BusinessException类：

<?php

namespace app\common\exception;
use app\common\utils\ResponseUtils;
use think\Exception;

class BusinessException extends Exception
{
    /**
     * 异常数据信息
     * @var object|string
     */
    private $errData;

    /**
     * BusinessException constructor.
     * @param array  $businessStatus 异常状态及提示
     * @param object $data 异常数据信息
     */
    public function __construct($businessStatus) {
        $this->errData =$businessStatus[1];
        parent::__construct($businessStatus[1], $businessStatus[0]);
    }

    /**
     * 获取异常数据
     * @return object|string
     */
    public function getError() {
        return ResponseUtils::retError($this->errData);
    }
}

BusinessExceptionHandler类：

<?php

namespace app\common\exception;
use think\exception\Handle;
use think\exception\HttpException;
use think\exception\ValidateException;
use think\Response;
use Throwable;
class BusinessExceptionHandler extends Handle {

    public function render($request, Throwable $e): Response
    {
        // 参数验证错误
        if ($e instanceof BusinessException) {
            return json($e->getError(), 200);
        }
        // 其他错误交给系统处理
        return parent::render($request, $e);
    }
}

错误枚举类：

<?php

namespace app\common\exception;

class BusinessExceptionEnum
{
    const SUCCESS = [200, "成功"];

    const PASSWORD_WRONG=[400,"密码错误"];
    const USERNAME_WRONG=[401,'用户名不存在'];
    const USERNAME_ALREADY=[402,'用户名已存在'];
    const SIGN_WRONG=[403,'签名错误'];
    const USERNAME_PASSWORD_WRONG=[404,'用户名或密码错误'];
    const JWT_WRONG=[500,'token错误'];
    const FILE_EMPTY=[501,'文件为空'];
    const FILE_WRONG=[502,'文件格式不被支持'];
    const SYSTEM_ERROR=[600,'系统错误'];

}

抛出错误： throw new BusinessException(BusinessExceptionEnum::SYSTEM_ERROR); 这样就可以抛出指定格式的JSON串给前端