Laravel自定义CustomerHasVoucherException的getMessage()返回空值问题

问题描述 #

创建了CustomerHasVoucherException自定义异常类，但在控制器中捕获该异常后，调用$e->getMessage()返回空错误信息。

异常类代码 #

<?php

namespace Modules\Customer\Exceptions;

use Exception;

class CustomerHasVoucherException extends Exception
{
    public function report()
    {
        return false;
    }

    public function render($request, $exception)
    {
        $request->headers->set('Accept', 'application/json');
        
        return response()->json((['message' => 'customer already has a voucher!']), 406);
    }
}

控制器方法代码 #

public function reserveVoucher(CustomerRepository $customerRepository, CampaignRepository $campaignRepository, Request $request, $customer_id, $campaign_code)
{
    // dd($campaign_code, $customer_id);
    try {

        $customer = $customerRepository->checkEligibility($customer_id);

        $campaignRepository->beginTransaction();
        $voucher = $campaignRepository->reserveVoucher($campaign_code, $customer);
        $campaignRepository->commitTransaction();

        return response()->json(
            ['message' => "Your voucher is reserved! Procced to next step within " . \Config::get('voucher.campaign.voucher.max_reservation_time') . " minutes."],
            200
        );
    } catch (CustomerHasVoucherException $e) {
        report($e);
        return response()->json(['error' => $e->getMessage()]);
    } catch (\Throwable $th) {
        report($th);
        return response()->json(['error' => $th->getMessage()]);
    }
}

返回响应 #

{
    "error": ""
}

问题原因 #

自定义异常类未调用父类Exception的构造函数初始化错误消息，也未重写getMessage()方法。当抛出异常时，父类的$message属性为空，导致$e->getMessage()返回空字符串。

解决方法 #

方案一：调用父类构造并传递消息 #

1. 修改异常类，添加构造函数调用父类方法：

<?php

namespace Modules\Customer\Exceptions;

use Exception;
use Throwable;

class CustomerHasVoucherException extends Exception
{
    public function __construct($message = "", $code = 0, Throwable $previous = null)
    {
        parent::__construct($message, $code, $previous);
    }

    public function report()
    {
        return false;
    }

    public function render($request, $exception)
    {
        $request->headers->set('Accept', 'application/json');
        
        return response()->json(['message' => 'customer already has a voucher!'], 406);
    }
}

2. 抛出异常时传入错误消息：

throw new CustomerHasVoucherException('customer already has a voucher!');

方案二：重写getMessage()方法返回固定消息 #

直接在异常类中重写getMessage()，返回预设的错误内容：

<?php

namespace Modules\Customer\Exceptions;

use Exception;

class CustomerHasVoucherException extends Exception
{
    public function report()
    {
        return false;
    }

    public function getMessage()
    {
        return 'customer already has a voucher!';
    }

    public function render($request, $exception)
    {
        $request->headers->set('Accept', 'application/json');
        
        return response()->json(['message' => $this->getMessage()], 406);
    }
}

两种方案都能让控制器中$e->getMessage()返回正确的错误信息。

内容的提问来源于stack exchange，提问作者Amit Shah