Avoid create file everytime

initializer-backend/src/main/java/com/schbrain/archetype/initializer/service/ArchetypeService.java

 package com.schbrain.archetype.initializer.service;
 
 import cn.hutool.cache.impl.TimedCache;
+import cn.hutool.core.io.file.PathUtil;
 import cn.hutool.core.util.ZipUtil;
+import cn.hutool.system.SystemUtil;
 import com.schbrain.archetype.initializer.maven.MavenUtils;
 import com.schbrain.archetype.initializer.param.ArchetypeGenerateParam;
 import com.schbrain.archetype.initializer.response.PreviewFileTree;
+import com.schbrain.common.exception.BaseException;
 import com.schbrain.common.web.utils.ServletUtils;
+import lombok.extern.slf4j.Slf4j;
 import org.springframework.http.ContentDisposition;
 import org.springframework.http.HttpHeaders;
 import org.springframework.http.MediaType;
@@ -31,11 +35,16 @@ import java.util.stream.Collectors;
  * @author liaozan
  * @since 2022/3/20
  */
+@Slf4j
 @Service
 public class ArchetypeService {
 
+    private static final String GITKEEP = ".gitkeep";
+
     private final TimedCache<String, String> archetypeNameCache = new TimedCache<>(Duration.ofHours(1).toMillis());
 
+    private final Path gitKeepFile = createGitKeepFile(SystemUtil.getUserInfo().getTempDir());
+
     public String generate(ArchetypeGenerateParam param) {
         String generateId = MavenUtils.generate(param);
         archetypeNameCache.put(generateId, param.getArtifactId());
@@ -59,10 +68,8 @@ public class ArchetypeService {
     private PreviewFileTree buildFileTree(File root) {
         File[] fileItems = Optional.ofNullable(root.listFiles()).orElse(new File[0]);
         if (fileItems.length == 0) {
-            File gitKeepFile = createGitKeepFile(root);
-            if (gitKeepFile != null) {
-                fileItems = new File[]{gitKeepFile};
-            }
+            Path target = Path.of(root.getPath(), GITKEEP);
+            fileItems = new File[]{PathUtil.copy(gitKeepFile, target).toFile()};
         }
         List<PreviewFileTree> children = Arrays.stream(fileItems)
                 .map(fileItem -> {
@@ -79,13 +86,13 @@ public class ArchetypeService {
         return new PreviewFileTree(root, children);
     }
 
-    private File createGitKeepFile(File root) {
+    private Path createGitKeepFile(String directory) {
         try {
-            Path created = Files.createFile(Path.of(root.getPath(), ".gitkeep"));
+            Path created = Files.createFile(Path.of(directory, GITKEEP));
             Files.writeString(created, "This file is used to keep an empty folder when git uploads, If you put other files in the folder, delete this file please");
-            return created.toFile();
-        } catch (IOException ignore) {
-            return null;
+            return created;
+        } catch (IOException e) {
+            throw new BaseException("Failed to create .gitkeep file", e);
         }
     }