Updates WeightCalculatorWebFilter to be more testable.

Since Random can't be mocked in jdk17+, replace the settable Random with Supplier<Double>. Production should still use ThreadLoacalRandom unless the supplier is set.

spring-cloud-gateway-server/src/main/java/org/springframework/cloud/gateway/filter/WeightCalculatorWebFilter.java

@@ -25,6 +25,7 @@ import java.util.concurrent.ConcurrentHashMap;
 import java.util.concurrent.ThreadLocalRandom;
 import java.util.concurrent.atomic.AtomicBoolean;
 import java.util.concurrent.atomic.AtomicInteger;
+import java.util.function.Supplier;
 
 import org.apache.commons.logging.Log;
 import org.apache.commons.logging.LogFactory;
@@ -64,7 +65,7 @@ public class WeightCalculatorWebFilter implements WebFilter, Ordered, SmartAppli
 
 	private final ConfigurationService configurationService;
 
-	private Random random = null;
+	private Supplier<Double> randomSupplier = null;
 
 	private int order = WEIGHT_CALC_FILTER_ORDER;
 
@@ -98,8 +99,13 @@ public class WeightCalculatorWebFilter implements WebFilter, Ordered, SmartAppli
 		this.order = order;
 	}
 
+	@Deprecated
 	public void setRandom(Random random) {
-		this.random = random;
+		this.randomSupplier = random::nextDouble;
+	}
+
+	public void setRandomSupplier(Supplier<Double> randomSupplier) {
+		this.randomSupplier = randomSupplier;
 	}
 
 	@Override
@@ -236,9 +242,13 @@ public class WeightCalculatorWebFilter implements WebFilter, Ordered, SmartAppli
 			 * Usually, multiple threads accessing the same random object will have some
 			 * performance problems, so we can use ThreadLocalRandom by default
 			 */
-			Random useRandom = this.random;
-			useRandom = useRandom == null ? ThreadLocalRandom.current() : useRandom;
-			double r = useRandom.nextDouble();
+			double r;
+			if (this.randomSupplier != null) {
+				r = randomSupplier.get();
+			}
+			else {
+				r = ThreadLocalRandom.current().nextDouble();
+			}
 
 			List<Double> ranges = config.ranges;
 

spring-cloud-gateway-server/src/test/java/org/springframework/cloud/gateway/filter/WeightCalculatorWebFilterTests.java

@@ -19,11 +19,9 @@ package org.springframework.cloud.gateway.filter;
 import java.util.HashMap;
 import java.util.List;
 import java.util.Map;
-import java.util.Random;
+import java.util.function.Supplier;
 
 import org.junit.jupiter.api.Test;
-import org.junit.jupiter.api.condition.DisabledForJreRange;
-import org.junit.jupiter.api.condition.JRE;
 
 import org.springframework.cloud.gateway.event.PredicateArgsEvent;
 import org.springframework.cloud.gateway.filter.WeightCalculatorWebFilter.GroupWeightConfig;
@@ -95,20 +93,18 @@ public class WeightCalculatorWebFilterTests {
 		return "route" + i;
 	}
 
-	// TODO: modify implementation for testability on JDK17 for Spring 6
 	@Test
-	@DisabledForJreRange(min = JRE.JAVA_17)
 	public void testChooseRouteWithRandom() {
 		WeightCalculatorWebFilter filter = createFilter();
 		filter.addWeightConfig(new WeightConfig("groupa", "route1", 1));
 		filter.addWeightConfig(new WeightConfig("groupa", "route2", 3));
 		filter.addWeightConfig(new WeightConfig("groupa", "route3", 6));
 
-		Random random = mock(Random.class);
+		Supplier<Double> random = mock(Supplier.class);
 
-		when(random.nextDouble()).thenReturn(0.05).thenReturn(0.2).thenReturn(0.6);
+		when(random.get()).thenReturn(0.05).thenReturn(0.2).thenReturn(0.6);
 
-		filter.setRandom(random);
+		filter.setRandomSupplier(random);
 
 		MockServerWebExchange exchange = MockServerWebExchange
 				.from(MockServerHttpRequest.get("http://localhost").build());

spring-cloud-gateway-server/src/test/java/org/springframework/cloud/gateway/handler/predicate/WeightRoutePredicateFactoryIntegrationTests.java

@@ -16,12 +16,10 @@
 
 package org.springframework.cloud.gateway.handler.predicate;
 
-import java.util.Random;
 import java.util.function.Predicate;
+import java.util.function.Supplier;
 
 import org.junit.jupiter.api.Test;
-import org.junit.jupiter.api.condition.DisabledForJreRange;
-import org.junit.jupiter.api.condition.JRE;
 
 import org.springframework.beans.factory.annotation.Autowired;
 import org.springframework.beans.factory.annotation.Value;
@@ -45,21 +43,20 @@ import static org.springframework.boot.test.context.SpringBootTest.WebEnvironmen
 
 @SpringBootTest(webEnvironment = RANDOM_PORT)
 @DirtiesContext
-@DisabledForJreRange(min = JRE.JAVA_17)
 public class WeightRoutePredicateFactoryIntegrationTests extends BaseWebClientTests {
 
 	@Autowired
 	private WeightCalculatorWebFilter filter;
 
-	private static Random getRandom(double value) {
-		Random random = mock(Random.class);
-		when(random.nextDouble()).thenReturn(value);
+	private static Supplier<Double> getRandom(double value) {
+		Supplier<Double> random = mock(Supplier.class);
+		when(random.get()).thenReturn(value);
 		return random;
 	}
 
 	@Test
 	public void highWeight() {
-		filter.setRandom(getRandom(0.9));
+		filter.setRandomSupplier(getRandom(0.9));
 
 		testClient.get().uri("/get").header(HttpHeaders.HOST, "www.weighthigh.org").exchange().expectStatus().isOk()
 				.expectHeader().valueEquals(ROUTE_ID_HEADER, "weight_high_test");
@@ -67,7 +64,7 @@ public class WeightRoutePredicateFactoryIntegrationTests extends BaseWebClientTe
 
 	@Test
 	public void lowWeight() {
-		filter.setRandom(getRandom(0.1));
+		filter.setRandomSupplier(getRandom(0.1));
 
 		testClient.get().uri("/get").header(HttpHeaders.HOST, "www.weightlow.org").exchange().expectStatus().isOk()
 				.expectHeader().valueEquals(ROUTE_ID_HEADER, "weight_low_test");
@@ -89,9 +86,9 @@ public class WeightRoutePredicateFactoryIntegrationTests extends BaseWebClientTe
 		private String uri;
 
 		public TestConfig(WeightCalculatorWebFilter filter) {
-			Random random = getRandom(0.4);
+			Supplier<Double> random = getRandom(0.4);
 
-			filter.setRandom(random);
+			filter.setRandomSupplier(random);
 		}
 
 		@Bean

spring-cloud-gateway-server/src/test/java/org/springframework/cloud/gateway/handler/predicate/WeightRoutePredicateFactoryYaml404Tests.java

@@ -16,11 +16,9 @@
 
 package org.springframework.cloud.gateway.handler.predicate;
 
-import java.util.Random;
+import java.util.function.Supplier;
 
 import org.junit.jupiter.api.Test;
-import org.junit.jupiter.api.condition.DisabledForJreRange;
-import org.junit.jupiter.api.condition.JRE;
 
 import org.springframework.beans.factory.annotation.Autowired;
 import org.springframework.boot.SpringBootConfiguration;
@@ -40,21 +38,20 @@ import static org.springframework.boot.test.context.SpringBootTest.WebEnvironmen
 @SpringBootTest(webEnvironment = RANDOM_PORT)
 @ActiveProfiles("weights-404")
 @DirtiesContext
-@DisabledForJreRange(min = JRE.JAVA_17)
 class WeightRoutePredicateFactoryYaml404Tests extends BaseWebClientTests {
 
 	@Autowired
 	private WeightCalculatorWebFilter filter;
 
-	private static Random getRandom(double value) {
-		Random random = mock(Random.class);
-		when(random.nextDouble()).thenReturn(value);
+	private static Supplier<Double> getRandom(double value) {
+		Supplier<Double> random = mock(Supplier.class);
+		when(random.get()).thenReturn(value);
 		return random;
 	}
 
 	@Test
 	void weightsFromYamlNot404() {
-		filter.setRandom(getRandom(0.5));
+		filter.setRandomSupplier(getRandom(0.5));
 
 		testClient.get().uri("/get").header(HttpHeaders.HOST, "www.weight4041.org").exchange().expectStatus().isOk()
 				.expectHeader().valueEquals(ROUTE_ID_HEADER, "weight_first_404_test_1");
@@ -66,9 +63,9 @@ class WeightRoutePredicateFactoryYaml404Tests extends BaseWebClientTests {
 	static class TestConfig {
 
 		TestConfig(WeightCalculatorWebFilter filter) {
-			Random random = getRandom(0.4);
+			Supplier<Double> random = getRandom(0.4);
 
-			filter.setRandom(random);
+			filter.setRandomSupplier(random);
 		}
 
 	}