Implement @ConditionalOnThreading

Closes gh-36624

spring-boot-project/spring-boot-autoconfigure/src/main/java/org/springframework/boot/autoconfigure/condition/ConditionalOnThreading.java

@@ -0,0 +1,46 @@
+/*
+ * Copyright 2012-2023 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.autoconfigure.condition;
+
+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.boot.autoconfigure.thread.Threading;
+import org.springframework.context.annotation.Conditional;
+
+/**
+ * {@link Conditional @Conditional} that matches when the specified threading is active.
+ *
+ * @author Moritz Halbritter
+ * @since 3.2.0
+ */
+@Target({ ElementType.TYPE, ElementType.METHOD })
+@Retention(RetentionPolicy.RUNTIME)
+@Documented
+@Conditional(OnThreadingCondition.class)
+public @interface ConditionalOnThreading {
+
+	/**
+	 * The {@link Threading threading} that must be active.
+	 * @return the expected threading
+	 */
+	Threading value();
+
+}

spring-boot-project/spring-boot-autoconfigure/src/main/java/org/springframework/boot/autoconfigure/condition/OnThreadingCondition.java

@@ -0,0 +1,51 @@
+/*
+ * Copyright 2012-2023 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.autoconfigure.condition;
+
+import java.util.Map;
+
+import org.springframework.boot.autoconfigure.thread.Threading;
+import org.springframework.context.annotation.Condition;
+import org.springframework.context.annotation.ConditionContext;
+import org.springframework.core.env.Environment;
+import org.springframework.core.type.AnnotatedTypeMetadata;
+
+/**
+ * {@link Condition} that checks for a required {@link Threading}.
+ *
+ * @author Moritz Halbritter
+ * @see ConditionalOnThreading
+ */
+class OnThreadingCondition extends SpringBootCondition {
+
+	@Override
+	public ConditionOutcome getMatchOutcome(ConditionContext context, AnnotatedTypeMetadata metadata) {
+		Map<String, Object> attributes = metadata.getAnnotationAttributes(ConditionalOnThreading.class.getName());
+		Threading threading = (Threading) attributes.get("value");
+		return getMatchOutcome(context.getEnvironment(), threading);
+	}
+
+	private ConditionOutcome getMatchOutcome(Environment environment, Threading threading) {
+		String name = threading.name();
+		ConditionMessage.Builder message = ConditionMessage.forCondition(ConditionalOnThreading.class);
+		if (threading.isActive(environment)) {
+			return ConditionOutcome.match(message.foundExactly(name));
+		}
+		return ConditionOutcome.noMatch(message.didNotFind(name).atAll());
+	}
+
+}

spring-boot-project/spring-boot-autoconfigure/src/main/java/org/springframework/boot/autoconfigure/thread/Threading.java

@@ -0,0 +1,59 @@
+/*
+ * Copyright 2012-2023 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.autoconfigure.thread;
+
+import org.springframework.boot.system.JavaVersion;
+import org.springframework.core.env.Environment;
+
+/**
+ * Threading of the application.
+ *
+ * @author Moritz Halbritter
+ * @since 3.2.0
+ */
+public enum Threading {
+
+	/**
+	 * Platform threads. Active if virtual threads are not active.
+	 */
+	PLATFORM {
+		@Override
+		public boolean isActive(Environment environment) {
+			return !VIRTUAL.isActive(environment);
+		}
+	},
+	/**
+	 * Virtual threads. Active if {@code spring.threads.virtual.enabled} is {@code true}
+	 * and running on Java 21 or later.
+	 */
+	VIRTUAL {
+		@Override
+		public boolean isActive(Environment environment) {
+			boolean virtualThreadsEnabled = environment.getProperty("spring.threads.virtual.enabled", boolean.class,
+					false);
+			return virtualThreadsEnabled && JavaVersion.getJavaVersion().isEqualOrNewerThan(JavaVersion.TWENTY_ONE);
+		}
+	};
+
+	/**
+	 * Determines whether the threading is active.
+	 * @param environment the environment
+	 * @return whether the threading is active
+	 */
+	public abstract boolean isActive(Environment environment);
+
+}

spring-boot-project/spring-boot-autoconfigure/src/test/java/org/springframework/boot/autoconfigure/condition/ConditionalOnThreadingTests.java

@@ -0,0 +1,91 @@
+/*
+ * Copyright 2012-2023 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.autoconfigure.condition;
+
+import org.junit.jupiter.api.Test;
+import org.junit.jupiter.api.condition.EnabledForJreRange;
+import org.junit.jupiter.api.condition.JRE;
+
+import org.springframework.boot.autoconfigure.thread.Threading;
+import org.springframework.boot.test.context.runner.ApplicationContextRunner;
+import org.springframework.context.annotation.Bean;
+import org.springframework.context.annotation.Configuration;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+/**
+ * Tests for {@link ConditionalOnThreading}.
+ *
+ * @author Moritz Halbritter
+ */
+class ConditionalOnThreadingTests {
+
+	private final ApplicationContextRunner contextRunner = new ApplicationContextRunner()
+		.withUserConfiguration(BasicConfiguration.class);
+
+	@Test
+	@EnabledForJreRange(max = JRE.JAVA_20)
+	void platformThreadsOnJdkBelow21IfVirtualThreadsPropertyIsEnabled() {
+		this.contextRunner.withPropertyValues("spring.threads.virtual.enabled=true")
+			.run((context) -> assertThat(context.getBean(ThreadType.class)).isEqualTo(ThreadType.PLATFORM));
+	}
+
+	@Test
+	@EnabledForJreRange(max = JRE.JAVA_20)
+	void platformThreadsOnJdkBelow21IfVirtualThreadsPropertyIsDisabled() {
+		this.contextRunner.withPropertyValues("spring.threads.virtual.enabled=false")
+			.run((context) -> assertThat(context.getBean(ThreadType.class)).isEqualTo(ThreadType.PLATFORM));
+	}
+
+	@Test
+	@EnabledForJreRange(min = JRE.JAVA_21)
+	void virtualThreadsOnJdk21IfVirtualThreadsPropertyIsEnabled() {
+		this.contextRunner.withPropertyValues("spring.threads.virtual.enabled=true")
+			.run((context) -> assertThat(context.getBean(ThreadType.class)).isEqualTo(ThreadType.VIRTUAL));
+	}
+
+	@Test
+	@EnabledForJreRange(min = JRE.JAVA_21)
+	void platformThreadsOnJdk21IfVirtualThreadsPropertyIsDisabled() {
+		this.contextRunner.withPropertyValues("spring.threads.virtual.enabled=false")
+			.run((context) -> assertThat(context.getBean(ThreadType.class)).isEqualTo(ThreadType.PLATFORM));
+	}
+
+	private enum ThreadType {
+
+		PLATFORM, VIRTUAL
+
+	}
+
+	@Configuration(proxyBeanMethods = false)
+	static class BasicConfiguration {
+
+		@Bean
+		@ConditionalOnThreading(Threading.VIRTUAL)
+		ThreadType virtual() {
+			return ThreadType.VIRTUAL;
+		}
+
+		@Bean
+		@ConditionalOnThreading(Threading.PLATFORM)
+		ThreadType platform() {
+			return ThreadType.PLATFORM;
+		}
+
+	}
+
+}