Add XML support to PropertiesPropertySourceLoader

Fixes gh-1777
Closes 1783

spring-boot/src/main/java/org/springframework/boot/env/PropertiesPropertySourceLoader.java

@@ -34,7 +34,7 @@ public class PropertiesPropertySourceLoader implements PropertySourceLoader {
 
 	@Override
 	public String[] getFileExtensions() {
-		return new String[] { "properties" };
+		return new String[] { "properties", "xml" };
 	}
 
 	@Override

spring-boot/src/test/java/org/springframework/boot/env/PropertySourcesLoaderTests.java

@@ -34,6 +34,7 @@ public class PropertySourcesLoaderTests {
 		assertTrue(this.loader.getAllFileExtensions().contains("yml"));
 		assertTrue(this.loader.getAllFileExtensions().contains("yaml"));
 		assertTrue(this.loader.getAllFileExtensions().contains("properties"));
+		assertTrue(this.loader.getAllFileExtensions().contains("xml"));
 	}
 
 }