Laravel Eloquent模型中樂觀鎖的實現

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在app/Utils/Traits目錄下建立OptimisticLockTrait.php，程式碼如下：

namespace App\Utils\Traits;use Illuminate\Database\Eloquent\Builder;trait OptimisticLockTrait{

    /**
     * @var array $optimisticConditions
     * @var array $bindings
     */
    protected $optimisticConditions, $bindings;
    /**
     * @var string $optimisticConditionRaw
     */
    protected $optimisticConditionRaw;

    /**
     * save 时增加乐观锁条件
     * @param Builder $builder
     */
    protected function performUpdate(Builder $builder)
    {
        if (!empty($this->optimisticConditions)) {
            foreach ($this->optimisticConditions as $field => $value) {
                if (is_array($value)) {
                    $count = count($value);
                    if ($count >= 3) {
                        switch (strtoupper($value[1])) {
                            case 'IN':
                                $builder->whereIn($value[0], $value[2]);
                                break;
                            case 'NOT IN':
                                $builder->whereNotIn($value[0], $value[2]);
                                break;
                            case 'BETWEEN':
                                $builder->whereBetween($value[0], $value[2]);
                                break;
                            case 'NOT BETWEEN':
                                $builder->whereNotBetween($value[0], $value[2]);
                                break;
                            default:
                                $builder->where($value[0], $value[1], $value[2]);
                        }
                    } else {
                        $builder->where($value);
                    }
                } else {
                    $builder->where($field, $value);
                }
            }
        }
        // 原始条件注入
        if ($this->optimisticConditionRaw)
            $builder->whereRaw($this->optimisticConditionRaw, $this->bindings);

        return $this->clearOptimistic()->perFormUpdating($builder);

    }


    /**
     * updating with optimistic
     *
     * @param Builder $builder
     * @return bool
     */
    protected function perFormUpdating(Builder $builder)
    {

        // If the updating event returns false, we will cancel the update operation so
        // developers can hook Validation systems into their models and cancel this
        // operation if the model does not pass validation. Otherwise, we update.
        if ($this->fireModelEvent('updating') === false) {
            return false;
        }

        // First we need to create a fresh query instance and touch the creation and
        // update timestamp on the model which are maintained by us for developer
        // convenience. Then we will just continue saving the model instances.
        if ($this->usesTimestamps()) {
            $this->updateTimestamps();
        }

        // Once we have run the update operation, we will fire the "updated" event for
        // this model instance. This will allow developers to hook into these after
        // models are updated, giving them a chance to do any special processing.
        $dirty = $this->getDirty();
        $res = 0;
        if (count($dirty) > 0) {
            $res = $this->setKeysForSaveQuery($builder)->update($dirty);

            $this->syncChanges();

            $this->fireModelEvent('updated', false);
        }
        return !empty($res);
    }

    // 清除乐观锁条件
    function clearOptimistic()
    {
        $this->optimisticConditions = null;
        $this->optimisticConditionRaw = null;
        return $this;
    }


    // 设置乐观锁条件字段名列表
    function setOptimistic(array $optimisticConditions)
    {
        $this->optimisticConditions = $optimisticConditions;
        return $this;
    }

    // 设置乐观锁原始条件字段名列表
    function setOptimisticRaw(string $optimisticConditionRaw, array $bindings = [])
    {
        $this->optimisticConditionRaw = $optimisticConditionRaw;
        $this->bindings = $bindings;
        return $this;
    }}

樂觀鎖定使用說明

#1、在模型中(Models)或模型父類別使用

/**
* App\Models\BaseModel
* @mixin \Eloquent
* @method static \Illuminate\Database\Eloquent\Builder|BaseModel newModelQuery()
* @method static \Illuminate\Database\Eloquent\Builder|BaseModel newQuery()
* @method static \Illuminate\Database\Eloquent\Builder|BaseModel query()
*/class BaseModel extends Model{
  use OptimisticLockTrait;}

2、使用方法：

 $ord = Order::find(1);
 $ord->payment_status = 1;
 if(!$model->setOptimistic(['payment_status' => 0]))->save())
   throws new Exception('订单已付过款了');

或使用原始SQL方式:

 $ord = Order::find(1);
 $ord->payment_status = 1;
 if(!$model->setOptimisticRaw('payment_status = ?',[1]))->save())
   throws new Exception('订单已付过款了');

如果相同物件小涉及到多次更新，則可以清除鎖定條件

$ord->clearOptimistic();

以上就是樂觀鎖的實作方式，在實際開發中比較常用也很有必要。

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