From ffb882444d5b29368acfb6c19c3c01e33dd0670f Mon Sep 17 00:00:00 2001
From: seonghobae <8172694+seonghobae@users.noreply.github.com>
Date: Tue, 30 Jun 2026 21:05:04 +0000
Subject: [PATCH] =?UTF-8?q?=EC=84=B1=EB=8A=A5:=20DefaultDocumentConversion?=
 =?UTF-8?q?Service=EC=97=90=EC=84=9C=20String.format=EC=9D=84=20HexFormat?=
 =?UTF-8?q?=EC=9C=BC=EB=A1=9C=20=EA=B5=90=EC=B2=B4=ED=95=98=EC=97=AC=20?=
 =?UTF-8?q?=EC=86=8D=EB=8F=84=20=EA=B0=9C=EC=84=A0?=
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

---
 .jules/bolt.md                                            | 3 +++
 CHANGELOG.md                                              | 1 +
 .../viewer/service/DefaultDocumentConversionService.java  | 8 ++------
 3 files changed, 6 insertions(+), 6 deletions(-)
 create mode 100644 .jules/bolt.md
 create mode 100644 CHANGELOG.md

diff --git a/.jules/bolt.md b/.jules/bolt.md
new file mode 100644
index 0000000..872bd24
--- /dev/null
+++ b/.jules/bolt.md
@@ -0,0 +1,3 @@
+## 2026-06-30 - Java HexFormat Optimization
+**Learning:** In Java 21, `java.util.HexFormat.of().formatHex(bytes)` is highly preferred over iterating and using `String.format(\"%02x\", b)` for converting a byte array to a hex string.
+**Action:** Replaced String.format in a loop with HexFormat in DefaultDocumentConversionService to enhance performance during content hash generation.
diff --git a/CHANGELOG.md b/CHANGELOG.md
new file mode 100644
index 0000000..9ce75e9
--- /dev/null
+++ b/CHANGELOG.md
@@ -0,0 +1 @@
+# Changelog\n\n## [Unreleased]\n- ⚡ `DefaultDocumentConversionService` 내부 해시 생성 시 `String.format`을 `HexFormat`으로 교체하여 성능 개선
diff --git a/src/main/java/com/clearfolio/viewer/service/DefaultDocumentConversionService.java b/src/main/java/com/clearfolio/viewer/service/DefaultDocumentConversionService.java
index 9c59593..a3a6829 100644
--- a/src/main/java/com/clearfolio/viewer/service/DefaultDocumentConversionService.java
+++ b/src/main/java/com/clearfolio/viewer/service/DefaultDocumentConversionService.java
@@ -121,12 +121,8 @@ 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();
+            // 성능 향상을 위해 String.format 대신 HexFormat 사용
+            return java.util.HexFormat.of().formatHex(raw);
         } catch (NoSuchAlgorithmException ex) {
             throw new IllegalStateException("SHA-256 digest unavailable", ex);
         } catch (IOException ex) {