Support XML properties in ResourcePropertySource

JDK 5 introduced an XML-based properties file syntax. This commit
ensures that when such files are supplied as the underlying resource
for a ResourcePropertySource instance, they are routed appropriately
to Properties#loadFromXML as opposed to Properties#load.

Issue: SPR-9896

spring-core/src/main/java/org/springframework/core/io/support/ResourcePropertySource.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2011 the original author or authors.
+ * Copyright 2002-2013 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.
@@ -28,7 +28,11 @@ import org.springframework.util.StringUtils;
 /**
  * Subclass of {@link PropertiesPropertySource} that loads a {@link Properties}
  * object from a given {@link org.springframework.core.io.Resource} or resource location such as
- * {@code "classpath:/com/myco/foo.properties"} or {@code "file:/path/to/file.properties"}.
+ * {@code "classpath:/com/myco/foo.properties"} or {@code "file:/path/to/file.xml"}.
+ * Both traditional and XML-based properties file formats are supported, however in order
+ * for XML processing to take effect, the underlying {@code Resource}'s
+ * {@link org.springframework.core.io.Resource#getFilename() getFilename()} method must
+ * return non-{@code null} and end in ".xml".
  *
  * @author Chris Beams
  * @since 3.1
@@ -99,7 +103,13 @@ public class ResourcePropertySource extends PropertiesPropertySource {
 	private static Properties loadPropertiesForResource(Resource resource) throws IOException {
 		Properties props = new Properties();
 		InputStream is = resource.getInputStream();
-		props.load(is);
+		String filename = resource.getFilename();
+		if (filename != null && filename.endsWith(".xml")) {
+			props.loadFromXML(is);
+		}
+		else {
+			props.load(is);
+		}
 		try {
 			is.close();
 		} catch (IOException ex) {

spring-core/src/test/java/org/springframework/core/io/example.xml

@@ -0,0 +1,6 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<!DOCTYPE properties SYSTEM "http://java.sun.com/dtd/properties.dtd">
+<properties version="1.0">
+	<entry key="foo">bar</entry>
+</properties>
+

spring-core/src/test/java/org/springframework/core/io/support/ResourcePropertySourceTests.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2011 the original author or authors.
+ * Copyright 2002-2013 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.
@@ -39,6 +39,10 @@ public class ResourcePropertySourceTests {
 	private static final String PROPERTIES_LOCATION = "classpath:" + PROPERTIES_PATH;
 	private static final String PROPERTIES_RESOURCE_DESCRIPTION = "class path resource [" + PROPERTIES_PATH + "]";
 
+	private static final String XML_PROPERTIES_PATH = "org/springframework/core/io/example.xml";
+	private static final String XML_PROPERTIES_LOCATION = "classpath:" + XML_PROPERTIES_PATH;
+	private static final String XML_PROPERTIES_RESOURCE_DESCRIPTION = "class path resource [" + XML_PROPERTIES_PATH + "]";
+
 	@Test
 	public void withLocationAndGeneratedName() throws IOException {
 		PropertySource<?> ps = new ResourcePropertySource(PROPERTIES_LOCATION);
@@ -46,6 +50,13 @@ public class ResourcePropertySourceTests {
 		assertThat(ps.getName(), is(PROPERTIES_RESOURCE_DESCRIPTION));
 	}
 
+	@Test
+	public void xmlWithLocationAndGeneratedName() throws IOException {
+		PropertySource<?> ps = new ResourcePropertySource(XML_PROPERTIES_LOCATION);
+		assertEquals(ps.getProperty("foo"), "bar");
+		assertThat(ps.getName(), is(XML_PROPERTIES_RESOURCE_DESCRIPTION));
+	}
+
 	@Test
 	public void withLocationAndExplicitName() throws IOException {
 		PropertySource<?> ps = new ResourcePropertySource("ps1", PROPERTIES_LOCATION);