Add RestTemplate constructor with custom converters

Prior to this commit, RestTemplate's constructors were all initializing
default HTTPMessageConverters. Its API provides a way to replace
those converters with custom ones, but default converters are already
defined and initialized at that point, which can be an issue in some
cases (performance, classpath...).

This commits adds a new constructor for RestTemplate with a list
of message converters as argument. With this new constructor,
default message converters are never initialized.

Issue: SPR-11351

spring-web/src/main/java/org/springframework/web/client/RestTemplate.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2013 the original author or authors.
+ * Copyright 2002-2014 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.
@@ -115,6 +115,7 @@ import org.springframework.web.util.UriTemplate;
  * requestFactory} and {@link #setErrorHandler(ResponseErrorHandler) errorHandler} bean properties.
  *
  * @author Arjen Poutsma
+ * @author Brian Clozel
  * @since 3.0
  * @see HttpMessageConverter
  * @see RequestCallback
@@ -141,13 +142,14 @@ public class RestTemplate extends InterceptingHttpAccessor implements RestOperat
 
 	private final ResponseExtractor<HttpHeaders> headersExtractor = new HeadersExtractor();
 
-	private List<HttpMessageConverter<?>> messageConverters = new ArrayList<HttpMessageConverter<?>>();
+	private final List<HttpMessageConverter<?>> messageConverters = new ArrayList<HttpMessageConverter<?>>();
 
 	private ResponseErrorHandler errorHandler = new DefaultResponseErrorHandler();
 
 
 	/**
 	 * Create a new instance of the {@link RestTemplate} using default settings.
+	 * Default {@link HttpMessageConverter}s are initialized.
 	 */
 	@SuppressWarnings("deprecation")
 	public RestTemplate() {
@@ -182,6 +184,17 @@ public class RestTemplate extends InterceptingHttpAccessor implements RestOperat
 		setRequestFactory(requestFactory);
 	}
 
+	/**
+	 * Create a new instance of the {@link RestTemplate} using the given list of
+	 * {@link HttpMessageConverter} to use
+	 * @param messageConverters the list of {@link HttpMessageConverter} to use
+	 * @since 4.0.1
+	 */
+	public RestTemplate(List<HttpMessageConverter<?>> messageConverters) {
+		Assert.notEmpty(messageConverters, "'messageConverters' must not be empty");
+		this.messageConverters.addAll(messageConverters);
+	}
+
 
 	/**
 	 * Set the message body converters to use.
@@ -189,7 +202,8 @@ public class RestTemplate extends InterceptingHttpAccessor implements RestOperat
 	 */
 	public void setMessageConverters(List<HttpMessageConverter<?>> messageConverters) {
 		Assert.notEmpty(messageConverters, "'messageConverters' must not be empty");
-		this.messageConverters = messageConverters;
+		this.messageConverters.clear();
+		this.messageConverters.addAll(messageConverters);
 	}
 
 	/**

spring-web/src/test/java/org/springframework/web/client/RestTemplateTests.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2013 the original author or authors.
+ * Copyright 2002-2014 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.
@@ -68,9 +68,9 @@ public class RestTemplateTests {
 		response = mock(ClientHttpResponse.class);
 		errorHandler = mock(ResponseErrorHandler.class);
 		converter = mock(HttpMessageConverter.class);
-		template = new RestTemplate(requestFactory);
+		template = new RestTemplate(Collections.<HttpMessageConverter<?>>singletonList(converter));
+		template.setRequestFactory(requestFactory);
 		template.setErrorHandler(errorHandler);
-		template.setMessageConverters(Collections.<HttpMessageConverter<?>>singletonList(converter));
 	}
 
 	@Test