Provide a condition for detecting war deployments

Closes gh-19421

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

@@ -0,0 +1,40 @@
+/*
+ * Copyright 2012-2020 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.context.annotation.Conditional;
+
+/**
+ * {@link Conditional @Conditional} that matches when the application is a traditional WAR
+ * deployment. For applications with embedded servers, this condition will return false.
+ *
+ * @author Madhura Bhave
+ * @since 2.3.0
+ */
+@Target({ ElementType.TYPE, ElementType.METHOD })
+@Retention(RetentionPolicy.RUNTIME)
+@Documented
+@Conditional(OnWarDeploymentCondition.class)
+public @interface ConditionalOnWarDeployment {
+
+}

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

@@ -0,0 +1,49 @@
+/*
+ * Copyright 2012-2020 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 javax.servlet.ServletContext;
+
+import org.springframework.context.annotation.Condition;
+import org.springframework.context.annotation.ConditionContext;
+import org.springframework.core.io.ResourceLoader;
+import org.springframework.core.type.AnnotatedTypeMetadata;
+import org.springframework.web.context.WebApplicationContext;
+
+/**
+ * {@link Condition} that checks if the application is running as a traditional war
+ * deployment.
+ *
+ * @author Madhura Bhave
+ */
+class OnWarDeploymentCondition extends SpringBootCondition {
+
+	@Override
+	public ConditionOutcome getMatchOutcome(ConditionContext context, AnnotatedTypeMetadata metadata) {
+		ResourceLoader resourceLoader = context.getResourceLoader();
+		if (resourceLoader instanceof WebApplicationContext) {
+			WebApplicationContext applicationContext = (WebApplicationContext) resourceLoader;
+			ServletContext servletContext = applicationContext.getServletContext();
+			if (servletContext != null) {
+				return ConditionOutcome.match("Application is deployed as a WAR file.");
+			}
+		}
+		return ConditionOutcome.noMatch(ConditionMessage.forCondition(ConditionalOnWarDeployment.class)
+				.because("the application is not deployed as a WAR file."));
+	}
+
+}

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

@@ -0,0 +1,79 @@
+/*
+ * Copyright 2012-2019 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.springframework.boot.test.context.runner.ApplicationContextRunner;
+import org.springframework.boot.test.context.runner.ReactiveWebApplicationContextRunner;
+import org.springframework.boot.test.context.runner.WebApplicationContextRunner;
+import org.springframework.boot.web.servlet.context.AnnotationConfigServletWebApplicationContext;
+import org.springframework.context.annotation.Bean;
+import org.springframework.context.annotation.Configuration;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+/**
+ * Tests for {@link ConditionalOnWarDeployment @ConditionalOnWarDeployment}.
+ *
+ * @author Madhura Bhave
+ */
+class ConditionalOnWarDeploymentTests {
+
+	@Test
+	void nonWebApplicationShouldNotMatch() {
+		ApplicationContextRunner contextRunner = new ApplicationContextRunner();
+		contextRunner.withUserConfiguration(TestConfiguration.class)
+				.run((context) -> assertThat(context).doesNotHaveBean("forWar"));
+	}
+
+	@Test
+	void reactiveWebApplicationShouldNotMatch() {
+		ReactiveWebApplicationContextRunner contextRunner = new ReactiveWebApplicationContextRunner();
+		contextRunner.withUserConfiguration(TestConfiguration.class)
+				.run((context) -> assertThat(context).doesNotHaveBean("forWar"));
+	}
+
+	@Test
+	void embeddedServletWebApplicationShouldNotMatch() {
+		WebApplicationContextRunner contextRunner = new WebApplicationContextRunner(
+				AnnotationConfigServletWebApplicationContext::new);
+		contextRunner.withUserConfiguration(TestConfiguration.class)
+				.run((context) -> assertThat(context).doesNotHaveBean("forWar"));
+	}
+
+	@Test
+	void warDeployedServletWebApplicationShouldMatch() {
+		// sets a mock servletContext before context refresh which is what the
+		// SpringBootServletInitializer does for WAR deployments.
+		WebApplicationContextRunner contextRunner = new WebApplicationContextRunner();
+		contextRunner.withUserConfiguration(TestConfiguration.class)
+				.run((context) -> assertThat(context).hasBean("forWar"));
+	}
+
+	@Configuration(proxyBeanMethods = false)
+	@ConditionalOnWarDeployment
+	static class TestConfiguration {
+
+		@Bean
+		String forWar() {
+			return "forWar";
+		}
+
+	}
+
+}