• 放弃 AutoMapper ，拥抱 Mapster

    性能测试结论：使用 new {} 的方式性能最佳，其次是 Mapster ，最后是 AutoMapper

    最近在对一个业务接口做代码重构时，发现在使用 AutoMapper 做对象转换时，接口响应速度极慢，100多条数据，请求时长都超过了8秒。为了找出原因所在，我尝试将 EF Core 的相关查询和 实体转换拆分开来做分析，最终发现是由于使用 AutoMapper 时，性能出现了瓶颈。于是我尝试使用 select new {} 的 Linq 方式来硬编码转换，发现效率提升了几倍，基本 2秒内就能完成。出于好奇，我尝试对 AutoMapper 做一下性能对比测试。

    测试步骤

    测试环境

    • OS：Windows 10.0.19042.1348 (20H2/October2020Update)
    • CPU：Intel Core i5-7500 CPU 3.40GHz (Kaby Lake), 1 CPU, 4 logical and 4 physical cores
    • SDK：NET SDK=6.0.100
    • 压测工具：BenchmarkDotNet=v0.13.1

    创建项目

    dotnet new console -o ConsoleApp1

    安装依赖包

    dotnet add package BenchmarkDotNet --version 0.13.1
dotnet add package AutoMapper --version 10.1.1
dotnet add package Mapster --version 7.2.0

    定义用于测试 Entity 和 DTO

    public enum MyEnum
{
    [Description("进行中")]
    Doing,
    [Description("完成")]
    Done
}
public class Entity
{
    public int Id { get; set; }
    public Guid Oid { get; set; }
    public string? NickName { get; set; }
    public bool Created { get; set; }
    public MyEnum State { get; set; }
}

public class EntityDto
{
    public int Id { get; set; }
    public Guid Oid { get; set; }
    public string? NickName { get; set; }
    public bool Created { get; set; }
    public MyEnum Enum { get; set; }
    public string? EnumString { get; set; }
}

    配置 Entity 和 DTO 之间的转换关系

    AutoMapper 配置

      public class AutoMapperProfile : Profile
  {
      public AutoMapperProfile()
      {
          CreateMap<Entity, EntityDto>()
               .ForMember(dest => dest.Id, opt => opt.MapFrom(src => src.Id))
               .ForMember(dest => dest.Oid, opt => opt.MapFrom(src => src.Oid))
               .ForMember(dest => dest.NickName, opt => opt.MapFrom(src => src.NickName))
               .ForMember(dest => dest.Created, opt => opt.MapFrom(src => src.Created))
               .ForMember(dest => dest.Enum, opt => opt.MapFrom(src => src.State))
               .ForMember(dest => dest.EnumString, opt => opt.MapFrom(src => src.State.GetDescription()));
      }
  }

    Mapster 配置

    public class MapsterProfile : TypeAdapterConfig
{
    public MapsterProfile()
    {
        ForType<Entity, EntityDto>()
             .Map(dest => dest.Id, src => src.Id)
             .Map(dest => dest.Oid, src => src.Oid)
             .Map(dest => dest.NickName, src => src.NickName)
             .Map(dest => dest.Created, src => src.Created)
             .Map(dest => dest.Enum, src => src.State)
             .Map(dest => dest.EnumString, src => src.State.GetDescription());
    }
}

    创建性能测试类

    public class PerformanceTest
{
    private IReadOnlyList<entity> _entities;
    private readonly AutoMapper.IMapper _autoMapper;
    private readonly Mapper _mapsterMapper;

    public PerformanceTest()
    {
        var mocker = new AutoMocker();
        _entities = Enumerable.Range(0, 1000000).Select(x => mocker.CreateInstance<entity>()).ToList();

        var configuration = new AutoMapper.MapperConfiguration(cfg => cfg.AddProfile<AutoMapperProfile>());
         _autoMapper = configuration.CreateMapper();
         _mapsterMapper = new MapsterMapper.Mapper(new MapsterProfile());
    }

    [Benchmark]
    public void Constructor()
    {
        var dtos = _entities.Select(x => new EntityDto
        {
            Id = x.Id,
            Oid = x.Oid,
            NickName = x.NickName,
            Created = x.Created,
            Enum = x.State,
            EnumString = x.State.GetDescription(),
        });
    }

    [Benchmark]
    public void AutoMapper()
    {
        var dtos = _autoMapper.Map<ienumerable<entitydto>>(_entities);

    }
    [Benchmark]
    public void Mapster()
    {
        var dtos = _mapsterMapper.Map<ienumerable<entitydto>>(_entities);
    }
}

    执行性能测试

    var summary = BenchmarkRunner.Run<PerformanceTest>();

    dotnet run --project .\ConsoleApp1.csproj -c Release

    结果对比

    通过使用 BenchmarkDotNet 来进行压测对比。从上图我们可以看出，使用 Constructor(直接创建对象) 的方式性能是最高的，然后就是 Mapster，最后才是 AutoMapper。

    使用 ReadableExpressions.Visualizers 查看 Execution Plan

    在项目中一直在使用 AutoMapper 来做对象转换，看 Github 活跃度，按理说不应该出现这么明显的性能问题。好奇心驱使我项研究一下，通过和作者沟通后了解到，'AutoMapper' 本身会有一个所谓的执行计划 execution plan，可以通过安装插件 ReadableExpressions.Visualizers 来查看。

    在 AutoMapper 的配置地方添加如下代码：

    var executionPlan = configuration.BuildExecutionPlan(typeof(Entity), typeof(EntityDto));
var executionPlanStr = executionPlan.ToReadableString();

    查看 executionPlanStr 值，如下所示：

    (src, dest, ctxt) =>
{
    EntityDto typeMapDestination;
    return (src == null)
        ? null
        : {
            typeMapDestination = dest ?? new EntityDto();
            try
            {
                var resolvedValue =
                {
                    try
                    {
                        Entity src;
                        return (((src = src) == null) || false) ? default(int) : src.Id;
                    }
                    catch (NullReferenceException)
                    {
                        return default(int);
                    }
                    catch (ArgumentNullException)
                    {
                        return default(int);
                    }
                };

                typeMapDestination.Id = resolvedValue;
            }
            catch (Exception ex)
            {
                return throw new AutoMapperMappingException(
                    "Error mapping types.",
                    ex,
                    AutoMapper.TypePair,
                    TypeMap,
                    PropertyMap);
            }
            try
            {
                var resolvedValue =
                {
                    try
                    {
                        Entity src;
                        return (((src = src) == null) || false) ? default(Guid) : src.Oid;
                    }
                    catch (NullReferenceException)
                    {
                        return default(Guid);
                    }
                    catch (ArgumentNullException)
                    {
                        return default(Guid);
                    }
                };

                typeMapDestination.Oid = resolvedValue;
            }
            catch (Exception ex)
            {
                return throw new AutoMapperMappingException(
                    "Error mapping types.",
                    ex,
                    AutoMapper.TypePair,
                    TypeMap,
                    PropertyMap);
            }
            try
            {
                var resolvedValue =
                {
                    try
                    {
                        Entity src;
                        return (((src = src) == null) || false) ? null : src.NickName;
                    }
                    catch (NullReferenceException)
                    {
                        return null;
                    }
                    catch (ArgumentNullException)
                    {
                        return null;
                    }
                };

                var propertyValue = (resolvedValue == null) ? null : resolvedValue;
                typeMapDestination.NickName = propertyValue;
            }
            catch (Exception ex)
            {
                return throw new AutoMapperMappingException(
                    "Error mapping types.",
                    ex,
                    AutoMapper.TypePair,
                    TypeMap,
                    PropertyMap);
            }
            try
            {
                var resolvedValue =
                {
                    try
                    {
                        Entity src;
                        return (((src = src) == null) || false) ? default(bool) : src.Created;
                    }
                    catch (NullReferenceException)
                    {
                        return default(bool);
                    }
                    catch (ArgumentNullException)
                    {
                        return default(bool);
                    }
                };

                typeMapDestination.Created = resolvedValue;
            }
            catch (Exception ex)
            {
                return throw new AutoMapperMappingException(
                    "Error mapping types.",
                    ex,
                    AutoMapper.TypePair,
                    TypeMap,
                    PropertyMap);
            }
            try
            {
                var resolvedValue =
                {
                    try
                    {
                        Entity src;
                        return (((src = src) == null) || false) ? default(MyEnum) : src.State;
                    }
                    catch (NullReferenceException)
                    {
                        return default(MyEnum);
                    }
                    catch (ArgumentNullException)
                    {
                        return default(MyEnum);
                    }
                };

                typeMapDestination.Enum = resolvedValue;
            }
            catch (Exception ex)
            {
                return throw new AutoMapperMappingException(
                    "Error mapping types.",
                    ex,
                    AutoMapper.TypePair,
                    TypeMap,
                    PropertyMap);
            }
            try
            {
                var resolvedValue =
                {
                    try
                    {
                        return ((Enum)src.State).GetDescription();
                    }
                    catch (NullReferenceException)
                    {
                        return null;
                    }
                    catch (ArgumentNullException)
                    {
                        return null;
                    }
                };

                var propertyValue = (resolvedValue == null) ? null : resolvedValue;
                typeMapDestination.EnumString = propertyValue;
            }
            catch (Exception ex)
            {
                return throw new AutoMapperMappingException(
                    "Error mapping types.",
                    ex,
                    AutoMapper.TypePair,
                    TypeMap,
                    PropertyMap);
            }

            return typeMapDestination;
        };
}

    使用 dotTrace 进行性能跟踪

    通过使用 JetBrains dotTrace 来查看程序执行情况，如下图所示：

    从图中我们可以看到，GetDescription 方法性能占用高达 8.38%。我尝试将这个枚举转字符串的扩展方法每次都返回固定值，如下所示：

    public static class Extension
{
    public static string GetDescription(this Enum value)
    {
        return "aaa";
        //var field = value.GetType().GetField(value.ToString());
        //if (field == null) return "";
        //return Attribute.GetCustomAttribute(field,
        //    typeof(DescriptionAttribute)) is not DescriptionAttribute attribute
        //    ? value.ToString()
        //    : attribute.Description;
    }
}

    再次进行性能测试，发现 AutoMapper 的性能提升了不少。

    但是，由于本身性能基数比较大，所有依然存在性能问题

    相关参考
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  • 原文地址：https://www.cnblogs.com/hippieZhou/p/15590457.html
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