notNull(interceptor, "'interceptor' must not be null");
 		this.interceptors.add(index, interceptor);
 	}
 

spring-web/src/main/java/org/springframework/http/client/support/InterceptingHttpAccessor.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2019 the original author or authors.
+ * Copyright 2002-2020 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.
@@ -24,6 +24,7 @@ import org.springframework.http.client.ClientHttpRequestFactory;
 import org.springframework.http.client.ClientHttpRequestInterceptor;
 import org.springframework.http.client.InterceptingClientHttpRequestFactory;
 import org.springframework.lang.Nullable;
+import org.springframework.util.Assert;
 import org.springframework.util.CollectionUtils;
 
 /**
@@ -57,6 +58,7 @@ public abstract class InterceptingHttpAccessor extends HttpAccessor {
 	 * @see AnnotationAwareOrderComparator
 	 */
 	public void setInterceptors(List<ClientHttpRequestInterceptor> interceptors) {
+		Assert.noNullElements(interceptors, "'interceptors' must not contain null elements");
 		// Take getInterceptors() List as-is when passed in here
 		if (this.interceptors != interceptors) {
 			this.interceptors.clear();

src/docs/asciidoc/core/core-expressions.adoc

@@ -539,8 +539,12 @@ example shows:
 	</bean>
 ----
 
-The `systemProperties` variable is predefined, so you can use it in your expressions, as
-the following example shows:
+All beans in the application context are available as predefined variables with their
+common bean name. This includes standard context beans such as `environment` (of type
+`org.springframework.core.env.Environment`) as well as `systemProperties` and
+`systemEnvironment` (of type `Map<String, Object>`) for access to the runtime environment.
+
+The following example shows access to the `systemProperties` bean as a SpEL variable:
 
 [source,xml,indent=0,subs="verbatim"]
 ----
@@ -551,8 +555,7 @@ the following example shows:
 	</bean>
 ----
 
-Note that you do not have to prefix the predefined variable with the `#`
-symbol in this context.
+Note that you do not have to prefix the predefined variable with the `#` symbol here.
 
 You can also refer to other bean properties by name, as the following example shows:
 
@@ -576,8 +579,8 @@ You can also refer to other bean properties by name, as the following example sh
 [[expressions-beandef-annotation-based]]
 === Annotation Configuration
 
-To specify a default value, you can place the `@Value` annotation on fields, methods, and method or constructor
-parameters.
+To specify a default value, you can place the `@Value` annotation on fields, methods,
+and method or constructor parameters.
 
 The following example sets the default value of a field variable:
 
@@ -1675,7 +1678,7 @@ The following example shows how to use the Elvis operator:
 ----
 	ExpressionParser parser = new SpelExpressionParser();
 
-	String name = parser.parseExpression("name?:'Unknown'").getValue(String.class);
+	String name = parser.parseExpression("name?:'Unknown'").getValue(new Inventor(), String.class);
 	System.out.println(name);  // 'Unknown'
 ----
 [source,kotlin,indent=0,subs="verbatim,quotes",role="secondary"]
@@ -1683,7 +1686,7 @@ The following example shows how to use the Elvis operator:
 ----
 	val parser = SpelExpressionParser()
 
-	val name = parser.parseExpression("name?:'Unknown'").getValue(String::class.java)
+	val name = parser.parseExpression("name?:'Unknown'").getValue(Inventor(), String::class.java)
 	println(name)  // 'Unknown'
 ----