Missing path variable is now a 500 error

Before this change a missing path variable value resulted in a 400
error where in fact the error is due to a mismatch between the
declared @PathVariable and the URI template, i.e. a 500 error.

This change introduced a MissingPathVariableException as a sub-class
of ServletRequestBindingException (the exception previously thrown)
and results in a response status code of 500 by default.

Issue: SPR-13121

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

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2014 the original author or authors.
+ * Copyright 2002-2015 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.
@@ -25,6 +25,7 @@ import org.springframework.core.convert.ConversionService;
 import org.springframework.core.convert.TypeDescriptor;
 import org.springframework.core.convert.converter.Converter;
 import org.springframework.util.StringUtils;
+import org.springframework.web.bind.MissingPathVariableException;
 import org.springframework.web.bind.ServletRequestBindingException;
 import org.springframework.web.bind.WebDataBinder;
 import org.springframework.web.bind.annotation.PathVariable;
@@ -101,9 +102,10 @@ public class PathVariableMethodArgumentResolver extends AbstractNamedValueMethod
 	}
 
 	@Override
-	protected void handleMissingValue(String name, MethodParameter parameter) throws ServletRequestBindingException {
-		throw new ServletRequestBindingException("Missing URI template variable '" + name +
-				"' for method parameter of type " + parameter.getParameterType().getSimpleName());
+	protected void handleMissingValue(String name, MethodParameter parameter)
+			throws ServletRequestBindingException {
+
+		throw new MissingPathVariableException(name, parameter);
 	}
 
 	@Override

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

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2013 the original author or authors.
+ * Copyright 2002-2015 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.
@@ -37,6 +37,7 @@ import org.springframework.web.HttpMediaTypeNotAcceptableException;
 import org.springframework.web.HttpMediaTypeNotSupportedException;
 import org.springframework.web.HttpRequestMethodNotSupportedException;
 import org.springframework.web.bind.MethodArgumentNotValidException;
+import org.springframework.web.bind.MissingPathVariableException;
 import org.springframework.web.bind.MissingServletRequestParameterException;
 import org.springframework.web.bind.ServletRequestBindingException;
 import org.springframework.web.bind.annotation.ControllerAdvice;
@@ -96,6 +97,7 @@ public abstract class ResponseEntityExceptionHandler {
 			HttpRequestMethodNotSupportedException.class,
 			HttpMediaTypeNotSupportedException.class,
 			HttpMediaTypeNotAcceptableException.class,
+			MissingPathVariableException.class,
 			MissingServletRequestParameterException.class,
 			ServletRequestBindingException.class,
 			ConversionNotSupportedException.class,
@@ -127,6 +129,10 @@ public abstract class ResponseEntityExceptionHandler {
 			HttpStatus status = HttpStatus.NOT_ACCEPTABLE;
 			return handleHttpMediaTypeNotAcceptable((HttpMediaTypeNotAcceptableException) ex, headers, status, request);
 		}
+		else if (ex instanceof MissingPathVariableException) {
+			HttpStatus status = HttpStatus.INTERNAL_SERVER_ERROR;
+			return handleMissingPathVariable((MissingPathVariableException) ex, headers, status, request);
+		}
 		else if (ex instanceof MissingServletRequestParameterException) {
 			HttpStatus status = HttpStatus.BAD_REQUEST;
 			return handleMissingServletRequestParameter((MissingServletRequestParameterException) ex, headers, status, request);
@@ -270,6 +276,22 @@ public abstract class ResponseEntityExceptionHandler {
 		return handleExceptionInternal(ex, null, headers, status, request);
 	}
 
+	/**
+	 * Customize the response for MissingPathVariableException.
+	 * This method delegates to {@link #handleExceptionInternal(Exception, Object, HttpHeaders, HttpStatus, WebRequest)}.
+	 * @param ex the exception
+	 * @param headers the headers to be written to the response
+	 * @param status the selected response status
+	 * @param request the current request
+	 * @return a {@code ResponseEntity} instance
+	 * @since 4.2
+	 */
+	protected ResponseEntity<Object> handleMissingPathVariable(MissingPathVariableException ex,
+			HttpHeaders headers, HttpStatus status, WebRequest request) {
+
+		return handleExceptionInternal(ex, null, headers, status, request);
+	}
+
 	/**
 	 * Customize the response for MissingServletRequestParameterException.
 	 * This method delegates to {@link #handleExceptionInternal(Exception, Object, HttpHeaders, HttpStatus, WebRequest)}.

spring-webmvc/src/main/java/org/springframework/web/servlet/mvc/support/DefaultHandlerExceptionResolver.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2013 the original author or authors.
+ * Copyright 2002-2015 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.
@@ -38,6 +38,7 @@ import org.springframework.web.HttpMediaTypeNotAcceptableException;
 import org.springframework.web.HttpMediaTypeNotSupportedException;
 import org.springframework.web.HttpRequestMethodNotSupportedException;
 import org.springframework.web.bind.MethodArgumentNotValidException;
+import org.springframework.web.bind.MissingPathVariableException;
 import org.springframework.web.bind.MissingServletRequestParameterException;
 import org.springframework.web.bind.ServletRequestBindingException;
 import org.springframework.web.bind.annotation.ModelAttribute;
@@ -119,6 +120,10 @@ public class DefaultHandlerExceptionResolver extends AbstractHandlerExceptionRes
 				return handleHttpMediaTypeNotAcceptable((HttpMediaTypeNotAcceptableException) ex, request, response,
 						handler);
 			}
+			else if (ex instanceof MissingPathVariableException) {
+				return handleMissingPathVariable((MissingPathVariableException) ex, request,
+						response, handler);
+			}
 			else if (ex instanceof MissingServletRequestParameterException) {
 				return handleMissingServletRequestParameter((MissingServletRequestParameterException) ex, request,
 						response, handler);
@@ -247,6 +252,26 @@ public class DefaultHandlerExceptionResolver extends AbstractHandlerExceptionRes
 		return new ModelAndView();
 	}
 
+	/**
+	 * Handle the case when a declared path variable does not match any extracted URI variable.
+	 * <p>The default implementation sends an HTTP 500 error, and returns an empty {@code ModelAndView}.
+	 * Alternatively, a fallback view could be chosen, or the MissingPathVariableException
+	 * could be rethrown as-is.
+	 * @param ex the MissingPathVariableException to be handled
+	 * @param request current HTTP request
+	 * @param response current HTTP response
+	 * @param handler the executed handler
+	 * @return an empty ModelAndView indicating the exception was handled
+	 * @throws IOException potentially thrown from response.sendError()
+	 * @since 4.2
+	 */
+	protected ModelAndView handleMissingPathVariable(MissingPathVariableException ex,
+			HttpServletRequest request, HttpServletResponse response, Object handler) throws IOException {
+
+		response.sendError(HttpServletResponse.SC_INTERNAL_SERVER_ERROR, ex.getMessage());
+		return new ModelAndView();
+	}
+
 	/**
 	 * Handle the case when a required parameter is missing.
 	 * <p>The default implementation sends an HTTP 400 error, and returns an empty {@code ModelAndView}.