From a86e672639659fd11dbc42b747ab1f5084aa65be Mon Sep 17 00:00:00 2001
From: seonghobae <8172694+seonghobae@users.noreply.github.com>
Date: Mon, 29 Jun 2026 21:53:52 +0000
Subject: [PATCH] =?UTF-8?q?=E2=9A=A1=20Bolt:=20Java=2021=20`HexFormat`?=
 =?UTF-8?q?=EC=9D=84=20=EC=9D=B4=EC=9A=A9=ED=95=9C=20=EB=B0=94=EC=9D=B4?=
 =?UTF-8?q?=ED=8A=B8=20=EB=B0=B0=EC=97=B4=20=EB=B3=80=ED=99=98=20=EC=B5=9C?=
 =?UTF-8?q?=EC=A0=81=ED=99=94?=
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

`DefaultDocumentConversionService` 파일의 `contentHash` 메서드 내에서 바이트 배열을 16진수 문자열로 변환할 때 사용하던 비효율적인 `String.format` 로직을 Java 21의 네이티브 클래스인 `java.util.HexFormat.of().formatHex(raw)`로 최적화했습니다.
---
 .jules/bolt.md                                           | 3 +++
 .../viewer/service/DefaultDocumentConversionService.java | 9 ++-------
 2 files changed, 5 insertions(+), 7 deletions(-)
 create mode 100644 .jules/bolt.md

diff --git a/.jules/bolt.md b/.jules/bolt.md
new file mode 100644
index 00000000..c8d052dd
--- /dev/null
+++ b/.jules/bolt.md
@@ -0,0 +1,3 @@
+## 2026-06-29 - Use HexFormat for Byte Array to Hex String Conversion
+**Learning:** In Java 21, using `String.format("%02x", b)` inside a loop to convert a byte array to a hex string is inefficient and causes unnecessary object allocations and CPU overhead.
+**Action:** Always prefer using `java.util.HexFormat.of().formatHex(bytes)` for converting byte arrays to hex strings in this Java 21 codebase to improve performance.
diff --git a/src/main/java/com/clearfolio/viewer/service/DefaultDocumentConversionService.java b/src/main/java/com/clearfolio/viewer/service/DefaultDocumentConversionService.java
index 9c595937..4a55e7d4 100644
--- a/src/main/java/com/clearfolio/viewer/service/DefaultDocumentConversionService.java
+++ b/src/main/java/com/clearfolio/viewer/service/DefaultDocumentConversionService.java
@@ -110,7 +110,7 @@ public RetryDeadLetterResult retryDeadLettered(UUID jobId, String operatorId) {
         return RetryDeadLetterResult.ACCEPTED;
     }
 
-    private String contentHash(MultipartFile file) {
+    private String contentHash(final MultipartFile file) {
         try (InputStream stream = file.getInputStream()) {
             MessageDigest digest = MessageDigest.getInstance("SHA-256");
             byte[] buffer = new byte[8192];
@@ -121,12 +121,7 @@ private String contentHash(MultipartFile file) {
             }
 
             byte[] raw = digest.digest();
-            StringBuilder hex = new StringBuilder(raw.length * 2);
-            for (byte b : raw) {
-                hex.append(String.format("%02x", b));
-            }
-
-            return hex.toString();
+            return java.util.HexFormat.of().formatHex(raw);
         } catch (NoSuchAlgorithmException ex) {
             throw new IllegalStateException("SHA-256 digest unavailable", ex);
         } catch (IOException ex) {