ABP 源码分析汇总之 AutoMapper

AutoMapper 是一个对象映射工具，

安装时只需要安装 如下即可：

有关于它的介绍，参考官网：http://automapper.org/

AutoMapper使用比较简单，还是直奔主题，看一下ABP是如何使用它的：

首先Abp使用AutoMapper专门写的了一个模块Abp.AutoMapper,如下：

跟其它模块一样，有一个继承自AbpModule的AbpAutoMapperModule类。

在ABP自动生成的项目中，是在应用层依赖这个模块，从而对AutoMapper进行了初始化的配置：

    [DependsOn(typeof(AuditCoreModule), typeof(AbpAutoMapperModule))]  //这里
    public class AuditApplicationModule : AbpModule
    {
        public override void PreInitialize()
        {
        }

        public override void Initialize()
        {
            IocManager.RegisterAssemblyByConvention(Assembly.GetExecutingAssembly());
        }
    }

在AbpAutoMapperModule类中，我们看到这句：

public override void PreInitialize()
        {
            IocManager.Register<IAbpAutoMapperConfiguration, AbpAutoMapperConfiguration>();

            Configuration.ReplaceService<ObjectMapping.IObjectMapper, AutoMapperObjectMapper>();//这句

            Configuration.Modules.AbpAutoMapper().Configurators.Add(CreateCoreMappings);
        }

原来只要实现了IObjectMapper的对象映射工具，可以在abp项目中使用。

再来看看，模块是如何创建映射配置的，CreateMappings方法调用FindAndAutoMapTypes()

[DependsOn(typeof(AbpKernelModule))]
    public class AbpAutoMapperModule : AbpModule
    {
        private readonly ITypeFinder _typeFinder;

        private static volatile bool _createdMappingsBefore;
        private static readonly object SyncObj = new object();
        
        public AbpAutoMapperModule(ITypeFinder typeFinder)
        {
            _typeFinder = typeFinder;
        }
public override void PostInitialize()
        {
            CreateMappings();
        }

        private void CreateMappings()
        {
            lock (SyncObj)
            {
                Action<IMapperConfigurationExpression> configurer = configuration =>
                {
                    FindAndAutoMapTypes(configuration);
                    foreach (var configurator in Configuration.Modules.AbpAutoMapper().Configurators)
                    {
                        configurator(configuration);
                    }
                };

                if (Configuration.Modules.AbpAutoMapper().UseStaticMapper)
                {
                    //We should prevent duplicate mapping in an application, since Mapper is static.
                    if (!_createdMappingsBefore)
                    {
                        Mapper.Initialize(configurer);
                        _createdMappingsBefore = true;
                    }

                    IocManager.IocContainer.Register(
                        Component.For<IMapper>().Instance(Mapper.Instance).LifestyleSingleton()
                    );
                }
                else
                {
                    var config = new MapperConfiguration(configurer);
                    IocManager.IocContainer.Register(
                        Component.For<IMapper>().Instance(config.CreateMapper()).LifestyleSingleton()
                    );
                }
            }
        }

        private void FindAndAutoMapTypes(IMapperConfigurationExpression configuration)
        {
            var types = _typeFinder.Find(type =>
                {
                    var typeInfo = type.GetTypeInfo();
                    return typeInfo.IsDefined(typeof(AutoMapAttribute)) ||
                           typeInfo.IsDefined(typeof(AutoMapFromAttribute)) ||
                           typeInfo.IsDefined(typeof(AutoMapToAttribute));
                }
            );

            Logger.DebugFormat("Found {0} classes define auto mapping attributes", types.Length);

            foreach (var type in types)
            {
                Logger.Debug(type.FullName);
                configuration.CreateAutoAttributeMaps(type);
            }
        }

    }

FindAndAutoMapTypes方法中_typeFinder.Find()，看名字就知道是根据里面的条件，找到符合条件的类型。看一下源码，它是如何找的，

 public AbpAutoMapperModule(ITypeFinder typeFinder)
        {
            _typeFinder = typeFinder;
        }

typeFinder是接口，那它默认实现就是TypeFinder,我们在源码中很快找到了它：

    public class TypeFinder : ITypeFinder
    {public TypeFinder(IAssemblyFinder assemblyFinder)
        {
            _assemblyFinder = assemblyFinder;
            Logger = NullLogger.Instance;
        }

        public Type[] Find(Func<Type, bool> predicate)
        {
            return GetAllTypes().Where(predicate).ToArray();
        }
private Type[] GetAllTypes()
        {
            if (_types == null)
            {
                lock (_syncObj)
                {
                    if (_types == null)
                    {
                        _types = CreateTypeList().ToArray();
                    }
                }
            }

            return _types;
        }

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

            var assemblies = _assemblyFinder.GetAllAssemblies().Distinct();

            foreach (var assembly in assemblies)
            {
                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;
        }
    }

可以看到_assemblyFinder.GetAllAssemblies().Distinct();

通过_assemblyFinder 是接口IAssemblyFinder，那它的实现是谁呢，看下面的代码。 这里是castle Windsor实现注册的方式之一。

internal class AbpCoreInstaller : IWindsorInstaller
    {
        public void Install(IWindsorContainer container, IConfigurationStore store)
        {
            container.Register(
                Component.For<IAbpModuleManager, AbpModuleManager>().ImplementedBy<AbpModuleManager>().LifestyleSingleton(),
                Component.For<IAssemblyFinder, AbpAssemblyFinder>().ImplementedBy<AbpAssemblyFinder>().LifestyleSingleton(),
                );
        }
    }

我们看到AbpAssemblyFinder是我们要找到的类。

public class AbpAssemblyFinder : IAssemblyFinder
    {
        private readonly IAbpModuleManager _moduleManager;

        public AbpAssemblyFinder(IAbpModuleManager moduleManager)
        {
            _moduleManager = moduleManager;
        }

        public List<Assembly> GetAllAssemblies()
        {
            var assemblies = new List<Assembly>();

            foreach (var module in _moduleManager.Modules)
            {
                assemblies.Add(module.Assembly);
                assemblies.AddRange(module.Instance.GetAdditionalAssemblies());
            }

            return assemblies.Distinct().ToList();
        }
    }

看到这里就可以知道，ABP是通过module来找到assemblies的。 我们可以 AbpModuleManager : IAbpModuleManager这个类得到所有的模块。

得到assemblies之后，可以得到所有Type信息，再根据过滤条件，得到autoMapper需要映射的类。

再来看来这里的过滤条件：

 var types = _typeFinder.Find(type =>
                {
                    var typeInfo = type.GetTypeInfo();
                    return typeInfo.IsDefined(typeof(AutoMapAttribute)) ||
                           typeInfo.IsDefined(typeof(AutoMapFromAttribute)) ||
                           typeInfo.IsDefined(typeof(AutoMapToAttribute));
                }
            );

三个Attribute. AutoMapAttribute, AutoMapFromAttribute, AutoMapToAttribute,通过名称可以知道它们的用途。

此外，ABP还给我们提供了一个有用的扩展AutoMapExtensions，使用起来更加方便

public static class AutoMapExtensions
    {
        /// <summary>
        /// Converts an object to another using AutoMapper library. Creates a new object of <typeparamref name="TDestination"/>.
        /// There must be a mapping between objects before calling this method.
        /// </summary>
        /// <typeparam name="TDestination">Type of the destination object</typeparam>
        /// <param name="source">Source object</param>
        public static TDestination MapTo<TDestination>(this object source)
        {
            return Mapper.Map<TDestination>(source);
        }

        /// <summary>
        /// Execute a mapping from the source object to the existing destination object
        /// There must be a mapping between objects before calling this method.
        /// </summary>
        /// <typeparam name="TSource">Source type</typeparam>
        /// <typeparam name="TDestination">Destination type</typeparam>
        /// <param name="source">Source object</param>
        /// <param name="destination">Destination object</param>
        /// <returns></returns>
        public static TDestination MapTo<TSource, TDestination>(this TSource source, TDestination destination)
        {
            return Mapper.Map(source, destination);
        }
    }