[HUDI-4336] Fix records overwritten bug with binary primary key (#5996)

hudi-common/src/main/java/org/apache/hudi/common/util/StringUtils.java

@@ -19,6 +19,7 @@
 package org.apache.hudi.common.util;
 
 import javax.annotation.Nullable;
+import java.nio.ByteBuffer;
 import java.util.Collections;
 import java.util.List;
 import java.util.stream.Collectors;
@@ -88,7 +89,10 @@ public class StringUtils {
   }
 
   public static String objToString(@Nullable Object obj) {
-    return obj == null ? null : obj.toString();
+    if (obj == null) {
+      return null;
+    }
+    return obj instanceof ByteBuffer ? toHexString(((ByteBuffer) obj).array()) : obj.toString();
   }
 
   /**

hudi-common/src/test/java/org/apache/hudi/common/util/TestStringUtils.java

@@ -20,6 +20,7 @@ package org.apache.hudi.common.util;
 
 import org.junit.jupiter.api.Test;
 
+import java.nio.ByteBuffer;
 import java.util.ArrayList;
 import java.util.Arrays;
 
@@ -51,6 +52,20 @@ public class TestStringUtils {
     assertEquals("", StringUtils.nullToEmpty(null));
   }
 
+  @Test
+  public void testStringObjToString() {
+    assertNull(StringUtils.objToString(null));
+    assertEquals("Test String", StringUtils.objToString("Test String"));
+
+    // assert byte buffer
+    ByteBuffer byteBuffer1 = ByteBuffer.wrap("1234".getBytes());
+    ByteBuffer byteBuffer2 = ByteBuffer.wrap("5678".getBytes());
+    // assert equal because ByteBuffer has overwritten the toString to return a summary string
+    assertEquals(byteBuffer1.toString(), byteBuffer2.toString());
+    // assert not equal
+    assertNotEquals(StringUtils.objToString(byteBuffer1), StringUtils.objToString(byteBuffer2));
+  }
+
   @Test
   public void testStringEmptyToNull() {
     assertNull(StringUtils.emptyToNull(""));