yxk-20260721

bug修复，kk的在线预览报错：原因是生产环境前后端隔离，但是配置还是localhost

jeecg-module-system/jeecg-system-biz/src/main/java/org/jeecg/modules/system/controller/FileController.java

@@ -58,6 +58,8 @@ public class FileController {
     private BaseCommonService baseCommonService;
     @Value(value = "${jeecg.appName}")
     private String applicationName;
+    @Value(value = "${jeecg.file-preview-download-domain:}")
+    private String filePreviewDownloadDomain;
 
     private static final String FILE_PREVIEW_REDIS_PREFIX = "sys:file:preview:";
     private static final long FILE_PREVIEW_TOKEN_EXPIRE_SECONDS = 600L;
@@ -619,7 +621,22 @@ public class FileController {
 
     private String buildPreviewDownloadUrl(HttpServletRequest request, String token, String fileName) {
         // kkFileView judges the preview handler by file suffix; stream APIs without suffix need fullfilename.
-        return buildRequestBaseUrl(request) + "/sys/file/previewDownload?token=" + token + "&fullfilename=" + encodeUrlParam(fileName);
+        return getPreviewDownloadBaseUrl(request) + "/sys/file/previewDownload?token=" + token + "&fullfilename=" + encodeUrlParam(fileName);
+    }
+
+    private String getPreviewDownloadBaseUrl(HttpServletRequest request) {
+        if (!StringUtils.isEmpty(filePreviewDownloadDomain) && !StringUtils.isEmpty(filePreviewDownloadDomain.trim())) {
+            // kkFileView may run on another host, so its download address must not depend on proxy headers.
+            return trimTrailingSlash(filePreviewDownloadDomain.trim());
+        }
+        return buildRequestBaseUrl(request);
+    }
+
+    private String trimTrailingSlash(String value) {
+        while (value.endsWith("/")) {
+            value = value.substring(0, value.length() - 1);
+        }
+        return value;
     }
 
     private JSONObject parsePreviewInfo(Object cache) {