Merge branch 'spring-projects/2.1.x'

Closes gh-17018

Author: philwebb

spring-boot-project/spring-boot/src/main/java/org/springframework/boot/context/properties/source/SpringIterableConfigurationPropertySource.java

@@ -18,6 +18,7 @@
 
 import java.util.ArrayList;
 import java.util.Collections;
+import java.util.ConcurrentModificationException;
 import java.util.HashSet;
 import java.util.Iterator;
 import java.util.List;
@@ -44,8 +45,6 @@
 class SpringIterableConfigurationPropertySource extends SpringConfigurationPropertySource
 		implements IterableConfigurationPropertySource {
 
-	private volatile Object cacheKey;
-
 	private volatile Cache cache;
 
 	SpringIterableConfigurationPropertySource(EnumerablePropertySource<?> propertySource,
@@ -131,13 +130,23 @@ private PropertyMapping[] getPropertyMappings(Cache cache) {
 	}
 
 	private Cache getCache() {
-		CacheKey cacheKey = CacheKey.get(getPropertySource());
-		if (ObjectUtils.nullSafeEquals(cacheKey, this.cacheKey)) {
-			return this.cache;
+		CacheKey key = CacheKey.get(getPropertySource());
+		if (key == null) {
+			return null;
+		}
+		Cache cache = this.cache;
+		try {
+			if (cache != null && cache.hasKeyEqualTo(key)) {
+				return cache;
+			}
+			cache = new Cache(key.copy());
+			this.cache = cache;
+			return cache;
+		}
+		catch (ConcurrentModificationException ex) {
+			// Not fatal at this point, we can continue without a cache
+			return null;
 		}
-		this.cache = new Cache();
-		this.cacheKey = cacheKey.copy();
-		return this.cache;
 	}
 
 	@Override
@@ -147,10 +156,20 @@ protected EnumerablePropertySource<?> getPropertySource() {
 
 	private static class Cache {
 
+		private final CacheKey key;
+
 		private List<ConfigurationPropertyName> names;
 
 		private PropertyMapping[] mappings;
 
+		Cache(CacheKey key) {
+			this.key = key;
+		}
+
+		public boolean hasKeyEqualTo(CacheKey key) {
+			return this.key.equals(key);
+		}
+
 		public List<ConfigurationPropertyName> getNames() {
 			return this.names;
 		}

spring-boot-project/spring-boot/src/test/java/org/springframework/boot/context/properties/source/SpringIterableConfigurationPropertySourceTests.java

@@ -16,8 +16,12 @@
 
 package org.springframework.boot.context.properties.source;
 
+import java.util.ConcurrentModificationException;
+import java.util.Iterator;
 import java.util.LinkedHashMap;
+import java.util.LinkedHashSet;
 import java.util.Map;
+import java.util.Set;
 
 import org.junit.Test;
 
@@ -169,6 +173,21 @@ public void propertySourceKeyDataChangeInvalidatesCache() {
 		assertThat(adapter.stream().count()).isEqualTo(3);
 	}
 
+	@Test
+	public void concurrentModificationExceptionInvalidatesCache() {
+		// gh-17013
+		ConcurrentModificationThrowingMap<String, Object> map = new ConcurrentModificationThrowingMap<>();
+		map.put("key1", "value1");
+		map.put("key2", "value2");
+		EnumerablePropertySource<?> source = new MapPropertySource("test", map);
+		SpringIterableConfigurationPropertySource adapter = new SpringIterableConfigurationPropertySource(
+				source, DefaultPropertyMapper.INSTANCE);
+		assertThat(adapter.stream().count()).isEqualTo(2);
+		map.setThrowException(true);
+		map.put("key3", "value3");
+		assertThat(adapter.stream().count()).isEqualTo(3);
+	}
+
 	/**
 	 * Test {@link PropertySource} that's also an {@link OriginLookup}.
 	 */
@@ -206,4 +225,37 @@ public String toString() {
 
 	}
 
+	private static class ConcurrentModificationThrowingMap<K, V>
+			extends LinkedHashMap<K, V> {
+
+		private boolean throwException;
+
+		public void setThrowException(boolean throwException) {
+			this.throwException = throwException;
+		}
+
+		@Override
+		public Set<K> keySet() {
+			return new KeySet(super.keySet());
+		}
+
+		private class KeySet extends LinkedHashSet<K> {
+
+			KeySet(Set<K> keySet) {
+				super(keySet);
+			}
+
+			@Override
+			public Iterator<K> iterator() {
+				if (ConcurrentModificationThrowingMap.this.throwException) {
+					ConcurrentModificationThrowingMap.this.throwException = false;
+					throw new ConcurrentModificationException();
+				}
+				return super.iterator();
+			}
+
+		}
+
+	}
+
 }