AutoMapper之ABP项目中的使用介绍

最近在研究ABP项目，昨天写了Castle Windsor常用介绍以及其在ABP项目的应用介绍欢迎各位拍砖，有关ABP的介绍请看阳光铭睿博客

AutoMapper只要用来数据转换，在园里已经有很多这方面文章了，本文主要介绍其在实际项目常用总结，以及在ABP项目中的应用介绍。AutoMapper应用非常简单，大家稍微看下文档就可以上手，但是性能不好啊，所以一般用在后台项目，对外的项目千万不要用。就那NOP来说吧，它也是把AutoMapper放在后台项目使用，商城前台的项目是不敢用的。

有关性能的问题本文没有涉及到，想了解的请参考EmitMapper,AutoMapper,NLiteMapper和手工映射性能大比拼和 NLiteMapper与EmitMapper性能简单比较。

下面主要讲下项目的入门和项目中的使用。

AutoMapper使用只要两步，配置和Mapper，一般的在项目中我们会在Global中进行配置

配置映射关系

public class Source
{
   public int SomeValue { get; set; }
}

public class Destination
{
   public int SomeValue { get; set; }
}

//这个就是配置映射关系
Mapper.CreateMap<Source, Destination>();

然后就是Mapper

Source source = new Source()
{
    SomeValue = 1
};

var destination = Mapper.Map<Source, Destination>(source);
Console.WriteLine(destination.SomeValue);//1

是不是很简单，这是最简单的使用了，当然AutoMapper是个“机关枪”，这个只是它的最简单使用。下面在介绍几点常用的功能。还是上面那个例子，只是字段变了

    public class Source
    {
        public int SomeValue { get; set; }
    }

    public class Destination
    {
        public int SomeValuefff { get; set; }
    }

    Mapper.CreateMap<AddressDto, Address>();

这样子字段都不一样明细是不能映射的嘛，所有呢我们可以用Mapper.AssertConfigurationIsValid()来验证，就会AutoMapperConfigurationException异常，

选择忽略相关字段

Mapper.CreateMap<Source, Destination>()
        .ForMember(dest => dest.SomeValuefff, opt => opt.Ignore());

类型转换，自定义类型转换

    public class Source
    {
        public string Value1 { get; set; }
        public string Value2 { get; set; }
        public string Value3 { get; set; }
    }

    public class Destination
    {
        public int Value1 { get; set; }
        public DateTime Value2 { get; set; }
        public Type Value3 { get; set; }
    }

Source要转Destination，但是第二和第三的字段类型都不一致，所以我们可以自定义类型转换，下面看下转换函数ConvertUsing一般最常用第二种，接受一个ITypeConverter

    void ConvertUsing(Func<TSource, TDestination> mappingFunction);
    void ConvertUsing(ITypeConverter<TSource, TDestination> converter);
    void ConvertUsing<TTypeConverter>() where TTypeConverter : ITypeConverter<TSource, TDestination>;

下面看下ITypeConverter接口

    public interface ITypeConverter<TSource, TDestination>
    {
        TDestination Convert(ResolutionContext context);
    }

我们可以继承这个接口队Convert进行重写

    public class DateTimeTypeConverter : ITypeConverter<string, DateTime>
    {
        public DateTime Convert(ResolutionContext context)
        {
            return System.Convert.ToDateTime(context.SourceValue);
        }
    }

    public class TypeTypeConverter : ITypeConverter<string, Type>
    {
        public Type Convert(ResolutionContext context)
        {
              return context.SourceType;
        }
    }

这样我们就可以映射了，下面看下完整代码

    public void Example()
    {
        Mapper.CreateMap<string, int>().ConvertUsing(Convert.ToInt32);
        Mapper.CreateMap<string, DateTime>().ConvertUsing(new DateTimeTypeConverter());
        Mapper.CreateMap<string, Type>().ConvertUsing<TypeTypeConverter>();
        Mapper.CreateMap<Source, Destination>();
        Mapper.AssertConfigurationIsValid();

        var source = new Source
        {
            Value1 = "5",
            Value2 = "01/01/2000",
            Value3 = "AutoMapperSamples.GlobalTypeConverters.GlobalTypeConverters+Destination"
        };

        Destination result = Mapper.Map<Source, Destination>(source);
        result.Value3.ShouldEqual(typeof (Destination));
    }

    public class DateTimeTypeConverter : ITypeConverter<string, DateTime>
    {
        public DateTime Convert(ResolutionContext context)
        {
            return System.Convert.ToDateTime(context.SourceValue);
        }
    }

    public class TypeTypeConverter : ITypeConverter<string, Type>
    {
        public Type Convert(ResolutionContext context)
        {
              return context.SourceType;
        }
    }

好了，上面把 AutoMapper在项目中常用的方法都介绍完了，再介绍ABP之前我们先看下NOP是怎么使用的吧，由于代码较长省略部分

    public class AutoMapperStartupTask : IStartupTask
    {
        public void Execute()
        {
            //TODO remove 'CreatedOnUtc' ignore mappings because now presentation layer models have 'CreatedOn' property and core entities have 'CreatedOnUtc' property (distinct names)
            
            //address
            Mapper.CreateMap<Address, AddressModel>()
                .ForMember(dest => dest.AddressHtml, mo => mo.Ignore())
                .ForMember(dest => dest.CustomAddressAttributes, mo => mo.Ignore())
                .ForMember(dest => dest.FormattedCustomAddressAttributes, mo => mo.Ignore())
                .ForMember(dest => dest.AvailableCountries, mo => mo.Ignore())
                .ForMember(dest => dest.AvailableStates, mo => mo.Ignore())
                .ForMember(dest => dest.FirstNameEnabled, mo => mo.Ignore())
                .ForMember(dest => dest.FirstNameRequired, mo => mo.Ignore())
                .ForMember(dest => dest.LastNameEnabled, mo => mo.Ignore())
                .ForMember(dest => dest.LastNameRequired, mo => mo.Ignore())
                .ForMember(dest => dest.EmailEnabled, mo => mo.Ignore())
                .ForMember(dest => dest.EmailRequired, mo => mo.Ignore())
                .ForMember(dest => dest.CompanyEnabled, mo => mo.Ignore())
                .ForMember(dest => dest.CompanyRequired, mo => mo.Ignore())
                .ForMember(dest => dest.CountryEnabled, mo => mo.Ignore())
                .ForMember(dest => dest.StateProvinceEnabled, mo => mo.Ignore())
...

好了，终于可以到ABP的了，ABP对AutoMapper的使用总结出来两点，1、在模块中初始化配置，2、遍历bin目录下所有的Types判断哪些类是否被定义为需要转换的Attribute

在模块中初始化配置

    public class AbpAutoMapperModule : AbpModule
    {
        private readonly ITypeFinder _typeFinder;

        private static bool _createdMappingsBefore;
        private static readonly object _syncObj = new object();
        
        public AbpAutoMapperModule(ITypeFinder typeFinder)
        {
            _typeFinder = typeFinder;
        }

        private void FindAndAutoMapTypes()
        {
            var types = _typeFinder.Find(type =>
                type.IsDefined(typeof(AutoMapAttribute)) ||
                type.IsDefined(typeof(AutoMapFromAttribute)) ||
                type.IsDefined(typeof(AutoMapToAttribute))
                );

            foreach (var type in types)
            {
                AutoMapperHelper.CreateMap(type);
            }
        }
    }

AbpAutoMapperModule 模块会在Global的时候被初始化，然后在PreInitialize的时候回调用到FindAndAutoMapTypes，有关模块是怎么初始化的我想再写一篇介绍。下面我们看下_typeFinder吧

上面_typeFinder.Find调用的是TypeFinder的Find方法

        public Type[] Find(Func<Type, bool> predicate)
        {
            return GetAllTypes().Where(predicate).ToArray();
        }

        public Type[] FindAll()
        {
            return GetAllTypes().ToArray();
        }

        private List<Type> GetAllTypes()
        {
            var allTypes = new List<Type>();

            foreach (var assembly in AssemblyFinder.GetAllAssemblies().Distinct())
            {
                try
                {
                    Type[] typesInThisAssembly;

                    try
                    {
                        typesInThisAssembly = assembly.GetTypes();
                    }
                    catch (ReflectionTypeLoadException ex)
                    {
                        typesInThisAssembly = ex.Types;
                    }

                    if (typesInThisAssembly.IsNullOrEmpty())
                    {
                        continue;
                    }

                    allTypes.AddRange(typesInThisAssembly.Where(type => type != null));
                }
                catch (Exception ex)
                {
                    Logger.Warn(ex.ToString(), ex);
                }
            }

            return allTypes;
        }

好吧，上面代码有点多，但是很简单，就是获取所有的Types，我们看下关键代码AssemblyFinder.GetAllAssemblies()

    public class WebAssemblyFinder : IAssemblyFinder
    {
        /// <summary>
        /// This return all assemblies in bin folder of the web application.
        /// </summary>
        /// <returns>List of assemblies</returns>
        public List<Assembly> GetAllAssemblies()
        {
            var assembliesInBinFolder = new List<Assembly>();

            var allReferencedAssemblies = BuildManager.GetReferencedAssemblies().Cast<Assembly>().ToList();
            var dllFiles = Directory.GetFiles(HttpRuntime.AppDomainAppPath + "bin\", "*.dll", SearchOption.TopDirectoryOnly).ToList();

            foreach (string dllFile in dllFiles)
            {
                var locatedAssembly = allReferencedAssemblies.FirstOrDefault(asm => AssemblyName.ReferenceMatchesDefinition(asm.GetName(), AssemblyName.GetAssemblyName(dllFile)));
                if (locatedAssembly != null)
                {
                    assembliesInBinFolder.Add(locatedAssembly);
                }
            }

            return assembliesInBinFolder;
        }
    }

看看吧，这代码是或bin目录下面的dll，好丧心病狂啊，回到刚刚AbpAutoMapperModule 的获取FindAndAutoMapTypes方法。在获取所有的Types之后我们就要判断这个类是否是被标识了

AutoMapAttribute、AutoMapFromAttribute和AutoMapToAttribute

        private void FindAndAutoMapTypes()
        {
            var types = _typeFinder.Find(type =>
                type.IsDefined(typeof(AutoMapAttribute)) ||
                type.IsDefined(typeof(AutoMapFromAttribute)) ||
                type.IsDefined(typeof(AutoMapToAttribute))
                );

            foreach (var type in types)
            {
                AutoMapperHelper.CreateMap(type);
            }
        }

获取之后再我下的Demo中就只有一个UserDto类被标识了　

namespace AbpDemo.Application.Users.Dto
{
    [AutoMapFrom(typeof(User))]
    public class UserDto : EntityDto<long>
    {
        public string UserName { get; set; }

        public string Name { get; set; }
        
        public string Surname { get; set; }
        
        public string EmailAddress { get; set; }
    }
}

接下来就是遍历所有的types进行配置了AutoMapperHelper.CreateMap(type);配置也很简单看下代码

        public static void CreateMap<TAttribute>(Type type)
            where TAttribute : AutoMapAttribute
        {
            if (!type.IsDefined(typeof (TAttribute)))
            {
                return;
            }

            foreach (var autoMapToAttribute in type.GetCustomAttributes<TAttribute>())
            {
                if (autoMapToAttribute.TargetTypes.IsNullOrEmpty())
                {
                    continue;
                }

                foreach (var targetType in autoMapToAttribute.TargetTypes)
                {
                    if (autoMapToAttribute.Direction.HasFlag(AutoMapDirection.To))
                    {
                        Mapper.CreateMap(type, targetType);
                    }

                    if (autoMapToAttribute.Direction.HasFlag(AutoMapDirection.From))
                    {
                        Mapper.CreateMap(targetType, type);                                
                    }
                }
            }
        }

好了，表达能力不是很好，各位就勉强看下吧。终于写完了。发现作者很喜欢用Attribute来过滤。这边AutoMapper是这样，UnitOfWork也是这样，其实这样也是挺方便的，有点AOP的切面的感觉，值得学习。　

参考文章：

http://www.cnblogs.com/netcasewqs/archive/2011/04/13/2014684.html

http://www.cnblogs.com/repository/archive/2011/04/08/2009713.html

https://github.com/AutoMapper/AutoMapper/wiki/Configuration-validation

http://www.cnblogs.com/youring2/p/automapper.html

http://www.cnblogs.com/1-2-3/p/AutoMapper-Best-Practice.html

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原文地址：https://www.cnblogs.com/huaizuo/p/4835289.html