diff --git a/src/main/java/com/filesystem/controller/FileController.java b/src/main/java/com/filesystem/controller/FileController.java
index 4fd85ba..78e2869 100644
--- a/src/main/java/com/filesystem/controller/FileController.java
+++ b/src/main/java/com/filesystem/controller/FileController.java
@@ -5,23 +5,17 @@ import com.filesystem.entity.FileShare;
 import com.filesystem.security.UserPrincipal;
 import com.filesystem.service.FileService;
 import com.filesystem.utils.ApiResult;
+import com.filesystem.utils.CommonUtil;
+import com.filesystem.utils.FileUtil;
 import jakarta.annotation.Resource;
 import jakarta.servlet.http.HttpServletResponse;
 import org.springframework.beans.factory.annotation.Value;
-import org.springframework.http.HttpHeaders;
-import org.springframework.http.MediaType;
 import org.springframework.http.ResponseEntity;
 import org.springframework.security.core.annotation.AuthenticationPrincipal;
 import org.springframework.web.bind.annotation.*;
 import org.springframework.web.multipart.MultipartFile;
 
 import java.io.IOException;
-import java.net.URLEncoder;
-import java.nio.charset.StandardCharsets;
-import java.nio.file.Files;
-import java.nio.file.Path;
-import java.nio.file.Paths;
-import java.util.ArrayList;
 import java.util.List;
 import java.util.Map;
 
@@ -95,8 +89,8 @@ public class FileController {
     public ApiResult<FileEntity> createFolder(
             @AuthenticationPrincipal UserPrincipal principal,
             @RequestBody Map<String, Object> request) {
-        String name = (String) request.get("name");
-        Long parentId = request.get("parentId") != null ? Long.valueOf(request.get("parentId").toString()) : null;
+        String name = CommonUtil.getString(request, "name");
+        Long parentId = CommonUtil.getLong(request, "parentId");
         FileEntity folder = fileService.createFolder(name, principal.getUserId(), parentId);
         return ApiResult.success("创建成功", folder);
     }
@@ -148,7 +142,7 @@ public class FileController {
     }
 
     /**
-     * 下载文件（返回 ResponseEntity<byte[]> 用于二进制响应）
+     * 下载文件
      */
     @GetMapping("/{id}/download")
     public ResponseEntity<byte[]> downloadFile(
@@ -159,18 +153,14 @@ public class FileController {
             if (file == null) return ResponseEntity.notFound().build();
             byte[] content = fileService.getFileContent(file);
             if (content == null) return ResponseEntity.notFound().build();
-            String encodedName = URLEncoder.encode(file.getName(), StandardCharsets.UTF_8).replace("+", "%20");
-            return ResponseEntity.ok()
-                    .header(HttpHeaders.CONTENT_DISPOSITION, "attachment; filename=\"" + encodedName + "\"")
-                    .contentType(MediaType.APPLICATION_OCTET_STREAM)
-                    .body(content);
+            return FileUtil.buildDownloadResponse(content, file.getName());
         } catch (RuntimeException e) {
             return ResponseEntity.badRequest().build();
         }
     }
 
     /**
-     * 预览文件（返回 ResponseEntity<byte[]> 用于二进制响应）
+     * 预览文件
      */
     @GetMapping("/{id}/preview")
     public ResponseEntity<byte[]> previewFile(
@@ -181,11 +171,7 @@ public class FileController {
             if (file == null) return ResponseEntity.notFound().build();
             byte[] content = fileService.getFileContent(file);
             if (content == null) return ResponseEntity.notFound().build();
-            String encodedName = URLEncoder.encode(file.getName(), StandardCharsets.UTF_8).replace("+", "%20");
-            return ResponseEntity.ok()
-                    .header(HttpHeaders.CONTENT_DISPOSITION, "inline; filename=\"" + encodedName + "\"")
-                    .contentType(getMediaType(file.getName()))
-                    .body(content);
+            return FileUtil.buildPreviewResponse(content, file.getName());
         } catch (RuntimeException e) {
             return ResponseEntity.badRequest().build();
         }
@@ -197,8 +183,8 @@ public class FileController {
             @PathVariable Long id,
             @RequestBody Map<String, Object> request) {
         try {
-            Long shareToUserId = Long.valueOf(request.get("userId").toString());
-            String permission = (String) request.getOrDefault("permission", "view");
+            Long shareToUserId = CommonUtil.getLong(request, "userId");
+            String permission = CommonUtil.getString(request, "permission", "view");
             FileShare share = fileService.shareFile(id, principal.getUserId(), shareToUserId, permission);
             return ApiResult.success("共享成功", share);
         } catch (RuntimeException e) {
@@ -219,43 +205,21 @@ public class FileController {
     }
 
     /**
-     * 获取头像图片（返回 ResponseEntity<byte[]> 用于二进制响应）
+     * 获取头像图片
      */
     @GetMapping("/avatar/**")
     public ResponseEntity<byte[]> getAvatar(jakarta.servlet.http.HttpServletRequest request) throws IOException {
         String uri = request.getRequestURI();
         String prefix = "/api/files/avatar/";
         String relativePath = uri.substring(uri.indexOf(prefix) + prefix.length());
-        // relativePath = "2026/04/xxx.jpg"
 
-        Path filePath = Paths.get(storagePath).toAbsolutePath().resolve("avatars").resolve(relativePath);
-        if (!Files.exists(filePath)) {
+        java.nio.file.Path filePath = java.nio.file.Paths.get(storagePath).toAbsolutePath().resolve("avatars").resolve(relativePath);
+        if (!java.nio.file.Files.exists(filePath)) {
             return ResponseEntity.notFound().build();
         }
-        byte[] content = Files.readAllBytes(filePath);
+        byte[] content = java.nio.file.Files.readAllBytes(filePath);
         String fileName = relativePath.contains("/") ? relativePath.substring(relativePath.lastIndexOf("/") + 1) : relativePath;
-        String ext = fileName.contains(".") ? fileName.substring(fileName.lastIndexOf(".") + 1).toLowerCase() : "jpg";
-        String contentType = switch (ext) {
-            case "png" -> "image/png";
-            case "gif" -> "image/gif";
-            case "webp" -> "image/webp";
-            default -> "image/jpeg";
-        };
-        return ResponseEntity.ok()
-                .contentType(org.springframework.http.MediaType.parseMediaType(contentType))
-                .header(HttpHeaders.CACHE_CONTROL, "max-age=86400")
-                .body(content);
-    }
-
-    private MediaType getMediaType(String filename) {
-        String ext = filename.contains(".") ? filename.substring(filename.lastIndexOf(".")).toLowerCase() : "";
-        return switch (ext) {
-            case ".jpg", ".jpeg" -> MediaType.IMAGE_JPEG;
-            case ".png" -> MediaType.IMAGE_PNG;
-            case ".gif" -> MediaType.IMAGE_GIF;
-            case ".pdf" -> MediaType.APPLICATION_PDF;
-            default -> MediaType.APPLICATION_OCTET_STREAM;
-        };
+        return FileUtil.buildImageResponse(content, fileName);
     }
 
     @PutMapping("/{id}/rename")
@@ -264,7 +228,7 @@ public class FileController {
             @PathVariable Long id,
             @RequestBody Map<String, String> request) {
         String newName = request.get("name");
-        if (newName == null || newName.trim().isEmpty()) {
+        if (CommonUtil.isBlank(newName)) {
             return ApiResult.error("名称不能为空");
         }
         try {
@@ -280,11 +244,7 @@ public class FileController {
             @AuthenticationPrincipal UserPrincipal principal,
             @PathVariable Long id,
             @RequestBody Map<String, Object> request) {
-        Object folderIdObj = request.get("folderId");
-        Long folderId = null;
-        if (folderIdObj != null && !folderIdObj.toString().isEmpty() && !"null".equals(folderIdObj.toString()) && !"undefined".equals(folderIdObj.toString())) {
-            folderId = Long.parseLong(folderIdObj.toString());
-        }
+        Long folderId = CommonUtil.getLong(request, "folderId");
         try {
             fileService.moveFile(id, principal.getUserId(), folderId);
             return ApiResult.success("移动成功");
@@ -294,48 +254,27 @@ public class FileController {
     }
 
     /**
-     * 批量下载（返回 ZIP 文件，使用 HttpServletResponse 直接写入）
+     * 批量下载
      */
     @PostMapping("/batchDownload")
     public void batchDownload(
             @AuthenticationPrincipal UserPrincipal principal,
             @RequestBody Map<String, Object> request,
             HttpServletResponse response) throws IOException {
-        Object idsObj = request.get("ids");
-        if (idsObj == null) {
-            response.setContentType("application/json;charset=UTF-8");
-            response.getWriter().write("{\"code\":400,\"message\":\"请选择要下载的文件\"}");
-            return;
-        }
-        
-        List<Long> ids = new ArrayList<>();
-        if (idsObj instanceof List) {
-            for (Object id : (List<?>) idsObj) {
-                if (id instanceof Number) {
-                    ids.add(((Number) id).longValue());
-                } else if (id instanceof String) {
-                    ids.add(Long.parseLong((String) id));
-                }
-            }
-        }
+        List<Long> ids = CommonUtil.parseIds(request.get("ids"));
         
         if (ids.isEmpty()) {
-            response.setContentType("application/json;charset=UTF-8");
-            response.getWriter().write("{\"code\":400,\"message\":\"请选择要下载的文件\"}");
+            com.filesystem.utils.ServletUtil.writeErrorJson(response, 400, "请选择要下载的文件");
             return;
         }
         
         try {
             byte[] zipBytes = fileService.createZipArchive(ids, principal.getUserId());
-            
-            response.setContentType("application/zip");
-            response.setHeader("Content-Disposition", "attachment; filename=\"download.zip\"");
-            response.setContentLength(zipBytes.length);
+            com.filesystem.utils.ServletUtil.setZipDownloadHeaders(response, zipBytes.length);
             response.getOutputStream().write(zipBytes);
             response.getOutputStream().flush();
         } catch (RuntimeException e) {
-            response.setContentType("application/json;charset=UTF-8");
-            response.getWriter().write("{\"code\":400,\"message\":\"" + e.getMessage().replace("\"", "\\\"") + "\"}");
+            com.filesystem.utils.ServletUtil.writeErrorJson(response, 400, e.getMessage());
         }
     }
 
@@ -352,20 +291,10 @@ public class FileController {
     public ApiResult<Void> batchCancelShare(
             @AuthenticationPrincipal UserPrincipal principal,
             @RequestBody Map<String, Object> request) {
-        Object idsObj = request.get("ids");
-        if (idsObj == null) {
+        List<Long> ids = CommonUtil.parseIds(request.get("ids"));
+        if (ids.isEmpty()) {
             return ApiResult.error("请选择要取消共享的文件");
         }
-        List<Long> ids = new ArrayList<>();
-        if (idsObj instanceof List) {
-            for (Object id : (List<?>) idsObj) {
-                if (id instanceof Number) {
-                    ids.add(((Number) id).longValue());
-                } else if (id instanceof String) {
-                    ids.add(Long.parseLong((String) id));
-                }
-            }
-        }
         for (Long fileId : ids) {
             fileService.cancelShare(fileId, principal.getUserId());
         }
@@ -376,20 +305,10 @@ public class FileController {
     public ApiResult<Void> batchRestore(
             @AuthenticationPrincipal UserPrincipal principal,
             @RequestBody Map<String, Object> request) {
-        Object idsObj = request.get("ids");
-        if (idsObj == null) {
+        List<Long> ids = CommonUtil.parseIds(request.get("ids"));
+        if (ids.isEmpty()) {
             return ApiResult.error("请选择要还原的文件");
         }
-        List<Long> ids = new ArrayList<>();
-        if (idsObj instanceof List) {
-            for (Object id : (List<?>) idsObj) {
-                if (id instanceof Number) {
-                    ids.add(((Number) id).longValue());
-                } else if (id instanceof String) {
-                    ids.add(Long.parseLong((String) id));
-                }
-            }
-        }
         for (Long fileId : ids) {
             fileService.restoreFile(fileId, principal.getUserId());
         }
diff --git a/src/main/java/com/filesystem/controller/MessageController.java b/src/main/java/com/filesystem/controller/MessageController.java
index 83dfc77..01b9a20 100644
--- a/src/main/java/com/filesystem/controller/MessageController.java
+++ b/src/main/java/com/filesystem/controller/MessageController.java
@@ -6,24 +6,22 @@ import com.filesystem.security.UserPrincipal;
 import com.filesystem.service.MessageService;
 import com.filesystem.service.UserService;
 import com.filesystem.utils.ApiResult;
+import com.filesystem.utils.CommonUtil;
+import com.filesystem.utils.FileUtil;
+import com.filesystem.utils.ServletUtil;
 import jakarta.annotation.Resource;
+import jakarta.servlet.http.HttpServletRequest;
+import jakarta.servlet.http.HttpServletResponse;
 import org.springframework.beans.factory.annotation.Value;
-import org.springframework.http.HttpHeaders;
-import org.springframework.http.MediaType;
 import org.springframework.http.ResponseEntity;
 import org.springframework.security.core.annotation.AuthenticationPrincipal;
 import org.springframework.web.bind.annotation.*;
 import org.springframework.web.multipart.MultipartFile;
 
-import jakarta.servlet.http.HttpServletRequest;
 import java.io.IOException;
-import java.net.URLEncoder;
-import java.nio.charset.StandardCharsets;
 import java.nio.file.Files;
 import java.nio.file.Path;
 import java.nio.file.Paths;
-import java.time.LocalDateTime;
-import java.time.format.DateTimeFormatter;
 import java.util.*;
 import java.util.stream.Collectors;
 import java.util.LinkedHashMap;
@@ -41,8 +39,6 @@ public class MessageController {
     @Value("${file.storage.path:./uploads}")
     private String storagePath;
 
-    private static final DateTimeFormatter DATE_FMT = DateTimeFormatter.ofPattern("yyyy/MM");
-
     // ==================== 聊天文件上传 ====================
 
     @PostMapping("/upload")
@@ -55,10 +51,9 @@ public class MessageController {
         }
 
         String originalName = file.getOriginalFilename();
-        String ext = originalName != null && originalName.contains(".")
-                ? originalName.substring(originalName.lastIndexOf(".")) : "";
+        String ext = FileUtil.getExtensionWithDot(originalName);
         String storedName = UUID.randomUUID().toString() + ext;
-        String datePath = LocalDateTime.now().format(DATE_FMT);
+        String datePath = CommonUtil.getDatePath();
 
         Path targetDir = Paths.get(storagePath).toAbsolutePath().resolve("chat").resolve(datePath);
         if (!Files.exists(targetDir)) {
@@ -72,7 +67,7 @@ public class MessageController {
         return ApiResult.success("上传成功", Map.of("url", fileUrl));
     }
 
-    // ==================== 聊天文件访问（返回 ResponseEntity<byte[]> 用于二进制响应）====================
+    // ==================== 聊天文件访问 ====================
 
     @GetMapping("/file/**")
     public ResponseEntity<byte[]> getChatFile(HttpServletRequest request) throws IOException {
@@ -80,7 +75,6 @@ public class MessageController {
         String prefix = "/api/messages/file/";
         String relativePath = uri.substring(uri.indexOf(prefix) + prefix.length());
 
-        // relativePath = "2026/04/xxx.jpg"
         int lastSlash = relativePath.lastIndexOf('/');
         String datePath = relativePath.substring(0, lastSlash);
         String fileName = relativePath.substring(lastSlash + 1);
@@ -93,31 +87,11 @@ public class MessageController {
         }
 
         byte[] content = Files.readAllBytes(filePath);
-        String ext = fileName.contains(".") ? fileName.substring(fileName.lastIndexOf(".") + 1).toLowerCase() : "";
-
-        boolean isImage = Set.of("png", "jpg", "jpeg", "gif", "webp", "bmp", "svg").contains(ext);
-
-        String contentType = switch (ext) {
-            case "pdf" -> "application/pdf";
-            case "png" -> "image/png";
-            case "gif" -> "image/gif";
-            case "webp" -> "image/webp";
-            case "jpg", "jpeg" -> "image/jpeg";
-            case "bmp" -> "image/bmp";
-            case "svg" -> "image/svg+xml";
-            default -> "application/octet-stream";
-        };
-
-        String encodedName = URLEncoder.encode(fileName, StandardCharsets.UTF_8).replace("+", "%20");
-        String disposition = isImage
-                ? "inline; filename=\"" + encodedName + "\""
-                : "attachment; filename=\"" + encodedName + "\"";
-
-        return ResponseEntity.ok()
-                .contentType(MediaType.parseMediaType(contentType))
-                .header(HttpHeaders.CONTENT_DISPOSITION, disposition)
-                .header(HttpHeaders.CACHE_CONTROL, "max-age=86400")
-                .body(content);
+        boolean isImage = FileUtil.isImage(fileName);
+        
+        return isImage 
+                ? FileUtil.buildImageResponse(content, fileName)
+                : FileUtil.buildDownloadResponse(content, fileName);
     }
 
     // ==================== 消息收发 ====================
@@ -158,7 +132,7 @@ public class MessageController {
             m.put("fileName", msg.getFileName());
             m.put("fileSize", msg.getFileSize());
             m.put("isRead", msg.getIsRead());
-            m.put("createTime", msg.getCreateTime() != null ? msg.getCreateTime().toString() : "");
+            m.put("createTime", CommonUtil.formatDateTime(msg.getCreateTime()));
 
             User fromUser = userMap.get(msg.getFromUserId());
             if (fromUser != null) {
@@ -196,12 +170,11 @@ public class MessageController {
     public ApiResult<Map<String, Object>> sendMessage(
             @AuthenticationPrincipal UserPrincipal principal,
             @RequestBody Map<String, Object> request) {
-        Long toUserId = Long.valueOf(request.get("toUserId").toString());
-        String content = (String) request.get("content");
-        String type = (String) request.getOrDefault("type", "text");
-        String fileName = (String) request.get("fileName");
-        Object fileSizeObj = request.get("fileSize");
-        Long fileSize = fileSizeObj != null ? Long.valueOf(fileSizeObj.toString()) : null;
+        Long toUserId = CommonUtil.getLong(request, "toUserId");
+        String content = CommonUtil.getString(request, "content");
+        String type = CommonUtil.getString(request, "type", "text");
+        String fileName = CommonUtil.getString(request, "fileName");
+        Long fileSize = CommonUtil.getLong(request, "fileSize");
 
         Message message = messageService.sendMessage(principal.getUserId(), toUserId, content, type);
 
@@ -219,7 +192,7 @@ public class MessageController {
         result.put("type", message.getType());
         result.put("fileName", message.getFileName());
         result.put("fileSize", message.getFileSize());
-        result.put("createTime", message.getCreateTime() != null ? message.getCreateTime().toString() : "");
+        result.put("createTime", CommonUtil.formatDateTime(message.getCreateTime()));
 
         User fromUser = userService.findById(principal.getUserId());
         if (fromUser != null) {
@@ -241,7 +214,6 @@ public class MessageController {
     public ApiResult<List<Map<String, Object>>> getUnreadList(@AuthenticationPrincipal UserPrincipal principal) {
         List<Message> unreadMessages = messageService.getUnreadMessages(principal.getUserId());
 
-        // 按发送人分组
         Map<Long, List<Message>> grouped = unreadMessages.stream()
                 .collect(Collectors.groupingBy(Message::getFromUserId, LinkedHashMap::new, Collectors.toList()));
 
@@ -249,7 +221,7 @@ public class MessageController {
         for (Map.Entry<Long, List<Message>> entry : grouped.entrySet()) {
             Long fromUserId = entry.getKey();
             List<Message> msgs = entry.getValue();
-            Message lastMsg = msgs.get(0); // 已按时间倒序，第一条就是最新的
+            Message lastMsg = msgs.get(0);
             User fromUser = userService.findById(fromUserId);
 
             Map<String, Object> item = new HashMap<>();
@@ -259,7 +231,7 @@ public class MessageController {
                     ? "[图片]" : (lastMsg.getType() != null && lastMsg.getType().equals("file")
                     ? "[文件]" : (lastMsg.getContent() != null && lastMsg.getContent().length() > 30
                     ? lastMsg.getContent().substring(0, 30) + "..." : lastMsg.getContent())));
-            item.put("lastTime", lastMsg.getCreateTime() != null ? lastMsg.getCreateTime().toString() : "");
+            item.put("lastTime", CommonUtil.formatDateTime(lastMsg.getCreateTime()));
             if (fromUser != null) {
                 item.put("username", fromUser.getUsername());
                 item.put("nickname", fromUser.getNickname() != null ? fromUser.getNickname() : fromUser.getUsername());
diff --git a/src/main/java/com/filesystem/controller/UserController.java b/src/main/java/com/filesystem/controller/UserController.java
index f585c3f..24a8ab2 100644
--- a/src/main/java/com/filesystem/controller/UserController.java
+++ b/src/main/java/com/filesystem/controller/UserController.java
@@ -4,6 +4,8 @@ import com.filesystem.entity.User;
 import com.filesystem.security.UserPrincipal;
 import com.filesystem.service.UserService;
 import com.filesystem.utils.ApiResult;
+import com.filesystem.utils.CommonUtil;
+import com.filesystem.utils.FileUtil;
 import jakarta.annotation.Resource;
 import org.springframework.beans.factory.annotation.Value;
 import org.springframework.security.core.annotation.AuthenticationPrincipal;
@@ -14,8 +16,6 @@ import java.io.IOException;
 import java.nio.file.Files;
 import java.nio.file.Path;
 import java.nio.file.Paths;
-import java.time.LocalDateTime;
-import java.time.format.DateTimeFormatter;
 import java.util.*;
 import java.util.stream.Collectors;
 
@@ -29,8 +29,6 @@ public class UserController {
     @Value("${file.storage.path:./uploads}")
     private String storagePath;
     
-    private static final DateTimeFormatter DATE_FMT = DateTimeFormatter.ofPattern("yyyy/MM");
-    
     /**
      * 获取所有可用用户（用于文件共享等场景）
      */
@@ -38,7 +36,7 @@ public class UserController {
     public ApiResult<List<Map<String, Object>>> getAllUsers(@AuthenticationPrincipal UserPrincipal principal) {
         List<User> users = userService.getAllUsersExcept(principal.getUserId());
         List<Map<String, Object>> result = users.stream()
-            .filter(u -> u.getStatus() == 1) // 只返回启用状态的用户
+            .filter(u -> u.getStatus() == 1)
             .map(u -> {
                 Map<String, Object> m = new HashMap<>();
                 m.put("id", u.getId());
@@ -64,20 +62,14 @@ public class UserController {
             return ApiResult.error("请选择图片");
         }
         
-        // 限制文件大小 2MB
         if (file.getSize() > 2 * 1024 * 1024) {
             return ApiResult.error("图片大小不能超过2MB");
         }
         
-        // 保存文件
-        String originalFilename = file.getOriginalFilename();
-        String ext = originalFilename != null && originalFilename.contains(".") 
-            ? originalFilename.substring(originalFilename.lastIndexOf(".")) 
-            : ".jpg";
+        String ext = FileUtil.getExtensionWithDot(file.getOriginalFilename());
         String fileName = UUID.randomUUID().toString() + ext;
-        String datePath = LocalDateTime.now().format(DATE_FMT);
+        String datePath = CommonUtil.getDatePath();
         
-        // 使用配置文件中的路径 + 日期目录
         Path uploadPath = Paths.get(storagePath).toAbsolutePath().resolve("avatars").resolve(datePath);
         if (!Files.exists(uploadPath)) {
             Files.createDirectories(uploadPath);
@@ -86,7 +78,6 @@ public class UserController {
         Path filePath = uploadPath.resolve(fileName);
         Files.copy(file.getInputStream(), filePath);
         
-        // 更新用户头像
         String avatarUrl = "/api/files/avatar/" + datePath + "/" + fileName;
         userService.updateAvatar(principal.getUserId(), avatarUrl);
         
@@ -118,11 +109,13 @@ public class UserController {
             @AuthenticationPrincipal UserPrincipal principal,
             @RequestBody Map<String, String> request) {
         try {
-            String nickname = request.get("nickname");
-            String signature = request.get("signature");
-            String phone = request.get("phone");
-            String email = request.get("email");
-            userService.updateProfile(principal.getUserId(), nickname, signature, phone, email);
+            userService.updateProfile(
+                principal.getUserId(),
+                request.get("nickname"),
+                request.get("signature"),
+                request.get("phone"),
+                request.get("email")
+            );
             return ApiResult.success("更新成功");
         } catch (RuntimeException e) {
             return ApiResult.error(e.getMessage());
@@ -139,7 +132,7 @@ public class UserController {
         String oldPassword = request.get("oldPassword");
         String newPassword = request.get("newPassword");
         
-        if (oldPassword == null || oldPassword.isEmpty() || newPassword == null || newPassword.isEmpty()) {
+        if (CommonUtil.isBlank(oldPassword) || CommonUtil.isBlank(newPassword)) {
             return ApiResult.error("请填写完整信息");
         }
         
diff --git a/src/main/java/com/filesystem/utils/CommonUtil.java b/src/main/java/com/filesystem/utils/CommonUtil.java
new file mode 100644
index 0000000..289df4c
--- /dev/null
+++ b/src/main/java/com/filesystem/utils/CommonUtil.java
@@ -0,0 +1,133 @@
+package com.filesystem.utils;
+
+import java.time.LocalDateTime;
+import java.time.format.DateTimeFormatter;
+import java.util.ArrayList;
+import java.util.List;
+import java.util.Map;
+
+/**
+ * 通用工具类
+ */
+public class CommonUtil {
+    
+    private CommonUtil() {}
+    
+    // ========== 日期格式化 ==========
+    
+    private static final DateTimeFormatter DATE_TIME_FORMATTER = DateTimeFormatter.ofPattern("yyyy-MM-dd HH:mm:ss");
+    private static final DateTimeFormatter DATE_PATH_FORMATTER = DateTimeFormatter.ofPattern("yyyy/MM");
+    
+    /**
+     * 格式化日期时间（yyyy-MM-dd HH:mm:ss）
+     */
+    public static String formatDateTime(LocalDateTime dateTime) {
+        if (dateTime == null) return "";
+        return dateTime.format(DATE_TIME_FORMATTER);
+    }
+    
+    /**
+     * 获取日期路径格式（yyyy/MM）用于文件存储路径
+     */
+    public static String getDatePath() {
+        return LocalDateTime.now().format(DATE_PATH_FORMATTER);
+    }
+    
+    /**
+     * 获取当前时间字符串
+     */
+    public static String now() {
+        return formatDateTime(LocalDateTime.now());
+    }
+    
+    // ========== ID 列表解析 ==========
+    
+    /**
+     * 从 Map 中解析 ID 列表
+     * 支持 List<Number>、List<String>、Number、String 等多种格式
+     */
+    public static List<Long> parseIds(Object idsObj) {
+        List<Long> ids = new ArrayList<>();
+        
+        if (idsObj == null) {
+            return ids;
+        }
+        
+        if (idsObj instanceof List) {
+            for (Object id : (List<?>) idsObj) {
+                if (id instanceof Number) {
+                    ids.add(((Number) id).longValue());
+                } else if (id instanceof String) {
+                    String str = ((String) id).trim();
+                    if (!str.isEmpty()) {
+                        ids.add(Long.parseLong(str));
+                    }
+                }
+            }
+        } else if (idsObj instanceof Number) {
+            ids.add(((Number) idsObj).longValue());
+        } else if (idsObj instanceof String) {
+            String str = ((String) idsObj).trim();
+            if (!str.isEmpty()) {
+                ids.add(Long.parseLong(str));
+            }
+        }
+        
+        return ids;
+    }
+    
+    /**
+     * 从请求体中解析 ID 列表
+     */
+    public static List<Long> parseIdsFromRequest(Map<String, Object> request, String key) {
+        return parseIds(request.get(key));
+    }
+    
+    // ========== 参数提取 ==========
+    
+    /**
+     * 从 Map 中获取 Long 值
+     */
+    public static Long getLong(Map<String, Object> map, String key) {
+        Object value = map.get(key);
+        if (value == null) return null;
+        if (value instanceof Number) {
+            return ((Number) value).longValue();
+        }
+        String str = value.toString();
+        if (str.isEmpty() || "null".equals(str) || "undefined".equals(str)) {
+            return null;
+        }
+        return Long.parseLong(str);
+    }
+    
+    /**
+     * 从 Map 中获取 String 值
+     */
+    public static String getString(Map<String, Object> map, String key) {
+        Object value = map.get(key);
+        return value != null ? value.toString() : null;
+    }
+    
+    /**
+     * 从 Map 中获取指定默认值的 String
+     */
+    public static String getString(Map<String, Object> map, String key, String defaultValue) {
+        String value = getString(map, key);
+        return value != null ? value : defaultValue;
+    }
+    
+    /**
+     * 判断字符串是否为空或空白
+     */
+    public static boolean isBlank(String str) {
+        return str == null || str.trim().isEmpty();
+    }
+    
+    /**
+     * 判断字符串是否不为空
+     */
+    public static boolean isNotBlank(String str) {
+        return !isBlank(str);
+    }
+}
diff --git a/src/main/java/com/filesystem/utils/FileUtil.java b/src/main/java/com/filesystem/utils/FileUtil.java
new file mode 100644
index 0000000..8b50a96
--- /dev/null
+++ b/src/main/java/com/filesystem/utils/FileUtil.java
@@ -0,0 +1,161 @@
+package com.filesystem.utils;
+
+import org.springframework.http.HttpHeaders;
+import org.springframework.http.MediaType;
+import org.springframework.http.ResponseEntity;
+
+import java.net.URLEncoder;
+import java.nio.charset.StandardCharsets;
+import java.util.Map;
+
+/**
+ * 文件相关工具类
+ */
+public class FileUtil {
+    
+    private FileUtil() {}
+    
+    // ========== 文件名编码 ==========
+    
+    /**
+     * URL 编码文件名（用于 Content-Disposition 头）
+     */
+    public static String encodeFileName(String fileName) {
+        return URLEncoder.encode(fileName, StandardCharsets.UTF_8).replace("+", "%20");
+    }
+    
+    // ========== 扩展名提取 ==========
+    
+    /**
+     * 获取文件扩展名（不带点，如 "jpg"）
+     */
+    public static String getExtension(String fileName) {
+        if (fileName == null || !fileName.contains(".")) {
+            return "";
+        }
+        return fileName.substring(fileName.lastIndexOf(".") + 1).toLowerCase();
+    }
+    
+    /**
+     * 获取文件扩展名（带点，如 ".jpg"）
+     */
+    public static String getExtensionWithDot(String fileName) {
+        if (fileName == null || !fileName.contains(".")) {
+            return "";
+        }
+        return fileName.substring(fileName.lastIndexOf(".")).toLowerCase();
+    }
+    
+    // ========== Content-Type 判断 ==========
+    
+    /**
+     * 根据文件名获取图片 Content-Type
+     */
+    public static String getImageContentType(String fileName) {
+        String ext = getExtension(fileName);
+        return switch (ext) {
+            case "png" -> "image/png";
+            case "gif" -> "image/gif";
+            case "webp" -> "image/webp";
+            case "svg" -> "image/svg+xml";
+            case "bmp" -> "image/bmp";
+            case "ico" -> "image/x-icon";
+            default -> "image/jpeg";
+        };
+    }
+    
+    /**
+     * 根据文件名获取 MediaType（用于 Spring ResponseEntity）
+     */
+    public static MediaType getMediaType(String fileName) {
+        String ext = getExtensionWithDot(fileName);
+        return switch (ext) {
+            case ".jpg", ".jpeg" -> MediaType.IMAGE_JPEG;
+            case ".png" -> MediaType.IMAGE_PNG;
+            case ".gif" -> MediaType.IMAGE_GIF;
+            case ".webp" -> MediaType.parseMediaType("image/webp");
+            case ".pdf" -> MediaType.APPLICATION_PDF;
+            case ".svg" -> MediaType.parseMediaType("image/svg+xml");
+            default -> MediaType.APPLICATION_OCTET_STREAM;
+        };
+    }
+    
+    /**
+     * 根据文件名判断是否为图片
+     */
+    public static boolean isImage(String fileName) {
+        String ext = getExtension(fileName);
+        return java.util.Set.of("jpg", "jpeg", "png", "gif", "webp", "svg", "bmp", "ico").contains(ext);
+    }
+    
+    // ========== 文件类型判断 ==========
+    
+    /**
+     * 根据扩展名获取文件类型
+     */
+    public static String getFileType(String extension) {
+        if (extension == null || extension.isEmpty()) {
+            return "file";
+        }
+        String ext = extension.toLowerCase().replace(".", "");
+        
+        // 图片
+        if (java.util.Set.of("jpg", "jpeg", "png", "gif", "webp", "svg", "bmp", "ico").contains(ext)) {
+            return "image";
+        }
+        // 视频
+        if (java.util.Set.of("mp4", "avi", "mov", "wmv", "flv", "mkv", "webm").contains(ext)) {
+            return "video";
+        }
+        // 音频
+        if (java.util.Set.of("mp3", "wav", "flac", "aac", "ogg", "wma").contains(ext)) {
+            return "audio";
+        }
+        // PDF
+        if ("pdf".equals(ext)) {
+            return "pdf";
+        }
+        // 文档
+        if (java.util.Set.of("doc", "docx", "xls", "xlsx", "ppt", "pptx").contains(ext)) {
+            return "document";
+        }
+        // 压缩包
+        if (java.util.Set.of("zip", "rar", "7z", "tar", "gz").contains(ext)) {
+            return "archive";
+        }
+        return "file";
+    }
+    
+    // ========== 响应构建 ==========
+    
+    /**
+     * 构建文件下载响应
+     */
+    public static ResponseEntity<byte[]> buildDownloadResponse(byte[] content, String fileName) {
+        return ResponseEntity.ok()
+                .header(HttpHeaders.CONTENT_DISPOSITION, "attachment; filename=\"" + encodeFileName(fileName) + "\"")
+                .contentType(MediaType.APPLICATION_OCTET_STREAM)
+                .body(content);
+    }
+    
+    /**
+     * 构建文件预览响应
+     */
+    public static ResponseEntity<byte[]> buildPreviewResponse(byte[] content, String fileName) {
+        return ResponseEntity.ok()
+                .header(HttpHeaders.CONTENT_DISPOSITION, "inline; filename=\"" + encodeFileName(fileName) + "\"")
+                .contentType(getMediaType(fileName))
+                .header(HttpHeaders.CACHE_CONTROL, "max-age=86400")
+                .body(content);
+    }
+    
+    /**
+     * 构建图片响应
+     */
+    public static ResponseEntity<byte[]> buildImageResponse(byte[] content, String fileName) {
+        return ResponseEntity.ok()
+                .contentType(MediaType.parseMediaType(getImageContentType(fileName)))
+                .header(HttpHeaders.CACHE_CONTROL, "max-age=86400")
+                .body(content);
+    }
+}
diff --git a/src/main/java/com/filesystem/utils/ServletUtil.java b/src/main/java/com/filesystem/utils/ServletUtil.java
new file mode 100644
index 0000000..a1a9f91
--- /dev/null
+++ b/src/main/java/com/filesystem/utils/ServletUtil.java
@@ -0,0 +1,74 @@
+package com.filesystem.utils;
+
+import jakarta.servlet.http.HttpServletResponse;
+import org.springframework.http.HttpHeaders;
+
+import java.io.IOException;
+import java.io.PrintWriter;
+import java.nio.charset.StandardCharsets;
+
+/**
+ * Servlet 响应工具类
+ */
+public class ServletUtil {
+    
+    private ServletUtil() {}
+    
+    /**
+     * 输出 JSON 响应
+     */
+    public static void writeJson(HttpServletResponse response, int status, String json) throws IOException {
+        response.setStatus(status);
+        response.setContentType("application/json;charset=UTF-8");
+        response.setCharacterEncoding("UTF-8");
+        PrintWriter writer = response.getWriter();
+        writer.write(json);
+        writer.flush();
+    }
+    
+    /**
+     * 输出错误 JSON 响应
+     */
+    public static void writeErrorJson(HttpServletResponse response, int code, String message) throws IOException {
+        String json = String.format("{\"code\":%d,\"message\":\"%s\"}", code, escapeJson(message));
+        writeJson(response, code == 400 ? 400 : code, json);
+    }
+    
+    /**
+     * 输出成功 JSON 响应
+     */
+    public static void writeSuccessJson(HttpServletResponse response, String message) throws IOException {
+        writeJson(response, 200, String.format("{\"code\":200,\"message\":\"%s\"}", escapeJson(message)));
+    }
+    
+    /**
+     * 设置文件下载响应头
+     */
+    public static void setDownloadHeaders(HttpServletResponse response, String fileName, long contentLength) {
+        response.setContentType("application/octet-stream");
+        response.setHeader(HttpHeaders.CONTENT_DISPOSITION, "attachment; filename=\"" + FileUtil.encodeFileName(fileName) + "\"");
+        response.setHeader(HttpHeaders.CONTENT_LENGTH, String.valueOf(contentLength));
+        response.setHeader(HttpHeaders.CACHE_CONTROL, "no-cache");
+    }
+    
+    /**
+     * 设置 ZIP 下载响应头
+     */
+    public static void setZipDownloadHeaders(HttpServletResponse response, long contentLength) {
+        response.setContentType("application/zip");
+        response.setHeader(HttpHeaders.CONTENT_DISPOSITION, "attachment; filename=\"download.zip\"");
+        response.setContentLengthLong(contentLength);
+    }
+    
+    /**
+     * 转义 JSON 字符串中的特殊字符
+     */
+    public static String escapeJson(String str) {
+        if (str == null) return "";
+        return str.replace("\\", "\\\\")
+                  .replace("\"", "\\\"")
+                  .replace("\n", "\\n")
+                  .replace("\r", "\\r")
+                  .replace("\t", "\\t");
+    }
+}