Created DefaultObjectMapper and implemented specific mappers.

src/Volo.Abp.AutoMapper/Volo/Abp/AutoMapper/AutoMapperObjectMapper.cs

@@ -1,25 +1,28 @@
-using AutoMapper;
+using System;
+using AutoMapper;
 using Microsoft.Extensions.DependencyInjection;
+using Volo.Abp.ObjectMapping;
 using Volo.DependencyInjection;
 
 namespace Volo.Abp.AutoMapper
 {
     [Dependency(ServiceLifetime.Transient, ReplaceServices = true)]
-    public class AutoMapperObjectMapper : Volo.Abp.ObjectMapping.IObjectMapper
+    public class AutoMapperObjectMapper : DefaultObjectMapper
     {
         private readonly IMapper _mapper;
 
-        public AutoMapperObjectMapper(IMapperAccessor mapper)
+        public AutoMapperObjectMapper(IMapperAccessor mapper, IServiceProvider serviceProvider)
+            : base(serviceProvider)
         {
             _mapper = mapper.Mapper;
         }
 
-        public TDestination Map<TDestination>(object source)
+        protected override TDestination AutoMap<TSource, TDestination>(object source)
         {
             return _mapper.Map<TDestination>(source);
         }
 
-        public TDestination Map<TSource, TDestination>(TSource source, TDestination destination)
+        protected override TDestination AutoMap<TSource, TDestination>(TSource source, TDestination destination)
         {
             return _mapper.Map(source, destination);
         }

src/Volo.Abp/Volo/Abp/ObjectMapping/DefaultObjectMapper.cs

@@ -0,0 +1,68 @@
+using System;
+using Microsoft.Extensions.DependencyInjection;
+using Volo.DependencyInjection;
+
+namespace Volo.Abp.ObjectMapping
+{
+    //TODO: It can be slow to always check if service is available. Test it and optimize if necessary.
+
+    public class DefaultObjectMapper : IObjectMapper, ISingletonDependency
+    {
+        private readonly IServiceProvider _serviceProvider;
+
+        public DefaultObjectMapper(IServiceProvider serviceProvider)
+        {
+            _serviceProvider = serviceProvider;
+        }
+
+        public virtual TDestination Map<TSource, TDestination>(TSource source)
+        {
+            if (source == null)
+            {
+                return default(TDestination);
+            }
+
+            //Check if a specific mapper is registered
+            using (var scope = _serviceProvider.CreateScope())
+            {
+                var specificMapper = scope.ServiceProvider.GetService<IObjectMapper<TSource, TDestination>>();
+                if (specificMapper != null)
+                {
+                    return specificMapper.Map(source);
+                }
+            }
+
+            return AutoMap<TSource, TDestination>(source);
+        }
+
+        public virtual TDestination Map<TSource, TDestination>(TSource source, TDestination destination)
+        {
+            if (source == null)
+            {
+                return default(TDestination);
+            }
+
+            //Check if a specific mapper is registered
+            using (var scope = _serviceProvider.CreateScope())
+            {
+                var specificMapper = scope.ServiceProvider.GetService<IObjectMapper<TSource, TDestination>>();
+                if (specificMapper != null)
+                {
+                    return specificMapper.Map(source, destination);
+                }
+            }
+
+            return AutoMap(source, destination);
+        }
+
+        protected virtual TDestination AutoMap<TSource, TDestination>(object source)
+        {
+            throw new NotImplementedException($"Can not map from given object ({source}) to {typeof(TDestination).AssemblyQualifiedName}.");
+        }
+
+        protected virtual TDestination AutoMap<TSource, TDestination>(TSource source, TDestination destination)
+        {
+            throw new NotImplementedException($"Can no map from {typeof(TSource).AssemblyQualifiedName} to {typeof(TDestination).AssemblyQualifiedName}.");
+        }
+    }
+}

src/Volo.Abp/Volo/Abp/ObjectMapping/IObjectMapper.cs

@@ -9,8 +9,9 @@
         /// Converts an object to another. Creates a new object of <see cref="TDestination"/>.
         /// </summary>
         /// <typeparam name="TDestination">Type of the destination object</typeparam>
+        /// <typeparam name="TSource">Type of the source object</typeparam>
         /// <param name="source">Source object</param>
-        TDestination Map<TDestination>(object source);
+        TDestination Map<TSource, TDestination>(TSource source);
 
         /// <summary>
         /// Execute a mapping from the source object to the existing destination object
@@ -22,4 +23,11 @@
         /// <returns>Returns the same <see cref="destination"/> object after mapping operation</returns>
         TDestination Map<TSource, TDestination>(TSource source, TDestination destination);
     }
+
+    public interface IObjectMapper<in TSource, TDestination>
+    {
+        TDestination Map(TSource source);
+
+        TDestination Map(TSource source, TDestination destination);
+    }
 }

src/Volo.Abp/Volo/Abp/ObjectMapping/NotImplementedObjectMapper.cs

@@ -1,23 +0,0 @@
-using System;
-using Volo.DependencyInjection;
-
-namespace Volo.Abp.ObjectMapping
-{
-    public sealed class NotImplementedObjectMapper : IObjectMapper, ISingletonDependency
-    {
-        /// <summary>
-        /// Singleton instance.
-        /// </summary>
-        public static NotImplementedObjectMapper Instance { get; } = new NotImplementedObjectMapper();
-
-        public TDestination Map<TDestination>(object source)
-        {
-            throw new NotImplementedException("Abp.ObjectMapping.IObjectMapper should be implemented in order to map objects.");
-        }
-
-        public TDestination Map<TSource, TDestination>(TSource source, TDestination destination)
-        {
-            throw new NotImplementedException("Abp.ObjectMapping.IObjectMapper should be implemented in order to map objects.");
-        }
-    }
-}

test/Volo.Abp.AutoMapper.Tests/Volo/Abp/AutoMapper/AbpAutoMapperModule_Basic_Tests.cs

@@ -10,30 +10,32 @@ namespace Volo.Abp.AutoMapper
 {
     public class AbpAutoMapperModule_Basic_Tests : AbpIntegratedTest<AutoMapperTestModule>
     {
+        private readonly IObjectMapper _objectMapper;
+
+        public AbpAutoMapperModule_Basic_Tests()
+        {
+            _objectMapper = ServiceProvider.GetRequiredService<IObjectMapper>();
+        }
+
         [Fact]
         public void Should_Replace_ObjectMapper()
         {
-            var objectMapper = ServiceProvider.GetRequiredService<IObjectMapper>();
-            Assert.True(objectMapper is AutoMapperObjectMapper);
+            Assert.True(_objectMapper is AutoMapperObjectMapper);
         }
 
         [Fact]
         public void Should_Map_Objects_With_AutoMap_Attributes()
         {
-            var objectMapper = ServiceProvider.GetRequiredService<IObjectMapper>();
-
-            var dto = objectMapper.Map<MyEntityDto>(new MyEntity {Number = 42});
+            var dto = _objectMapper.Map<MyEntity, MyEntityDto>(new MyEntity {Number = 42});
             dto.Number.ShouldBe(42);
         }
 
         [Fact]
         public void Should_Not_Map_Objects_With_AutoMap_Attributes()
         {
-            var objectMapper = ServiceProvider.GetRequiredService<IObjectMapper>();
-
             Assert.ThrowsAny<Exception>(() =>
             {
-                objectMapper.Map<MyNotMappedDto>(new MyEntity {Number = 42});
+                _objectMapper.Map<MyEntity, MyNotMappedDto>(new MyEntity {Number = 42});
             });
         }
     }

test/Volo.Abp.AutoMapper.Tests/Volo/Abp/AutoMapper/AbpAutoMapperModule_Specific_ObjectMapper_Tests.cs

@@ -0,0 +1,26 @@
+using Microsoft.Extensions.DependencyInjection;
+using Shouldly;
+using Volo.Abp.AutoMapper.SampleClasses;
+using Volo.Abp.ObjectMapping;
+using Volo.Abp.TestBase;
+using Xunit;
+
+namespace Volo.Abp.AutoMapper
+{
+    public class AbpAutoMapperModule_Specific_ObjectMapper_Tests : AbpIntegratedTest<AutoMapperTestModule>
+    {
+        private readonly IObjectMapper _objectMapper;
+
+        public AbpAutoMapperModule_Specific_ObjectMapper_Tests()
+        {
+            _objectMapper = ServiceProvider.GetRequiredService<IObjectMapper>();
+        }
+
+        [Fact]
+        public void Should_Use_Specific_Object_Mapper_If_Registered()
+        {
+            var dto = _objectMapper.Map<MyEntity, MyEntityDto2>(new MyEntity { Number = 42 });
+            dto.Number.ShouldBe(43); //MyEntityToMyEntityDto2Mapper adds 1 to number of the source.
+        }
+    }
+}

test/Volo.Abp.AutoMapper.Tests/Volo/Abp/AutoMapper/AutofacTestModule.cs

@@ -8,7 +8,7 @@ namespace Volo.Abp.AutoMapper
     {
         public override void ConfigureServices(IServiceCollection services)
         {
-            services.AddAssemblyOf<AbpAutoMapperModule>();
+            services.AddAssemblyOf<AutoMapperTestModule>();
         }
     }
 }

test/Volo.Abp.AutoMapper.Tests/Volo/Abp/AutoMapper/SampleClasses/MyEntityDto2.cs

@@ -0,0 +1,9 @@
+using Volo.Abp.Application.Services.Dtos;
+
+namespace Volo.Abp.AutoMapper.SampleClasses
+{
+    public class MyEntityDto2 : EntityDto
+    {
+        public int Number { get; set; }
+    }
+}

test/Volo.Abp.AutoMapper.Tests/Volo/Abp/AutoMapper/SampleClasses/MyEntityToMyEntityDto2Mapper.cs

@@ -0,0 +1,25 @@
+using Volo.Abp.ObjectMapping;
+using Volo.DependencyInjection;
+
+namespace Volo.Abp.AutoMapper.SampleClasses
+{
+    [ExposeServices(typeof(IObjectMapper<MyEntity, MyEntityDto2>))]
+    public class MyEntityToMyEntityDto2Mapper : IObjectMapper<MyEntity, MyEntityDto2>, ITransientDependency
+    {
+        public MyEntityDto2 Map(MyEntity source)
+        {
+            return new MyEntityDto2
+            {
+                Id = source.Id,
+                Number = source.Number + 1
+            };
+        }
+
+        public MyEntityDto2 Map(MyEntity source, MyEntityDto2 destination)
+        {
+            destination.Id = source.Id;
+            destination.Number = source.Number + 1;
+            return destination;
+        }
+    }
+}