Permit use of https for configuring Prometheus push gateway

See gh-16084

spring-boot-project/spring-boot-actuator-autoconfigure/src/main/java/org/springframework/boot/actuate/autoconfigure/metrics/export/prometheus/PrometheusMetricsExportAutoConfiguration.java

@@ -16,6 +16,8 @@
 
 package org.springframework.boot.actuate.autoconfigure.metrics.export.prometheus;
 
+import java.net.MalformedURLException;
+import java.net.URL;
 import java.time.Duration;
 import java.util.Map;
 
@@ -119,13 +121,22 @@ public class PrometheusMetricsExportAutoConfiguration {
 				PrometheusProperties prometheusProperties, Environment environment) {
 			PrometheusProperties.Pushgateway properties = prometheusProperties
 					.getPushgateway();
-			PushGateway pushGateway = new PushGateway(properties.getBaseUrl());
 			Duration pushRate = properties.getPushRate();
 			String job = getJob(properties, environment);
 			Map<String, String> groupingKey = properties.getGroupingKey();
 			ShutdownOperation shutdownOperation = properties.getShutdownOperation();
-			return new PrometheusPushGatewayManager(pushGateway, collectorRegistry,
+			return new PrometheusPushGatewayManager(
-					pushRate, job, groupingKey, shutdownOperation);
+					getPushGateway(properties.getBaseUrl()), collectorRegistry, pushRate,
+					job, groupingKey, shutdownOperation);
+		}
+
+		private PushGateway getPushGateway(String url) {
+			try {
+				return new PushGateway(new URL(url));
+			}
+			catch (MalformedURLException ex) {
+				return new PushGateway(url);
+			}
 		}
 
 		private String getJob(PrometheusProperties.Pushgateway properties,

spring-boot-project/spring-boot-actuator-autoconfigure/src/test/java/org/springframework/boot/actuate/autoconfigure/metrics/export/prometheus/PrometheusMetricsExportAutoConfigurationTests.java

@@ -26,10 +26,12 @@ import org.springframework.boot.actuate.autoconfigure.web.server.ManagementConte
 import org.springframework.boot.actuate.metrics.export.prometheus.PrometheusPushGatewayManager;
 import org.springframework.boot.actuate.metrics.export.prometheus.PrometheusScrapeEndpoint;
 import org.springframework.boot.autoconfigure.AutoConfigurations;
+import org.springframework.boot.test.context.assertj.AssertableApplicationContext;
 import org.springframework.boot.test.context.runner.ApplicationContextRunner;
 import org.springframework.context.annotation.Bean;
 import org.springframework.context.annotation.Configuration;
 import org.springframework.context.annotation.Import;
+import org.springframework.test.util.ReflectionTestUtils;
 
 import static org.assertj.core.api.Assertions.assertThat;
 
@@ -151,8 +153,29 @@ public class PrometheusMetricsExportAutoConfigurationTests {
 				.withPropertyValues(
 						"management.metrics.export.prometheus.pushgateway.enabled=true")
 				.withUserConfiguration(BaseConfiguration.class)
-				.run((context) -> assertThat(context)
+				.run((context) -> hasGatewayURL(context,
-						.hasSingleBean(PrometheusPushGatewayManager.class));
+						"http://localhost:9091/metrics/job/"));
+	}
+
+	@Test
+	public void withCustomPushGatewayURL() {
+		this.contextRunner
+				.withConfiguration(
+						AutoConfigurations.of(ManagementContextAutoConfiguration.class))
+				.withPropertyValues(
+						"management.metrics.export.prometheus.pushgateway.enabled=true",
+						"management.metrics.export.prometheus.pushgateway.base-url=https://localhost:8080/push")
+				.withUserConfiguration(BaseConfiguration.class)
+				.run((context) -> hasGatewayURL(context,
+						"https://localhost:8080/push/metrics/job/"));
+	}
+
+	private void hasGatewayURL(AssertableApplicationContext context, String url) {
+		assertThat(context).hasSingleBean(PrometheusPushGatewayManager.class);
+		PrometheusPushGatewayManager gatewayManager = context
+				.getBean(PrometheusPushGatewayManager.class);
+		Object pushGateway = ReflectionTestUtils.getField(gatewayManager, "pushGateway");
+		assertThat(pushGateway).hasFieldOrPropertyWithValue("gatewayBaseURL", url);
 	}
 
 	@Configuration(proxyBeanMethods = false)