Enhance post creation api

src/main/java/cc/ryanc/halo/repository/PostCategoryRepository.java

@@ -5,6 +5,7 @@ import cc.ryanc.halo.repository.base.BaseRepository;
 import org.springframework.data.jpa.repository.Query;
 import org.springframework.lang.NonNull;
 
+import java.util.Collection;
 import java.util.List;
 import java.util.Set;
 
@@ -44,4 +45,13 @@ public interface PostCategoryRepository extends BaseRepository<PostCategory, Int
      */
     @NonNull
     List<PostCategory> findAllByPostIdIn(@NonNull Iterable<Integer> postIds);
+
+    /**
+     * Finds all post categories by post id.
+     *
+     * @param postId post id must not be null
+     * @return a list of post categories
+     */
+    @NonNull
+    List<PostCategory> findAllByPostId(@NonNull Integer postId);
 }

src/main/java/cc/ryanc/halo/service/impl/PostCategoryServiceImpl.java

@@ -96,12 +96,15 @@ public class PostCategoryServiceImpl extends AbstractCrudService<PostCategory, I
         }
 
         // Build post categories
-        List<PostCategory> postCategories = categoryIds.stream().map(categoryId -> {
+        Set<PostCategory> postCategories = categoryIds.stream().map(categoryId -> {
             PostCategory postCategory = new PostCategory();
             postCategory.setPostId(postId);
             postCategory.setCategoryId(categoryId);
             return postCategory;
-        }).collect(Collectors.toList());
+        }).collect(Collectors.toSet());
+
+        // List all post categories and remove them
+        postCategories.removeAll(postCategoryRepository.findAllByPostId(postId));
 
         // Create them
         return createInBatch(postCategories);

src/main/java/cc/ryanc/halo/service/impl/PostTagServiceImpl.java

@@ -120,6 +120,9 @@ public class PostTagServiceImpl extends AbstractCrudService<PostTag, Integer> im
             return postTag;
         }).collect(Collectors.toSet());
 
+        // Get post tag exist and remove them
+        postTags.removeAll(postTagRepository.findAllByPostId(postId));
+
         // Create in batch
         return createInBatch(postTags);
     }

src/main/java/cc/ryanc/halo/web/controller/admin/api/PostController.java

@@ -31,24 +31,8 @@ public class PostController {
 
     private final PostService postService;
 
-    private final TagService tagService;
+    public PostController(PostService postService) {
-
-    private final CategoryService categoryService;
-
-    private final PostTagService postTagService;
-
-    private final PostCategoryService postCategoryService;
-
-    public PostController(PostService postService,
-                          TagService tagService,
-                          CategoryService categoryService,
-                          PostTagService postTagService,
-                          PostCategoryService postCategoryService) {
         this.postService = postService;
-        this.tagService = tagService;
-        this.categoryService = categoryService;
-        this.postTagService = postTagService;
-        this.postCategoryService = postCategoryService;
     }
 
     @GetMapping("latest")