Avoid String concatenation for lookup in StaticMessageSource

Closes gh-22451

spring-context/src/main/java/org/springframework/context/support/StaticMessageSource.java

 /*
- * Copyright 2002-2018 the original author or authors.
+ * Copyright 2002-2019 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.
@@ -36,33 +36,35 @@ import org.springframework.util.Assert;
  */
 public class StaticMessageSource extends AbstractMessageSource {
 
-	/** Map from 'code + locale' keys to message Strings. */
-	private final Map<String, String> messages = new HashMap<>();
-
-	private final Map<String, MessageFormat> cachedMessageFormats = new HashMap<>();
+	private final Map<String, Map<Locale, MessageHolder>> messageMap = new HashMap<>();
 
 
 	@Override
+	@Nullable
 	protected String resolveCodeWithoutArguments(String code, Locale locale) {
-		return this.messages.get(code + '_' + locale.toString());
+		Map<Locale, MessageHolder> localeMap = this.messageMap.get(code);
+		if (localeMap == null) {
+			return null;
+		}
+		MessageHolder holder = localeMap.get(locale);
+		if (holder == null) {
+			return null;
+		}
+		return holder.getMessage();
 	}
 
 	@Override
 	@Nullable
 	protected MessageFormat resolveCode(String code, Locale locale) {
-		String key = code + '_' + locale.toString();
-		String msg = this.messages.get(key);
-		if (msg == null) {
+		Map<Locale, MessageHolder> localeMap = this.messageMap.get(code);
+		if (localeMap == null) {
 			return null;
 		}
-		synchronized (this.cachedMessageFormats) {
-			MessageFormat messageFormat = this.cachedMessageFormats.get(key);
-			if (messageFormat == null) {
-				messageFormat = createMessageFormat(msg, locale);
-				this.cachedMessageFormats.put(key, messageFormat);
-			}
-			return messageFormat;
+		MessageHolder holder = localeMap.get(locale);
+		if (holder == null) {
+			return null;
 		}
+		return holder.getMessageFormat();
 	}
 
 	/**
@@ -75,7 +77,7 @@ public class StaticMessageSource extends AbstractMessageSource {
 		Assert.notNull(code, "Code must not be null");
 		Assert.notNull(locale, "Locale must not be null");
 		Assert.notNull(msg, "Message must not be null");
-		this.messages.put(code + '_' + locale.toString(), msg);
+		this.messageMap.computeIfAbsent(code, key -> new HashMap<>(4)).put(locale, new MessageHolder(msg, locale));
 		if (logger.isDebugEnabled()) {
 			logger.debug("Added message [" + msg + "] for code [" + code + "] and Locale [" + locale + "]");
 		}
@@ -95,7 +97,41 @@ public class StaticMessageSource extends AbstractMessageSource {
 
 	@Override
 	public String toString() {
-		return getClass().getName() + ": " + this.messages;
+		return getClass().getName() + ": " + this.messageMap;
+	}
+
+
+	private class MessageHolder {
+
+		private final String message;
+
+		private final Locale locale;
+
+		@Nullable
+		private volatile MessageFormat cachedFormat;
+
+		public MessageHolder(String message, Locale locale) {
+			this.message = message;
+			this.locale = locale;
+		}
+
+		public String getMessage() {
+			return this.message;
+		}
+
+		public MessageFormat getMessageFormat() {
+			MessageFormat messageFormat = this.cachedFormat;
+			if (messageFormat == null) {
+				messageFormat = createMessageFormat(this.message, this.locale);
+				this.cachedFormat = messageFormat;
+			}
+			return messageFormat;
+		}
+
+		@Override
+		public String toString() {
+			return this.message;
+		}
 	}
 
 }

spring-context/src/test/java/org/springframework/context/support/StaticMessageSourceTests.java

@@ -59,7 +59,6 @@ public class StaticMessageSourceTests extends AbstractApplicationContextTests {
 	@Test
 	@Override
 	public void count() {
-		// These are only checked for current Ctx (not parent ctx)
 		assertCount(15);
 	}