Fix logic error in ErrorPageFilter (fixes gh-1149)

spring-boot-samples/spring-boot-sample-web-jsp/src/main/java/sample/jsp/WelcomeController.java

@@ -36,4 +36,9 @@ public class WelcomeController {
 		return "welcome";
 	}
 
+	@RequestMapping("/foo")
+	public String foo(Map<String, Object> model) {
+		throw new RuntimeException("Foo");
+	}
+
 }

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

@@ -135,13 +135,13 @@ class ErrorPageFilter extends AbstractConfigurableEmbeddedServletContainer imple
 		setErrorAttributes(request, 500, ex.getMessage());
 		request.setAttribute(ERROR_EXCEPTION, ex);
 		request.setAttribute(ERROR_EXCEPTION_TYPE, type.getName());
-		wrapped.sendError(500, ex.getMessage());
 		forwardToErrorPage(errorPath, request, wrapped, ex);
 	}
 
 	private void forwardToErrorPage(String path, HttpServletRequest request,
-			ServletResponse response, Throwable ex) throws ServletException, IOException {
-		if (!response.isCommitted()) {
+			HttpServletResponse response, Throwable ex) throws ServletException,
+			IOException {
+		if (response.isCommitted()) {
 			String message = "Cannot forward to error page for" + request.getRequestURI()
 					+ " (response is committed), so this response may have "
 					+ "the wrong status code";
@@ -151,6 +151,7 @@ class ErrorPageFilter extends AbstractConfigurableEmbeddedServletContainer imple
 			return;
 		}
 		response.reset();
+		response.sendError(500, ex.getMessage());
 		request.getRequestDispatcher(path).forward(request, response);
 	}
 

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

@@ -59,6 +59,44 @@ public class ErrorPageFilterTests {
 				equalTo((ServletResponse) this.response));
 	}
 
+	@Test
+	public void responseCommitted() throws Exception {
+		this.filter.addErrorPages(new ErrorPage("/error"));
+		this.response.setCommitted(true);
+		this.chain = new MockFilterChain() {
+			@Override
+			public void doFilter(ServletRequest request, ServletResponse response)
+					throws IOException, ServletException {
+				((HttpServletResponse) response).sendError(400, "BAD");
+				super.doFilter(request, response);
+			}
+		};
+		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));
+		assertThat(((HttpServletResponseWrapper) this.chain.getResponse()).getStatus(),
+				equalTo(400));
+	}
+
+	@Test
+	public void responseUncommitted() throws Exception {
+		this.chain = new MockFilterChain() {
+			@Override
+			public void doFilter(ServletRequest request, ServletResponse response)
+					throws IOException, ServletException {
+				((HttpServletResponse) response).sendError(400, "BAD");
+				super.doFilter(request, response);
+			}
+		};
+		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));
+		assertThat(((HttpServletResponseWrapper) this.chain.getResponse()).getStatus(),
+				equalTo(400));
+	}
+
 	@Test
 	public void globalError() throws Exception {
 		this.filter.addErrorPages(new ErrorPage("/error"));