Add AOT and native image support

docs/src/main/asciidoc/spring-cloud-openfeign.adoc

@@ -78,6 +78,15 @@ TIP: To use `@EnableFeignClients` annotation on `@Configuration`-annotated-class
 or list them explicitly:
 `@EnableFeignClients(clients = InventoryServiceFeignClient.class)`
 
+[[attribute-resolution-mode]]
+==== Attribute resolution mode
+
+While creating `Feign` client beans, we resolve the values passed via the `@FeignClient` annotation. As of `4.x`, the values are being resolved eagerly. This is a good solution for most use-cases, and it also allows for AOT support.
+
+If you need the attributes to be resolved lazily, set the `spring.cloud.openfeign.lazy-attributes-resolution` property value to `true`.
+
+TIP: For Spring Cloud Contract test integration, lazy attribute resolution should be used.
+
 [[spring-cloud-feign-overriding-defaults]]
 === Overriding Feign Defaults
 
@@ -905,6 +914,17 @@ The URL provided in the configuration properties remains unused.
 
 |===
 
+=== AOT and Native Image Support
+
+Spring Cloud OpenFeign supports Spring AOT transformations and native images, however, only with refresh mode disabled, Feign clients refresh disabled (default setting) and <<attribute-resolution-mode,lazy `@FeignClient` attribute resolution>> disabled (default setting).
+
+WARNING: If you want to run Spring Cloud OpenFeign clients in AOT or native image modes, make sure to set `spring.cloud.refresh.enabled` to `false`.
+
+TIP: If you want to run Spring Cloud OpenFeign clients in AOT or native image modes, ensure `spring.cloud.openfeign.client.refresh-enabled` has not been set to `true`.
+
+TIP: If you want to run Spring Cloud OpenFeign clients in AOT or native image modes, ensure `spring.cloud.openfeign.lazy-attributes-resolution` has not been set to `true`.
+
+
 == Configuration properties
 
 To see the list of all Spring Cloud OpenFeign related configuration properties please check link:appendix.html[the Appendix page].

pom.xml

@@ -228,7 +228,7 @@
 						<artifactId>maven-surefire-plugin</artifactId>
 						<configuration>
 							<!-- Sets the VM argument line used when unit tests are run. -->
-							<argLine>${surefireArgLine}</argLine>
+							<argLine>${surefireArgLine} --add-opens=java.base/java.net=ALL-UNNAMED</argLine>
 						</configuration>
 					</plugin>
 				</plugins>

spring-cloud-openfeign-core/pom.xml

@@ -191,6 +191,11 @@
 			<version>2.11.0</version>
 			<scope>test</scope>
 		</dependency>
+		<dependency>
+			<groupId>org.springframework</groupId>
+			<artifactId>spring-core-test</artifactId>
+			<scope>test</scope>
+		</dependency>
 		<dependency>
 			<groupId>org.springframework.security</groupId>
 			<artifactId>spring-security-oauth2-client</artifactId>

spring-cloud-openfeign-core/src/main/java/org/springframework/cloud/openfeign/DefaultTargeter.java

@@ -25,7 +25,7 @@
 class DefaultTargeter implements Targeter {
 
 	@Override
-	public <T> T target(FeignClientFactoryBean factory, Feign.Builder feign, FeignContext context,
+	public <T> T target(FeignClientFactoryBean factory, Feign.Builder feign, FeignClientFactory context,
 			Target.HardCodedTarget<T> target) {
 		return feign.target(target);
 	}

spring-cloud-openfeign-core/src/main/java/org/springframework/cloud/openfeign/FeignAutoConfiguration.java

@@ -44,6 +44,10 @@
 import org.apache.commons.logging.Log;
 import org.apache.commons.logging.LogFactory;
 
+import org.springframework.aot.hint.MemberCategory;
+import org.springframework.aot.hint.RuntimeHints;
+import org.springframework.aot.hint.RuntimeHintsRegistrar;
+import org.springframework.aot.hint.TypeReference;
 import org.springframework.beans.factory.annotation.Autowired;
 import org.springframework.beans.factory.annotation.Value;
 import org.springframework.boot.autoconfigure.condition.ConditionalOnBean;
@@ -55,6 +59,8 @@
 import org.springframework.cloud.client.actuator.HasFeatures;
 import org.springframework.cloud.client.circuitbreaker.CircuitBreaker;
 import org.springframework.cloud.client.circuitbreaker.CircuitBreakerFactory;
+import org.springframework.cloud.openfeign.aot.FeignChildContextInitializer;
+import org.springframework.cloud.openfeign.aot.FeignClientBeanFactoryInitializationAotProcessor;
 import org.springframework.cloud.openfeign.security.OAuth2AccessTokenInterceptor;
 import org.springframework.cloud.openfeign.support.FeignEncoderProperties;
 import org.springframework.cloud.openfeign.support.FeignHttpClientProperties;
@@ -64,12 +70,14 @@
 import org.springframework.context.annotation.Conditional;
 import org.springframework.context.annotation.Configuration;
 import org.springframework.context.annotation.Import;
+import org.springframework.context.support.GenericApplicationContext;
 import org.springframework.data.domain.Page;
 import org.springframework.data.domain.Sort;
 import org.springframework.security.oauth2.client.AuthorizedClientServiceOAuth2AuthorizedClientManager;
 import org.springframework.security.oauth2.client.OAuth2AuthorizedClientManager;
 import org.springframework.security.oauth2.client.OAuth2AuthorizedClientService;
 import org.springframework.security.oauth2.client.registration.ClientRegistrationRepository;
+import org.springframework.util.ClassUtils;
 
 /**
  * @author Spencer Gibb
@@ -102,12 +110,24 @@ public HasFeatures feignFeature() {
 	}
 
 	@Bean
-	public FeignContext feignContext() {
-		FeignContext context = new FeignContext();
+	public FeignClientFactory feignContext() {
+		FeignClientFactory context = new FeignClientFactory();
 		context.setConfigurations(this.configurations);
 		return context;
 	}
 
+	@Bean
+	static FeignChildContextInitializer feignChildContextInitializer(GenericApplicationContext parentContext,
+			FeignClientFactory feignClientFactory) {
+		return new FeignChildContextInitializer(parentContext, feignClientFactory);
+	}
+
+	@Bean
+	static FeignClientBeanFactoryInitializationAotProcessor feignClientBeanFactoryInitializationCodeGenerator(
+			GenericApplicationContext applicationContext, FeignClientFactory feignClientFactory) {
+		return new FeignClientBeanFactoryInitializationAotProcessor(applicationContext, feignClientFactory);
+	}
+
 	@Bean
 	@ConditionalOnProperty(value = "spring.cloud.openfeign.cache.enabled", matchIfMissing = true)
 	@ConditionalOnBean(CacheInterceptor.class)
@@ -358,3 +378,17 @@ public OAuth2AccessTokenInterceptor defaultOAuth2AccessTokenInterceptor(
 	}
 
 }
+
+class FeignHints implements RuntimeHintsRegistrar {
+
+	@Override
+	public void registerHints(RuntimeHints hints, ClassLoader classLoader) {
+		if (!ClassUtils.isPresent("feign.Feign", classLoader)) {
+			return;
+		}
+		hints.reflection().registerType(TypeReference.of(FeignClientFactoryBean.class),
+				hint -> hint.withMembers(MemberCategory.INVOKE_DECLARED_CONSTRUCTORS,
+						MemberCategory.INVOKE_DECLARED_METHODS, MemberCategory.DECLARED_FIELDS));
+	}
+
+}

spring-cloud-openfeign-core/src/main/java/org/springframework/cloud/openfeign/FeignCircuitBreakerTargeter.java

@@ -39,7 +39,7 @@ class FeignCircuitBreakerTargeter implements Targeter {
 	}
 
 	@Override
-	public <T> T target(FeignClientFactoryBean factory, Feign.Builder feign, FeignContext context,
+	public <T> T target(FeignClientFactoryBean factory, Feign.Builder feign, FeignClientFactory context,
 			Target.HardCodedTarget<T> target) {
 		if (!(feign instanceof FeignCircuitBreaker.Builder builder)) {
 			return feign.target(target);
@@ -56,20 +56,20 @@ public <T> T target(FeignClientFactoryBean factory, Feign.Builder feign, FeignCo
 		return builder(name, builder).target(target);
 	}
 
-	private <T> T targetWithFallbackFactory(String feignClientName, FeignContext context,
+	private <T> T targetWithFallbackFactory(String feignClientName, FeignClientFactory context,
 			Target.HardCodedTarget<T> target, FeignCircuitBreaker.Builder builder, Class<?> fallbackFactoryClass) {
 		FallbackFactory<? extends T> fallbackFactory = (FallbackFactory<? extends T>) getFromContext("fallbackFactory",
 				feignClientName, context, fallbackFactoryClass, FallbackFactory.class);
 		return builder(feignClientName, builder).target(target, fallbackFactory);
 	}
 
-	private <T> T targetWithFallback(String feignClientName, FeignContext context, Target.HardCodedTarget<T> target,
-			FeignCircuitBreaker.Builder builder, Class<?> fallback) {
+	private <T> T targetWithFallback(String feignClientName, FeignClientFactory context,
+			Target.HardCodedTarget<T> target, FeignCircuitBreaker.Builder builder, Class<?> fallback) {
 		T fallbackInstance = getFromContext("fallback", feignClientName, context, fallback, target.type());
 		return builder(feignClientName, builder).target(target, fallbackInstance);
 	}
 
-	private <T> T getFromContext(String fallbackMechanism, String feignClientName, FeignContext context,
+	private <T> T getFromContext(String fallbackMechanism, String feignClientName, FeignClientFactory context,
 			Class<?> beanType, Class<T> targetType) {
 		Object fallbackInstance = context.getInstance(feignClientName, beanType);
 		if (fallbackInstance == null) {

spring-cloud-openfeign-core/src/main/java/org/springframework/cloud/openfeign/FeignContext.java → spring-cloud-openfeign-core/src/main/java/org/springframework/cloud/openfeign/FeignClientFactory.java

@@ -16,11 +16,14 @@
 
 package org.springframework.cloud.openfeign;
 
+import java.util.HashMap;
 import java.util.Map;
 
 import org.springframework.beans.BeansException;
 import org.springframework.beans.factory.BeanFactoryUtils;
 import org.springframework.cloud.context.named.NamedContextFactory;
+import org.springframework.context.ApplicationContextInitializer;
+import org.springframework.context.support.GenericApplicationContext;
 import org.springframework.lang.Nullable;
 
 /**
@@ -31,11 +34,18 @@
  * @author Dave Syer
  * @author Matt King
  * @author Jasbir Singh
+ * @author Olga Maciaszek-Sharma
  */
-public class FeignContext extends NamedContextFactory<FeignClientSpecification> {
+public class FeignClientFactory extends NamedContextFactory<FeignClientSpecification> {
 
-	public FeignContext() {
-		super(FeignClientsConfiguration.class, "spring.cloud.openfeign", "spring.cloud.openfeign.client.name");
+	public FeignClientFactory() {
+		this(new HashMap<>());
+	}
+
+	public FeignClientFactory(
+			Map<String, ApplicationContextInitializer<GenericApplicationContext>> applicationContextInitializers) {
+		super(FeignClientsConfiguration.class, "spring.cloud.openfeign", "spring.cloud.openfeign.client.name",
+				applicationContextInitializers);
 	}
 
 	@Nullable
@@ -57,4 +67,14 @@ public <T> T getInstance(String contextName, String beanName, Class<T> type) {
 		return getContext(contextName).getBean(beanName, type);
 	}
 
+	@SuppressWarnings("unchecked")
+	public FeignClientFactory withApplicationContextInitializers(Map<String, Object> applicationContextInitializers) {
+		Map<String, ApplicationContextInitializer<GenericApplicationContext>> convertedInitializers = new HashMap<>();
+		applicationContextInitializers.keySet()
+				.forEach(contextId -> convertedInitializers.put(contextId,
+						(ApplicationContextInitializer<GenericApplicationContext>) applicationContextInitializers
+								.get(contextId)));
+		return new FeignClientFactory(convertedInitializers);
+	}
+
 }

spring-cloud-openfeign-core/src/main/java/org/springframework/cloud/openfeign/FeignClientFactoryBean.java

@@ -113,13 +113,22 @@ public class FeignClientFactoryBean
 
 	private final List<FeignBuilderCustomizer> additionalCustomizers = new ArrayList<>();
 
+	private String[] qualifiers = new String[] {};
+
+	// For AOT testing
+	public FeignClientFactoryBean() {
+		if (LOG.isDebugEnabled()) {
+			LOG.debug("Creating a FeignClientFactoryBean.");
+		}
+	}
+
 	@Override
 	public void afterPropertiesSet() {
 		Assert.hasText(contextId, "Context id must be set");
 		Assert.hasText(name, "Name must be set");
 	}
 
-	protected Feign.Builder feign(FeignContext context) {
+	protected Feign.Builder feign(FeignClientFactory context) {
 		FeignLoggerFactory loggerFactory = get(context, FeignLoggerFactory.class);
 		Logger logger = loggerFactory.create(type);
 
@@ -137,7 +146,7 @@ protected Feign.Builder feign(FeignContext context) {
 		return builder;
 	}
 
-	private void applyBuildCustomizers(FeignContext context, Feign.Builder builder) {
+	private void applyBuildCustomizers(FeignClientFactory context, Feign.Builder builder) {
 		Map<String, FeignBuilderCustomizer> customizerMap = context.getInstances(contextId,
 				FeignBuilderCustomizer.class);
 
@@ -148,7 +157,7 @@ private void applyBuildCustomizers(FeignContext context, Feign.Builder builder)
 		additionalCustomizers.forEach(customizer -> customizer.customize(builder));
 	}
 
-	protected void configureFeign(FeignContext context, Feign.Builder builder) {
+	protected void configureFeign(FeignClientFactory context, Feign.Builder builder) {
 		FeignClientProperties properties = beanFactory != null ? beanFactory.getBean(FeignClientProperties.class)
 				: applicationContext.getBean(FeignClientProperties.class);
 
@@ -172,7 +181,7 @@ protected void configureFeign(FeignContext context, Feign.Builder builder) {
 		}
 	}
 
-	protected void configureUsingConfiguration(FeignContext context, Feign.Builder builder) {
+	protected void configureUsingConfiguration(FeignClientFactory context, Feign.Builder builder) {
 		Logger.Level level = getInheritedAwareOptional(context, Logger.Level.class);
 		if (level != null) {
 			builder.logLevel(level);
@@ -340,19 +349,19 @@ private <T> T getOrInstantiate(Class<T> tClass) {
 		}
 	}
 
-	protected <T> T get(FeignContext context, Class<T> type) {
+	protected <T> T get(FeignClientFactory context, Class<T> type) {
 		T instance = context.getInstance(contextId, type);
 		if (instance == null) {
 			throw new IllegalStateException("No bean found of type " + type + " for " + contextId);
 		}
 		return instance;
 	}
 
-	protected <T> T getOptional(FeignContext context, Class<T> type) {
+	protected <T> T getOptional(FeignClientFactory context, Class<T> type) {
 		return context.getInstance(contextId, type);
 	}
 
-	protected <T> T getInheritedAwareOptional(FeignContext context, Class<T> type) {
+	protected <T> T getInheritedAwareOptional(FeignClientFactory context, Class<T> type) {
 		if (inheritParentContext) {
 			return getOptional(context, type);
 		}
@@ -361,7 +370,7 @@ protected <T> T getInheritedAwareOptional(FeignContext context, Class<T> type) {
 		}
 	}
 
-	protected <T> Map<String, T> getInheritedAwareInstances(FeignContext context, Class<T> type) {
+	protected <T> Map<String, T> getInheritedAwareInstances(FeignClientFactory context, Class<T> type) {
 		if (inheritParentContext) {
 			return context.getInstances(contextId, type);
 		}
@@ -370,7 +379,7 @@ protected <T> Map<String, T> getInheritedAwareInstances(FeignContext context, Cl
 		}
 	}
 
-	protected <T> T loadBalance(Feign.Builder builder, FeignContext context, HardCodedTarget<T> target) {
+	protected <T> T loadBalance(Feign.Builder builder, FeignClientFactory context, HardCodedTarget<T> target) {
 		Client client = getOptional(context, Client.class);
 		if (client != null) {
 			builder.client(client);
@@ -389,7 +398,7 @@ protected <T> T loadBalance(Feign.Builder builder, FeignContext context, HardCod
 	 * @param contextId name of feign client
 	 * @return returns Options found in context
 	 */
-	protected Request.Options getOptionsByName(FeignContext context, String contextId) {
+	protected Request.Options getOptionsByName(FeignClientFactory context, String contextId) {
 		if (refreshableClient) {
 			return context.getInstance(contextId, Request.Options.class.getCanonicalName() + "-" + contextId,
 					Request.Options.class);
@@ -409,9 +418,9 @@ public Object getObject() {
 	 */
 	@SuppressWarnings("unchecked")
 	<T> T getTarget() {
-		FeignContext context = beanFactory != null ? beanFactory.getBean(FeignContext.class)
-				: applicationContext.getBean(FeignContext.class);
-		Feign.Builder builder = feign(context);
+		FeignClientFactory feignClientFactory = beanFactory != null ? beanFactory.getBean(FeignClientFactory.class)
+				: applicationContext.getBean(FeignClientFactory.class);
+		Feign.Builder builder = feign(feignClientFactory);
 		if (!StringUtils.hasText(url) && !isUrlAvailableInConfig(contextId)) {
 
 			if (LOG.isInfoEnabled()) {
@@ -424,13 +433,13 @@ <T> T getTarget() {
 				url = name;
 			}
 			url += cleanPath();
-			return (T) loadBalance(builder, context, new HardCodedTarget<>(type, name, url));
+			return (T) loadBalance(builder, feignClientFactory, new HardCodedTarget<>(type, name, url));
 		}
 		if (StringUtils.hasText(url) && !url.startsWith("http")) {
 			url = "http://" + url;
 		}
 		String url = this.url + cleanPath();
-		Client client = getOptional(context, Client.class);
+		Client client = getOptional(feignClientFactory, Client.class);
 		if (client != null) {
 			if (client instanceof FeignBlockingLoadBalancerClient) {
 				// not load balancing because we have a url,
@@ -445,10 +454,10 @@ <T> T getTarget() {
 			builder.client(client);
 		}
 
-		applyBuildCustomizers(context, builder);
+		applyBuildCustomizers(feignClientFactory, builder);
 
-		Targeter targeter = get(context, Targeter.class);
-		return targeter.target(this, builder, context, resolveTarget(context, contextId, url));
+		Targeter targeter = get(feignClientFactory, Targeter.class);
+		return targeter.target(this, builder, feignClientFactory, resolveTarget(feignClientFactory, contextId, url));
 	}
 
 	private String cleanPath() {
@@ -468,7 +477,7 @@ private String cleanPath() {
 	}
 
 	@SuppressWarnings({ "unchecked", "rawtypes" })
-	private <T> HardCodedTarget<T> resolveTarget(FeignContext context, String contextId, String url) {
+	private <T> HardCodedTarget<T> resolveTarget(FeignClientFactory context, String contextId, String url) {
 		if (StringUtils.hasText(url)) {
 			return new HardCodedTarget(type, name, url);
 		}
@@ -600,6 +609,14 @@ public void setRefreshableClient(boolean refreshableClient) {
 		this.refreshableClient = refreshableClient;
 	}
 
+	public String[] getQualifiers() {
+		return qualifiers;
+	}
+
+	public void setQualifiers(String[] qualifiers) {
+		this.qualifiers = qualifiers;
+	}
+
 	@Override
 	public boolean equals(Object o) {
 		if (this == o) {