ObjectUtils uses HexFormat to format byte[]

Also remove equivalent, applied temporarily in FieldError in 6.2.x.

Closes gh-35675

Author: rstoyanchev

spring-context/src/main/java/org/springframework/validation/FieldError.java

@@ -16,8 +16,6 @@
 
 package org.springframework.validation;
 
-import java.util.HexFormat;
-
 import org.jspecify.annotations.Nullable;
 
 import org.springframework.util.Assert;
@@ -127,18 +125,8 @@ public String toString() {
 		// We would preferably use ObjectUtils.nullSafeConciseToString(rejectedValue) here but
 		// keep including the full nullSafeToString representation for backwards compatibility.
 		return "Field error in object '" + getObjectName() + "' on field '" + this.field +
-				"': rejected value [" + formatRejectedValue() + "]; " +
+				"': rejected value [" + ObjectUtils.nullSafeToString(this.rejectedValue) + "]; " +
 				resolvableToString();
 	}
 
-	private String formatRejectedValue() {
-
-		// Special handling of byte[], to be moved into ObjectUtils in 7.0
-		if (this.rejectedValue instanceof byte[] bytes && bytes.length != 0) {
-			return "{" + HexFormat.of().formatHex(bytes) + "}";
-		}
-
-		return ObjectUtils.nullSafeToString(this.rejectedValue);
-	}
-
 }

spring-core/src/main/java/org/springframework/util/ObjectUtils.java

@@ -21,6 +21,7 @@
 import java.time.ZoneId;
 import java.util.Arrays;
 import java.util.Collection;
+import java.util.HexFormat;
 import java.util.Map;
 import java.util.Objects;
 import java.util.Optional;
@@ -695,9 +696,9 @@ public static String nullSafeToString(boolean @Nullable [] array) {
 
 	/**
 	 * Return a String representation of the contents of the specified array.
-	 * <p>The String representation consists of a list of the array's elements,
-	 * enclosed in curly braces ({@code "{}"}). Adjacent elements are separated
-	 * by the characters {@code ", "} (a comma followed by a space).
+	 * <p>As of 7.0, the String representation is a hex-encoded string enclosed
+	 * in curly braces ({@code "{}"}). The String consists of 2 hexadecimal
+	 * chars per element, and without a delimiter between adjacent elements.
 	 * Returns a {@code "null"} String if {@code array} is {@code null}.
 	 * @param array the array to build a String representation for
 	 * @return a String representation of {@code array}
@@ -709,11 +710,7 @@ public static String nullSafeToString(byte @Nullable [] array) {
 		if (array.length == 0) {
 			return EMPTY_ARRAY;
 		}
-		StringJoiner stringJoiner = new StringJoiner(ARRAY_ELEMENT_SEPARATOR, ARRAY_START, ARRAY_END);
-		for (byte b : array) {
-			stringJoiner.add(String.valueOf(b));
-		}
-		return stringJoiner.toString();
+		return ARRAY_START + HexFormat.of().formatHex(array) + ARRAY_END;
 	}
 
 	/**

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

@@ -630,8 +630,8 @@ void nullSafeToStringWithBooleanArrayEqualToNull() {
 
 	@Test
 	void nullSafeToStringWithByteArray() {
-		byte[] array = {5, 8};
-		assertThat(ObjectUtils.nullSafeToString(array)).isEqualTo("{5, 8}");
+		byte[] array = {5, 38};
+		assertThat(ObjectUtils.nullSafeToString(array)).isEqualTo("{0526}");
 	}
 
 	@Test