综合练习：做题平台后端

这一课你将能做到

1. 搭建「题目—提交—异步判分」闭环 API：出题、提交答案、查询结果
2. 用 FormRequest 验证、Policy 授权、Event/Listener 解耦统计
3. 用工厂+Feature 测试证明核心流程正确，并产出上线检查清单

为什么要学

单个知识点都不难，真实项目要求组合：一次「提交答案」同时涉及路由、认证、验证、Eloquent、事务、队列、事件、测试。项目选在线做题平台后端（本站题库极简版）：教师出题，学生提交，系统异步判分。

先建立图像

users 1──N questions 1──N choices（is_correct 标记正误）
users 1──N submissions N──1 questions

POST /api/questions/{q}/submissions
  → 验证答案属于该题 → 写 pending → dispatch JudgeSubmission
worker → 判分 → graded → event SubmissionGraded → UpdateUserStats（ShouldQueue）

Laravel ↔ Spring：

Laravel	Spring Boot
Controller + FormRequest	@RestController + @Valid
Job / Queue (Redis)	@Async + RabbitMQ
Event / Listener	ApplicationEvent
Policy	@PreAuthorize
Factory / RefreshDatabase	DataLoader + @Transactional

跟着做

步骤 1：数据层

先 install:api，再 make:model Question -mf、Choice -m、Submission -mf。迁移字段：

$table->foreignId('created_by')->constrained('users');
$table->string('stem');
$table->string('type', 16);
$table->unsignedSmallInteger('score')->default(5);
$table->foreignId('question_id')->constrained()->cascadeOnDelete();
$table->string('content');
$table->boolean('is_correct')->default(false);
$table->foreignId('user_id')->constrained();
$table->foreignId('question_id')->constrained();
$table->json('answers');
$table->unsignedSmallInteger('score')->default(0);
$table->string('status', 16)->default('pending')->index();
$table->timestamp('graded_at')->nullable();
$table->timestamps();
$table->unique(['user_id', 'question_id']);

模型：

class Question extends Model
{
    use HasFactory;
    protected $fillable = ['stem', 'type', 'score', 'created_by'];
    public function choices(): HasMany { return $this->hasMany(Choice::class); }
}

class Submission extends Model
{
    use HasFactory;
    protected $fillable = ['question_id', 'answers', 'score', 'status', 'graded_at'];
    protected $casts = ['answers' => 'array', 'graded_at' => 'datetime'];
    public function question(): BelongsTo { return $this->belongsTo(Question::class); }
}