Add support for global @ExceptionHandler methods

Before this change @ExceptionHandler methods could be located in and
apply locally within a controller. The change makes it possible to have
such methods applicable globally regardless of the controller that
raised the exception.

The easiest way to do that is to add them to a class annotated with
`@ExceptionResolver`, a new annotation that is also an `@Component`
annotation (and therefore works with component scanning). It is also
possible to register classes containing `@ExceptionHandler` methods
directly with the ExceptionHandlerExceptionResolver.

When multiple `@ExceptionResolver` classes are detected, or registered
directly, the order in which they're used depends on the the `@Order`
annotation (if present) or on the value of the order field (if the
Ordered interface is implemented).

Issue: SPR-9112

spring-web/src/main/java/org/springframework/web/bind/annotation/ExceptionHandler.java

@@ -76,6 +76,15 @@ import java.lang.annotation.Target;
  * {@link org.springframework.web.servlet.RequestToViewNameTranslator}.
  * <li>A {@link org.springframework.web.servlet.View} object.
  * <li>A {@link java.lang.String} value which is interpreted as view name.
+ * <li>{@link ResponseBody @ResponseBody} annotated methods (Servlet-only)
+ * to set the response content. The return value will be converted to the
+ * response stream using
+ * {@linkplain org.springframework.http.converter.HttpMessageConverter message converters}.
+ * <li>An {@link org.springframework.http.HttpEntity HttpEntity&lt;?&gt;} or
+ * {@link org.springframework.http.ResponseEntity ResponseEntity&lt;?&gt;} object
+ * (Servlet-only) to set response headers and content. The ResponseEntity body
+ * will be converted and written to the response stream using
+ * {@linkplain org.springframework.http.converter.HttpMessageConverter message converters}.
  * <li><code>void</code> if the method handles the response itself (by
  * writing the response content directly, declaring an argument of type
  * {@link javax.servlet.ServletResponse} / {@link javax.servlet.http.HttpServletResponse}

spring-web/src/main/java/org/springframework/web/bind/annotation/ExceptionResolver.java

@@ -0,0 +1,57 @@
+/*
+ * Copyright 2002-2012 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.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.springframework.web.bind.annotation;
+
+import java.lang.annotation.Documented;
+import java.lang.annotation.ElementType;
+import java.lang.annotation.Retention;
+import java.lang.annotation.RetentionPolicy;
+import java.lang.annotation.Target;
+
+import org.springframework.core.Ordered;
+import org.springframework.core.annotation.Order;
+import org.springframework.stereotype.Component;
+
+/**
+ * An {@linkplain Component @Component} annotation that indicates the annotated class
+ * contains {@linkplain ExceptionHandler @ExceptionHandler} methods. Such methods
+ * will be used in addition to {@code @ExceptionHandler} methods in
+ * {@code @Controller}-annotated classes.
+ *
+ * <p>In order for the the annotation to detected, an instance of
+ * {@code org.springframework.web.servlet.mvc.method.annotation.ExceptionHandlerExceptionResolver}
+ * is configured.
+ *
+ * <p>Classes with this annotation may use the {@linkplain Order @Order} annotation
+ * or implement the {@link Ordered} interface to indicate the order in which they
+ * should be used relative to other such annotated components. However, note that
+ * the order is only for components registered through {@code @ExceptionResolver},
+ * i.e. within an
+ * {@code org.springframework.web.servlet.mvc.method.annotation.ExceptionHandlerExceptionResolver}.
+ *
+ * @author Rossen Stoyanchev
+ * @since 3.2
+ *
+ * @see org.springframework.web.servlet.mvc.method.annotation.ExceptionHandlerExceptionResolver
+ */
+@Target(ElementType.TYPE)
+@Retention(RetentionPolicy.RUNTIME)
+@Documented
+@Component
+public @interface ExceptionResolver {
+
+}