Add test and fix bug in MessageConverters

spring-boot-autoconfigure/src/main/java/org/springframework/boot/autoconfigure/web/MessageConverters.java

@@ -19,6 +19,7 @@ package org.springframework.boot.autoconfigure.web;
 import java.util.ArrayList;
 import java.util.Collection;
 import java.util.Collections;
+import java.util.LinkedHashSet;
 import java.util.List;
 
 import org.springframework.http.converter.HttpMessageConverter;
@@ -54,23 +55,27 @@ public class MessageConverters {
 		if (this.converters == null) {
 			synchronized (this.lock) {
 				if (this.converters == null) {
-					this.converters = new ArrayList<HttpMessageConverter<?>>();
 					getDefaultMessageConverters(); // ensure they are available
+					Collection<HttpMessageConverter<?>> fallbacks = new LinkedHashSet<HttpMessageConverter<?>>();
 					for (HttpMessageConverter<?> fallback : this.defaults) {
 						boolean overridden = false;
 						for (HttpMessageConverter<?> converter : this.overrides) {
 							if (fallback.getClass()
 									.isAssignableFrom(converter.getClass())) {
-								if (!this.converters.contains(converter)) {
-									this.converters.add(converter);
+								if (!fallbacks.contains(converter)) {
+									fallbacks.add(converter);
 									overridden = true;
 								}
 							}
 						}
 						if (!overridden) {
-							this.converters.add(fallback);
+							fallbacks.add(fallback);
 						}
 					}
+					Collection<HttpMessageConverter<?>> converters = new LinkedHashSet<HttpMessageConverter<?>>(
+							this.overrides);
+					converters.addAll(fallbacks);
+					this.converters = new ArrayList<HttpMessageConverter<?>>(converters);
 				}
 			}
 		}

spring-boot-autoconfigure/src/test/java/org/springframework/boot/autoconfigure/web/MessageConvertersTests.java

@@ -0,0 +1,58 @@
+/*
+ * Copyright 2012-2013 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.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.springframework.boot.autoconfigure.web;
+
+import java.util.Arrays;
+
+import org.junit.Test;
+import org.mockito.Mockito;
+import org.springframework.http.converter.HttpMessageConverter;
+import org.springframework.http.converter.json.MappingJackson2HttpMessageConverter;
+
+import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.assertFalse;
+import static org.junit.Assert.assertTrue;
+
+/**
+ * @author Dave Syer
+ */
+public class MessageConvertersTests {
+
+	@Test
+	public void defaultsCreated() {
+		MessageConverters messageConverters = new MessageConverters();
+		assertFalse(messageConverters.getDefaultMessageConverters().isEmpty());
+	}
+
+	@Test
+	public void overrideExistingConverter() {
+		MappingJackson2HttpMessageConverter converter = new MappingJackson2HttpMessageConverter();
+		MessageConverters messageConverters = new MessageConverters(
+				Arrays.<HttpMessageConverter<?>> asList(converter));
+		assertTrue(messageConverters.getMessageConverters().contains(converter));
+	}
+
+	@Test
+	public void addNewOne() {
+		HttpMessageConverter<?> converter = Mockito.mock(HttpMessageConverter.class);
+		MessageConverters messageConverters = new MessageConverters(
+				Arrays.<HttpMessageConverter<?>> asList(converter));
+		assertTrue(messageConverters.getMessageConverters().contains(converter));
+		assertEquals(converter, messageConverters.getMessageConverters().get(0));
+	}
+
+}