Add category module and require post category

src/main/java/com/openisle/controller/CategoryController.java

@@ -0,0 +1,58 @@
+package com.openisle.controller;
+
+import com.openisle.model.Category;
+import com.openisle.service.CategoryService;
+import lombok.Data;
+import lombok.RequiredArgsConstructor;
+import org.springframework.web.bind.annotation.*;
+
+import java.util.List;
+import java.util.stream.Collectors;
+
+@RestController
+@RequestMapping("/api/categories")
+@RequiredArgsConstructor
+public class CategoryController {
+    private final CategoryService categoryService;
+
+    @PostMapping
+    public CategoryDto create(@RequestBody CategoryRequest req) {
+        Category c = categoryService.createCategory(req.getName());
+        return toDto(c);
+    }
+
+    @DeleteMapping("/{id}")
+    public void delete(@PathVariable Long id) {
+        categoryService.deleteCategory(id);
+    }
+
+    @GetMapping
+    public List<CategoryDto> list() {
+        return categoryService.listCategories().stream()
+                .map(this::toDto)
+                .collect(Collectors.toList());
+    }
+
+    @GetMapping("/{id}")
+    public CategoryDto get(@PathVariable Long id) {
+        return toDto(categoryService.getCategory(id));
+    }
+
+    private CategoryDto toDto(Category c) {
+        CategoryDto dto = new CategoryDto();
+        dto.setId(c.getId());
+        dto.setName(c.getName());
+        return dto;
+    }
+
+    @Data
+    private static class CategoryRequest {
+        private String name;
+    }
+
+    @Data
+    private static class CategoryDto {
+        private Long id;
+        private String name;
+    }
+}

src/main/java/com/openisle/controller/PostController.java

@@ -39,7 +39,7 @@ public class PostController {
 
     @PostMapping
     public ResponseEntity<PostDto> createPost(@RequestBody PostRequest req, Authentication auth) {
-        Post post = postService.createPost(auth.getName(), req.getTitle(), req.getContent());
+        Post post = postService.createPost(auth.getName(), req.getCategoryId(), req.getTitle(), req.getContent());
         return ResponseEntity.ok(toDto(post));
     }
 
@@ -61,6 +61,7 @@ public class PostController {
         dto.setContent(post.getContent());
         dto.setCreatedAt(post.getCreatedAt());
         dto.setAuthor(post.getAuthor().getUsername());
+        dto.setCategory(post.getCategory().getName());
         dto.setViews(post.getViews());
 
         List<ReactionDto> reactions = reactionService.getReactionsForPost(post.getId())
@@ -119,6 +120,7 @@ public class PostController {
 
     @Data
     private static class PostRequest {
+        private Long categoryId;
         private String title;
         private String content;
     }
@@ -130,6 +132,7 @@ public class PostController {
         private String content;
         private LocalDateTime createdAt;
         private String author;
+        private String category;
         private long views;
         private List<CommentDto> comments;
         private List<ReactionDto> reactions;