Polish 'Auto-configure OtlpMetricsSender if available'

Update `OtlpMetricsExportAutoConfiguration` to use the new
`OtlpMetricsSender`interface that allows users to customize the
sending of OTLP metrics using the `OtlpMeterRegistry`.

See gh-45204

Author: philwebb

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

@@ -1,5 +1,5 @@
 /*
- * Copyright 2012-2024 the original author or authors.
+ * Copyright 2012-2025 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.
@@ -19,7 +19,6 @@
 import io.micrometer.core.instrument.Clock;
 import io.micrometer.registry.otlp.OtlpConfig;
 import io.micrometer.registry.otlp.OtlpMeterRegistry;
-import io.micrometer.registry.otlp.OtlpMeterRegistry.Builder;
 import io.micrometer.registry.otlp.OtlpMetricsSender;
 
 import org.springframework.beans.factory.ObjectProvider;
@@ -81,22 +80,23 @@ OtlpConfig otlpConfig(OpenTelemetryProperties openTelemetryProperties,
 	@ConditionalOnThreading(Threading.PLATFORM)
 	public OtlpMeterRegistry otlpMeterRegistry(OtlpConfig otlpConfig, Clock clock,
 			ObjectProvider<OtlpMetricsSender> metricsSender) {
-		Builder builder = OtlpMeterRegistry.builder(otlpConfig).clock(clock);
-		metricsSender.ifAvailable(builder::metricsSender);
-		return builder.build();
+		return builder(otlpConfig, clock, metricsSender).build();
 	}
 
 	@Bean
 	@ConditionalOnMissingBean
 	@ConditionalOnThreading(Threading.VIRTUAL)
 	public OtlpMeterRegistry otlpMeterRegistryVirtualThreads(OtlpConfig otlpConfig, Clock clock,
 			ObjectProvider<OtlpMetricsSender> metricsSender) {
-		VirtualThreadTaskExecutor taskExecutor = new VirtualThreadTaskExecutor("otlp-meter-registry-");
-		Builder builder = OtlpMeterRegistry.builder(otlpConfig)
-			.clock(clock)
-			.threadFactory(taskExecutor.getVirtualThreadFactory());
+		VirtualThreadTaskExecutor executor = new VirtualThreadTaskExecutor("otlp-meter-registry-");
+		return builder(otlpConfig, clock, metricsSender).threadFactory(executor.getVirtualThreadFactory()).build();
+	}
+
+	private OtlpMeterRegistry.Builder builder(OtlpConfig otlpConfig, Clock clock,
+			ObjectProvider<OtlpMetricsSender> metricsSender) {
+		OtlpMeterRegistry.Builder builder = OtlpMeterRegistry.builder(otlpConfig).clock(clock);
 		metricsSender.ifAvailable(builder::metricsSender);
-		return builder.build();
+		return builder;
 	}
 
 	/**

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

@@ -1,5 +1,5 @@
 /*
- * Copyright 2012-2024 the original author or authors.
+ * Copyright 2012-2025 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.
@@ -28,6 +28,7 @@
 
 import org.springframework.boot.actuate.autoconfigure.metrics.export.otlp.OtlpMetricsExportAutoConfiguration.PropertiesOtlpMetricsConnectionDetails;
 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.boot.testsupport.assertj.ScheduledExecutorServiceAssert;
 import org.springframework.context.annotation.Bean;
@@ -136,27 +137,22 @@ void testConnectionFactoryWithOverridesWhenUsingCustomConnectionDetails() {
 	@Test
 	void allowsCustomMetricsSenderToBeUsed() {
 		this.contextRunner.withUserConfiguration(BaseConfiguration.class, CustomMetricsSenderConfiguration.class)
-			.run((context) -> {
-				assertThat(context).hasSingleBean(OtlpMeterRegistry.class);
-				OtlpMeterRegistry registry = context.getBean(OtlpMeterRegistry.class);
-				assertThat(registry).extracting("metricsSender")
-					.satisfies((sender) -> assertThat(sender)
-						.isSameAs(CustomMetricsSenderConfiguration.customMetricsSender));
-			});
+			.run(this::assertHasCustomMetricsSender);
 	}
 
 	@Test
 	@EnabledForJreRange(min = JRE.JAVA_21)
 	void allowsCustomMetricsSenderToBeUsedWithVirtualThreads() {
 		this.contextRunner.withUserConfiguration(BaseConfiguration.class, CustomMetricsSenderConfiguration.class)
 			.withPropertyValues("spring.threads.virtual.enabled=true")
-			.run((context) -> {
-				assertThat(context).hasSingleBean(OtlpMeterRegistry.class);
-				OtlpMeterRegistry registry = context.getBean(OtlpMeterRegistry.class);
-				assertThat(registry).extracting("metricsSender")
-					.satisfies((sender) -> assertThat(sender)
-						.isSameAs(CustomMetricsSenderConfiguration.customMetricsSender));
-			});
+			.run(this::assertHasCustomMetricsSender);
+	}
+
+	private void assertHasCustomMetricsSender(AssertableApplicationContext context) {
+		assertThat(context).hasSingleBean(OtlpMeterRegistry.class);
+		OtlpMeterRegistry registry = context.getBean(OtlpMeterRegistry.class);
+		assertThat(registry).extracting("metricsSender")
+			.satisfies((sender) -> assertThat(sender).isSameAs(CustomMetricsSenderConfiguration.customMetricsSender));
 	}
 
 	@Configuration(proxyBeanMethods = false)