Implement equals() and hashCode() in StateTransition

This commit prevents duplicate state transition entries
in flow definitions

Resolves spring-projects#3674

Author: Kyoungwoong

spring-batch-core/src/main/java/org/springframework/batch/core/job/flow/support/StateTransition.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2006-2023 the original author or authors.
+ * Copyright 2006-2024 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -22,6 +22,8 @@
 import org.springframework.util.Assert;
 import org.springframework.util.StringUtils;
 
+import java.util.Objects;
+
 /**
  * Value object representing a potential transition from one {@link State} to another. The
  * originating State name and the next {@link State} to execute are linked by a pattern
@@ -31,6 +33,7 @@
  * @author Dave Syer
  * @author Michael Minella
  * @author Mahmoud Ben Hassine
+ * @author Kim Youngwoong
  * @since 2.0
  */
 public final class StateTransition {
@@ -159,6 +162,22 @@ public boolean isEnd() {
 		return next == null;
 	}
 
+	@Override
+	public boolean equals(Object o) {
+		if (this == o)
+			return true;
+		if (o == null || getClass() != o.getClass())
+			return false;
+		StateTransition that = (StateTransition) o;
+		return Objects.equals(state, that.state) && Objects.equals(pattern, that.pattern)
+				&& Objects.equals(next, that.next);
+	}
+
+	@Override
+	public int hashCode() {
+		return Objects.hash(state, pattern, next);
+	}
+
 	@Override
 	public String toString() {
 		return String.format("StateTransition: [state=%s, pattern=%s, next=%s]", state == null ? null : state.getName(),

spring-batch-core/src/test/java/org/springframework/batch/core/job/flow/support/StateTransitionTests.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2006-2022 the original author or authors.
+ * Copyright 2006-2024 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -15,6 +15,8 @@
  */
 package org.springframework.batch.core.job.flow.support;
 
+import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.junit.jupiter.api.Assertions.assertNotEquals;
 import static org.junit.jupiter.api.Assertions.assertNull;
 import static org.junit.jupiter.api.Assertions.assertTrue;
 
@@ -25,7 +27,7 @@
 /**
  * @author Dave Syer
  * @author Michael Minella
- *
+ * @author Kim Youngwoong
  */
 class StateTransitionTests {
 
@@ -74,6 +76,18 @@ void testMatchesPlaceholder() {
 		assertTrue(transition.matches("CONTINUABLE"));
 	}
 
+	@Test
+	void testEquals() {
+		StateTransition transition1 = StateTransition.createStateTransition(state, "pattern1", "next1");
+		StateTransition transition2 = StateTransition.createStateTransition(state, "pattern1", "next1");
+		StateTransition transition3 = StateTransition.createStateTransition(state, "pattern2", "next2");
+
+		assertEquals(transition1, transition2);
+		assertNotEquals(transition1, transition3);
+		assertEquals(transition1, transition1);
+		assertNotEquals(null, transition1);
+	}
+
 	@Test
 	void testToString() {
 		StateTransition transition = StateTransition.createStateTransition(state, "CONTIN???LE", "start");