Conditional initialization of messageConverters

Closes gh-27854

spring-webmvc/src/main/java/org/springframework/web/servlet/mvc/method/annotation/ExceptionHandlerExceptionResolver.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2021 the original author or authors.
+ * Copyright 2002-2022 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.
@@ -97,7 +97,7 @@ public class ExceptionHandlerExceptionResolver extends AbstractHandlerMethodExce
 	@Nullable
 	private HandlerMethodReturnValueHandlerComposite returnValueHandlers;
 
-	private List<HttpMessageConverter<?>> messageConverters;
+	private List<HttpMessageConverter<?>> messageConverters = new ArrayList<>();
 
 	private ContentNegotiationManager contentNegotiationManager = new ContentNegotiationManager();
 
@@ -113,22 +113,6 @@ public class ExceptionHandlerExceptionResolver extends AbstractHandlerMethodExce
 			new LinkedHashMap<>();
 
 
-	public ExceptionHandlerExceptionResolver() {
-		this.messageConverters = new ArrayList<>();
-		this.messageConverters.add(new ByteArrayHttpMessageConverter());
-		this.messageConverters.add(new StringHttpMessageConverter());
-		if(!shouldIgnoreXml) {
-			try {
-				this.messageConverters.add(new SourceHttpMessageConverter<>());
-			}
-			catch (Error err) {
-				// Ignore when no TransformerFactory implementation is available
-			}
-		}
-		this.messageConverters.add(new AllEncompassingFormHttpMessageConverter());
-	}
-
-
 	/**
 	 * Provide resolvers for custom argument types. Custom resolvers are ordered
 	 * after built-in ones. To override the built-in support for argument
@@ -214,7 +198,8 @@ public class ExceptionHandlerExceptionResolver extends AbstractHandlerMethodExce
 	 * <p>These converters are used to convert from and to HTTP requests and responses.
 	 */
 	public void setMessageConverters(List<HttpMessageConverter<?>> messageConverters) {
-		this.messageConverters = messageConverters;
+		this.messageConverters.clear();
+		this.messageConverters.addAll(messageConverters);
 	}
 
 	/**
@@ -266,6 +251,7 @@ public class ExceptionHandlerExceptionResolver extends AbstractHandlerMethodExce
 	public void afterPropertiesSet() {
 		// Do this first, it may add ResponseBodyAdvice beans
 		initExceptionHandlerAdviceCache();
+		initMessageConverters();
 
 		if (this.argumentResolvers == null) {
 			List<HandlerMethodArgumentResolver> resolvers = getDefaultArgumentResolvers();
@@ -277,6 +263,23 @@ public class ExceptionHandlerExceptionResolver extends AbstractHandlerMethodExce
 		}
 	}
 
+	private void initMessageConverters() {
+		if (!this.messageConverters.isEmpty()) {
+			return;
+		}
+		this.messageConverters.add(new ByteArrayHttpMessageConverter());
+		this.messageConverters.add(new StringHttpMessageConverter());
+		if (!shouldIgnoreXml) {
+			try {
+				this.messageConverters.add(new SourceHttpMessageConverter<>());
+			}
+			catch (Error err) {
+				// Ignore when no TransformerFactory implementation is available
+			}
+		}
+		this.messageConverters.add(new AllEncompassingFormHttpMessageConverter());
+	}
+
 	private void initExceptionHandlerAdviceCache() {
 		if (getApplicationContext() == null) {
 			return;

spring-webmvc/src/main/java/org/springframework/web/servlet/mvc/method/annotation/RequestMappingHandlerAdapter.java

@@ -158,7 +158,7 @@ public class RequestMappingHandlerAdapter extends AbstractHandlerMethodAdapter
 
 	private ContentNegotiationManager contentNegotiationManager = new ContentNegotiationManager();
 
-	private List<HttpMessageConverter<?>> messageConverters;
+	private List<HttpMessageConverter<?>> messageConverters = new ArrayList<>();
 
 	private final List<Object> requestResponseBodyAdvice = new ArrayList<>();
 
@@ -200,22 +200,6 @@ public class RequestMappingHandlerAdapter extends AbstractHandlerMethodAdapter
 	private final Map<ControllerAdviceBean, Set<Method>> modelAttributeAdviceCache = new LinkedHashMap<>();
 
 
-	public RequestMappingHandlerAdapter() {
-		this.messageConverters = new ArrayList<>(4);
-		this.messageConverters.add(new ByteArrayHttpMessageConverter());
-		this.messageConverters.add(new StringHttpMessageConverter());
-		if (!shouldIgnoreXml) {
-			try {
-				this.messageConverters.add(new SourceHttpMessageConverter<>());
-			}
-			catch (Error err) {
-				// Ignore when no TransformerFactory implementation is available
-			}
-		}
-		this.messageConverters.add(new AllEncompassingFormHttpMessageConverter());
-	}
-
-
 	/**
 	 * Provide resolvers for custom argument types. Custom resolvers are ordered
 	 * after built-in ones. To override the built-in support for argument
@@ -358,7 +342,8 @@ public class RequestMappingHandlerAdapter extends AbstractHandlerMethodAdapter
 	 * request and response.
 	 */
 	public void setMessageConverters(List<HttpMessageConverter<?>> messageConverters) {
-		this.messageConverters = messageConverters;
+		this.messageConverters.clear();
+		this.messageConverters.addAll(messageConverters);
 	}
 
 	/**
@@ -569,6 +554,7 @@ public class RequestMappingHandlerAdapter extends AbstractHandlerMethodAdapter
 	public void afterPropertiesSet() {
 		// Do this first, it may add ResponseBody advice beans
 		initControllerAdviceCache();
+		initMessageConverters();
 
 		if (this.argumentResolvers == null) {
 			List<HandlerMethodArgumentResolver> resolvers = getDefaultArgumentResolvers();
@@ -584,6 +570,23 @@ public class RequestMappingHandlerAdapter extends AbstractHandlerMethodAdapter
 		}
 	}
 
+	private void initMessageConverters() {
+		if (!this.messageConverters.isEmpty()) {
+			return;
+		}
+		this.messageConverters.add(new ByteArrayHttpMessageConverter());
+		this.messageConverters.add(new StringHttpMessageConverter());
+		if (!shouldIgnoreXml) {
+			try {
+				this.messageConverters.add(new SourceHttpMessageConverter<>());
+			}
+			catch (Error err) {
+				// Ignore when no TransformerFactory implementation is available
+			}
+		}
+		this.messageConverters.add(new AllEncompassingFormHttpMessageConverter());
+	}
+
 	private void initControllerAdviceCache() {
 		if (getApplicationContext() == null) {
 			return;