Ensure that ErrorPageFilter handles errors during async dispatch

Previously, the ErrorPageFilter was not invoked for async dispatches.
This meant that an error that was set during an async dispatch would
go undetected and a 200 response with an empty body would be returned.

This commit updates ErrorPageFilter to configure its
OncePerRequestFilter so that async dispatches are filtered and the
correct error handling is performed.

Closes gh-2711

Author: wilkinsona

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

@@ -88,6 +88,11 @@ protected void doFilterInternal(HttpServletRequest request,
 			ErrorPageFilter.this.doFilter(request, response, chain);
 		}
 
+		@Override
+		protected boolean shouldNotFilterAsyncDispatch() {
+			return false;
+		}
+
 	};
 
 	@Override

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

@@ -34,6 +34,10 @@
 import org.springframework.mock.web.MockFilterConfig;
 import org.springframework.mock.web.MockHttpServletRequest;
 import org.springframework.mock.web.MockHttpServletResponse;
+import org.springframework.web.context.request.async.DeferredResult;
+import org.springframework.web.context.request.async.StandardServletAsyncWebRequest;
+import org.springframework.web.context.request.async.WebAsyncManager;
+import org.springframework.web.context.request.async.WebAsyncUtils;
 
 import static org.hamcrest.Matchers.containsString;
 import static org.hamcrest.Matchers.equalTo;
@@ -373,6 +377,62 @@ public void doFilter(ServletRequest request, ServletResponse response)
 		assertTrue(this.response.isCommitted());
 	}
 
+	@Test
+	public void responseIsNotCommitedDuringAsyncDispatch() throws Exception {
+		setUpAsyncDispatch();
+
+		this.filter.doFilter(this.request, this.response, this.chain);
+
+		assertThat(this.chain.getRequest(), equalTo((ServletRequest) this.request));
+		assertThat(((HttpServletResponseWrapper) this.chain.getResponse()).getResponse(),
+				equalTo((ServletResponse) this.response));
+		assertFalse(this.response.isCommitted());
+	}
+
+	@Test
+	public void responseIsCommitedWhenExceptionIsThrownDuringAsyncDispatch()
+			throws Exception {
+		this.filter.addErrorPages(new ErrorPage("/error"));
+		setUpAsyncDispatch();
+		this.chain = new MockFilterChain() {
+			@Override
+			public void doFilter(ServletRequest request, ServletResponse response)
+					throws IOException, ServletException {
+				super.doFilter(request, response);
+				throw new RuntimeException("BAD");
+			}
+		};
+
+		this.filter.doFilter(this.request, this.response, this.chain);
+
+		assertThat(this.chain.getRequest(), equalTo((ServletRequest) this.request));
+		assertThat(((HttpServletResponseWrapper) this.chain.getResponse()).getResponse(),
+				equalTo((ServletResponse) this.response));
+		assertTrue(this.response.isCommitted());
+	}
+
+	@Test
+	public void responseIsCommitedWhenStatusIs400PlusDuringAsyncDispatch()
+			throws Exception {
+		this.filter.addErrorPages(new ErrorPage("/error"));
+		setUpAsyncDispatch();
+		this.chain = new MockFilterChain() {
+			@Override
+			public void doFilter(ServletRequest request, ServletResponse response)
+					throws IOException, ServletException {
+				super.doFilter(request, response);
+				((HttpServletResponse) response).sendError(400, "BAD");
+			}
+		};
+
+		this.filter.doFilter(this.request, this.response, this.chain);
+
+		assertThat(this.chain.getRequest(), equalTo((ServletRequest) this.request));
+		assertThat(((HttpServletResponseWrapper) this.chain.getResponse()).getResponse(),
+				equalTo((ServletResponse) this.response));
+		assertTrue(this.response.isCommitted());
+	}
+
 	@Test
 	public void responseIsNotFlushedIfStatusIsLessThan400AndItHasAlreadyBeenCommitted()
 			throws Exception {
@@ -419,4 +479,14 @@ public void doFilter(ServletRequest request, ServletResponse response)
 		assertThat(this.output.toString(), containsString("request [/test/alpha]"));
 	}
 
+	private void setUpAsyncDispatch() throws Exception {
+		this.request.setAsyncSupported(true);
+		this.request.setAsyncStarted(true);
+		DeferredResult<String> result = new DeferredResult<String>();
+		WebAsyncManager asyncManager = WebAsyncUtils.getAsyncManager(this.request);
+		asyncManager.setAsyncWebRequest(new StandardServletAsyncWebRequest(this.request,
+				this.response));
+		asyncManager.startDeferredResultProcessing(result);
+	}
+
 }