Refine SyncInvocableHandlerMethod error handling

Ensure the error is wrapped as ServerErrorException

spring-web/src/main/java/org/springframework/web/server/ServerErrorException.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2017 the original author or authors.
+ * Copyright 2002-2018 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.
@@ -19,11 +19,12 @@ package org.springframework.web.server;
 import org.springframework.core.MethodParameter;
 import org.springframework.http.HttpStatus;
 import org.springframework.lang.Nullable;
+import org.springframework.web.method.HandlerMethod;
 
 /**
- * Exception for errors that fit response status 500 (bad request) for use in
- * Spring Web applications. The exception provides additional fields (e.g.
- * an optional {@link MethodParameter} if related to the error).
+ * Exception for an {@link HttpStatus#INTERNAL_SERVER_ERROR} that exposes extra
+ * information about a controller method that failed, or a controller method
+ * argument that could not be resolved.
  *
  * @author Rossen Stoyanchev
  * @since 5.0
@@ -31,6 +32,9 @@ import org.springframework.lang.Nullable;
 @SuppressWarnings("serial")
 public class ServerErrorException extends ResponseStatusException {
 
+	@Nullable
+	private final HandlerMethod handlerMethod;
+
 	@Nullable
 	private final MethodParameter parameter;
 
@@ -39,27 +43,60 @@ public class ServerErrorException extends ResponseStatusException {
 	 * Constructor with an explanation only.
 	 */
 	public ServerErrorException(String reason) {
-		this(reason, null, null);
+		super(HttpStatus.INTERNAL_SERVER_ERROR, reason, null);
+		this.handlerMethod = null;
+		this.parameter = null;
 	}
 
 	/**
-	 * Constructor for a 500 error linked to a specific {@code MethodParameter}.
+	 * Constructor with a reason and root cause.
+	 * @since 5.0.5
 	 */
-	public ServerErrorException(String reason, MethodParameter parameter) {
-		this(reason, parameter, null);
+	public ServerErrorException(String reason, Throwable cause) {
+		super(HttpStatus.INTERNAL_SERVER_ERROR, reason, cause);
+		this.handlerMethod = null;
+		this.parameter = null;
 	}
 
 	/**
-	 * Constructor for a 500 error with a root cause.
+	 * Constructor for a 500 error with a {@link MethodParameter}.
 	 */
-	public ServerErrorException(String reason, @Nullable MethodParameter parameter, @Nullable Throwable cause) {
+	public ServerErrorException(String reason, MethodParameter parameter, @Nullable Throwable cause) {
 		super(HttpStatus.INTERNAL_SERVER_ERROR, reason, cause);
+		this.handlerMethod = null;
 		this.parameter = parameter;
 	}
 
+	/**
+	 * Constructor for a 500 error with a root cause.
+	 */
+	public ServerErrorException(String reason, HandlerMethod handlerMethod, @Nullable Throwable cause) {
+		super(HttpStatus.INTERNAL_SERVER_ERROR, reason, cause);
+		this.handlerMethod = handlerMethod;
+		this.parameter = null;
+	}
+
+	/**
+	 * Constructor for a 500 error linked to a specific {@code MethodParameter}.
+	 * @deprecated in favor of {@link #ServerErrorException(String, MethodParameter, Throwable)}
+	 */
+	@Deprecated
+	public ServerErrorException(String reason, MethodParameter parameter) {
+		this(reason, parameter, null);
+	}
+
+
+	/**
+	 * Return the controller method associated with the error, if any.
+	 * @since 5.0.5
+	 */
+	@Nullable
+	public HandlerMethod getHandlerMethod() {
+		return this.handlerMethod;
+	}
 
 	/**
-	 * Return the {@code MethodParameter} associated with this error, if any.
+	 * Return the controller method argument associated with this error, if any.
 	 */
 	@Nullable
 	public MethodParameter getMethodParameter() {

spring-webflux/src/main/java/org/springframework/web/reactive/BindingContext.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2017 the original author or authors.
+ * Copyright 2002-2018 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.
@@ -21,6 +21,7 @@ import org.springframework.ui.Model;
 import org.springframework.validation.support.BindingAwareConcurrentModel;
 import org.springframework.web.bind.support.WebBindingInitializer;
 import org.springframework.web.bind.support.WebExchangeDataBinder;
+import org.springframework.web.server.ServerErrorException;
 import org.springframework.web.server.ServerWebExchange;
 
 /**
@@ -75,6 +76,7 @@ public class BindingContext {
 	 * @param target the object to create a data binder for
 	 * @param name the name of the target object
 	 * @return the created data binder
+	 * @throws ServerErrorException if {@code @InitBinder} method invocation fails
 	 */
 	public WebExchangeDataBinder createDataBinder(ServerWebExchange exchange, @Nullable Object target, String name) {
 		WebExchangeDataBinder dataBinder = new WebExchangeDataBinder(target, name);
@@ -86,6 +88,7 @@ public class BindingContext {
 
 	/**
 	 * Initialize the data binder instance for the given exchange.
+	 * @throws ServerErrorException if {@code @InitBinder} method invocation fails
 	 */
 	protected WebExchangeDataBinder initDataBinder(WebExchangeDataBinder binder, ServerWebExchange exchange) {
 		return binder;
@@ -97,6 +100,7 @@ public class BindingContext {
 	 * @param exchange the current exchange
 	 * @param name the name of the target object
 	 * @return the created data binder
+	 * @throws ServerErrorException if {@code @InitBinder} method invocation fails
 	 */
 	public WebExchangeDataBinder createDataBinder(ServerWebExchange exchange, String name) {
 		return createDataBinder(exchange, null, name);

spring-webflux/src/main/java/org/springframework/web/reactive/result/method/SyncInvocableHandlerMethod.java

@@ -29,6 +29,7 @@ import org.springframework.lang.Nullable;
 import org.springframework.web.method.HandlerMethod;
 import org.springframework.web.reactive.BindingContext;
 import org.springframework.web.reactive.HandlerResult;
+import org.springframework.web.server.ServerErrorException;
 import org.springframework.web.server.ServerWebExchange;
 
 /**
@@ -95,6 +96,7 @@ public class SyncInvocableHandlerMethod extends HandlerMethod {
 	 * @param bindingContext the binding context to use
 	 * @param providedArgs optional list of argument values to match by type
 	 * @return Mono with a {@link HandlerResult}.
+	 * @throws ServerErrorException if method argument resolution or method invocation fails
 	 */
 	@Nullable
 	public HandlerResult invokeForHandlerResult(ServerWebExchange exchange,
@@ -104,9 +106,10 @@ public class SyncInvocableHandlerMethod extends HandlerMethod {
 		this.delegate.invoke(exchange, bindingContext, providedArgs).subscribeWith(processor);
 
 		if (processor.isTerminated()) {
-			Throwable error = processor.getError();
-			if (error != null) {
-				throw (RuntimeException) error;
+			Throwable ex = processor.getError();
+			if (ex != null) {
+				throw (ex instanceof ServerErrorException ? (ServerErrorException) ex :
+						new ServerErrorException("Failed to invoke: " + getShortLogMessage(), this, ex));
 			}
 			return processor.peek();
 		}

spring-webflux/src/main/java/org/springframework/web/reactive/result/method/annotation/PathVariableMethodArgumentResolver.java

@@ -92,7 +92,7 @@ public class PathVariableMethodArgumentResolver extends AbstractNamedValueSyncAr
 
 	@Override
 	protected void handleMissingValue(String name, MethodParameter parameter) {
-		throw new ServerErrorException(name, parameter);
+		throw new ServerErrorException(name, parameter, null);
 	}
 
 	@Override