WordPress 基础配置与 Java 后端开发实战笔记

2. Controller 层实现

@RestController
@RequestMapping("/friends")
@RequiredArgsConstructor
public class FriendController {
    private final FriendService friendService;

    @PostMapping
    public Result<Boolean> addFriend(@RequestBody @Valid FriendRequest request) {
        return Result.success(friendService.addFriend(request.getUserId(), request.getFriendId()));
    }

    @DeleteMapping
    public Result<Boolean> deleteFriend(@RequestBody @Valid FriendRequest request) {
        return Result.success(friendService.deleteFriend(request.getUserId(), request.getFriendId()));
    }

    @GetMapping("/{userId}")
    public Result<List<FriendDTO>> getFriends(@PathVariable Integer userId) {
        return Result.success(friendService.getFriends(userId));
    }

    @GetMapping("/check")
    public Result<Boolean> isFriend(@RequestParam Integer userId, @RequestParam Integer friendId) {
        return Result.success(friendService.isFriend(userId, friendId));
    }

    @Data
    static class FriendRequest {
        @NotNull
        private Integer userId;
        @NotNull
        private Integer friendId;
    }
}

3. Service 层实现

@Service
@RequiredArgsConstructor
public class FriendServiceImpl implements FriendService {
    private final UserMapper userMapper;
    private final FriendRelationMapper relationMapper;

    @Override
    @Transactional
    public boolean addFriend(Integer userId, Integer friendId) {
        checkUserExists(userId);
        checkUserExists(friendId);
        if (relationMapper.existsRelation(userId, friendId)) {
            return false;
        }
        relationMapper.insert(new FriendRelation(userId, friendId));
        relationMapper.insert(new FriendRelation(friendId, userId));
        return true;
    }

    @Override
    @Transactional
    public boolean deleteFriend(Integer userId, Integer friendId) {
        relationMapper.deleteRelation(userId, friendId);
        relationMapper.deleteRelation(friendId, userId);
        return true;
    }

    @Override
    public List<FriendDTO> getFriends(Integer userId) {
        return relationMapper.selectFriendList(userId).stream()
                .map(user -> new FriendDTO(user.getId(), user.getNickname(), user.getAvatar()))
                .collect(Collectors.toList());
    }

    @Override
    public boolean isFriend(Integer userId, Integer friendId) {
        return relationMapper.existsRelation(userId, friendId);
    }

    private void checkUserExists(Integer userId) {
        if (userMapper.selectById(userId) == null) {
            throw new BusinessException("用户不存在");
        }
    }
}

4. Mapper 层（MyBatis-Plus）

实体类定义：

@Data
@TableName("user_friend_relation")
public class FriendRelation {
    @TableId(type = IdType.AUTO)
    private Long id;
    private Integer userId;
    private Integer friendId;
    private LocalDateTime createTime;
}

Mapper 接口：

public interface FriendRelationMapper extends BaseMapper<FriendRelation> {
    @Select("SELECT COUNT(1) FROM user_friend_relation " +
            "WHERE user_id = #{userId} AND friend_id = #{friendId}")
    boolean existsRelation(@Param("userId") Integer userId, @Param("friendId") Integer friendId);

    @Delete("DELETE FROM user_friend_relation " +
            "WHERE user_id = #{userId} AND friend_id = #{friendId}")
    int deleteRelation(@Param("userId") Integer userId, @Param("friendId") Integer friendId);

    @Select("SELECT u.* FROM user u " +
            "JOIN user_friend_relation r ON u.id = r.friend_id " +
            "WHERE r.user_id = #{userId}")
    List<User> selectFriendList(Integer userId);
}

5. 统一返回结构

@Data
public class Result<T> {
    private int code;
    private String msg;
    private T data;

    public static <T> Result<T> success(T data) {
        Result<T> result = new Result<>();
        result.setCode(200);
        result.setMsg("success");
        result.setData(data);
        return result;
    }
}

数据库索引优化实践

为 email 字段建立索引是提升查询性能的关键手段。

核心原因

1. 提高查询性能：将查找复杂度从 O(n) 降至 O(log n)，加速登录、密码重置等操作。
2. 保证唯一性：通过唯一索引防止重复注册。
3. 支持高级查询：优化前缀匹配或特定条件的模糊查询。

注意事项

• 写入权衡：索引会轻微降低增删改速度，但读取频繁场景下利大于弊。
• 类型选择：根据需求选择普通索引或唯一索引。长字段可考虑前缀索引。

示例

CREATE UNIQUE INDEX idx_email ON users(email);
EXPLAIN SELECT * FROM users WHERE email = '[email protected]';

前端 OpenAPI 依赖报错修复

运行 npm run openapi 时报错 Cannot find module 'tslib'，通常因缺少 TypeScript 运行时库导致。

解决方案

1. 手动安装 tslib

   npm install tslib --save
   # 或使用 yarn
   yarn add tslib
   

2. 验证依赖 检查 node_modules/tslib 是否存在，并确保 package.json 中包含该依赖项。
3. 重新运行

   npm run openapi
   

总结

本文涵盖了从 WordPress 基础搭建到 Java 后端接口开发的完整流程，重点解决了数据库连接配置、MyBatis-Plus 代码生成及常见的前端依赖缺失问题。掌握这些基础技能有助于快速构建稳定的 Web 应用架构。