Make sure ErrorPageFilter is only applied once per request

Fixes gh-1257

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

@@ -38,6 +38,7 @@ import org.springframework.boot.context.embedded.ErrorPage;
 import org.springframework.core.Ordered;
 import org.springframework.core.annotation.Order;
 import org.springframework.stereotype.Component;
+import org.springframework.web.filter.OncePerRequestFilter;
 
 /**
  * A special {@link AbstractConfigurableEmbeddedServletContainer} for non-embedded
@@ -77,20 +78,27 @@ class ErrorPageFilter extends AbstractConfigurableEmbeddedServletContainer imple
 
 	private final Map<Class<?>, Class<?>> subtypes = new HashMap<Class<?>, Class<?>>();
 	
+	private final OncePerRequestFilter delegate = new OncePerRequestFilter(
+			) {
+		
+		@Override
+		protected void doFilterInternal(HttpServletRequest request,
+				HttpServletResponse response, FilterChain chain)
+				throws ServletException, IOException {
+			ErrorPageFilter.this.doFilter(request, response, chain);
+		}
+
+	};
+
 	@Override
 	public void init(FilterConfig filterConfig) throws ServletException {
+		delegate.init(filterConfig);
 	}
 
 	@Override
 	public void doFilter(ServletRequest request, ServletResponse response,
 			FilterChain chain) throws IOException, ServletException {
-		if (request instanceof HttpServletRequest
-				&& response instanceof HttpServletResponse) {
-			doFilter((HttpServletRequest) request, (HttpServletResponse) response, chain);
-		}
-		else {
-			chain.doFilter(request, response);
-		}
+		delegate.doFilter(request, response, chain);
 	}
 
 	private void doFilter(HttpServletRequest request, HttpServletResponse response,

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

@@ -16,6 +16,11 @@
 
 package org.springframework.boot.context.web;
 
+import static org.hamcrest.Matchers.equalTo;
+import static org.junit.Assert.assertNotNull;
+import static org.junit.Assert.assertThat;
+import static org.junit.Assert.assertTrue;
+
 import java.io.IOException;
 
 import javax.servlet.RequestDispatcher;
@@ -29,13 +34,10 @@ import org.junit.Test;
 import org.springframework.boot.context.embedded.ErrorPage;
 import org.springframework.http.HttpStatus;
 import org.springframework.mock.web.MockFilterChain;
+import org.springframework.mock.web.MockFilterConfig;
 import org.springframework.mock.web.MockHttpServletRequest;
 import org.springframework.mock.web.MockHttpServletResponse;
 
-import static org.hamcrest.Matchers.equalTo;
-import static org.junit.Assert.assertThat;
-import static org.junit.Assert.assertTrue;
-
 /**
  * Tests for {@link ErrorPageFilter}.
  *
@@ -97,6 +99,21 @@ public class ErrorPageFilterTests {
 				equalTo(400));
 	}
 
+	@Test
+	public void oncePerRequest() throws Exception {
+		this.chain = new MockFilterChain() {
+			@Override
+			public void doFilter(ServletRequest request, ServletResponse response)
+					throws IOException, ServletException {
+				((HttpServletResponse) response).sendError(400, "BAD");
+				assertNotNull(request.getAttribute("FILTER.FILTERED"));
+				super.doFilter(request, response);
+			}
+		};
+		filter.init(new MockFilterConfig("FILTER"));
+		this.filter.doFilter(this.request, this.response, this.chain);
+	}
+
 	@Test
 	public void globalError() throws Exception {
 		this.filter.addErrorPages(new ErrorPage("/error"));