Checks for null list if there are no query parameters.

fixes gh-374

spring-cloud-gateway-core/src/main/java/org/springframework/cloud/gateway/handler/RoutePredicateHandlerMapping.java

@@ -92,7 +92,12 @@ public class RoutePredicateHandlerMapping extends AbstractHandlerMapping {
 				.filterWhen(route ->  {
 					// add the current route we are testing
 					exchange.getAttributes().put(GATEWAY_PREDICATE_ROUTE_ATTR, route.getId());
-					return route.getPredicate().apply(exchange);
+					try {
+						return route.getPredicate().apply(exchange);
+					} catch (Exception e) {
+						logger.error("Error applying predicate for route: "+route.getId(), e);
+					}
+					return Mono.just(false);
 				})
 				// .defaultIfEmpty() put a static Route not found
 				// or .switchIfEmpty()

spring-cloud-gateway-core/src/main/java/org/springframework/cloud/gateway/handler/predicate/QueryRoutePredicateFactory.java

@@ -54,6 +54,9 @@ public class QueryRoutePredicateFactory extends AbstractRoutePredicateFactory<Qu
 
 
 			List<String> values = exchange.getRequest().getQueryParams().get(config.param);
+			if (values == null) {
+				return false;
+			}
 			for (String value : values) {
 				if (value.matches(config.regexp)) {
 					return true;

spring-cloud-gateway-core/src/test/java/org/springframework/cloud/gateway/handler/predicate/QueryRoutePredicateFactoryTests.java

@@ -0,0 +1,86 @@
+/*
+ * Copyright 2013-2018 the original author or authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ *
+ */
+
+package org.springframework.cloud.gateway.handler.predicate;
+
+import org.junit.Rule;
+import org.junit.Test;
+import org.junit.runner.RunWith;
+
+import org.springframework.beans.factory.annotation.Value;
+import org.springframework.boot.SpringBootConfiguration;
+import org.springframework.boot.autoconfigure.EnableAutoConfiguration;
+import org.springframework.boot.test.context.SpringBootTest;
+import org.springframework.boot.test.rule.OutputCapture;
+import org.springframework.cloud.gateway.route.RouteLocator;
+import org.springframework.cloud.gateway.route.builder.RouteLocatorBuilder;
+import org.springframework.cloud.gateway.test.BaseWebClientTests;
+import org.springframework.context.annotation.Bean;
+import org.springframework.context.annotation.Import;
+import org.springframework.test.annotation.DirtiesContext;
+import org.springframework.test.context.junit4.SpringRunner;
+
+import static org.hamcrest.Matchers.containsString;
+import static org.hamcrest.Matchers.not;
+import static org.springframework.boot.test.context.SpringBootTest.WebEnvironment.RANDOM_PORT;
+
+@RunWith(SpringRunner.class)
+@SpringBootTest(webEnvironment = RANDOM_PORT)
+@DirtiesContext
+public class QueryRoutePredicateFactoryTests extends BaseWebClientTests {
+
+	@Rule
+	public OutputCapture output = new OutputCapture();
+
+	@Test
+	public void noQueryParamWorks() {
+		testClient.get().uri("/get")
+				.exchange()
+				.expectStatus().isOk()
+				.expectHeader().valueEquals(ROUTE_ID_HEADER, "default_path_to_httpbin");;
+
+		output.expect(not(containsString("Error applying predicate for route: foo_query_param")));
+	}
+
+	@Test
+	public void queryParamWorks() {
+		testClient.get().uri("/get?foo=bar")
+				.exchange()
+				.expectStatus().isOk()
+				.expectHeader().valueEquals(ROUTE_ID_HEADER, "foo_query_param");;
+	}
+
+	@EnableAutoConfiguration
+	@SpringBootConfiguration
+	@Import(DefaultTestConfig.class)
+	public static class TestConfig {
+
+		@Value("${test.uri}")
+		private String uri;
+
+		@Bean
+		RouteLocator queryRouteLocator(RouteLocatorBuilder builder) {
+			return builder.routes()
+					.route("foo_query_param", r ->
+							r.query("foo", "bar")
+							.filters(f -> f.prefixPath("/httpbin"))
+							.uri(uri))
+					.build();
+		}
+	}
+
+}