protect against a null RequestDispatcher

spring-cloud-netflix-core/src/main/java/org/springframework/cloud/netflix/zuul/filters/post/SendErrorFilter.java

@@ -6,6 +6,8 @@ import com.netflix.zuul.context.RequestContext;
 import lombok.extern.slf4j.Slf4j;
 import org.springframework.beans.factory.annotation.Value;
 
+import javax.servlet.RequestDispatcher;
+
 /**
  * @author Spencer Gibb
  */
@@ -42,10 +44,17 @@ public class SendErrorFilter extends ZuulFilter {
                 ctx.getRequest().setAttribute("javax.servlet.error.exception", e);
             }
             ctx.getRequest().setAttribute("javax.servlet.error.status_code", statusCode);
-            ctx.getRequest().getRequestDispatcher(errorPath).forward(ctx.getRequest(), ctx.getResponse());
+            RequestDispatcher dispatcher = ctx.getRequest().getRequestDispatcher(errorPath);
+            if (dispatcher != null) {
+                dispatcher.forward(ctx.getRequest(), ctx.getResponse());
+            }
         } catch (Exception e) {
             Throwables.propagate(e);
         }
         return null;
     }
+
+    public void setErrorPath(String errorPath) {
+        this.errorPath = errorPath;
+    }
 }

spring-cloud-netflix-core/src/test/java/org/springframework/cloud/netflix/zuul/SampleZuulProxyApplicationTests.java

@@ -81,6 +81,14 @@ public class SampleZuulProxyApplicationTests {
 		assertEquals("Deleted!", result.getBody());
 	}
 
+	@Test
+	public void testNotFound() {
+		ResponseEntity<String> result = new TestRestTemplate().exchange(
+				"http://localhost:" + port + "/myinvalidpath", HttpMethod.GET,
+				new HttpEntity<Void>((Void) null), String.class);
+		assertEquals(HttpStatus.NOT_FOUND, result.getStatusCode());
+	}
+
 }
 
 //Don't use @SpringBootApplication because we don't want to component scan

spring-cloud-netflix-core/src/test/java/org/springframework/cloud/netflix/zuul/filters/post/SendErrorFilterTests.java

@@ -0,0 +1,51 @@
+package org.springframework.cloud.netflix.zuul.filters.post;
+
+import com.netflix.zuul.context.RequestContext;
+import org.junit.After;
+import org.junit.Test;
+import org.springframework.http.HttpStatus;
+import org.springframework.mock.web.MockHttpServletRequest;
+import org.springframework.mock.web.MockHttpServletResponse;
+
+import javax.servlet.http.HttpServletRequest;
+
+import static org.junit.Assert.*;
+import static org.mockito.Mockito.*;
+
+/**
+ * @author Spencer Gibb
+ */
+public class SendErrorFilterTests {
+
+	@After
+	public void reset() {
+		RequestContext.testSetCurrentContext(null);
+	}
+
+	@Test
+	public void runsNormally() {
+		SendErrorFilter filter = createSendErrorFilter(new MockHttpServletRequest());
+
+		assertTrue("shouldFilter returned false", filter.shouldFilter());
+		filter.run();
+	}
+
+	private SendErrorFilter createSendErrorFilter(HttpServletRequest request) {
+		RequestContext context = new RequestContext();
+		context.setRequest(request);
+		context.setResponse(new MockHttpServletResponse());
+		context.set("error.status_code", HttpStatus.NOT_FOUND.value());
+		RequestContext.testSetCurrentContext(context);
+		SendErrorFilter filter = new SendErrorFilter();
+		filter.setErrorPath("/error");
+		return filter;
+	}
+
+	@Test
+	public void noRequestDispatcher() {
+		SendErrorFilter filter = createSendErrorFilter(mock(HttpServletRequest.class));
+
+		assertTrue("shouldFilter returned false", filter.shouldFilter());
+		filter.run();
+	}
+}