AutoMapper是让人又爱又恨的项目
- 爱它是因为它解决了一些问题,很多项目都有用,下载量很大,受众很广。
- 恨它是因为它诸多反人类的设计。
- 为此本人开源项目PocoEmit对标AutoMapper。
1. AutoMapper反人类设计
1.1 AutoMapper注册代码
csharp
services.AddAutoMapper(cfg => cfg.CreateMap<User, UserDTO>());User和UserDTO除了类名不一样,其他都一样,怎么看这行代码都多余。
需要转化的类型越多,多余的代码就越多。
类型转化不应该就是个静态方法吗?而且AutoMapper注册却依赖微软容器,
本人觉得AutoMapper设计的太反人类了。
1.2 PocoEmit对于大部分转化是不需要手动配置
- PocoEmit可以轻松的定义静态实例
- PocoEmit静态实例可以用来定义静态委托字段,当静态方法使用
csharp
UserDTO dto = PocoEmit.Mapper.Default.Convert<User, UserDTO>(new User());
csharp
public static readonly Func<User, UserDTO> UserDTOConvert = PocoEmit.Mapper.Default.GetConvertFunc<User, UserDTO>();2. AutoMapper的性能差强人意
2.1 以下是AutoMapper官网例子与PocoEmit.Mapper的对比
- Customer转化为CustomerDTO(嵌套多个子对象、数组及列表)
- Auto是执行AutoMapper的IMapper.Map方法
- Poco是执行PocoEmit.Mapper的IMapper.Convert方法
- PocoFunc是执行PocoEmit.Mapper生成的委托
| Method | Mean | Error | StdDev | Median | Ratio | RatioSD | Gen0 | Allocated | Alloc Ratio |
|---|---|---|---|---|---|---|---|---|---|
| Auto | 89.30 ns | 1.006 ns | 1.118 ns | 90.17 ns | 1.46 | 0.03 | 0.0260 | 448 B | 1.08 |
| Poco | 61.31 ns | 1.036 ns | 1.194 ns | 61.25 ns | 1.00 | 0.03 | 0.0241 | 416 B | 1.00 |
| PocoFunc | 42.56 ns | 0.066 ns | 0.073 ns | 42.56 ns | 0.69 | 0.01 | 0.0223 | 384 B | 0.92 |
- Auto耗时比Poco多50%左右
- Auto耗时是PocoFunc的两倍多
2.2 能不能用AutoMapper生成委托来提高性能呢
- 既可以说能也可以说不能
- 说能是因为AutoMapper确实提供了该功能
- 说不能是因为AutoMapper没打算给用户用
2.2.1 AutoMapper生成委托有点麻烦
csharp
var configuration = _auto.ConfigurationProvider.Internal();
var mapRequest = new MapRequest(new TypePair(typeof(Customer), typeof(CustomerDTO)));
Func<Customer, CustomerDTO, ResolutionContext, CustomerDTO> autoFunc = configuration.GetExecutionPlan<Customer, CustomerDTO>(mapRequest);作为对比PocoEmit.Mapper就简单的多了
csharp
Func<Customer, CustomerDTO> pocoFunc = PocoEmit.Mapper.Default.GetConvertFunc<Customer, CustomerDTO>();2.2.2 调用AutoMapper生成的委托更麻烦
- 参数ResolutionContext没有公开的构造函数,也找不到公开的实例
- 只能通过反射获得ResolutionContext的实例
csharp
var field = typeof(AutoMapper.Mapper).GetField("_defaultContext", System.Reflection.BindingFlags.Instance | System.Reflection.BindingFlags.NonPublic);
ResolutionContext resolutionContext = field.GetValue(_auto) as ResolutionContext;2.2.3 加入AutoMapper生成委托再对比一下
| Method | Mean | Error | StdDev | Median | Ratio | RatioSD | Gen0 | Allocated | Alloc Ratio |
|---|---|---|---|---|---|---|---|---|---|
| Auto | 89.30 ns | 1.006 ns | 1.118 ns | 90.17 ns | 1.46 | 0.03 | 0.0260 | 448 B | 1.08 |
| AutoFunc | 56.04 ns | 0.103 ns | 0.119 ns | 56.03 ns | 0.91 | 0.02 | 0.0260 | 448 B | 1.08 |
| Poco | 61.31 ns | 1.036 ns | 1.194 ns | 61.25 ns | 1.00 | 0.03 | 0.0241 | 416 B | 1.00 |
| PocoFunc | 42.56 ns | 0.066 ns | 0.073 ns | 42.56 ns | 0.69 | 0.01 | 0.0223 | 384 B | 0.92 |
- AutoMapper生成委托确实也快了不少
- 从百分比来看即使不生成委托,AutoMapper也慢不了多少？没有数量级的区别,能忍? --- 反问句
2.3 简单类型转化对比
- User转UserDTO,只有两个简单属性
| Method | Mean | Error | StdDev | Ratio | Gen0 | Allocated | Alloc Ratio |
|---|---|---|---|---|---|---|---|
| Auto | 35.436 ns | 0.0455 ns | 0.0505 ns | 1.57 | 0.0019 | 32 B | 0.50 |
| AutoFunc | 4.159 ns | 0.0847 ns | 0.0906 ns | 0.18 | 0.0019 | 32 B | 0.50 |
| Poco | 22.607 ns | 0.1754 ns | 0.1801 ns | 1.00 | 0.0037 | 64 B | 1.00 |
| PocoFunc | 3.818 ns | 0.0176 ns | 0.0180 ns | 0.17 | 0.0019 | 32 B | 0.50 |
- Auto耗时是AutoFunc差不多十倍,差出一个数量级了(回答了前面的反问)
- AutoFunc耗时比PocoFunc稍多,这说明AutoMapper复杂类型转化性能非常不好,简单类型转化可能还能凑合
- 关键是性能好生成的委托AutoMapper不给用啊,"婶可忍叔不可忍"啊!
3. AutoMapper生成的代码能通过代码审核吗?
3.1 还是AutoMapper官网那个例子生成以下代码
csharp
T __f<T>(System.Func<T> f) => f();
CustomerDTO _autoMap(Customer source, CustomerDTO destination, ResolutionContext context)
{
return (source == null) ?
(destination == null) ? (CustomerDTO)null : destination :
__f(() => {
CustomerDTO typeMapDestination = null;
typeMapDestination = destination ?? new CustomerDTO();
try
{
typeMapDestination.Id = source.Id;
}
catch (Exception ex)
{
throw TypeMapPlanBuilder.MemberMappingError(
ex,
default(PropertyMap)/*NOTE: Provide the non-default value for the Constant!*/);
}
try
{
typeMapDestination.Name = source.Name;
}
catch (Exception ex)
{
throw TypeMapPlanBuilder.MemberMappingError(
ex,
default(PropertyMap)/*NOTE: Provide the non-default value for the Constant!*/);
}
try
{
Address resolvedValue = null;
Address mappedValue = null;
resolvedValue = source.Address;
mappedValue = (resolvedValue == null) ? (Address)null :
((Func<Address, Address, ResolutionContext, Address>)((
Address source_1,
Address destination_1,
ResolutionContext context) => //Address
(source_1 == null) ?
(destination_1 == null) ? (Address)null : destination_1 :
__f(() => {
Address typeMapDestination_1 = null;
typeMapDestination_1 = destination_1 ?? new Address();
try
{
typeMapDestination_1.Id = source_1.Id;
}
catch (Exception ex)
{
throw TypeMapPlanBuilder.MemberMappingError(
ex,
default(PropertyMap)/*NOTE: Provide the non-default value for the Constant!*/);
}
try
{
typeMapDestination_1.Street = source_1.Street;
}
catch (Exception ex)
{
throw TypeMapPlanBuilder.MemberMappingError(
ex,
default(PropertyMap)/*NOTE: Provide the non-default value for the Constant!*/);
}
try
{
typeMapDestination_1.City = source_1.City;
}
catch (Exception ex)
{
throw TypeMapPlanBuilder.MemberMappingError(
ex,
default(PropertyMap)/*NOTE: Provide the non-default value for the Constant!*/);
}
try
{
typeMapDestination_1.Country = source_1.Country;
}
catch (Exception ex)
{
throw TypeMapPlanBuilder.MemberMappingError(
ex,
default(PropertyMap)/*NOTE: Provide the non-default value for the Constant!*/);
}
return typeMapDestination_1;
})))
.Invoke(
resolvedValue,
(destination == null) ? (Address)null :
typeMapDestination.Address,
context);
typeMapDestination.Address = mappedValue;
}
catch (Exception ex)
{
throw TypeMapPlanBuilder.MemberMappingError(
ex,
default(PropertyMap)/*NOTE: Provide the non-default value for the Constant!*/);
}
try
{
Address resolvedValue_1 = null;
AddressDTO mappedValue_1 = null;
resolvedValue_1 = source.HomeAddress;
mappedValue_1 = (resolvedValue_1 == null) ? (AddressDTO)null :
((Func<Address, AddressDTO, ResolutionContext, AddressDTO>)((
Address source_2,
AddressDTO destination_2,
ResolutionContext context) => //AddressDTO
(source_2 == null) ?
(destination_2 == null) ? (AddressDTO)null : destination_2 :
__f(() => {
AddressDTO typeMapDestination_2 = null;
typeMapDestination_2 = destination_2 ?? new AddressDTO();
try
{
typeMapDestination_2.Id = source_2.Id;
}
catch (Exception ex)
{
throw TypeMapPlanBuilder.MemberMappingError(
ex,
default(PropertyMap)/*NOTE: Provide the non-default value for the Constant!*/);
}
try
{
typeMapDestination_2.City = source_2.City;
}
catch (Exception ex)
{
throw TypeMapPlanBuilder.MemberMappingError(
ex,
default(PropertyMap)/*NOTE: Provide the non-default value for the Constant!*/);
}
try
{
typeMapDestination_2.Country = source_2.Country;
}
catch (Exception ex)
{
throw TypeMapPlanBuilder.MemberMappingError(
ex,
default(PropertyMap)/*NOTE: Provide the non-default value for the Constant!*/);
}
return typeMapDestination_2;
})))
.Invoke(
resolvedValue_1,
(destination == null) ? (AddressDTO)null :
typeMapDestination.HomeAddress,
context);
typeMapDestination.HomeAddress = mappedValue_1;
}
catch (Exception ex)
{
throw TypeMapPlanBuilder.MemberMappingError(
ex,
default(PropertyMap)/*NOTE: Provide the non-default value for the Constant!*/);
}
try
{
Address[] resolvedValue_2 = null;
AddressDTO[] mappedValue_2 = null;
resolvedValue_2 = source.Addresses;
mappedValue_2 = (resolvedValue_2 == null) ?
Array.Empty<AddressDTO>() :
__f(() => {
AddressDTO[] destinationArray = null;
int destinationArrayIndex = default;
destinationArray = new AddressDTO[resolvedValue_2.Length];
destinationArrayIndex = default(int);
int sourceArrayIndex = default;
Address sourceItem = null;
sourceArrayIndex = default(int);
while (true)
{
if ((sourceArrayIndex < resolvedValue_2.Length))
{
sourceItem = resolvedValue_2[sourceArrayIndex];
destinationArray[destinationArrayIndex++] = ((Func<Address, AddressDTO, ResolutionContext, AddressDTO>)((
Address source_2,
AddressDTO destination_2,
ResolutionContext context) => //AddressDTO
(source_2 == null) ?
(destination_2 == null) ? (AddressDTO)null : destination_2 :
__f(() => {
AddressDTO typeMapDestination_2 = null;
typeMapDestination_2 = destination_2 ?? new AddressDTO();
try
{
typeMapDestination_2.Id = source_2.Id;
}
catch (Exception ex)
{
throw TypeMapPlanBuilder.MemberMappingError(
ex,
default(PropertyMap)/*NOTE: Provide the non-default value for the Constant!*/);
}
try
{
typeMapDestination_2.City = source_2.City;
}
catch (Exception ex)
{
throw TypeMapPlanBuilder.MemberMappingError(
ex,
default(PropertyMap)/*NOTE: Provide the non-default value for the Constant!*/);
}
try
{
typeMapDestination_2.Country = source_2.Country;
}
catch (Exception ex)
{
throw TypeMapPlanBuilder.MemberMappingError(
ex,
default(PropertyMap)/*NOTE: Provide the non-default value for the Constant!*/);
}
return typeMapDestination_2;
})))
.Invoke(
sourceItem,
(AddressDTO)null,
context);
sourceArrayIndex++;
}
else
{
goto LoopBreak;
}
}
LoopBreak:;
return destinationArray;
});
typeMapDestination.Addresses = mappedValue_2;
}
catch (Exception ex)
{
throw TypeMapPlanBuilder.MemberMappingError(
ex,
default(PropertyMap)/*NOTE: Provide the non-default value for the Constant!*/);
}
try
{
List<Address> resolvedValue_3 = null;
List<AddressDTO> mappedValue_3 = null;
resolvedValue_3 = source.WorkAddresses;
mappedValue_3 = (resolvedValue_3 == null) ?
new List<AddressDTO>() :
__f(() => {
List<AddressDTO> collectionDestination = null;
List<AddressDTO> passedDestination = null;
passedDestination = (destination == null) ? (List<AddressDTO>)null :
typeMapDestination.WorkAddresses;
collectionDestination = passedDestination ?? new List<AddressDTO>();
collectionDestination.Clear();
List<Address>.Enumerator enumerator = default;
Address item = null;
enumerator = resolvedValue_3.GetEnumerator();
try
{
while (true)
{
if (enumerator.MoveNext())
{
item = enumerator.Current;
collectionDestination.Add(((Func<Address, AddressDTO, ResolutionContext, AddressDTO>)((
Address source_2,
AddressDTO destination_2,
ResolutionContext context) => //AddressDTO
(source_2 == null) ?
(destination_2 == null) ? (AddressDTO)null : destination_2 :
__f(() => {
AddressDTO typeMapDestination_2 = null;
typeMapDestination_2 = destination_2 ?? new AddressDTO();
try
{
typeMapDestination_2.Id = source_2.Id;
}
catch (Exception ex)
{
throw TypeMapPlanBuilder.MemberMappingError(
ex,
default(PropertyMap)/*NOTE: Provide the non-default value for the Constant!*/);
}
try
{
typeMapDestination_2.City = source_2.City;
}
catch (Exception ex)
{
throw TypeMapPlanBuilder.MemberMappingError(
ex,
default(PropertyMap)/*NOTE: Provide the non-default value for the Constant!*/);
}
try
{
typeMapDestination_2.Country = source_2.Country;
}
catch (Exception ex)
{
throw TypeMapPlanBuilder.MemberMappingError(
ex,
default(PropertyMap)/*NOTE: Provide the non-default value for the Constant!*/);
}
return typeMapDestination_2;
})))
.Invoke(
item,
(AddressDTO)null,
context));
}
else
{
goto LoopBreak_1;
}
}
LoopBreak_1:;
}
finally
{
enumerator.Dispose();
}
return collectionDestination;
});
typeMapDestination.WorkAddresses = mappedValue_3;
}
catch (Exception ex)
{
throw TypeMapPlanBuilder.MemberMappingError(
ex,
default(PropertyMap)/*NOTE: Provide the non-default value for the Constant!*/);
}
return typeMapDestination;
});
} 3.2 以下是PocoEmit.Mapper生成的代码
csharp
T __f<T>(System.Func<T> f) => f();
CustomerDTO _pocoConvert(Customer source)
{
CustomerDTO dest = null;
return (source == (Customer)null) ? (CustomerDTO)null :
__f(() => {
dest = new CustomerDTO();
int member0 = default;
string member1 = null;
Address member2 = null;
Address member3 = null;
Address[] member4 = null;
List<Address> member5 = null;
member0 = source.Id;
dest.Id = member0;
member1 = source.Name;
dest.Name = member1;
member2 = source.Address;
if ((member2 != null))
{
dest.Address = member2;
}
member3 = source.HomeAddress;
if ((member3 != null))
{
// { The block result will be assigned to `dest.HomeAddress`
AddressDTO dest_1 = null;
dest.HomeAddress = (member3 == (Address)null) ? (AddressDTO)null :
__f(() => {
dest_1 = new AddressDTO();
int member0_1 = default;
string member1_1 = null;
string member2_1 = null;
member0_1 = member3.Id;
dest_1.Id = member0_1;
member1_1 = member3.City;
dest_1.City = member1_1;
member2_1 = member3.Country;
dest_1.Country = member2_1;
return dest_1;
});
// } end of block assignment;
}
member4 = source.Addresses;
if ((member4 != null))
{
// { The block result will be assigned to `dest.Addresses`
int count = default;
AddressDTO[] dest_2 = null;
int index = default;
Address sourceItem = null;
count = member4.Length;
dest_2 = new AddressDTO[count];
index = 0;
while (true)
{
if ((index < count))
{
sourceItem = member4[index];
// { The block result will be assigned to `dest_2[index]`
AddressDTO dest_3 = null;
dest_2[index] = (sourceItem == (Address)null) ? (AddressDTO)null :
__f(() => {
dest_3 = new AddressDTO();
int member0_2 = default;
string member1_2 = null;
string member2_2 = null;
member0_2 = sourceItem.Id;
dest_3.Id = member0_2;
member1_2 = sourceItem.City;
dest_3.City = member1_2;
member2_2 = sourceItem.Country;
dest_3.Country = member2_2;
return dest_3;
});
// } end of block assignment
index++;
}
else
{
goto forLabel;
}
}
forLabel:;
dest.Addresses = dest_2;
// } end of block assignment;
}
member5 = source.WorkAddresses;
if ((member5 != null))
{
// { The block result will be assigned to `dest.WorkAddresses`
List<AddressDTO> dest_4 = null;
dest_4 = new List<AddressDTO>(member5.Count);
int index_1 = default;
int len = default;
index_1 = 0;
len = member5.Count;
while (true)
{
if ((index_1 < len))
{
Address sourceItem_1 = null;
AddressDTO destItem = null;
sourceItem_1 = member5[index_1];
// { The block result will be assigned to `destItem`
AddressDTO dest_5 = null;
destItem = (sourceItem_1 == (Address)null) ? (AddressDTO)null :
__f(() => {
dest_5 = new AddressDTO();
int member0_3 = default;
string member1_3 = null;
string member2_3 = null;
member0_3 = sourceItem_1.Id;
dest_5.Id = member0_3;
member1_3 = sourceItem_1.City;
dest_5.City = member1_3;
member2_3 = sourceItem_1.Country;
dest_5.Country = member2_3;
return dest_5;
});
// } end of block assignment;
dest_4.Add(destItem);
index_1++;
}
else
{
goto forLabel_1;
}
}
forLabel_1:;
dest.WorkAddresses = dest_4;
// } end of block assignment;
}
CustomerConvertBench.ConvertAddressCity(
source,
dest);
return dest;
});
}3.3 简单对比如下
- AutoMapper生成代码三百多行,PocoEmit.Mapper一百多行,AutoMapper代码量是两倍以上
- AutoMapper生成大量try catch,哪怕是int对int赋值也要try
- AutoMapper用迭代器Enumerator访问列表,PocoEmit.Mapper用索引器
- AutoMapper这些区别应该是导致性能差的部分原因
3.4 如何获取AutoMapper生成的代码
csharp
LambdaExpression expression = _auto.ConfigurationProvider.BuildExecutionPlan(typeof(Customer), typeof(CustomerDTO)); 3.4.1 如果要查看更可读的代码推荐使用FastExpressionCompiler
- 可以使用nuget安装
- 前面的例子就是使用FastExpressionCompiler再手动整理了一下
csharp
string code = FastExpressionCompiler.ToCSharpPrinter.ToCSharpString(expression);3.4.2 PocoEmit获取生成代码更简单
csharp
Expression<Func<Customer, CustomerDTO>> expression = PocoEmit.Mapper.Default.BuildConverter<Customer, CustomerDTO>();
string code = FastExpressionCompiler.ToCSharpPrinter.ToCSharpString(expression);3.4.3 PocoEmit生成代码扩展性
- PocoEmit可以获取委托表达式自己来编译委托
- PocoEmit通过PocoEmit.Builders.Compiler.Instance来编译,可以对Instance进行覆盖来扩展
- 通过实现Compiler类,只需要重写CompileFunc和CompileAction两个方法
- 可以使用FastExpressionCompiler来实现Compiler类
4. AutoMapper枚举逻辑问题
csharp
public enum MyColor
{
None = 0,
Red = 1,
Green = 2,
Blue = 3,
}
ConsoleColor color = ConsoleColor.DarkBlue;
// Red
MyColor autoColor = _auto.Map<ConsoleColor, MyColor>(color);
// None
MyColor pocoColor = PocoEmit.Mapper.Default.Convert<ConsoleColor, MyColor>(color);
- AutoMapper先按枚举名转化,失败再按值转化,不支持的DarkBlue被AutoMapper转化为Red
- 不同类型的枚举值转化没有意义,定义枚举可以不指定值
- AutoMapper这完全是犯了画蛇添足的错误
- AutoMapper还有哪些槽点欢迎大家在评论区指出
5. PocoEmit可扩展架构
5.1 nuget安装PocoEmit可获得基础功能
- 通过PocoEmit可以读写实体的属性
- PocoEmit可以通过PocoEmit.Poco转化基础类型和枚举
- PocoEmit.Poco支持注册转化表达式
5.2 nuget安装PocoEmit.Mapper获得更多功能
- PocoEmit.Mapper可以支持PocoEmit.Poco的所有功能
- PocoEmit.Mapper可以支持自定义实体类型(不支持集合(含数组、列表及字典)成员)的转化和复制
5.3 nuget安装PocoEmit.Collections扩展集合功能
- 通过UseCollection扩展方法给PocoEmit.Mapper增加集合功能
- 扩展后PocoEmit.Mapper支持集合(含数组、列表及字典)的转化和复制
- 支持实体类型包含集合成员的转化和复制
- 嫌麻烦的同学可以直接安装PocoEmit.Collections并配置UseCollection
源码托管地址: https://github.com/donetsoftwork/MyEmit ，也欢迎大家直接查看源码。
gitee同步更新:https://gitee.com/donetsoftwork/MyEmit
如果大家喜欢请动动您发财的小手手帮忙点一下Star。