Restrict file extension when importing markdown (#2104)

* fix #2090

* pass the check style

* Revision

* fix

* fix

* fix

* fix

* fix

* fix

* fix

* revision

* fix

* Revision

* revision

src/main/java/run/halo/app/controller/admin/api/BackupController.java

@@ -141,7 +141,9 @@ public class BackupController {
         backupService.deleteWorkDirBackup(filename);
     }
 
-    @PostMapping("markdown/import")
+    @PostMapping(value = "markdown/import", consumes = {
+        MediaType.TEXT_PLAIN_VALUE,
+        MediaType.TEXT_MARKDOWN_VALUE})
     @ApiOperation("Imports markdown")
     public BasePostDetailDTO backupMarkdowns(@RequestPart("file") MultipartFile file)
         throws IOException {

src/main/java/run/halo/app/service/impl/BackupServiceImpl.java

@@ -230,12 +230,16 @@ public class BackupServiceImpl implements BackupService {
 
     @Override
     public BasePostDetailDTO importMarkdown(MultipartFile file) throws IOException {
+        try {
+            // Read markdown content.
+            String markdown = FileUtils.readString(file.getInputStream());
+            // TODO sheet import
+            return postService.importMarkdown(markdown, file.getOriginalFilename());
+        } catch (OutOfMemoryError error) {
+            throw new ServiceException(
+                "文件内容过大，无法导入。", error);
+        }
 
-        // Read markdown content.
-        String markdown = FileUtils.readString(file.getInputStream());
-
-        // TODO sheet import
-        return postService.importMarkdown(markdown, file.getOriginalFilename());
     }
 
     @Override