Fix binding to bean with cloned arrays

Fixes gh-12478

spring-boot-project/spring-boot/src/main/java/org/springframework/boot/context/properties/bind/AggregateBinder.java

@@ -57,10 +57,10 @@ abstract class AggregateBinder<T> {
 			AggregateElementBinder elementBinder) {
 		Object result = bindAggregate(name, target, elementBinder);
 		Supplier<?> value = target.getValue();
-		if (result == null || value == null || value.get() == null) {
+		if (result == null || value == null) {
 			return result;
 		}
-		return merge((T) value.get(), (T) result);
+		return merge(value, (T) result);
 	}
 
 	/**
@@ -75,11 +75,11 @@ abstract class AggregateBinder<T> {
 
 	/**
 	 * Merge any additional elements into the existing aggregate.
-	 * @param existing the existing value
+	 * @param existing the supplier for the existing value
 	 * @param additional the additional elements to merge
 	 * @return the merged result
 	 */
-	protected abstract T merge(T existing, T additional);
+	protected abstract T merge(Supplier<?> existing, T additional);
 
 	/**
 	 * Return the context being used by this binder.

spring-boot-project/spring-boot/src/main/java/org/springframework/boot/context/properties/bind/ArrayBinder.java

@@ -19,6 +19,7 @@ package org.springframework.boot.context.properties.bind;
 import java.lang.reflect.Array;
 import java.util.ArrayList;
 import java.util.List;
+import java.util.function.Supplier;
 
 import org.springframework.boot.context.properties.bind.Binder.Context;
 import org.springframework.boot.context.properties.source.ConfigurationPropertyName;
@@ -55,7 +56,7 @@ class ArrayBinder extends IndexedElementsBinder<Object> {
 	}
 
 	@Override
-	protected Object merge(Object existing, Object additional) {
+	protected Object merge(Supplier<?> existing, Object additional) {
 		return additional;
 	}
 

spring-boot-project/spring-boot/src/main/java/org/springframework/boot/context/properties/bind/CollectionBinder.java

@@ -18,6 +18,7 @@ package org.springframework.boot.context.properties.bind;
 
 import java.util.Collection;
 import java.util.List;
+import java.util.function.Supplier;
 
 import org.springframework.boot.context.properties.bind.Binder.Context;
 import org.springframework.boot.context.properties.source.ConfigurationPropertyName;
@@ -54,12 +55,17 @@ class CollectionBinder extends IndexedElementsBinder<Collection<Object>> {
 	}
 
 	@Override
-	protected Collection<Object> merge(Collection<Object> existing,
+	@SuppressWarnings("unchecked")
+	protected Collection<Object> merge(Supplier<?> existing,
 			Collection<Object> additional) {
+		Collection<Object> existingCollection = (Collection<Object>) existing.get();
+		if (existingCollection == null) {
+			return additional;
+		}
 		try {
-			existing.clear();
-			existing.addAll(additional);
-			return existing;
+			existingCollection.clear();
+			existingCollection.addAll(additional);
+			return existingCollection;
 		}
 		catch (UnsupportedOperationException ex) {
 			return createNewCollection(additional);

spring-boot-project/spring-boot/src/main/java/org/springframework/boot/context/properties/bind/MapBinder.java

@@ -19,6 +19,7 @@ package org.springframework.boot.context.properties.bind;
 import java.util.Collection;
 import java.util.Map;
 import java.util.Properties;
+import java.util.function.Supplier;
 
 import org.springframework.boot.context.properties.bind.Binder.Context;
 import org.springframework.boot.context.properties.source.ConfigurationProperty;
@@ -82,10 +83,15 @@ class MapBinder extends AggregateBinder<Map<Object, Object>> {
 	}
 
 	@Override
-	protected Map<Object, Object> merge(Map<Object, Object> existing,
+	@SuppressWarnings("unchecked")
+	protected Map<Object, Object> merge(Supplier<?> existing,
 			Map<Object, Object> additional) {
-		existing.putAll(additional);
-		return existing;
+		Map<Object, Object> existingMap = (Map<Object, Object>) existing.get();
+		if (existingMap == null) {
+			return additional;
+		}
+		existingMap.putAll(additional);
+		return existingMap;
 	}
 
 	private class EntryBinder {

spring-boot-project/spring-boot/src/test/java/org/springframework/boot/context/properties/bind/CollectionBinderTests.java

@@ -384,6 +384,17 @@ public class CollectionBinderTests {
 		this.binder.bind("foo", target);
 	}
 
+	@Test
+	public void bindToBeanWithClonedArray() {
+		MockConfigurationPropertySource source = new MockConfigurationPropertySource();
+		source.put("foo.bar[0]", "hello");
+		this.sources.add(source);
+		Bindable<ClonedArrayBean> target = Bindable
+				.of(ClonedArrayBean.class);
+		ClonedArrayBean bean = this.binder.bind("foo", target).get();
+		assertThat(bean.getBar()).contains("hello");
+	}
+
 	public static class ExampleCollectionBean {
 
 		private List<String> items = new ArrayList<>();
@@ -457,4 +468,19 @@ public class CollectionBinderTests {
 		}
 	}
 
+
+	public static class ClonedArrayBean {
+
+		private String[] bar;
+
+		public String[] getBar() {
+			return this.bar.clone();
+		}
+
+		public void setBar(String[] bar) {
+			this.bar = bar;
+		}
+
+	}
+
 }