Re-calculate SimpleKey's hashCode field on deserialization

Closes gh-24320

spring-context/src/main/java/org/springframework/cache/interceptor/SimpleKey.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2018 the original author or authors.
+ * Copyright 2002-2020 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.
@@ -16,6 +16,8 @@
 
 package org.springframework.cache.interceptor;
 
+import java.io.IOException;
+import java.io.ObjectInputStream;
 import java.io.Serializable;
 import java.util.Arrays;
 
@@ -27,19 +29,23 @@ import org.springframework.util.StringUtils;
  * A simple key as returned from the {@link SimpleKeyGenerator}.
  *
  * @author Phillip Webb
+ * @author Juergen Hoeller
  * @since 4.0
  * @see SimpleKeyGenerator
  */
 @SuppressWarnings("serial")
 public class SimpleKey implements Serializable {
 
-	/** An empty key. */
+	/**
+	 * An empty key.
+	 */
 	public static final SimpleKey EMPTY = new SimpleKey();
 
 
 	private final Object[] params;
 
-	private final int hashCode;
+	// Effectively final, just re-calculated on deserialization
+	private transient int hashCode;
 
 
 	/**
@@ -49,6 +55,7 @@ public class SimpleKey implements Serializable {
 	public SimpleKey(Object... elements) {
 		Assert.notNull(elements, "Elements must not be null");
 		this.params = elements.clone();
+		// Pre-calculate hashCode field
 		this.hashCode = Arrays.deepHashCode(this.params);
 	}
 
@@ -61,6 +68,7 @@ public class SimpleKey implements Serializable {
 
 	@Override
 	public final int hashCode() {
+		// Expose pre-calculated hashCode field
 		return this.hashCode;
 	}
 
@@ -69,4 +77,10 @@ public class SimpleKey implements Serializable {
 		return getClass().getSimpleName() + " [" + StringUtils.arrayToCommaDelimitedString(this.params) + "]";
 	}
 
+	private void readObject(ObjectInputStream ois) throws IOException, ClassNotFoundException {
+		ois.defaultReadObject();
+		// Re-calculate hashCode field on deserialization
+		this.hashCode = Arrays.deepHashCode(this.params);
+	}
+
 }