Consider subtypes in exception error page mapping

Fixes gh-417

spring-boot/src/main/java/org/springframework/boot/context/web/ErrorPageFilter.java

@@ -71,6 +71,8 @@ class ErrorPageFilter extends AbstractConfigurableEmbeddedServletContainer imple
 
 	private final Map<Class<?>, String> exceptions = new HashMap<Class<?>, String>();
 
+	private final Map<Class<?>, Class<?>> subtypes = new HashMap<Class<?>, Class<?>>();
+
 	@Override
 	public void init(FilterConfig filterConfig) throws ServletException {
 	}
@@ -118,14 +120,34 @@ class ErrorPageFilter extends AbstractConfigurableEmbeddedServletContainer imple
 	private void handleException(HttpServletRequest request,
 			HttpServletResponse response, ErrorWrapperResponse wrapped, Throwable ex)
 			throws IOException, ServletException {
-		String errorPath = getErrorPath(this.exceptions, ex.getClass());
+		Class<?> type = ex.getClass();
+		String errorPath = this.global;
+		if (this.exceptions.containsKey(type)) {
+			errorPath = this.exceptions.get(type);
+		}
+		else {
+			if (this.subtypes.containsKey(type)) {
+				errorPath = this.exceptions.get(this.subtypes.get(type));
+			}
+			else {
+				Class<?> subtype = type;
+				while (subtype != Object.class) {
+					subtype = subtype.getSuperclass();
+					if (this.exceptions.containsKey(subtype)) {
+						this.subtypes.put(subtype, type);
+						errorPath = this.exceptions.get(subtype);
+						break;
+					}
+				}
+			}
+		}
 		if (errorPath == null) {
 			rethrow(ex);
 			return;
 		}
 		setErrorAttributes(request, 500, ex.getMessage());
 		request.setAttribute(ERROR_EXCEPTION, ex);
-		request.setAttribute(ERROR_EXCEPTION_TYPE, ex.getClass().getName());
+		request.setAttribute(ERROR_EXCEPTION_TYPE, type.getName());
 		wrapped.sendError(500, ex.getMessage());
 		request.getRequestDispatcher(errorPath).forward(request, response);
 	}

spring-boot/src/test/java/org/springframework/boot/context/web/ErrorPageFilterTests.java

@@ -40,7 +40,7 @@ import static org.junit.Assert.assertThat;
  * 
  * @author Dave Syer
  */
-public class ErrorWrapperEmbeddedServletContainerFactoryTests {
+public class ErrorPageFilterTests {
 
 	private ErrorPageFilter filter = new ErrorPageFilter();
 
@@ -119,4 +119,27 @@ public class ErrorWrapperEmbeddedServletContainerFactoryTests {
 		assertThat(this.request.getAttribute(RequestDispatcher.ERROR_EXCEPTION_TYPE),
 				equalTo((Object) RuntimeException.class.getName()));
 	}
+
+	@Test
+	public void subClassExceptionError() throws Exception {
+		this.filter.addErrorPages(new ErrorPage(RuntimeException.class, "/500"));
+		this.chain = new MockFilterChain() {
+			@Override
+			public void doFilter(ServletRequest request, ServletResponse response)
+					throws IOException, ServletException {
+				super.doFilter(request, response);
+				throw new IllegalStateException("BAD");
+			}
+		};
+		this.filter.doFilter(this.request, this.response, this.chain);
+		assertThat(((HttpServletResponseWrapper) this.chain.getResponse()).getStatus(),
+				equalTo(500));
+		assertThat(this.request.getAttribute(RequestDispatcher.ERROR_STATUS_CODE),
+				equalTo((Object) 500));
+		assertThat(this.request.getAttribute(RequestDispatcher.ERROR_MESSAGE),
+				equalTo((Object) "BAD"));
+		assertThat(this.request.getAttribute(RequestDispatcher.ERROR_EXCEPTION_TYPE),
+				equalTo((Object) IllegalStateException.class.getName()));
+	}
+
 }