Document RuntimeHints testing strategies

Closes gh-29523

framework-docs/framework-docs.gradle

@@ -10,6 +10,14 @@ configurations {
 	asciidoctorExtensions
 }
 
+dependencies {
+	api(project(":spring-context"))
+	api(project(":spring-web"))
+
+	implementation(project(":spring-core-test"))
+	implementation("org.assertj:assertj-core")
+}
+
 jar {
 	enabled = false
 }

framework-docs/src/docs/asciidoc/attributes.adoc

@@ -1,3 +1,4 @@
+:chomp: default headers packages
 :docs-site:                     https://docs.spring.io
 // Spring Framework
 :docs-spring-framework:         {docs-site}/spring-framework/docs/{spring-version}
@@ -13,3 +14,4 @@
 :gh-rsocket:                    https://github.com/rsocket
 :gh-rsocket-extensions:         {gh-rsocket}/rsocket/blob/master/Extensions
 :gh-rsocket-java:               {gh-rsocket}/rsocket-java
+:doc-graalvm: https://www.graalvm.org/22.3/reference-manual

framework-docs/src/docs/asciidoc/core/core-aot.adoc

@@ -52,27 +52,13 @@ An application context is created with any number of entry points, usually in th
 
 Let's look at a basic example:
 
-[source,java,indent=0,subs="verbatim,quotes",role="primary"]
+include::code:AotProcessingSample[tag=myapplication]
-.Java
-----
-@Configuration(proxyBeanMethods=false)
-@ComponentScan
-@Import({DataSourceConfiguration.class, ContainerConfiguration.class})
-public class MyApplication {
-}
-----
 
 Starting this application with the regular runtime involves a number of steps including classpath scanning, configuration class parsing, bean instantiation, and lifecycle callback handling.
 Refresh for AOT processing only applies a subset of what happens with a <<beans-introduction,regular `refresh`>>.
 AOT processing can be triggered as follows:
 
-[source,java,indent=0,subs="verbatim,quotes",role="primary"]
+include::code:AotProcessingSample[tag=aotcontext]
-.Java
-----
-GenericApplicationContext applicationContext = new AnnotatedConfigApplicationContext();
-context.register(MyApplication.class);
-context.refreshForAotProcessing();
-----
 
 In this mode, <<beans-factory-extension-factory-postprocessors,`BeanFactoryPostProcessor` implementations>> are invoked as usual.
 This includes configuration class parsing, import selectors, classpath scanning, etc.
@@ -229,24 +215,7 @@ A number of convenient annotations are also provided for common use cases.
 Implementations of this interface can be registered using `@ImportRuntimeHints` on any Spring bean or `@Bean` factory method.
 `RuntimeHintsRegistrar` implementations are detected and invoked at build time.
 
-[source,java,indent=0,subs="verbatim,quotes",role="primary"]
+include::code:SpellCheckService[]
-.Java
-----
-	@Component
-	@ImportRuntimeHints(MyComponentRuntimeHints.class)
-	public class MyComponent {
-
-		// ...
-
-		private static class MyComponentRuntimeHints implements RuntimeHintsRegistrar {
-
-			@Override
-			public void registerHints(RuntimeHints hints, ClassLoader classLoader) {
-				// ...
-			}
-		}
-	}
-----
 
 If at all possible, `@ImportRuntimeHints` should be used as close as possible to the component that requires the hints.
 This way, if the component is not contributed to the `BeanFactory`, the hints won't be contributed either.
@@ -290,3 +259,50 @@ The following example registers `Account` for serialization.
 
 	}
 ----
+
+[[core.aot.hints.testing]]
+=== Testing Runtime Hints
+
+Spring Core also ships `RuntimeHintsPredicates`, an utility for checking that existing hints match a particular use case.
+This can be used in your own tests, for validating that a `RuntimeHintsRegistrar` has the expected result.
+We can write a test for our `SpellCheckService` and ensure that we can load a dictionary at runtime:
+
+include::code:SpellCheckServiceTests[tag=hintspredicates]
+
+With `RuntimeHintsPredicates`, we can check for reflection, resource, serialization or proxy generation hints.
+This approach works well for unit tests but implies that the runtime behavior of a component is well known.
+
+You can learn more about the global runtime behavior of an application by running its test suite (or the app itself) with the {doc-graalvm}/native-image/metadata/AutomaticMetadataCollection/[GraalVM tracing agent].
+This agent will record all relevant calls requiring GraalVM hints at runtime and write them out as JSON configuration files.
+
+For more targeted discovery and testing, Spring Framework ships a dedicated module with core AOT testing utilities, `"org.springframework:spring-core-test"`.
+This module contains the RuntimeHints Agent, a Java agent that all method invocations that are related to runtime hints and helps you to assert that a given `RuntimeHints` instance covers all recorded invocations.
+Let's consider a piece of infrastructure for which we'd like to test the hints we're contributing during the AOT phase.
+
+
+include::code:SampleReflection[]
+
+We can then write a Java test (no native compilation required!) that checks our contributed hints:
+
+include::code:SampleReflectionRuntimeHintsTests[]
+
+If you forgot to contribute a hint, the test will fail and give some details on the invocation:
+
+[source,txt,indent=0,subs="verbatim,quotes"]
+----
+org.springframework.docs.core.aot.hints.testing.SampleReflection performReflection
+INFO: Spring version:6.0.0-SNAPSHOT
+
+Missing <"ReflectionHints"> for invocation <java.lang.Class#forName>
+with arguments ["org.springframework.core.SpringVersion",
+    false,
+    jdk.internal.loader.ClassLoaders$AppClassLoader@251a69d7].
+Stacktrace:
+<"org.springframework.util.ClassUtils#forName, Line 284
+io.spring.runtimehintstesting.SampleReflection#performReflection, Line 19
+io.spring.runtimehintstesting.SampleReflectionRuntimeHintsTests#lambda$shouldRegisterReflectionHints$0, Line 25
+----
+
+There are various ways to configure this Java agent into your build, please refer to your build tool and test execution plugin documentation.
+The agent itself can be configured to instrument some packages (by default, only `org.springframework` is instrumented).
+You'll find more details in the https://github.com/spring-projects/spring-framework/blob/main/buildSrc/README.md[Spring Framework buildSrc README].

framework-docs/src/main/java/org/springframework/docs/core/aot/hints/importruntimehints/SpellCheckService.java

@@ -0,0 +1,44 @@
+/*
+ * Copyright 2002-2022 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.docs.core.aot.hints.importruntimehints;
+
+import java.util.Locale;
+
+import org.springframework.aot.hint.RuntimeHints;
+import org.springframework.aot.hint.RuntimeHintsRegistrar;
+import org.springframework.context.annotation.ImportRuntimeHints;
+import org.springframework.core.io.ClassPathResource;
+import org.springframework.stereotype.Component;
+
+@Component
+@ImportRuntimeHints(SpellCheckService.SpellCheckServiceRuntimeHints.class)
+public class SpellCheckService {
+
+	public void loadDictionary(Locale locale) {
+		ClassPathResource resource = new ClassPathResource("dicts/" + locale.getLanguage() + ".txt");
+		//...
+	}
+
+	static class SpellCheckServiceRuntimeHints implements RuntimeHintsRegistrar {
+
+		@Override
+		public void registerHints(RuntimeHints hints, ClassLoader classLoader) {
+			hints.resources().registerPattern("dicts/*");
+		}
+	}
+
+}

framework-docs/src/main/java/org/springframework/docs/core/aot/hints/testing/SampleReflection.java

@@ -0,0 +1,41 @@
+/*
+ * Copyright 2002-2022 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.docs.core.aot.hints.testing;
+
+import java.lang.reflect.Method;
+
+import org.apache.commons.logging.Log;
+import org.apache.commons.logging.LogFactory;
+
+import org.springframework.util.ClassUtils;
+
+public class SampleReflection {
+
+	private final Log logger = LogFactory.getLog(SampleReflection.class);
+
+	public void performReflection() {
+		try {
+			Class<?> springVersion = ClassUtils.forName("org.springframework.core.SpringVersion", null);
+			Method getVersion = ClassUtils.getMethod(springVersion, "getVersion");
+			String version = (String) getVersion.invoke(null);
+			logger.info("Spring version:" + version);
+		}
+		catch (Exception exc) {
+			logger.error("reflection failed", exc);
+		}
+	}
+}

framework-docs/src/main/java/org/springframework/docs/core/aot/hints/testing/SampleReflectionRuntimeHintsTests.java

@@ -0,0 +1,54 @@
+/*
+ * Copyright 2002-2022 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.docs.core.aot.hints.testing;
+
+import java.util.List;
+
+import org.junit.jupiter.api.Test;
+
+import org.springframework.aot.hint.ExecutableMode;
+import org.springframework.aot.hint.RuntimeHints;
+import org.springframework.aot.test.agent.EnabledIfRuntimeHintsAgent;
+import org.springframework.aot.test.agent.RuntimeHintsInvocations;
+import org.springframework.aot.test.agent.RuntimeHintsRecorder;
+import org.springframework.core.SpringVersion;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+// This annotation conditions the execution of tests only if the agent is loaded in the current JVM
+// it also tags tests with the "RuntimeHints" JUnit tag
+@EnabledIfRuntimeHintsAgent
+class SampleReflectionRuntimeHintsTests {
+
+	@Test
+	void shouldRegisterReflectionHints() {
+		RuntimeHints runtimeHints = new RuntimeHints();
+		// Call a RuntimeHintsRegistrar that contributes hints like:
+		runtimeHints.reflection().registerType(SpringVersion.class, typeHint -> {
+			typeHint.withMethod("getVersion", List.of(), ExecutableMode.INVOKE);
+		});
+
+		// Invoke the relevant piece of code we want to test within a recording lambda
+		RuntimeHintsInvocations invocations = RuntimeHintsRecorder.record(() -> {
+			SampleReflection sample = new SampleReflection();
+			sample.performReflection();
+		});
+		// assert that the recorded invocations are covered by the contributed hints
+		assertThat(invocations).match(runtimeHints);
+	}
+
+}

framework-docs/src/main/java/org/springframework/docs/core/aot/hints/testing/SpellCheckServiceTests.java

@@ -0,0 +1,47 @@
+/*
+ * Copyright 2002-2022 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.docs.core.aot.hints.testing;
+
+import org.junit.jupiter.api.Test;
+
+import org.springframework.aot.hint.RuntimeHints;
+import org.springframework.aot.hint.RuntimeHintsRegistrar;
+import org.springframework.aot.hint.predicate.RuntimeHintsPredicates;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+public class SpellCheckServiceTests {
+
+	// tag::hintspredicates[]
+	@Test
+	void shouldRegisterResourceHints() {
+		RuntimeHints hints = new RuntimeHints();
+		new SpellCheckServiceRuntimeHints().registerHints(hints, getClass().getClassLoader());
+		assertThat(RuntimeHintsPredicates.resource().forResource("dicts/en.txt"))
+				.accepts(hints);
+	}
+	// end::hintspredicates[]
+
+	// Copied here because it is package private in SpellCheckService
+	static class SpellCheckServiceRuntimeHints implements RuntimeHintsRegistrar {
+
+		@Override
+		public void registerHints(RuntimeHints hints, ClassLoader classLoader) {
+			hints.resources().registerPattern("dicts/*");
+		}
+	}
+}

framework-docs/src/main/java/org/springframework/docs/core/aot/refresh/AotProcessingSample.java

@@ -0,0 +1,52 @@
+/*
+ * Copyright 2002-2022 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.docs.core.aot.refresh;
+
+import org.springframework.aot.hint.RuntimeHints;
+import org.springframework.context.annotation.AnnotationConfigApplicationContext;
+import org.springframework.context.annotation.ComponentScan;
+import org.springframework.context.annotation.Configuration;
+import org.springframework.context.annotation.Import;
+
+public class AotProcessingSample {
+
+	public void createAotContext() {
+		// tag::aotcontext[]
+		RuntimeHints hints = new RuntimeHints();
+		AnnotationConfigApplicationContext context = new AnnotationConfigApplicationContext();
+		context.register(MyApplication.class);
+		context.refreshForAotProcessing(hints);
+		// end::aotcontext[]
+	}
+
+	// tag::myapplication[]
+	@Configuration(proxyBeanMethods=false)
+	@ComponentScan
+	@Import({DataSourceConfiguration.class, ContainerConfiguration.class})
+	public class MyApplication {
+
+	}
+	// end::myapplication[]
+
+	class DataSourceConfiguration {
+
+	}
+
+	class ContainerConfiguration {
+
+	}
+}