add spring starter span logging

instrumentation/spring/spring-boot-autoconfigure/src/main/java/io/opentelemetry/instrumentation/spring/autoconfigure/internal/instrumentation/logging/LoggingExporterAutoConfiguration.java

@@ -0,0 +1,54 @@
+/*
+ * Copyright The OpenTelemetry Authors
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+package io.opentelemetry.instrumentation.spring.autoconfigure.internal.instrumentation.logging;
+
+import static java.util.Collections.emptyList;
+
+import io.opentelemetry.exporter.logging.LoggingSpanExporter;
+import io.opentelemetry.instrumentation.spring.autoconfigure.internal.SdkEnabled;
+import io.opentelemetry.sdk.autoconfigure.spi.AutoConfigurationCustomizerProvider;
+import io.opentelemetry.sdk.autoconfigure.spi.ConfigProperties;
+import io.opentelemetry.sdk.trace.SdkTracerProviderBuilder;
+import io.opentelemetry.sdk.trace.export.SimpleSpanProcessor;
+import org.springframework.boot.autoconfigure.condition.ConditionalOnClass;
+import org.springframework.boot.autoconfigure.condition.ConditionalOnProperty;
+import org.springframework.context.annotation.Bean;
+import org.springframework.context.annotation.Conditional;
+import org.springframework.context.annotation.Configuration;
+
+/**
+ * This class is internal and is hence not for public use. Its APIs are unstable and can change at
+ * any time.
+ */
+@Conditional(SdkEnabled.class)
+// to match "otel.javaagent.debug" system property
+@ConditionalOnProperty(name = "otel.spring-starter.debug", havingValue = "true")
+@ConditionalOnClass(LoggingSpanExporter.class)
+@Configuration
+public class LoggingExporterAutoConfiguration {
+
+  @Bean
+  public AutoConfigurationCustomizerProvider loggingOtelCustomizer() {
+    return p ->
+        p.addTracerProviderCustomizer(
+            (builder, config) -> {
+              enableLoggingExporter(builder, config);
+              return builder;
+            });
+  }
+
+  public static void enableLoggingExporter(
+      SdkTracerProviderBuilder builder, ConfigProperties config) {
+    // don't install another instance if the user has already explicitly requested it.
+    if (loggingExporterIsNotAlreadyConfigured(config)) {
+      builder.addSpanProcessor(SimpleSpanProcessor.create(LoggingSpanExporter.create()));
+    }
+  }
+
+  private static boolean loggingExporterIsNotAlreadyConfigured(ConfigProperties config) {
+    return !config.getList("otel.traces.exporter", emptyList()).contains("logging");
+  }
+}

instrumentation/spring/spring-boot-autoconfigure/src/test/java/io/opentelemetry/instrumentation/spring/autoconfigure/internal/instrumentation/logging/LoggingExporterAutoConfigurationTest.java

@@ -0,0 +1,56 @@
+/*
+ * Copyright The OpenTelemetry Authors
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+package io.opentelemetry.instrumentation.spring.autoconfigure.internal.instrumentation.logging;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+import io.opentelemetry.api.OpenTelemetry;
+import io.opentelemetry.instrumentation.spring.autoconfigure.OpenTelemetryAutoConfiguration;
+import io.opentelemetry.sdk.autoconfigure.spi.ConfigProperties;
+import io.opentelemetry.sdk.autoconfigure.spi.internal.DefaultConfigProperties;
+import java.util.Collections;
+import org.junit.jupiter.api.Test;
+import org.springframework.boot.autoconfigure.AutoConfigurations;
+import org.springframework.boot.test.context.runner.ApplicationContextRunner;
+
+class LoggingExporterAutoConfigurationTest {
+  private final ApplicationContextRunner runner =
+      new ApplicationContextRunner()
+          .withBean(
+              ConfigProperties.class,
+              () -> DefaultConfigProperties.createFromMap(Collections.emptyMap()))
+          .withConfiguration(
+              AutoConfigurations.of(
+                  LoggingExporterAutoConfiguration.class, OpenTelemetryAutoConfiguration.class));
+
+  @Test
+  void instrumentationEnabled() {
+    runner
+        .withPropertyValues("otel.spring-starter.debug=true", "otel.traces.exporter=none")
+        .run(
+            context ->
+                assertThat(context.getBean(OpenTelemetry.class).toString())
+                    .containsOnlyOnce("LoggingSpanExporter"));
+  }
+
+  @Test
+  void alreadyAdded() {
+    runner
+        .withPropertyValues("otel.spring-starter.debug=true", "otel.traces.exporter=logging")
+        .run(
+            context ->
+                assertThat(context.getBean(OpenTelemetry.class).toString())
+                    .containsOnlyOnce("LoggingSpanExporter"));
+  }
+
+  @Test
+  void instrumentationDisabled() {
+    runner.run(
+        context ->
+            assertThat(context.getBean(OpenTelemetry.class).toString())
+                .doesNotContain("LoggingSpanExporter"));
+  }
+}