ensure no warnings are emitted in spring starter startup (#11201)

instrumentation/spring/spring-boot-autoconfigure-3/src/main/java/io/opentelemetry/instrumentation/spring/autoconfigure/instrumentation/web/RestClientInstrumentationAutoConfiguration.java

@@ -34,7 +34,7 @@ import org.springframework.web.client.RestClient;
 public class RestClientInstrumentationAutoConfiguration {
 
   @Bean
-  RestClientBeanPostProcessor otelRestClientBeanPostProcessor(
+  static RestClientBeanPostProcessor otelRestClientBeanPostProcessor(
       ObjectProvider<OpenTelemetry> openTelemetryProvider) {
     return new RestClientBeanPostProcessor(openTelemetryProvider);
   }

instrumentation/spring/spring-boot-autoconfigure/src/main/java/io/opentelemetry/instrumentation/spring/autoconfigure/instrumentation/kafka/KafkaInstrumentationAutoConfiguration.java

@@ -33,6 +33,7 @@ public class KafkaInstrumentationAutoConfiguration {
     return producerFactory -> producerFactory.addPostProcessor(kafkaTelemetry::wrap);
   }
 
+  // static to avoid "is not eligible for getting processed by all BeanPostProcessors" warning
   @Bean
   static ConcurrentKafkaListenerContainerFactoryPostProcessor
       otelKafkaListenerContainerFactoryBeanPostProcessor(

instrumentation/spring/spring-boot-autoconfigure/src/main/java/io/opentelemetry/instrumentation/spring/autoconfigure/instrumentation/web/SpringWebInstrumentationAutoConfiguration.java

@@ -31,6 +31,7 @@ public class SpringWebInstrumentationAutoConfiguration {
 
   public SpringWebInstrumentationAutoConfiguration() {}
 
+  // static to avoid "is not eligible for getting processed by all BeanPostProcessors" warning
   @Bean
   static RestTemplateBeanPostProcessor otelRestTemplateBeanPostProcessor(
       ObjectProvider<OpenTelemetry> openTelemetryProvider) {
@@ -38,7 +39,7 @@ public class SpringWebInstrumentationAutoConfiguration {
   }
 
   @Bean
-  static RestTemplateCustomizer otelRestTemplateCustomizer(
+  RestTemplateCustomizer otelRestTemplateCustomizer(
       ObjectProvider<OpenTelemetry> openTelemetryProvider) {
     return restTemplate ->
         RestTemplateInstrumentation.addIfNotPresent(

instrumentation/spring/spring-boot-autoconfigure/src/main/java/io/opentelemetry/instrumentation/spring/autoconfigure/instrumentation/webflux/SpringWebfluxInstrumentationAutoConfiguration.java

@@ -30,6 +30,7 @@ public class SpringWebfluxInstrumentationAutoConfiguration {
 
   public SpringWebfluxInstrumentationAutoConfiguration() {}
 
+  // static to avoid "is not eligible for getting processed by all BeanPostProcessors" warning
   @Bean
   static WebClientBeanPostProcessor otelWebClientBeanPostProcessor(
       ObjectProvider<OpenTelemetry> openTelemetryProvider) {

smoke-tests-otel-starter/build.gradle.kts

@@ -16,6 +16,8 @@ dependencies {
   implementation("com.h2database:h2")
   implementation("org.apache.commons:commons-dbcp2")
   implementation(project(":instrumentation:jdbc:library"))
+  implementation("org.springframework.kafka:spring-kafka") // not tested here, just make sure there are no warnings when it's included
+  implementation("org.springframework.boot:spring-boot-starter-webflux") // not tested here, just make sure there are no warnings when it's included
   implementation("io.opentelemetry:opentelemetry-extension-trace-propagators")
   implementation(project(":instrumentation:spring:starters:spring-boot-starter"))
   implementation(platform(org.springframework.boot.gradle.plugin.SpringBootPlugin.BOM_COORDINATES))
@@ -25,6 +27,10 @@ dependencies {
 }
 
 tasks {
+  test {
+    // suppress warning about byte-buddy-agent being loaded dynamically
+    jvmArgs("-XX:+EnableDynamicAgentLoading")
+  }
   compileAotJava {
     with(options) {
       compilerArgs.add("-Xlint:-deprecation,-unchecked,none")

smoke-tests-otel-starter/src/test/java/io/opentelemetry/smoketest/OtelSpringStarterSmokeTest.java

@@ -48,19 +48,24 @@ import org.assertj.core.api.AbstractCharSequenceAssert;
 import org.awaitility.core.ConditionEvaluationLogger;
 import org.awaitility.core.EvaluatedCondition;
 import org.awaitility.core.TimeoutEvent;
+import org.junit.jupiter.api.AfterEach;
 import org.junit.jupiter.api.MethodOrderer;
 import org.junit.jupiter.api.Test;
 import org.junit.jupiter.api.TestMethodOrder;
+import org.junit.jupiter.api.extension.ExtendWith;
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
 import org.springframework.beans.factory.annotation.Autowired;
 import org.springframework.boot.test.context.SpringBootTest;
+import org.springframework.boot.test.system.CapturedOutput;
+import org.springframework.boot.test.system.OutputCaptureExtension;
 import org.springframework.boot.test.web.client.TestRestTemplate;
 import org.springframework.context.annotation.Bean;
 import org.springframework.context.annotation.Configuration;
 import org.springframework.core.annotation.Order;
 import org.springframework.core.env.Environment;
 
+@ExtendWith(OutputCaptureExtension.class)
 @SpringBootTest(
     classes = {
       OtelSpringStarterSmokeTestApplication.class,
@@ -176,6 +181,11 @@ class OtelSpringStarterSmokeTest {
     LOG_RECORD_EXPORTER.reset();
   }
 
+  @AfterEach
+  void tearDown(CapturedOutput output) {
+    assertThat(output).doesNotContain("WARN").doesNotContain("ERROR");
+  }
+
   @Test
   @org.junit.jupiter.api.Order(10)
   void propertyConversion() {