GH-34: Resolve Placeholders in Expressions

Further enhancement to #34

README.md

@@ -298,6 +298,8 @@ public void service3() {
 
 These use the familier Spring SpEL expression syntax (`#{...}`).
 
+Expressions can contain property placeholders such as `#{${max.delay}}` or `#{@exceptionChecker.${retry.method}(#root)}`
+
 - `exceptionExpression` is evaluated against the thrown exception as the `#root` object.
 - `maxAttemptsExpression` and the `@BackOff` expression attributes are evaluated once, during initialization; there is no root object for the evaluation but they can reference other beans in the context.
 

src/main/java/org/springframework/retry/annotation/AnnotationAwareRetryOperationsInterceptor.java

@@ -31,6 +31,7 @@ import org.springframework.aop.IntroductionInterceptor;
 import org.springframework.beans.BeansException;
 import org.springframework.beans.factory.BeanFactory;
 import org.springframework.beans.factory.BeanFactoryAware;
+import org.springframework.beans.factory.config.ConfigurableBeanFactory;
 import org.springframework.context.expression.BeanFactoryResolver;
 import org.springframework.core.annotation.AnnotationAwareOrderComparator;
 import org.springframework.core.annotation.AnnotationUtils;
@@ -288,11 +289,11 @@ public class AnnotationAwareRetryOperationsInterceptor implements IntroductionIn
 		Integer maxAttempts = (Integer) attrs.get("maxAttempts");
 		String maxAttemptsExpression = (String) attrs.get("maxAttemptsExpression");
 		if (StringUtils.hasText(maxAttemptsExpression)) {
-			maxAttempts = PARSER.parseExpression(maxAttemptsExpression, PARSER_CONTEXT).getValue(this.evaluationContext,
-					Integer.class);
+			maxAttempts = PARSER.parseExpression(resolve(maxAttemptsExpression), PARSER_CONTEXT)
+					.getValue(this.evaluationContext, Integer.class);
 		}
 		if (includes.length == 0 && excludes.length == 0) {
-			SimpleRetryPolicy simple = hasExpression ? new ExpressionRetryPolicy(exceptionExpression)
+			SimpleRetryPolicy simple = hasExpression ? new ExpressionRetryPolicy(resolve(exceptionExpression))
 															.withBeanFactory(this.beanFactory)
 													 : new SimpleRetryPolicy();
 			simple.setMaxAttempts(maxAttempts);
@@ -317,17 +318,17 @@ public class AnnotationAwareRetryOperationsInterceptor implements IntroductionIn
 	private BackOffPolicy getBackoffPolicy(Backoff backoff) {
 		long min = backoff.delay() == 0 ? backoff.value() : backoff.delay();
 		if (StringUtils.hasText(backoff.delayExpression())) {
-			min = PARSER.parseExpression(backoff.delayExpression(), PARSER_CONTEXT).getValue(this.evaluationContext,
-					Long.class);
+			min = PARSER.parseExpression(resolve(backoff.delayExpression()), PARSER_CONTEXT)
+					.getValue(this.evaluationContext, Long.class);
 		}
 		long max = backoff.maxDelay();
 		if (StringUtils.hasText(backoff.maxDelayExpression())) {
-			max = PARSER.parseExpression(backoff.maxDelayExpression(), PARSER_CONTEXT).getValue(this.evaluationContext,
-					Long.class);
+			max = PARSER.parseExpression(resolve(backoff.maxDelayExpression()), PARSER_CONTEXT)
+					.getValue(this.evaluationContext, Long.class);
 		}
 		double multiplier = backoff.multiplier();
 		if (StringUtils.hasText(backoff.multiplierExpression())) {
-			multiplier = PARSER.parseExpression(backoff.multiplierExpression(), PARSER_CONTEXT)
+			multiplier = PARSER.parseExpression(resolve(backoff.multiplierExpression()), PARSER_CONTEXT)
 					.getValue(this.evaluationContext, Double.class);
 		}
 		if (multiplier > 0) {
@@ -360,4 +361,16 @@ public class AnnotationAwareRetryOperationsInterceptor implements IntroductionIn
 		return policy;
 	}
 
+	/**
+	 * Resolve the specified value if possible.
+	 *
+	 * @see ConfigurableBeanFactory#resolveEmbeddedValue
+	 */
+	private String resolve(String value) {
+		if (this.beanFactory != null && this.beanFactory instanceof ConfigurableBeanFactory) {
+			return ((ConfigurableBeanFactory) this.beanFactory).resolveEmbeddedValue(value);
+		}
+		return value;
+	}
+
 }

src/test/java/org/springframework/retry/annotation/EnableRetryTests.java

@@ -24,6 +24,7 @@ import static org.junit.Assert.fail;
 
 import java.lang.reflect.Method;
 import java.util.Map;
+import java.util.Properties;
 
 import org.aopalliance.intercept.MethodInterceptor;
 import org.junit.Test;
@@ -33,6 +34,7 @@ import org.springframework.beans.DirectFieldAccessor;
 import org.springframework.context.annotation.AnnotationConfigApplicationContext;
 import org.springframework.context.annotation.Bean;
 import org.springframework.context.annotation.Configuration;
+import org.springframework.context.support.PropertySourcesPlaceholderConfigurer;
 import org.springframework.retry.backoff.ExponentialBackOffPolicy;
 import org.springframework.retry.backoff.Sleeper;
 import org.springframework.retry.interceptor.RetryInterceptorBuilder;
@@ -215,6 +217,18 @@ public class EnableRetryTests {
 	@EnableRetry
 	protected static class TestConfiguration {
 
+		@Bean
+		public static PropertySourcesPlaceholderConfigurer pspc() {
+			PropertySourcesPlaceholderConfigurer pspc = new PropertySourcesPlaceholderConfigurer();
+			Properties properties = new Properties();
+			properties.setProperty("one", "1");
+			properties.setProperty("five", "5");
+			properties.setProperty("onePointOne", "1.1");
+			properties.setProperty("retryMethod", "shouldRetry");
+			pspc.setProperties(properties);
+			return pspc;
+		}
+
 		@SuppressWarnings("serial")
 		@Bean
 		public Sleeper sleeper() {
@@ -447,9 +461,10 @@ public class EnableRetryTests {
 			throw new RuntimeException("this cannot be retried");
 		}
 
-		@Retryable(exceptionExpression="#{@exceptionChecker.shouldRetry(#root)}",
+		@Retryable(exceptionExpression="#{@exceptionChecker.${retryMethod}(#root)}",
 				maxAttemptsExpression = "#{@integerFiveBean}",
-			backoff = @Backoff(delayExpression = "#{1}", maxDelayExpression = "#{5}", multiplierExpression = "#{1.1}"))
+			backoff = @Backoff(delayExpression = "#{${one}}", maxDelayExpression = "#{${five}}",
+				multiplierExpression = "#{${onePointOne}}"))
 		public void service3() {
 			if (count++ < 8) {
 				throw new RuntimeException();