Add ProblemDetail "type" message code

See gh-30566

Author: rstoyanchev

framework-docs/modules/ROOT/pages/web/webflux/ann-rest-exceptions.adoc

@@ -71,20 +71,21 @@ from an existing `ProblemDetail`. This could be done centrally, e.g. from an
 [.small]#xref:web/webmvc/mvc-ann-rest-exceptions.adoc#mvc-ann-rest-exceptions-i18n[See equivalent in the Servlet stack]#
 
 It is a common requirement to internationalize error response details, and good practice
-to customize the problem details for Spring WebFlux exceptions. This is supported as follows:
+to customize the problem details for Spring WebFlux exceptions. This section describes the
+support for that.
 
-- Each `ErrorResponse` exposes a message code and arguments to resolve the "detail" field
-through a xref:core/beans/context-introduction.adoc#context-functionality-messagesource[MessageSource].
-The actual message code value is parameterized with placeholders, e.g.
-`+"HTTP method {0} not supported"+` to be expanded from the arguments.
-- Each `ErrorResponse` also exposes a message code to resolve the "title" field.
-- `ResponseEntityExceptionHandler` uses the message code and arguments to resolve the
-"detail" and the "title" fields.
+`ErrorResponse` exposes message codes for "type", "title", and "detail", in addition to
+message code arguments for the "detail" field. `ResponseEntityExceptionHandler` resolves
+these through a xref:core/beans/context-introduction.adoc#context-functionality-messagesource[MessageSource]
+and updates the `ProblemDetail` accordingly.
 
-By default, the message code for the "detail" field is "problemDetail." + the fully
-qualified exception class name. Some exceptions may expose additional message codes in
-which case a suffix is added to the default message code. The table below lists message
-arguments and codes for Spring WebFlux exceptions:
+The default strategy for message codes follows the pattern:
+
+`problemDetail.[type|title|detail].[fully qualified exception class name]`
+
+Some `ErrorResponse` may expose more than one message code, typically adding a suffix
+to the default message code. The table below lists message codes, and arguments for
+Spring WebFlux exceptions:
 
 [[webflux-ann-rest-exceptions-codes]]
 [cols="1,1,2", options="header"]
@@ -131,9 +132,6 @@ via `MessageSource`.
 
 |===
 
-By default, the message code for the "title" field is "problemDetail.title." + the fully
-qualified exception class name.
-
 
 
 

framework-docs/modules/ROOT/pages/web/webmvc/mvc-ann-rest-exceptions.adoc

@@ -71,20 +71,21 @@ from an existing `ProblemDetail`. This could be done centrally, e.g. from an
 [.small]#xref:web/webflux/ann-rest-exceptions.adoc#webflux-ann-rest-exceptions-i18n[See equivalent in the Reactive stack]#
 
 It is a common requirement to internationalize error response details, and good practice
-to customize the problem details for Spring MVC exceptions. This is supported as follows:
+to customize the problem details for Spring WebFlux exceptions. This section describes the
+support for that.
 
-- Each `ErrorResponse` exposes a message code and arguments to resolve the "detail" field
-through a xref:core/beans/context-introduction.adoc#context-functionality-messagesource[MessageSource].
-The actual message code value is parameterized with placeholders, e.g.
-`+"HTTP method {0} not supported"+` to be expanded from the arguments.
-- Each `ErrorResponse` also exposes a message code to resolve the "title" field.
-- `ResponseEntityExceptionHandler` uses the message code and arguments to resolve the
-"detail" and the "title" fields.
+`ErrorResponse` exposes message codes for "type", "title", and "detail", in addition to
+message code arguments for the "detail" field. `ResponseEntityExceptionHandler` resolves
+these through a xref:core/beans/context-introduction.adoc#context-functionality-messagesource[MessageSource]
+and updates the `ProblemDetail` accordingly.
 
-By default, the message code for the "detail" field is "problemDetail." + the fully
-qualified exception class name. Some exceptions may expose additional message codes in
-which case a suffix is added to the default message code. The table below lists message
-arguments and codes for Spring MVC exceptions:
+The default strategy for message codes follows the pattern:
+
+`problemDetail.[type|title|detail].[fully qualified exception class name]`
+
+Some `ErrorResponse` may expose more than one message code, typically adding a suffix
+to the default message code. The table below lists message codes, and arguments for
+Spring MVC exceptions:
 
 [[mvc-ann-rest-exceptions-codes]]
 [cols="1,1,2", options="header"]
@@ -171,8 +172,6 @@ arguments and codes for Spring MVC exceptions:
 
 |===
 
-By default, the message code for the "title" field is "problemDetail.title." + the fully
-qualified exception class name.
 
 
 

spring-web/src/main/java/org/springframework/web/ErrorResponse.java

@@ -64,6 +64,18 @@ default HttpHeaders getHeaders() {
 	 */
 	ProblemDetail getBody();
 
+	/**
+	 * Return a code to use to resolve the problem "type" for this exception
+	 * through a {@link MessageSource}. The type resolved through the
+	 * {@code MessageSource} will be passed into {@link URI#create(String)}
+	 * and therefore must be an encoded URI String.
+	 * <p>By default this is initialized via {@link #getDefaultTypeMessageCode(Class)}.
+	 * @since 6.1
+	 */
+	default String getTypeMessageCode() {
+		return getDefaultTypeMessageCode(getClass());
+	}
+
 	/**
 	 * Return a code to use to resolve the problem "detail" for this exception
 	 * through a {@link MessageSource}.
@@ -109,15 +121,19 @@ default String getTitleMessageCode() {
 	}
 
 	/**
-	 * Resolve the {@link #getDetailMessageCode() detailMessageCode} and the
-	 * {@link #getTitleMessageCode() titleMessageCode} through the given
-	 * {@link MessageSource}, and if found, update the "detail" and "title"
-	 * fields respectively.
+	 * Use the given {@link MessageSource} to resolve the
+	 * {@link #getTypeMessageCode() type}, {@link #getTitleMessageCode() title},
+	 * and {@link #getDetailMessageCode() detail} message codes, and then use the
+	 * resolved values to update the corresponding fields in {@link #getBody()}.
 	 * @param messageSource the {@code MessageSource} to use for the lookup
 	 * @param locale the {@code Locale} to use for the lookup
 	 */
 	default ProblemDetail updateAndGetBody(@Nullable MessageSource messageSource, Locale locale) {
 		if (messageSource != null) {
+			String type = messageSource.getMessage(getTypeMessageCode(), null, null, locale);
+			if (type != null) {
+				getBody().setType(URI.create(type));
+			}
 			Object[] arguments = getDetailMessageArguments(messageSource, locale);
 			String detail = messageSource.getMessage(getDetailMessageCode(), arguments, null, locale);
 			if (detail != null) {
@@ -132,6 +148,17 @@ default ProblemDetail updateAndGetBody(@Nullable MessageSource messageSource, Lo
 	}
 
 
+	/**
+	 * Build a message code for the "type" field, for the given exception type.
+	 * @param exceptionType the exception type associated with the problem
+	 * @return {@code "problemDetail.type."} followed by the fully qualified
+	 * {@link Class#getName() class name}
+	 * @since 6.1
+	 */
+	static String getDefaultTypeMessageCode(Class<?> exceptionType) {
+		return "problemDetail.type." + exceptionType.getName();
+	}
+
 	/**
 	 * Build a message code for the "detail" field, for the given exception type.
 	 * @param exceptionType the exception type associated with the problem

spring-webflux/src/test/java/org/springframework/web/reactive/result/method/annotation/ResponseEntityExceptionHandlerTests.java

@@ -18,6 +18,7 @@
 
 
 import java.lang.reflect.Method;
+import java.net.URI;
 import java.util.Collections;
 import java.util.List;
 import java.util.Locale;
@@ -130,29 +131,33 @@ void errorResponseProblemDetailViaMessageSource() {
 		Locale locale = Locale.UK;
 		LocaleContextHolder.setLocale(locale);
 
+		String type = "https://example.com/probs/unsupported-content";
+		String title = "Media type is not valid or not supported";
+
 		StaticMessageSource messageSource = new StaticMessageSource();
 		messageSource.addMessage(
 				ErrorResponse.getDefaultDetailMessageCode(UnsupportedMediaTypeStatusException.class, null), locale,
 				"Content-Type {0} not supported. Supported: {1}");
 		messageSource.addMessage(
-				ErrorResponse.getDefaultTitleMessageCode(UnsupportedMediaTypeStatusException.class), locale,
-				"Media type is not valid or not supported");
+				ErrorResponse.getDefaultTitleMessageCode(UnsupportedMediaTypeStatusException.class), locale, title);
+		messageSource.addMessage(
+				ErrorResponse.getDefaultTypeMessageCode(UnsupportedMediaTypeStatusException.class), locale, type);
 
 		this.exceptionHandler.setMessageSource(messageSource);
 
 		Exception ex = new UnsupportedMediaTypeStatusException(MediaType.APPLICATION_JSON,
 				List.of(MediaType.APPLICATION_ATOM_XML, MediaType.APPLICATION_XML));
 
-		MockServerWebExchange exchange = MockServerWebExchange.from(MockServerHttpRequest.get("/")
-				.acceptLanguageAsLocales(locale).build());
+		MockServerWebExchange exchange = MockServerWebExchange.from(
+				MockServerHttpRequest.get("/").acceptLanguageAsLocales(locale).build());
 
 		ResponseEntity<?> responseEntity = this.exceptionHandler.handleException(ex, exchange).block();
 
 		ProblemDetail body = (ProblemDetail) responseEntity.getBody();
 		assertThat(body.getDetail()).isEqualTo(
 				"Content-Type application/json not supported. Supported: [application/atom+xml, application/xml]");
-		assertThat(body.getTitle()).isEqualTo(
-				"Media type is not valid or not supported");
+		assertThat(body.getTitle()).isEqualTo(title);
+		assertThat(body.getType()).isEqualTo(URI.create(type));
 	}
 
 	@Test

spring-webmvc/src/test/java/org/springframework/web/servlet/mvc/method/annotation/ResponseEntityExceptionHandlerTests.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2022 the original author or authors.
+ * Copyright 2002-2023 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.
@@ -17,6 +17,7 @@
 package org.springframework.web.servlet.mvc.method.annotation;
 
 import java.beans.PropertyChangeEvent;
+import java.net.URI;
 import java.util.Arrays;
 import java.util.Collections;
 import java.util.List;
@@ -164,14 +165,18 @@ public void errorResponseProblemDetailViaMessageSource() {
 		Locale locale = Locale.UK;
 		LocaleContextHolder.setLocale(locale);
 
+		String type = "https://example.com/probs/unsupported-content";
+		String title = "Media type is not valid or not supported";
+
 		try {
 			StaticMessageSource messageSource = new StaticMessageSource();
 			messageSource.addMessage(
 					ErrorResponse.getDefaultDetailMessageCode(HttpMediaTypeNotSupportedException.class, null), locale,
 					"Content-Type {0} not supported. Supported: {1}");
 			messageSource.addMessage(
-					ErrorResponse.getDefaultTitleMessageCode(HttpMediaTypeNotSupportedException.class), locale,
-					"Media type is not valid or not supported");
+					ErrorResponse.getDefaultTitleMessageCode(HttpMediaTypeNotSupportedException.class), locale, title);
+			messageSource.addMessage(
+					ErrorResponse.getDefaultTypeMessageCode(HttpMediaTypeNotSupportedException.class), locale, type);
 
 			this.exceptionHandler.setMessageSource(messageSource);
 
@@ -181,8 +186,8 @@ public void errorResponseProblemDetailViaMessageSource() {
 			ProblemDetail body = (ProblemDetail) entity.getBody();
 			assertThat(body.getDetail()).isEqualTo(
 					"Content-Type application/json not supported. Supported: [application/atom+xml, application/xml]");
-			assertThat(body.getTitle()).isEqualTo(
-					"Media type is not valid or not supported");
+			assertThat(body.getTitle()).isEqualTo(title);
+			assertThat(body.getType()).isEqualTo(URI.create(type));
 		}
 		finally {
 			LocaleContextHolder.resetLocaleContext();