本節(jié)介紹Util應(yīng)用框架如何處理系統(tǒng)錯(cuò)誤.

概述

系統(tǒng)在運(yùn)行過(guò)程中可能發(fā)生錯(cuò)誤.

系統(tǒng)錯(cuò)誤可以簡(jiǎn)單分為兩類:

• 系統(tǒng)異常

  系統(tǒng)本身出現(xiàn)的錯(cuò)誤.

• 業(yè)務(wù)異常

  不滿足業(yè)務(wù)規(guī)則出現(xiàn)的錯(cuò)誤.

如何處理系統(tǒng)異常

如果發(fā)生系統(tǒng)異常,大多數(shù)情況下,你除了記錄異常日志外,可能無(wú)法處理它們.

一個(gè)例外是并發(fā)異常.

當(dāng)發(fā)生并發(fā)異常,可以通過(guò)重試再次提交,有可能成功處理.

另外一個(gè)問(wèn)題,是否應(yīng)該將系統(tǒng)異常消息返回給客戶端?

系統(tǒng)異常消息與技術(shù)相關(guān),客戶無(wú)法理解它們.

而且系統(tǒng)異常消息可能包含敏感信息,返回給客戶端可能更易受到攻擊.

如何處理業(yè)務(wù)異常

業(yè)務(wù)異常表明沒(méi)有滿足某些業(yè)務(wù)規(guī)則,通常也無(wú)法自動(dòng)處理.

如果能夠自動(dòng)處理的業(yè)務(wù)異常,應(yīng)定義專用異常類型.

對(duì)于業(yè)務(wù)異常,除了記錄異常日志外,還應(yīng)把業(yè)務(wù)異常消息返回給客戶端,以指示用戶調(diào)整操作.

基礎(chǔ)用法

.Net 使用異常 Exception 及派生異常來(lái)處理系統(tǒng)異常,但沒(méi)有明確規(guī)定處理業(yè)務(wù)異常的類型.

Warning 業(yè)務(wù)異常

Util應(yīng)用框架定義了 Util.Exceptions.Warning 異常類型,Warning 從 Exception 派生,代表業(yè)務(wù)異常.

當(dāng)你拋出 Exception 或派生異常類型時(shí),異常消息僅在開(kāi)發(fā)階段返回給客戶端.

一旦發(fā)布到生產(chǎn)環(huán)境,系統(tǒng)異常消息將被屏蔽,客戶端收到消息: 系統(tǒng)忙，請(qǐng)稍后再試 .

throw new Exception( "未將對(duì)象引用設(shè)置到對(duì)象的實(shí)例" );

對(duì)于業(yè)務(wù)規(guī)則導(dǎo)致的錯(cuò)誤,你需要拋出 Warning 異常.

Warning 拋出的異常消息將返回到客戶端,提示用戶進(jìn)行修改.

throw new Warning( "必須填寫(xiě)姓名" );

GetMessage 工具方法

Warning 除了代表業(yè)務(wù)異常外,還提供了一個(gè)靜態(tài)工具方法 GetMessage.

異常可能被其它異常包裹,要獲得異常真正的消息,需要使用遞歸.

Warning.GetMessage 工具方法傳入異常實(shí)例,遞歸獲取異常消息,

var message = Warning.GetMessage( exception );

ConcurrencyException 并發(fā)異常

Util應(yīng)用框架定義了并發(fā)異常 Util.Exceptions.ConcurrencyException.

不同的 .Net 組件拋出的并發(fā)異常類型可能不同, Util使用 ConcurrencyException 進(jìn)行統(tǒng)一包裝.

可以通過(guò)重試的方式來(lái)解決并發(fā)異常.

下面是Util應(yīng)用框架Dapr集成事件增加計(jì)數(shù)時(shí)并發(fā)處理的代碼片斷.

public virtual async Task IncrementAsync( CancellationToken cancellationToken = default ) {
    try {
        await Store.IncrementAsync( cancellationToken );
    }
    catch ( ConcurrencyException ) {
        Log.LogDebug( "更新集成事件計(jì)數(shù)出現(xiàn)并發(fā)異常,即將重試" );
        await IncrementAsync( cancellationToken );
    }
    catch ( Exception exception ) {
        Log.LogError( exception, "更新集成事件計(jì)數(shù)失敗" );
    }
}

全局錯(cuò)誤日志記錄

Util應(yīng)用框架使用 ErrorLogFilterAttribute 過(guò)濾器來(lái)記錄全局錯(cuò)誤日志.

已在 Web Api控制器基類 WebApiControllerBase 設(shè)置 [ErrorLogFilter] 過(guò)濾器.

全局異常處理

Util應(yīng)用框架使用 ExceptionHandlerAttribute 過(guò)濾器來(lái)處理全局異常.

已在 Web Api控制器基類 WebApiControllerBase 設(shè)置 [ExceptionHandler] 過(guò)濾器.

[ExceptionHandler] 過(guò)濾器對(duì)異常消息進(jìn)行處理,只有 Warning 異常消息才會(huì)返回給客戶端.

源碼解析

Warning 業(yè)務(wù)異常

Warning 代表業(yè)務(wù)異常,它的異常消息會(huì)返回給客戶端.

GetMessage 方法使用遞歸獲取內(nèi)部異常消息.

/// <summary>
/// 應(yīng)用程序異常
/// </summary>
public class Warning : Exception {
    /// <summary>
    /// 初始化應(yīng)用程序異常
    /// </summary>
    /// <param name="exception">異常</param>
    public Warning( Exception exception )
        : this( null, exception ) {
    }

    /// <summary>
    /// 初始化應(yīng)用程序異常
    /// </summary>
    /// <param name="message">錯(cuò)誤消息</param>
    /// <param name="exception">異常</param>
    /// <param name="code">錯(cuò)誤碼</param>
    /// <param name="httpStatusCode">Http狀態(tài)碼</param>
    public Warning( string message, Exception exception = null, string code = null, int? httpStatusCode = null )
        : base( message ?? "", exception ) {
        Code = code;
        HttpStatusCode = httpStatusCode;
        IsLocalization = true;
    }

    /// <summary>
    /// 錯(cuò)誤碼
    /// </summary>
    public string Code { get; set; }

    /// <summary>
    /// Http狀態(tài)碼
    /// </summary>
    public int? HttpStatusCode { get; set; }

    /// <summary>
    /// 是否本地化異常消息
    /// </summary>
    public bool IsLocalization { get; set; }

    /// <summary>
    /// 獲取錯(cuò)誤消息
    /// </summary>
    /// <param name="isProduction">是否生產(chǎn)環(huán)境</param>
    public virtual string GetMessage( bool isProduction = false ) {
        return GetMessage( this );
    }

    /// <summary>
    /// 獲取錯(cuò)誤消息
    /// </summary>
    public static string GetMessage( Exception ex ) {
        var result = new StringBuilder();
        var list = GetExceptions( ex );
        foreach( var exception in list )
            AppendMessage( result, exception );
        return result.ToString().Trim( Environment.NewLine.ToCharArray() );
    }

    /// <summary>
    /// 添加異常消息
    /// </summary>
    private static void AppendMessage( StringBuilder result, Exception exception ) {
        if( exception == null )
            return;
        result.AppendLine( exception.Message );
    }

    /// <summary>
    /// 獲取異常列表
    /// </summary>
    public IList<Exception> GetExceptions() {
        return GetExceptions( this );
    }

    /// <summary>
    /// 獲取異常列表
    /// </summary>
    /// <param name="ex">異常</param>
    public static IList<Exception> GetExceptions( Exception ex ) {
        var result = new List<Exception>();
        AddException( result, ex );
        return result;
    }

    /// <summary>
    /// 添加內(nèi)部異常
    /// </summary>
    private static void AddException( List<Exception> result, Exception exception ) {
        if( exception == null )
            return;
        result.Add( exception );
        AddException( result, exception.InnerException );
    }
}

ConcurrencyException 并發(fā)異常

ConcurrencyException 表示并發(fā)異常,統(tǒng)一包裝其它組件產(chǎn)生的并發(fā)異常,并處理異常消息.

/// <summary>
/// 并發(fā)異常
/// </summary>
public class ConcurrencyException : Warning {
    /// <summary>
    /// 消息
    /// </summary>
    private readonly string _message;

    /// <summary>
    /// 初始化并發(fā)異常
    /// </summary>
    public ConcurrencyException()
        : this( "" ) {
    }

    /// <summary>
    /// 初始化并發(fā)異常
    /// </summary>
    /// <param name="exception">異常</param>
    public ConcurrencyException( Exception exception )
        : this( "", exception ) {
    }

    /// <summary>
    /// 初始化并發(fā)異常
    /// </summary>
    /// <param name="message">錯(cuò)誤消息</param>
    /// <param name="exception">異常</param>
    /// <param name="code">錯(cuò)誤碼</param>
    /// <param name="httpStatusCode">Http狀態(tài)碼</param>
    public ConcurrencyException( string message, Exception exception = null, string code = null, int? httpStatusCode = null )
        : base( message, exception, code, httpStatusCode ) {
        _message = message;
    }

    /// <inheritdoc />
    public override string Message => $"{R.ConcurrencyExceptionMessage}.{_message}";

    /// <inheritdoc />
    public override string GetMessage( bool isProduction = false ) {
        if( isProduction )
            return R.ConcurrencyExceptionMessage;
        return GetMessage(this);
    }
}

ErrorLogFilterAttribute 錯(cuò)誤日志過(guò)濾器

[ErrorLogFilter] 錯(cuò)誤日志過(guò)濾器記錄全局異常日志.

/// <summary>
/// 錯(cuò)誤日志過(guò)濾器
/// </summary>
public class ErrorLogFilterAttribute : ExceptionFilterAttribute {
    /// <summary>
    /// 異常處理
    /// </summary>
    public override void OnException( ExceptionContext context ) {
        if( context == null )
            return;
        var log = context.HttpContext.RequestServices.GetService<ILogger<ErrorLogFilterAttribute>>();
        var exception = context.Exception.GetRawException();
        if( exception is Warning warning ) {
            log.LogWarning( warning, exception.Message );
            return;
        }
        log.LogError( exception, exception.Message );
    }
}

ExceptionHandlerAttribute 異常處理過(guò)濾器

[ExceptionHandler] 過(guò)濾器處理全局異常.

Exception 的擴(kuò)展方法 GetPrompt 獲取客戶端友好的異常消息.

對(duì)于生產(chǎn)環(huán)境, Exception 異常消息將被替換為 系統(tǒng)忙，請(qǐng)稍后再試.

[ExceptionHandler] 過(guò)濾器還對(duì)異常消息的本地化進(jìn)行了處理.

/// <summary>
/// 異常處理過(guò)濾器
/// </summary>
public class ExceptionHandlerAttribute : ExceptionFilterAttribute {
    /// <summary>
    /// 異常處理
    /// </summary>
    public override void OnException( ExceptionContext context ) {
        context.ExceptionHandled = true;
        var message = context.Exception.GetPrompt( Web.Environment.IsProduction() );
        message = GetLocalizedMessages( context, message );
        var errorCode = context.Exception.GetErrorCode() ?? StateCode.Fail;
        var httpStatusCode = context.Exception.GetHttpStatusCode() ?? 200;
        context.Result = GetResult( context, errorCode, message, httpStatusCode );
    }

    /// <summary>
    /// 獲取本地化異常消息
    /// </summary>
    protected virtual string GetLocalizedMessages( ExceptionContext context, string message ) {
        var exception = context.Exception.GetRawException();
        if ( exception is Warning { IsLocalization: false } ) 
            return message;
        var stringLocalizerFactory = context.HttpContext.RequestServices.GetService<IStringLocalizerFactory>();
        if ( stringLocalizerFactory == null )
            return message;
        var stringLocalizer = stringLocalizerFactory.Create( "Warning",null );
        var localizedString = stringLocalizer[message];
        if ( localizedString.ResourceNotFound == false )
            return localizedString.Value;
        stringLocalizer = context.HttpContext.RequestServices.GetService<IStringLocalizer>();
        if ( stringLocalizer == null )
            return message;
        return stringLocalizer[message];
    }

    /// <summary>
    /// 獲取結(jié)果
    /// </summary>
    protected virtual IActionResult GetResult( ExceptionContext context, string code, string message, int? httpStatusCode ) {
        var options = GetJsonSerializerOptions( context );
        var resultFactory = context.HttpContext.RequestServices.GetService<IResultFactory>();
        if ( resultFactory == null )
            return new Result( code, message, null, httpStatusCode, options );
        return resultFactory.CreateResult( code, message, null, httpStatusCode, options );
    }

    /// <summary>
    /// 獲取Json序列化配置
    /// </summary>
    private JsonSerializerOptions GetJsonSerializerOptions( ExceptionContext context ) {
        var factory = context.HttpContext.RequestServices.GetService<IJsonSerializerOptionsFactory>();
        if( factory != null )
            return factory.CreateOptions();
        return new JsonSerializerOptions {
            PropertyNamingPolicy = JsonNamingPolicy.CamelCase,
            Encoder = JavaScriptEncoder.Create( UnicodeRanges.All ),
            DefaultIgnoreCondition = JsonIgnoreCondition.WhenWritingNull,
            Converters = {
                new DateTimeJsonConverter(),
                new NullableDateTimeJsonConverter()
            }
        };
    }
}

/// <summary>
/// 異常擴(kuò)展
/// </summary>
public static class ExceptionExtensions {
    /// <summary>
    /// 獲取異常提示
    /// </summary>
    /// <param name="exception">異常</param>
    /// <param name="isProduction">是否生產(chǎn)環(huán)境</param>
    public static string GetPrompt( this Exception exception, bool isProduction = false ) {
        if( exception == null )
            return null;
        exception = exception.GetRawException();
        if( exception == null )
            return null;
        if( exception is Warning warning )
            return warning.GetMessage( isProduction );
        return isProduction ? R.SystemError : exception.Message;
    }

    /// <summary>
    /// 獲取Http狀態(tài)碼
    /// </summary>
    /// <param name="exception">異常</param>
    public static int? GetHttpStatusCode( this Exception exception ) {
        if ( exception == null )
            return null;
        exception = exception.GetRawException();
        if ( exception == null )
            return null;
        if ( exception is Warning warning )
            return warning.HttpStatusCode;
        return null;
    }

    /// <summary>
    /// 獲取錯(cuò)誤碼
    /// </summary>
    /// <param name="exception">異常</param>
    public static string GetErrorCode( this Exception exception ) {
        if ( exception == null )
            return null;
        exception = exception.GetRawException();
        if ( exception == null )
            return null;
        if ( exception is Warning warning )
            return warning.Code;
        return null;
    }
}