Because the default encoding for ResiurceBunldeMessageSource is ISO-8859-1,so you should define the defaultEncoding to UTF-8

ResourceBundleMessageSource.java

(stream != null) {
					String encoding = getDefaultEncoding();
					if (encoding == null) {
						encoding = "ISO-8859-1";
					}
					try {
						return loadBundle(new InputStreamReader(stream, encoding));
					}
					finally {
						stream.close();
					}
				}
				else {