Support i8n of ProblemDetail "title" field

Closes gh-29407

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

@@ -95,8 +95,19 @@ public interface ErrorResponse {
 	}
 
 	/**
-	 * Resolve the {@link #getDetailMessageCode() detailMessageCode} through the
-	 * given {@link MessageSource}, and if found, update the "detail" field.
+	 * Return a code to use to resolve the problem "detail" for this exception
+	 * through a {@link MessageSource}.
+	 * <p>By default this is initialized via
+	 * {@link #getDefaultDetailMessageCode(Class, String)}.
+	 */
+	default String getTitleCode() {
+		return getDefaultTitleMessageCode(getClass());
+	}
+
+	/**
+	 * Resolve the {@link #getDetailMessageCode() detailMessageCode} and the
+	 * {@link #getTitleCode() titleCode} through the given {@link MessageSource},
+	 * and if found, update the "detail" and "title!" fields respectively.
 	 * @param messageSource the {@code MessageSource} to use for the lookup
 	 * @param locale the {@code Locale} to use for the lookup
 	 */
@@ -107,22 +118,35 @@ public interface ErrorResponse {
 			if (detail != null) {
 				getBody().setDetail(detail);
 			}
+			String title = messageSource.getMessage(getTitleCode(), null, null, locale);
+			if (title != null) {
+				getBody().setTitle(title);
+			}
 		}
 		return getBody();
 	}
 
 
 	/**
-	 * Build a message code for the given exception type, which consists of
-	 * {@code "problemDetail."} followed by the full {@link Class#getName() class name}.
-	 * @param exceptionType the exception type for which to build a code
+	 * Build a message code for the "detail" field, for the given exception type.
+	 * @param exceptionType the exception type associated with the problem
 	 * @param suffix an optional suffix, e.g. for exceptions that may have multiple
 	 * error message with different arguments.
+	 * @return {@code "problemDetail."} followed by the full {@link Class#getName() class name}
 	 */
 	static String getDefaultDetailMessageCode(Class<?> exceptionType, @Nullable String suffix) {
 		return "problemDetail." + exceptionType.getName() + (suffix != null ? "." + suffix : "");
 	}
 
+	/**
+	 * Build a message code for the "title" field, for the given exception type.
+	 * @param exceptionType the exception type associated with the problem
+	 * @return {@code "problemDetail.title."} followed by the full {@link Class#getName() class name}
+	 */
+	static String getDefaultTitleMessageCode(Class<?> exceptionType) {
+		return "problemDetail.title." + exceptionType.getName();
+	}
+
 	/**
 	 * Map the given Exception to an {@link ErrorResponse}.
 	 * @param ex the Exception, mostly to derive message codes, if not provided

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

@@ -36,6 +36,7 @@ import org.springframework.http.ProblemDetail;
 import org.springframework.http.ResponseEntity;
 import org.springframework.util.LinkedMultiValueMap;
 import org.springframework.validation.BeanPropertyBindingResult;
+import org.springframework.web.ErrorResponse;
 import org.springframework.web.ErrorResponseException;
 import org.springframework.web.bind.support.WebExchangeBindException;
 import org.springframework.web.server.MethodNotAllowedException;
@@ -131,8 +132,11 @@ public class ResponseEntityExceptionHandlerTests {
 
 		StaticMessageSource messageSource = new StaticMessageSource();
 		messageSource.addMessage(
-				"problemDetail." + UnsupportedMediaTypeStatusException.class.getName(), locale,
+				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");
 
 		this.exceptionHandler.setMessageSource(messageSource);
 
@@ -147,6 +151,8 @@ public class ResponseEntityExceptionHandlerTests {
 		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");
 	}
 
 	@Test

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

@@ -42,6 +42,7 @@ import org.springframework.http.converter.HttpMessageNotWritableException;
 import org.springframework.stereotype.Controller;
 import org.springframework.validation.BindException;
 import org.springframework.validation.MapBindingResult;
+import org.springframework.web.ErrorResponse;
 import org.springframework.web.HttpMediaTypeNotAcceptableException;
 import org.springframework.web.HttpMediaTypeNotSupportedException;
 import org.springframework.web.HttpRequestMethodNotSupportedException;
@@ -166,8 +167,11 @@ public class ResponseEntityExceptionHandlerTests {
 		try {
 			StaticMessageSource messageSource = new StaticMessageSource();
 			messageSource.addMessage(
-					"problemDetail." + HttpMediaTypeNotSupportedException.class.getName(), locale,
+					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");
 
 			this.exceptionHandler.setMessageSource(messageSource);
 
@@ -177,6 +181,8 @@ public class ResponseEntityExceptionHandlerTests {
 			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");
 		}
 		finally {
 			LocaleContextHolder.resetLocaleContext();
@@ -201,7 +207,7 @@ public class ResponseEntityExceptionHandlerTests {
 		try {
 			StaticMessageSource messageSource = new StaticMessageSource();
 			messageSource.addMessage(
-					"problemDetail." + TypeMismatchException.class.getName(), locale,
+					ErrorResponse.getDefaultDetailMessageCode(TypeMismatchException.class, null), locale,
 					"Failed to set {0} to value: {1}");
 
 			this.exceptionHandler.setMessageSource(messageSource);

src/docs/asciidoc/web/webflux.adoc

@@ -3614,7 +3614,7 @@ and any `ErrorResponseException`, and renders an error response with a body.
 [.small]#<<webmvc.adoc#mvc-ann-rest-exceptions-render, Web MVC>>#
 
 You can return `ProblemDetail` or `ErrorResponse` from any `@ExceptionHandler` or from
-any `@RequestMapping` method to render an RFC 7807 response as follows:
+any `@RequestMapping` method to render an RFC 7807 response. This is processed as follows:
 
 - The `status` property of `ProblemDetail` determines the HTTP status.
 - The `instance` property of `ProblemDetail` is set from the current URL path, if not
@@ -3626,8 +3626,9 @@ and also falls back on it if no compatible media type is found.
 To enable RFC 7807 responses for Spring WebFlux exceptions and for any
 `ErrorResponseException`, extend `ResponseEntityExceptionHandler` and declare it as an
 <<webflux-ann-controller-advice,@ControllerAdvice>> in Spring configuration. The handler
-obtains HTTP status, headers, and error details from each exception and prepares a
-`ResponseEntity`.
+has an `@ExceptionHandler` method that handles any `ErrorResponse` exception, which
+includes all built-in web exceptions. You can add more exception handling methods, and
+use a protected method to map any exception to a `ProblemDetail`.
 
 
 
@@ -3644,7 +3645,7 @@ response, and likewise any unknown property during deserialization is inserted i
 this `Map`.
 
 You can also extend `ProblemDetail` to add dedicated non-standard properties.
-The copy constructor in `ProblemDetail` allows a sub-class to make it easy to be created
+The copy constructor in `ProblemDetail` allows a subclass to make it easy to be created
 from an existing `ProblemDetail`. This could be done centrally, e.g. from an
 `@ControllerAdvice` such as `ResponseEntityExceptionHandler` that re-creates the
 `ProblemDetail` of an exception into a subclass with the additional non-standard fields.
@@ -3658,17 +3659,18 @@ from an existing `ProblemDetail`. This could be done centrally, e.g. from an
 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:
 
-- Each `ErrorResponse` exposes a message code and message code arguments to resolve the
-problem "detail" field through a <<core.adoc#context-functionality-messagesource,MessageSource>>.
+- Each `ErrorResponse` exposes a message code and arguments to resolve the "detail" field
+through a <<core.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.
-- `ResponseEntityExceptionHandler` uses the message code and the message arguments
-to resolve the problem "detail" field.
+- 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.
 
-Message codes default to "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:
+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:
 
 [[webflux-ann-rest-exceptions-codes]]
 [cols="1,1,2", options="header"]
@@ -3715,6 +3717,10 @@ via `MessageSource`.
 
 |===
 
+By default, the message code for the "title" field is "problemDetail.title." + the fully
+qualified exception class name.
+
+
 
 
 [[webflux-ann-rest-exceptions-client]]

src/docs/asciidoc/web/webmvc.adoc

@@ -4910,7 +4910,7 @@ and any `ErrorResponseException`, and renders an error response with a body.
 [.small]#<<web-reactive.adoc#webflux-ann-rest-exceptions-render, WebFlux>>#
 
 You can return `ProblemDetail` or `ErrorResponse` from any `@ExceptionHandler` or from
-any `@RequestMapping` method to render an RFC 7807 response as follows:
+any `@RequestMapping` method to render an RFC 7807 response. This is processed as follows:
 
 - The `status` property of `ProblemDetail` determines the HTTP status.
 - The `instance` property of `ProblemDetail` is set from the current URL path, if not
@@ -4919,11 +4919,12 @@ already set.
 "application/problem+json" over "application/json" when rendering a `ProblemDetail`,
 and also falls back on it if no compatible media type is found.
 
-To enable RFC 7807 responses for Spring MVC exceptions and for any
+To enable RFC 7807 responses for Spring WebFlux exceptions and for any
 `ErrorResponseException`, extend `ResponseEntityExceptionHandler` and declare it as an
 <<mvc-ann-controller-advice,@ControllerAdvice>> in Spring configuration. The handler
-obtains HTTP status, headers, and error details from each exception and prepares a
-`ResponseEntity`.
+has an `@ExceptionHandler` method that handles any `ErrorResponse` exception, which
+includes all built-in web exceptions. You can add more exception handling methods, and
+use a protected method to map any exception to a `ProblemDetail`.
 
 
 
@@ -4940,7 +4941,7 @@ response, and likewise any unknown property during deserialization is inserted i
 this `Map`.
 
 You can also extend `ProblemDetail` to add dedicated non-standard properties.
-The copy constructor in `ProblemDetail` allows a sub-class to make it easy to be created
+The copy constructor in `ProblemDetail` allows a subclass to make it easy to be created
 from an existing `ProblemDetail`. This could be done centrally, e.g. from an
 `@ControllerAdvice` such as `ResponseEntityExceptionHandler` that re-creates the
 `ProblemDetail` of an exception into a subclass with the additional non-standard fields.
@@ -4954,20 +4955,18 @@ from an existing `ProblemDetail`. This could be done centrally, e.g. from an
 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:
 
-- Each `ErrorResponse` exposes a message code and message code arguments to resolve the
-problem "detail" field through a <<core.adoc#context-functionality-messagesource,MessageSource>>.
+- Each `ErrorResponse` exposes a message code and arguments to resolve the "detail" field
+through a <<core.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.
-- `ResponseEntityExceptionHandler` uses the message code and the message arguments
-to resolve the problem "detail" field.
-- Lower level exceptions that cannot implement `ErrorResponse`, e.g. `TypeMismatchException`,
-have their problem detail, including message code and arguments set in
-`ResponseEntityExceptionHandler`.
+- 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.
 
-Message codes default to "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:
+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:
 
 [[mvc-ann-rest-exceptions-codes]]
 [cols="1,1,2", options="header"]
@@ -5054,6 +5053,9 @@ MVC exceptions:
 
 |===
 
+By default, the message code for the "title" field is "problemDetail.title." + the fully
+qualified exception class name.
+
 
 
 [[mvc-ann-rest-exceptions-client]]