Add placeholder resolution support for @⁠ConcurrencyLimit

See gh-35461
Closes gh-35470

Signed-off-by: Hyunsang Han <gustkd3@gmail.com>

Author: HyunSangHan

spring-context/src/main/java/org/springframework/resilience/annotation/ConcurrencyLimit.java

@@ -42,6 +42,7 @@
  * {@link org.springframework.aop.interceptor.ConcurrencyThrottleInterceptor}.
  *
  * @author Juergen Hoeller
+ * @author Hyunsang Han
  * @since 7.0
  * @see EnableResilientMethods
  * @see ConcurrencyLimitBeanPostProcessor
@@ -62,4 +63,12 @@
 	 */
 	int value() default 1;
 
+	/**
+	 * The concurrency limit as a configurable String.
+	 * A non-empty value specified here overrides the {@link #value()} attribute.
+	 * <p>This supports Spring-style "${...}" placeholders as well as SpEL expressions.
+	 * @see #value()
+	 */
+	String valueString() default "";
+
 }

spring-context/src/main/java/org/springframework/resilience/annotation/ConcurrencyLimitBeanPostProcessor.java

@@ -31,20 +31,27 @@
 import org.springframework.aop.support.ComposablePointcut;
 import org.springframework.aop.support.DefaultPointcutAdvisor;
 import org.springframework.aop.support.annotation.AnnotationMatchingPointcut;
+import org.springframework.context.EmbeddedValueResolverAware;
 import org.springframework.core.annotation.AnnotatedElementUtils;
 import org.springframework.util.Assert;
 import org.springframework.util.ConcurrentReferenceHashMap;
+import org.springframework.util.StringUtils;
+import org.springframework.util.StringValueResolver;
 
 /**
  * A convenient {@link org.springframework.beans.factory.config.BeanPostProcessor
  * BeanPostProcessor} that applies a concurrency interceptor to all bean methods
  * annotated with {@link ConcurrencyLimit @ConcurrencyLimit}.
  *
  * @author Juergen Hoeller
+ * @author Hyunsang Han
  * @since 7.0
  */
 @SuppressWarnings("serial")
-public class ConcurrencyLimitBeanPostProcessor extends AbstractBeanFactoryAwareAdvisingPostProcessor {
+public class ConcurrencyLimitBeanPostProcessor extends AbstractBeanFactoryAwareAdvisingPostProcessor
+		implements EmbeddedValueResolverAware {
+
+	private @Nullable StringValueResolver embeddedValueResolver;
 
 	public ConcurrencyLimitBeanPostProcessor() {
 		setBeforeExistingAdvisors(true);
@@ -57,7 +64,13 @@ public ConcurrencyLimitBeanPostProcessor() {
 	}
 
 
-	private static class ConcurrencyLimitInterceptor implements MethodInterceptor {
+	@Override
+	public void setEmbeddedValueResolver(StringValueResolver resolver) {
+		this.embeddedValueResolver = resolver;
+	}
+
+
+	private class ConcurrencyLimitInterceptor implements MethodInterceptor {
 
 		private final Map<Object, ConcurrencyThrottleCache> cachePerInstance =
 				new ConcurrentReferenceHashMap<>(16, ConcurrentReferenceHashMap.ReferenceType.WEAK);
@@ -93,7 +106,8 @@ private static class ConcurrencyLimitInterceptor implements MethodInterceptor {
 						}
 						if (interceptor == null) {
 							Assert.state(limit != null, "No @ConcurrencyLimit annotation found");
-							interceptor = new ConcurrencyThrottleInterceptor(limit.value());
+							int concurrencyLimit = parseInt(limit.value(), limit.valueString());
+							interceptor = new ConcurrencyThrottleInterceptor(concurrencyLimit);
 							if (!perMethod) {
 								cache.classInterceptor = interceptor;
 							}
@@ -104,6 +118,18 @@ private static class ConcurrencyLimitInterceptor implements MethodInterceptor {
 			}
 			return interceptor.invoke(invocation);
 		}
+
+		private int parseInt(int value, String stringValue) {
+			if (StringUtils.hasText(stringValue)) {
+				if (embeddedValueResolver != null) {
+					stringValue = embeddedValueResolver.resolveStringValue(stringValue);
+				}
+				if (StringUtils.hasText(stringValue)) {
+					return Integer.parseInt(stringValue);
+				}
+			}
+			return value;
+		}
 	}
 
 

spring-context/src/test/java/org/springframework/resilience/ConcurrencyLimitTests.java

@@ -18,6 +18,7 @@
 
 import java.util.ArrayList;
 import java.util.List;
+import java.util.Properties;
 import java.util.concurrent.CompletableFuture;
 import java.util.concurrent.atomic.AtomicInteger;
 
@@ -28,13 +29,17 @@
 import org.springframework.aop.interceptor.ConcurrencyThrottleInterceptor;
 import org.springframework.beans.factory.support.DefaultListableBeanFactory;
 import org.springframework.beans.factory.support.RootBeanDefinition;
+import org.springframework.context.annotation.AnnotationConfigApplicationContext;
+import org.springframework.core.env.PropertiesPropertySource;
 import org.springframework.resilience.annotation.ConcurrencyLimit;
 import org.springframework.resilience.annotation.ConcurrencyLimitBeanPostProcessor;
+import org.springframework.resilience.annotation.EnableResilientMethods;
 
 import static org.assertj.core.api.Assertions.assertThat;
 
 /**
  * @author Juergen Hoeller
+ * @author Hyunsang Han
  * @since 7.0
  */
 class ConcurrencyLimitTests {
@@ -97,6 +102,28 @@ void withPostProcessorForClass() {
 		assertThat(target.current).hasValue(0);
 	}
 
+	@Test
+	void withPlaceholderResolution() {
+		Properties props = new Properties();
+		props.setProperty("test.concurrency.limit", "3");
+
+		AnnotationConfigApplicationContext ctx = new AnnotationConfigApplicationContext();
+		ctx.getEnvironment().getPropertySources().addFirst(new PropertiesPropertySource("test", props));
+		ctx.register(PlaceholderTestConfig.class, PlaceholderBean.class);
+		ctx.refresh();
+
+		PlaceholderBean proxy = ctx.getBean(PlaceholderBean.class);
+		PlaceholderBean target = (PlaceholderBean) AopProxyUtils.getSingletonTarget(proxy);
+
+		// Test with limit=3 from properties
+		List<CompletableFuture<?>> futures = new ArrayList<>(10);
+		for (int i = 0; i < 10; i++) {
+			futures.add(CompletableFuture.runAsync(proxy::concurrentOperation));
+		}
+		CompletableFuture.allOf(futures.toArray(new CompletableFuture[0])).join();
+		assertThat(target.current).hasValue(0);
+		ctx.close();
+	}
 
 	static class NonAnnotatedBean {
 
@@ -185,4 +212,29 @@ public void overrideOperation() {
 		}
 	}
 
+
+	@EnableResilientMethods
+	static class PlaceholderTestConfig {
+	}
+
+
+	static class PlaceholderBean {
+
+		AtomicInteger current = new AtomicInteger();
+
+		@ConcurrencyLimit(valueString = "${test.concurrency.limit}")
+		public void concurrentOperation() {
+			if (current.incrementAndGet() > 3) {  // Assumes test.concurrency.limit=3
+				throw new IllegalStateException();
+			}
+			try {
+				Thread.sleep(100);
+			}
+			catch (InterruptedException ex) {
+				throw new IllegalStateException(ex);
+			}
+			current.decrementAndGet();
+		}
+	}
+
 }