优势：

1.异常处理通常是防止未知错误产生所采取的处理措施。异常处理的好处是不用再绞尽脑汁去考虑各种错误，这为处理某一类错误提供了一个很有效的方法，使编程效率大大提高。
2.自定义抛出异常的好处，避免if else嵌套，增强代码可读性，返回给前端一个简化的json信息，进行相应处理。

TP6实例
在app目录下新建lib\exception文件夹
在文件夹下新建ExceptionHandle.php，BaseException.php

ExceptionHandle.php代码，重写render

<?php
namespace app\lib\exception;

use think\Exception;
use think\exception\Handle;
use think\Log;
use think\Response;
use Throwable;

/**
 * 应用异常处理类
 */
class ExceptionHandle extends Handle
{
    public $httpStatus =500 ;
    private $code;
    private $msg;
    private $errorCode;

    public function render($request, Throwable $e): Response
    {
        if($e instanceof BaseException){
            $this->code = $e->code;
            $this->msg = $e->msg;
            $this->errorCode = $e->errorCode;
        }else{
            if(env('APP_DEBUG', '0')){
                return parent::render($request, $e);
            }else{
                $this->code =500;
                $this->msg='服务器错误,请联系客服或者稍后再试';
                $this->errorCode=999;
                $this->recordErrorLog($e);
            }
        }
        $result = [
            'error_code' => $this->errorCode,
            'msg'  => $this->msg,
            'request_url' => request()->url()
        ];

        return json($result, $this->code);
    }
    //记录日志
    public function recordErrorLog(Exception $e){
        Log::record($e->getMessage(),'error');
    }
}

BaseException.php

<?php
namespace app\lib\exception;


use think\Exception;
use Throwable;

class BaseException extends Exception
{
    public $code = 400;
    public $msg = 'invalid parameters';
    public $errorCode = 999;
    public $paramsEnum = [];
    public $shouldToClient = true;

    public function __construct($params=[], $type=0)
    {
        if(!is_array($params)){
            return;
        }
        if(array_key_exists('code',$params)){
            $this->code = $params['code'];
        }
        if(array_key_exists('msg',$params)){
            $this->msg = $params['msg'];
        }
        if(array_key_exists('errorCode',$params)){
            $this->errorCode = $params['errorCode'];
        }

        if( $type ){
            $params = $this->paramsEnum[ $type ];
            $this->errorCode = $params['error_code'];
            $this->msg = $params['msg'];
        }
    }
}

使用

1、在app目录下的provider.php文件中绑定异常处理类，
坑1：如果按照开发手册来写的话，总是不会走自定义异常，报错500
解决方法如下代码

<?php
use app\lib\exception\ExceptionHandle;
use app\Request;

// 容器Provider定义文件
return [
    'think\Request'          => Request::class,
    'think\exception\Handle' => ExceptionHandle::class,
];

2、在app\lib\exception下新建异常处理类，例：
新建ActivityException.php代码如下

<?php
namespace app\lib\exception;

class ActivityException extends BaseException{
    public $code = 400;
    public $msg = 'activity is error';
    public $errorCode = 10700; // 10700-10799

    public $paramsEnum = [
        1 => ['error_code'=>10701, 'msg'=>'活动添加失败，请重试~'],
        2 => ['error_code'=>10702, 'msg'=>'活动添加失败，请重试'],
        3 => ['error_code'=>10703, 'msg'=>'票据规格添加，请重试'],
        4 => ['error_code'=>10704, 'msg'=>'活动不存在'],
        5 => ['error_code'=>10705, 'msg'=>'不可跨账号操作~'],
        6 => ['error_code'=>10706, 'msg'=>'活动不存在或已下架~'],
        7 => ['error_code'=>10707, 'msg'=>'票据不存在~'],
        8 => ['error_code'=>10708, 'msg'=>'该票据已售罄，请更换其他规格~'],
        9 => ['error_code'=>10709, 'msg'=>'活动名额已满，亲下次早来哦~'],
        10 => ['error_code'=>10710, 'msg'=>'下单失败，请重试~']
    ];

    public function __construct($params=[],$type=0)
    {
        parent::__construct($params, $type);
    }
}

3、使用时引入ActivityException，可使用定义好的抛出异常类型，也可以自定义抛出异常信息

throw new ActivityException([],1);

结果

返回Json信息