Add @ConditionalOnEnabledTracing condition

See gh-31308

spring-boot-project/spring-boot-actuator-autoconfigure/src/main/java/org/springframework/boot/actuate/autoconfigure/tracing/ConditionalOnEnabledTracing.java

@@ -0,0 +1,41 @@
+/*
+ * Copyright 2012-2022 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.
+ * You may obtain a copy of the License at
+ *
+ *      https://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.springframework.boot.actuate.autoconfigure.tracing;
+
+import java.lang.annotation.Documented;
+import java.lang.annotation.ElementType;
+import java.lang.annotation.Retention;
+import java.lang.annotation.RetentionPolicy;
+import java.lang.annotation.Target;
+
+import org.springframework.context.annotation.Conditional;
+
+/**
+ * {@link Conditional @Conditional} that checks whether tracing is enabled. It matches if
+ * the value of the {@code management.tracing.enabled} property is {@code true} or if it
+ * is not configured.
+ *
+ * @author Moritz Halbritter
+ * @since 3.0.0
+ */
+@Retention(RetentionPolicy.RUNTIME)
+@Target({ ElementType.TYPE, ElementType.METHOD })
+@Documented
+@Conditional(OnTracingEnabledCondition.class)
+public @interface ConditionalOnEnabledTracing {
+
+}

spring-boot-project/spring-boot-actuator-autoconfigure/src/main/java/org/springframework/boot/actuate/autoconfigure/tracing/OnTracingEnabledCondition.java

@@ -0,0 +1,43 @@
+/*
+ * Copyright 2012-2022 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.
+ * You may obtain a copy of the License at
+ *
+ *      https://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.springframework.boot.actuate.autoconfigure.tracing;
+
+import org.springframework.boot.autoconfigure.condition.ConditionMessage;
+import org.springframework.boot.autoconfigure.condition.ConditionOutcome;
+import org.springframework.boot.autoconfigure.condition.SpringBootCondition;
+import org.springframework.context.annotation.Condition;
+import org.springframework.context.annotation.ConditionContext;
+import org.springframework.core.type.AnnotatedTypeMetadata;
+
+/**
+ * {@link Condition} that checks if tracing is enabled.
+ *
+ * @author Moritz Halbritter
+ * @see ConditionalOnEnabledTracing
+ */
+class OnTracingEnabledCondition extends SpringBootCondition {
+
+	private static final String PROPERTY_NAME = "management.tracing.enabled";
+
+	@Override
+	public ConditionOutcome getMatchOutcome(ConditionContext context, AnnotatedTypeMetadata metadata) {
+		boolean match = context.getEnvironment().getProperty(PROPERTY_NAME, Boolean.class, true);
+		return new ConditionOutcome(match, ConditionMessage.forCondition(ConditionalOnEnabledTracing.class)
+				.because(PROPERTY_NAME + " is " + match));
+	}
+
+}

spring-boot-project/spring-boot-actuator-autoconfigure/src/test/java/org/springframework/boot/actuate/autoconfigure/tracing/OnTracingEnabledConditionTests.java

@@ -0,0 +1,67 @@
+/*
+ * Copyright 2012-2022 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.
+ * You may obtain a copy of the License at
+ *
+ *      https://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.springframework.boot.actuate.autoconfigure.tracing;
+
+import org.junit.jupiter.api.Test;
+
+import org.springframework.boot.autoconfigure.condition.ConditionOutcome;
+import org.springframework.context.annotation.ConditionContext;
+import org.springframework.core.env.Environment;
+import org.springframework.core.type.AnnotatedTypeMetadata;
+import org.springframework.mock.env.MockEnvironment;
+
+import static org.assertj.core.api.Assertions.assertThat;
+import static org.mockito.BDDMockito.given;
+import static org.mockito.Mockito.mock;
+
+/**
+ * @author Moritz Halbritter
+ */
+class OnTracingEnabledConditionTests {
+
+	private final OnTracingEnabledCondition condition = new OnTracingEnabledCondition();
+
+	@Test
+	void shouldMatchIfTrue() {
+		ConditionOutcome outcome = getMatchOutcome(
+				new MockEnvironment().withProperty("management.tracing.enabled", "true"));
+		assertThat(outcome.isMatch()).isTrue();
+		assertThat(outcome.getMessage()).isEqualTo("@ConditionalOnEnabledTracing management.tracing.enabled is true");
+	}
+
+	@Test
+	void shouldMatchIfMissing() {
+		ConditionOutcome outcome = getMatchOutcome(new MockEnvironment());
+		assertThat(outcome.isMatch()).isTrue();
+		assertThat(outcome.getMessage()).isEqualTo("@ConditionalOnEnabledTracing management.tracing.enabled is true");
+	}
+
+	@Test
+	void shouldNotMatchIfFalse() {
+		ConditionOutcome outcome = getMatchOutcome(
+				new MockEnvironment().withProperty("management.tracing.enabled", "false"));
+		assertThat(outcome.isMatch()).isFalse();
+		assertThat(outcome.getMessage()).isEqualTo("@ConditionalOnEnabledTracing management.tracing.enabled is false");
+	}
+
+	private ConditionOutcome getMatchOutcome(Environment environment) {
+		ConditionContext conditionContext = mock(ConditionContext.class);
+		given(conditionContext.getEnvironment()).willReturn(environment);
+		return this.condition.getMatchOutcome(conditionContext, mock(AnnotatedTypeMetadata.class));
+	}
+
+}