feat: setter for Log of RetryTemplate (#471)

GH-470: Add `RetryTemplate.setLogger()` to avoid reflection in other places

Fixes: #470
Issue link: https://github.com/spring-projects/spring-retry/issues/470

Spring Cloud Config does mutation in the `RetryTemplate` for its system loading logger via `RetryTemplateFactory`.

* Expose setter for `logger` property to avoid reflection.
* Add `RetryTemplateBuilder.withLogger()` for convenience

src/main/java/org/springframework/retry/support/RetryTemplate.java

@@ -78,6 +78,7 @@ import org.springframework.util.Assert;
  * @author Josh Long
  * @author Aleksandr Shamukov
  * @author Emanuele Ivaldi
+ * @author Tobias Soloschenko
  */
 public class RetryTemplate implements RetryOperations {
 
@@ -87,7 +88,7 @@ public class RetryTemplate implements RetryOperations {
 	 */
 	private static final String GLOBAL_STATE = "state.global";
 
-	protected final Log logger = LogFactory.getLog(getClass());
+	protected Log logger = LogFactory.getLog(getClass());
 
 	private volatile BackOffPolicy backOffPolicy = new NoBackOffPolicy();
 
@@ -186,6 +187,18 @@ public class RetryTemplate implements RetryOperations {
 		return this.listeners.length > 0;
 	}
 
+	/**
+	 * Setter for {@link Log}. If not applied the following is used:
+	 * <p>
+	 * {@code LogFactory.getLog(getClass())}
+	 * </p>
+	 * @param logger the logger the retry template uses for logging
+	 * @since 2.0.10
+	 */
+	public void setLogger(Log logger) {
+		this.logger = logger;
+	}
+
 	/**
 	 * Setter for {@link BackOffPolicy}.
 	 * @param backOffPolicy the {@link BackOffPolicy}

src/main/java/org/springframework/retry/support/RetryTemplateBuilder.java

@@ -21,6 +21,7 @@ import java.util.ArrayList;
 import java.util.List;
 import java.util.function.Predicate;
 
+import org.apache.commons.logging.Log;
 import org.springframework.classify.BinaryExceptionClassifier;
 import org.springframework.classify.BinaryExceptionClassifierBuilder;
 import org.springframework.retry.RetryListener;
@@ -79,12 +80,15 @@ import org.springframework.util.Assert;
  * @author Kim In Hoi
  * @author Andreas Ahlenstorf
  * @author Morulai Planinski
+ * @author Tobias Soloschenko
  * @since 1.3
  */
 public class RetryTemplateBuilder {
 
 	private RetryPolicy baseRetryPolicy;
 
+	private Log logger;
+
 	private BackOffPolicy backOffPolicy;
 
 	private List<RetryListener> listeners;
@@ -288,6 +292,23 @@ public class RetryTemplateBuilder {
 		return this.exponentialBackoff(initialInterval.toMillis(), multiplier, maxInterval.toMillis(), withRandom);
 	}
 
+	/**
+	 * Applies a dedicated logger to the {@link RetryTemplate}. If not applied the
+	 * following is used:
+	 * <p>
+	 * {@code LogFactory.getLog(getClass())}
+	 * </p>
+	 * @param logger the logger which should be used for logging
+	 * @return this
+	 * @since 2.0.10
+	 */
+	public RetryTemplateBuilder withLogger(Log logger) {
+		Assert.isNull(this.logger, "You have already applied a logger");
+		Assert.notNull(logger, "The given logger should not be null");
+		this.logger = logger;
+		return this;
+	}
+
 	/**
 	 * Perform each retry after a fixed amount of time.
 	 * @param interval fixed interval in milliseconds
@@ -584,6 +605,12 @@ public class RetryTemplateBuilder {
 		finalPolicy.setPolicies(new RetryPolicy[] { this.baseRetryPolicy, exceptionRetryPolicy });
 		retryTemplate.setRetryPolicy(finalPolicy);
 
+		// Logger
+
+		if (this.logger != null) {
+			retryTemplate.setLogger(this.logger);
+		}
+
 		// Backoff policy
 
 		if (this.backOffPolicy == null) {

src/test/java/org/springframework/retry/support/RetryTemplateBuilderTests.java

@@ -24,6 +24,7 @@ import java.util.Collections;
 import java.util.List;
 import java.util.function.Predicate;
 
+import org.apache.commons.logging.Log;
 import org.junit.jupiter.api.Test;
 import org.springframework.classify.BinaryExceptionClassifier;
 import org.springframework.retry.RetryListener;
@@ -58,6 +59,7 @@ import static org.springframework.retry.util.test.TestUtils.getPropertyValue;
  * @author Gary Russell
  * @author Andreas Ahlenstorf
  * @author Morulai Planinski
+ * @author Tobias Soloschenko
  */
 public class RetryTemplateBuilderTests {
 
@@ -346,6 +348,21 @@ public class RetryTemplateBuilderTests {
 			.isThrownBy(() -> RetryTemplate.builder().exponentialBackoff(0, 2, 200).build());
 	}
 
+	@Test
+	public void testBuilderWithLogger() {
+		Log logMock = mock(Log.class);
+		RetryTemplate retryTemplate = RetryTemplate.builder().withLogger(logMock).build();
+		Log logger = getPropertyValue(retryTemplate, "logger", Log.class);
+		assertThat(logger).isEqualTo(logMock);
+	}
+
+	@Test
+	public void testBuilderWithDefaultLogger() {
+		RetryTemplate retryTemplate = RetryTemplate.builder().build();
+		Log logger = getPropertyValue(retryTemplate, "logger", Log.class);
+		assertThat(logger).isNotNull();
+	}
+
 	/* ---------------- Utils -------------- */
 
 	private static class PolicyTuple {

src/test/java/org/springframework/retry/support/RetryTemplateTests.java

@@ -20,8 +20,10 @@ import java.util.Collections;
 import java.util.concurrent.atomic.AtomicBoolean;
 import java.util.concurrent.atomic.AtomicInteger;
 
+import org.apache.commons.logging.Log;
 import org.junit.jupiter.api.Test;
 
+import org.mockito.ArgumentCaptor;
 import org.springframework.classify.BinaryExceptionClassifier;
 import org.springframework.retry.RetryCallback;
 import org.springframework.retry.RetryContext;
@@ -45,6 +47,7 @@ import static org.mockito.ArgumentMatchers.any;
 import static org.mockito.BDDMockito.given;
 import static org.mockito.Mockito.mock;
 import static org.mockito.Mockito.verify;
+import static org.mockito.Mockito.when;
 
 /**
  * @author Rob Harrop
@@ -53,6 +56,7 @@ import static org.mockito.Mockito.verify;
  * @author Henning Pöttker
  * @author Emanuele Ivaldi
  * @author Morulai Planinski
+ * @author Tobias Soloschenko
  */
 public class RetryTemplateTests {
 
@@ -286,7 +290,6 @@ public class RetryTemplateTests {
 		}
 	}
 
-	@SuppressWarnings("serial")
 	@Test
 	public void testFailedPolicy() {
 		RetryTemplate retryTemplate = new RetryTemplate();
@@ -325,7 +328,6 @@ public class RetryTemplateTests {
 		tested.setRetryPolicy(new SimpleRetryPolicy(1));
 
 		BackOffPolicy bop = mock(BackOffPolicy.class);
-		@SuppressWarnings("serial")
 		BackOffContext backOffContext = new BackOffContext() {
 		};
 		tested.setBackOffPolicy(bop);
@@ -439,4 +441,17 @@ public class RetryTemplateTests {
 
 	}
 
+	@Test
+	public void testLoggingAppliedCorrectly() throws Exception {
+		ArgumentCaptor<String> logOutputCaptor = ArgumentCaptor.forClass(String.class);
+		RetryTemplate retryTemplate = new RetryTemplate();
+		Log logMock = mock(Log.class);
+		when(logMock.isTraceEnabled()).thenReturn(false);
+		when(logMock.isDebugEnabled()).thenReturn(true);
+		retryTemplate.setLogger(logMock);
+		retryTemplate.execute(new MockRetryCallback());
+		verify(logMock).debug(logOutputCaptor.capture());
+		assertThat(logOutputCaptor.getValue()).contains("Retry: count=0");
+	}
+
 }