Consistently implement toString() in BackOff strategies

Closes gh-35120

Author: sbrannen

spring-core/src/main/java/org/springframework/util/backoff/ExponentialBackOff.java

@@ -255,7 +255,7 @@ public BackOffExecution start() {
 
 	@Override
 	public String toString() {
-		return new StringJoiner(", ", ExponentialBackOff.class.getSimpleName() + "{", "}")
+		return new StringJoiner(", ", "ExponentialBackOff[", "]")
 				.add("initialInterval=" + this.initialInterval)
 				.add("jitter=" + this.jitter)
 				.add("multiplier=" + this.multiplier)
@@ -316,7 +316,7 @@ private long applyJitter(long interval) {
 		@Override
 		public String toString() {
 			String currentIntervalDescription = this.currentInterval < 0 ? "n/a" : this.currentInterval + "ms";
-			return new StringJoiner(", ", ExponentialBackOffExecution.class.getSimpleName() + "{", "}")
+			return new StringJoiner(", ", "ExponentialBackOffExecution[", "]")
 					.add("currentInterval=" + currentIntervalDescription)
 					.add("multiplier=" + getMultiplier())
 					.add("attempts=" + this.attempts)

spring-core/src/main/java/org/springframework/util/backoff/FixedBackOff.java

@@ -119,6 +119,13 @@ public BackOffExecution start() {
 		return new FixedBackOffExecution();
 	}
 
+	@Override
+	public String toString() {
+		String attemptValue = (this.maxAttempts == Long.MAX_VALUE ? "unlimited" :
+				String.valueOf(FixedBackOff.this.maxAttempts));
+		return "FixedBackOff[interval=" + this.interval +
+				", maxAttempts=" + attemptValue + ']';
+	}
 
 	private class FixedBackOffExecution implements BackOffExecution {
 
@@ -139,10 +146,10 @@ public long nextBackOff() {
 		public String toString() {
 			String attemptValue = (FixedBackOff.this.maxAttempts == Long.MAX_VALUE ?
 					"unlimited" : String.valueOf(FixedBackOff.this.maxAttempts));
-			return "FixedBackOff{interval=" + FixedBackOff.this.interval +
+			return "FixedBackOffExecution[interval=" + FixedBackOff.this.interval +
 					", currentAttempts=" + this.currentAttempts +
 					", maxAttempts=" + attemptValue +
-					'}';
+					']';
 		}
 	}
 

spring-core/src/test/java/org/springframework/util/ExponentialBackOffTests.java

@@ -32,6 +32,7 @@
  * Tests for {@link ExponentialBackOff}.
  *
  * @author Stephane Nicoll
+ * @author Sam Brannen
  */
 class ExponentialBackOffTests {
 
@@ -128,14 +129,24 @@ void maxIntervalReachedImmediately() {
 	}
 
 	@Test
-	void executionToStringContent() {
+	void toStringContent() {
 		ExponentialBackOff backOff = new ExponentialBackOff(2000L, 2.0);
+		assertThat(backOff).asString()
+				.isEqualTo("""
+						ExponentialBackOff[\
+						initialInterval=2000, \
+						jitter=0, \
+						multiplier=2.0, \
+						maxInterval=30000, \
+						maxElapsedTime=%d, \
+						maxAttempts=%d]""", Long.MAX_VALUE, Integer.MAX_VALUE);
+
 		BackOffExecution execution = backOff.start();
-		assertThat(execution.toString()).isEqualTo("ExponentialBackOffExecution{currentInterval=n/a, multiplier=2.0, attempts=0}");
+		assertThat(execution).asString().isEqualTo("ExponentialBackOffExecution[currentInterval=n/a, multiplier=2.0, attempts=0]");
 		execution.nextBackOff();
-		assertThat(execution.toString()).isEqualTo("ExponentialBackOffExecution{currentInterval=2000ms, multiplier=2.0, attempts=1}");
+		assertThat(execution).asString().isEqualTo("ExponentialBackOffExecution[currentInterval=2000ms, multiplier=2.0, attempts=1]");
 		execution.nextBackOff();
-		assertThat(execution.toString()).isEqualTo("ExponentialBackOffExecution{currentInterval=4000ms, multiplier=2.0, attempts=2}");
+		assertThat(execution).asString().isEqualTo("ExponentialBackOffExecution[currentInterval=4000ms, multiplier=2.0, attempts=2]");
 	}
 
 	@Test

spring-core/src/test/java/org/springframework/util/FixedBackOffTests.java

@@ -27,6 +27,7 @@
  * Tests for {@link FixedBackOff}.
  *
  * @author Stephane Nicoll
+ * @author Sam Brannen
  */
 class FixedBackOffTests {
 
@@ -86,12 +87,14 @@ void liveUpdate() {
 	@Test
 	void toStringContent() {
 		FixedBackOff backOff = new FixedBackOff(200L, 10);
+		assertThat(backOff).asString().isEqualTo("FixedBackOff[interval=200, maxAttempts=10]");
+
 		BackOffExecution execution = backOff.start();
-		assertThat(execution.toString()).isEqualTo("FixedBackOff{interval=200, currentAttempts=0, maxAttempts=10}");
+		assertThat(execution).asString().isEqualTo("FixedBackOffExecution[interval=200, currentAttempts=0, maxAttempts=10]");
 		execution.nextBackOff();
-		assertThat(execution.toString()).isEqualTo("FixedBackOff{interval=200, currentAttempts=1, maxAttempts=10}");
+		assertThat(execution).asString().isEqualTo("FixedBackOffExecution[interval=200, currentAttempts=1, maxAttempts=10]");
 		execution.nextBackOff();
-		assertThat(execution.toString()).isEqualTo("FixedBackOff{interval=200, currentAttempts=2, maxAttempts=10}");
+		assertThat(execution).asString().isEqualTo("FixedBackOffExecution[interval=200, currentAttempts=2, maxAttempts=10]");
 	}
 
 }