综合实战：从零件到整车的博客 API

@Entity
@Table(name = "posts")
public class Post {

    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private Long id;

    @Column(nullable = false, length = 120)
    private String title;

    @Column(columnDefinition = "TEXT")
    private String content;

    @Enumerated(EnumType.STRING)                // 纪律一：枚举存身份不存下标（090）
    private PostStatus status;

    @ManyToOne(fetch = FetchType.LAZY)          // 纪律二：关联一律显式 LAZY（090）
    @JoinColumn(name = "author_id", nullable = false)
    private User author;

    @ManyToMany
    @JoinTable(name = "post_tags",
            joinColumns = @JoinColumn(name = "post_id"),
            inverseJoinColumns = @JoinColumn(name = "tag_id"))
    private Set<Tag> tags = new HashSet<>();

    private long commentCount;

    private LocalDateTime createdAt;

    protected Post() {
    }
    // 领域方法与 getter 按需补全
}

public interface PostRepository extends JpaRepository<Post, Long> {

    Page<Post> findByStatus(PostStatus status, Pageable pageable);

    @Query("""
            select p from Post p join fetch p.author
            where p.status = :status
            order by p.createdAt desc
            """)
    List<Post> findPublishedWithAuthor(Pageable pageable);

    @Modifying
    @Query("update Post p set p.commentCount = p.commentCount + 1 where p.id = :id")
    void bumpCommentCount(@Param("id") Long id);
}

@Service
public class PostService {

    private final PostRepository posts;

    public PostService(PostRepository posts) {
        this.posts = posts;
    }

    @Transactional                                  // 一个用例一个事务方法（100）
    public Post publish(User author, PostRequest req, Set<Tag> tags) {
        Post post = Post.create(req.title(), req.content(), author, tags);
        post.publish();
        return posts.save(post);
    }

    @Transactional
    public Post update(Long id, User actor, PostRequest req) {
        Post post = findOwned(id, actor);
        post.update(req.title(), req.content());
        return post;                                // 托管状态，提交时自动 flush
    }

    @Transactional(readOnly = true)
    public Page<Post> findPublished(Pageable pageable) {
        return posts.findByStatus(PostStatus.PUBLISHED, pageable);
    }

    private Post findOwned(Long id, User actor) {
        Post post = posts.findById(id)
                .orElseThrow(() -> new BusinessException("1002", "文章不存在"));
        if (!post.getAuthor().getId().equals(actor.getId())) {
            throw new BusinessException("1103", "只能操作自己的文章");
        }
        return post;
    }
}

public record PostRequest(
        @NotBlank(message = "标题不能为空") @Size(max = 120) String title,
        @NotBlank(message = "正文不能为空") String content) {
}

@RestController
@RequestMapping("/api/posts")
public class PostController {

    private final PostService service;

    public PostController(PostService service) {
        this.service = service;
    }

    @GetMapping
    public Result<Page<PostResponse>> list(@RequestParam(defaultValue = "0") int page,
                                           @RequestParam(defaultValue = "10") int size) {
        return Result.ok(service.findPublished(PageRequest.of(page, Math.min(size, 50)))
                .map(PostResponse::from));
    }

    @PostMapping
    public Result<PostResponse> create(@Valid @RequestBody PostRequest req,
                                       @AuthenticationPrincipal UserPrincipal user) {
        return Result.ok(PostResponse.from(service.publish(user.toUser(), req, Set.of())));
    }
}

http.authorizeHttpRequests(auth -> auth
        .requestMatchers("/api/auth/**").permitAll()
        .requestMatchers(HttpMethod.GET, "/api/posts/**").permitAll()
        .anyRequest().authenticated())
    .addFilterBefore(jwtFilter, UsernamePasswordAuthenticationFilter.class);

@Cacheable(cacheNames = "post:hot", key = "'top'")       // 130 篇
public List<PostResponse> hotPosts() {
    return posts.findPublishedWithAuthor(PageRequest.of(0, 10))
            .stream().map(PostResponse::from).toList();
}

@CacheEvict(cacheNames = "post:hot", key = "'top'")      // 发文、改文、删文都要
@Transactional
public Post publish(User author, PostRequest req, Set<Tag> tags) { /* 同 3.3 */ }

@Async("counterExecutor")                        // 150 篇的分池纪律
public void bumpCommentCount(Long postId) {
    posts.bumpCommentCount(postId);
}

management:
  endpoints:
    web:
      exposure:
        include: health,metrics
  endpoint:
    health:
      probes:
        enabled: true

@WebMvcTest(PostController.class)
class PostControllerTest {

    @Autowired
    MockMvc mockMvc;

    @MockitoBean
    PostService service;

    @Test
    @DisplayName("越权异常翻译为 1103")
    void forbiddenTranslated() throws Exception {
        when(service.update(eq(9L), any(), any()))
                .thenThrow(new BusinessException("1103", "只能操作自己的文章"));

        mockMvc.perform(put("/api/posts/9")
                        .contentType(MediaType.APPLICATION_JSON)
                        .content("{\"title\":\"t\",\"content\":\"c\"}"))
                .andExpect(jsonPath("$.code").value("1103"));
    }
}

@SpringBootTest(webEnvironment = SpringBootTest.WebEnvironment.RANDOM_PORT)
@Testcontainers
class PostFlowIntegrationTest {

    @Container
    @ServiceConnection
    static MySQLContainer<?> mysql = new MySQLContainer<>("mysql:8.0");

    @Autowired
    TestRestTemplate rest;

    @Test
    @DisplayName("未登录发文被挡：401")
    void publishWithoutTokenRejected() {
        ResponseEntity<String> resp = rest.postForEntity("/api/posts",
                new PostRequest("t", "c"), String.class);

        assertThat(resp.getStatusCode()).isEqualTo(HttpStatus.UNAUTHORIZED);
    }
}