Deprecate Properties as bean for int global props

Having a bean as a `java.util.Properties` is not confusing
and may lead to some conflicts in the real application.
Plus it is not so easy to configure: need to know all
the possible integration properties - bad end-user experience

* Make an `IntegrationProperties` as a public POJO
for easy configuration of global properties
* Deprecate a presence of the `java.util.Properties`
* Leave framework-created `integrationGlobalProperties` as
a `Properties` instance for backward compatibility
* Fix tests to expose an `IntegrationProperties` bean instead
of deprecated `Properties`
* Fix docs according the change and current recommendations

Author: artembilan

spring-integration-core/src/main/java/org/springframework/integration/config/DefaultConfiguringBeanFactoryPostProcessor.java

@@ -19,10 +19,7 @@
 import java.io.IOException;
 import java.io.PrintWriter;
 import java.io.StringWriter;
-import java.util.Arrays;
 import java.util.HashSet;
-import java.util.LinkedList;
-import java.util.List;
 import java.util.Properties;
 import java.util.Set;
 import java.util.concurrent.ThreadPoolExecutor.CallerRunsPolicy;
@@ -328,17 +325,15 @@ private void registerIntegrationProperties() {
 		if (!this.beanFactory.containsBean(IntegrationContextUtils.INTEGRATION_GLOBAL_PROPERTIES_BEAN_NAME)) {
 			ResourcePatternResolver resourceResolver = new PathMatchingResourcePatternResolver(this.classLoader);
 			try {
-				Resource[] defaultResources =
-						resourceResolver.getResources("classpath*:META-INF/spring.integration.default.properties");
-				Resource[] userResources =
+				Resource[] resources =
 						resourceResolver.getResources("classpath*:META-INF/spring.integration.properties");
 
-				List<Resource> resources = new LinkedList<>(Arrays.asList(defaultResources));
-				resources.addAll(Arrays.asList(userResources));
-
+				// TODO Revise in favor of 'IntegrationProperties' instance in the next 6.0 version
 				BeanDefinitionBuilder integrationPropertiesBuilder = BeanDefinitionBuilder
 						.genericBeanDefinition(PropertiesFactoryBean.class)
-						.addPropertyValue("locations", resources);
+						.addPropertyValue("properties", IntegrationProperties.defaults())
+						.addPropertyValue("locations", resources)
+						.setRole(BeanDefinition.ROLE_INFRASTRUCTURE);
 
 				this.registry.registerBeanDefinition(IntegrationContextUtils.INTEGRATION_GLOBAL_PROPERTIES_BEAN_NAME,
 						integrationPropertiesBuilder.getBeanDefinition());

spring-integration-core/src/main/java/org/springframework/integration/context/IntegrationContextUtils.java

@@ -18,7 +18,12 @@
 
 import java.util.Properties;
 
+import org.apache.commons.logging.Log;
+import org.apache.commons.logging.LogFactory;
+import org.jetbrains.annotations.Nullable;
+
 import org.springframework.beans.factory.BeanFactory;
+import org.springframework.beans.factory.BeanNotOfRequiredTypeException;
 import org.springframework.beans.factory.NoSuchBeanDefinitionException;
 import org.springframework.beans.factory.config.BeanDefinition;
 import org.springframework.beans.factory.config.ConfigurableListableBeanFactory;
@@ -110,6 +115,8 @@ public abstract class IntegrationContextUtils {
 
 	public static final String LIST_MESSAGE_HANDLER_FACTORY_BEAN_NAME = "integrationListMessageHandlerMethodFactory";
 
+	private static final Log LOGGER = LogFactory.getLog(IntegrationContextUtils.class);
+
 	/**
 	 * @param beanFactory BeanFactory for lookup, must not be null.
 	 * @return The {@link MetadataStore} bean whose name is "metadataStore".
@@ -173,15 +180,15 @@ private static <T> T getBeanOfType(BeanFactory beanFactory, String beanName, Cla
 		return beanFactory.getBean(beanName, type);
 	}
 
+	// TODO Revise in favor of 'IntegrationProperties' instance in the next 6.0 version
 	/**
 	 * @param beanFactory The bean factory.
 	 * @return the global {@link IntegrationContextUtils#INTEGRATION_GLOBAL_PROPERTIES_BEAN_NAME}
 	 *         bean from provided {@code #beanFactory}, which represents the merged
-	 *         properties values from all 'META-INF/spring.integration.default.properties'
-	 *         and 'META-INF/spring.integration.properties'.
-	 *         Or user-defined {@link Properties} bean.
+	 *         properties values from all 'META-INF/spring.integration.properties'.
+	 *         Or user-defined {@link IntegrationProperties} bean.
 	 *         May return only {@link IntegrationProperties#defaults()} if there is no
-	 *         {@link IntegrationContextUtils#INTEGRATION_GLOBAL_PROPERTIES_BEAN_NAME} bean within
+	 *         {@link IntegrationContextUtils#INTEGRATION_GLOBAL_PROPERTIES_BEAN_NAME} bean in the
 	 *         provided {@code #beanFactory} or provided {@code #beanFactory} is null.
 	 */
 	public static Properties getIntegrationProperties(BeanFactory beanFactory) {
@@ -191,8 +198,7 @@ public static Properties getIntegrationProperties(BeanFactory beanFactory) {
 			if (properties == null) {
 				Properties propertiesToRegister = new Properties();
 				propertiesToRegister.putAll(IntegrationProperties.defaults());
-				Properties userProperties =
-						getBeanOfType(beanFactory, INTEGRATION_GLOBAL_PROPERTIES_BEAN_NAME, Properties.class);
+				Properties userProperties = obtainUserProperties(beanFactory);
 				if (userProperties != null) {
 					propertiesToRegister.putAll(userProperties);
 				}
@@ -215,6 +221,32 @@ public static Properties getIntegrationProperties(BeanFactory beanFactory) {
 		return properties;
 	}
 
+	@Nullable
+	private static Properties obtainUserProperties(BeanFactory beanFactory) {
+		Object userProperties = getBeanOfType(beanFactory, INTEGRATION_GLOBAL_PROPERTIES_BEAN_NAME, Object.class);
+		if (userProperties instanceof Properties) {
+			if (BeanDefinition.ROLE_INFRASTRUCTURE !=
+					((BeanDefinitionRegistry) beanFactory)
+							.getBeanDefinition(INTEGRATION_GLOBAL_PROPERTIES_BEAN_NAME)
+							.getRole()) {
+
+				LOGGER.warn("The 'integrationGlobalProperties' bean must be declared as an instance of " +
+						"'org.springframework.integration.context.IntegrationProperties'. " +
+						"A 'java.util.Properties' support as a bean is deprecated for " +
+						"'integrationGlobalProperties' since version 5.5.");
+			}
+			return (Properties) userProperties;
+		}
+		else if (userProperties instanceof IntegrationProperties) {
+			return ((IntegrationProperties) userProperties).toProperties();
+		}
+		else if (userProperties != null) {
+			throw new BeanNotOfRequiredTypeException(INTEGRATION_GLOBAL_PROPERTIES_BEAN_NAME,
+					IntegrationProperties.class, userProperties.getClass());
+		}
+		return null;
+	}
+
 	/**
 	 * Return a {@link BeanDefinition} with the given name,
 	 * obtained from the given {@link BeanFactory} or one of its parents.

spring-integration-core/src/main/java/org/springframework/integration/context/IntegrationObjectSupport.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2020 the original author or authors.
+ * Copyright 2002-2021 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.
@@ -294,12 +294,14 @@ protected ApplicationContext getApplicationContext() {
 	/**
 	 * @see IntegrationContextUtils#getIntegrationProperties(BeanFactory)
 	 * @return The global integration properties.
+	 * @deprecated since version 5.5 in favor of {@link #getIntegrationProperty(String, Class)};
+	 * will be replaced with {@link IntegrationProperties} variant in the next major version.
 	 */
+	@Deprecated
 	protected Properties getIntegrationProperties() {
 		return this.integrationProperties;
 	}
 
-
 	protected MessageBuilderFactory getMessageBuilderFactory() {
 		if (this.messageBuilderFactory == null) {
 			this.messageBuilderFactory = new DefaultMessageBuilderFactory();