如何使用PocoEmit.Mapper替代AutoMapper

2025年8月30日
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PocoEmit使用比较简单对于大部分转化是不需要手动配置
可以替代AutoMapper的大部分工作,实现精简代码,提高性能

一、获取Mapper实例

1. 获取Mapper默认实例

Default是一个静态延迟初始化的默认实例

IMapper mapper =  PocoEmit.Mapper.Default;

2. 构造Mapper新实例

  • 除了测试,不建议每次转化调用Create
  • Create的实例建议定义为静态字段或属性
  • 或者注入IOC容器内重复使用
IMapper mapper =  PocoEmit.Mapper.Create();

二、简单类型转化无需配置

什么样的类型转化对PocoEmit来说是简单的呢

1. 基础类型、枚举互转

基础类型、枚举互转无需配置

int intValue =  PocoEmit.Mapper.Default.Convert<string, long>("123");
long longValue =  PocoEmit.Mapper.Default.Convert<int, long>(123);
strting stringValue =  PocoEmit.Mapper.Default.Convert<int, string>(123);

public enum MyColor
{
    None = 0,
    Red = 1,
    Green = 2,
    Blue = 3,
}
ConsoleColor color = ConsoleColor.DarkBlue;
// Red
MyColor redColor = PocoEmit.Mapper.Default.Convert<ConsoleColor, MyColor>(ConsoleColor.Red);
string colorName =  PocoEmit.Mapper.Default.Convert<ConsoleColor, string>(ConsoleColor.Red);
// 1
long colorValue =  PocoEmit.Mapper.Default.Convert<MyColor, long>(MyColor.Red);
/ None
MyColor noneColor = PocoEmit.Mapper.Default.Convert<ConsoleColor, MyColor>(ConsoleColor.DarkBlue);

2. 可空类型转化

可空类型转化无需配置

int intValue =  PocoEmit.Mapper.Default.Convert<string?, long>("123");
long? longValue =  PocoEmit.Mapper.Default.Convert<int, long?>(123);
strting stringValue =  PocoEmit.Mapper.Default.Convert<int?, string>(123);
User user = PocoEmit.Mapper.Default.Convert<User?, User>(null);

3. 构造函数和属性互转

构造函数和属性互转无需配置

class MyId(int id)
{
    public int Id { get; } = id;
}
class MyId2(int? id)
{
    public int? Id { get; } = id;
}

3.1 构造函数转化

var myId = PocoEmit.Mapper.Default.Convert<int, MyId>(1);
var myId2 = PocoEmit.Mapper.Default.Convert<int?, MyId2>(2);
var myId3 = PocoEmit.Mapper.Default.Convert<int?, MyId>(3);
var myId4 = PocoEmit.Mapper.Default.Convert<int, MyId2>(4);

3.2 属性转化

var id = PocoEmit.Mapper.Default.Convert<MyId, int>(new MyId(1));
var id2 = PocoEmit.Mapper.Default.Convert<MyId2, int?>(new MyId2(2));
var id3 = PocoEmit.Mapper.Default.Convert<MyId, int?>(new MyId(3));
var id4 = PocoEmit.Mapper.Default.Convert<MyId2, int>(new MyId2(4));

4. 复合类型同名属性互转

复合类型同名属性互转无需配置

var dto =  PocoEmit.Mapper.Default.Convert<User, UserDTO>(new User { Id = 1, Name = "Jxj1" });
var user =  PocoEmit.Mapper.Default.Convert<UserDTO, User>(new UserDTO { Id = 2, Name = "Jxj2" });
var user3 =  PocoEmit.Mapper.Default.Convert<UserDTO2, User>(new UserDTO { Id = "3", Name = "张三" });

三、一键开启集合类型转化配置

  • 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

1. 启用集合配置

1.2 开启全局集合配置

  • 对所有Mapper启用集合
  • 应在使用所有Mapper实例之前配置,对已经完成初始化的Mapper实例无效
CollectionContainer.GlobalUseCollection();

1.1 对单个Mapper启用集合

PocoEmit.Mapper.UseCollection();

2.启用集合后集合互转无需配置

User[] source = [new User { Id = 1, Name = "Jxj" }, new User { Id = 2, Name = "张三" }];
UserDTO[] result = PocoEmit.Mapper.Default.Convert<User[], UserDTO[]>(source);

IEnumerable<User> source = [new User { Id = 1, Name = "Jxj" }, new User { Id = 2, Name = "张三" }];
UserDTO[] result = PocoEmit.Mapper.Default.Convert<IEnumerable<User>, UserDTO[]>(source);

User[] source = [new User { Id = 1, Name = "Jxj" }, new User { Id = 2, Name = "张三" }];
IEnumerable<UserDTO> result = PocoEmit.Mapper.Default.Convert<User[], IEnumerable<UserDTO>>(source);

Dictionary<int, User> source = new() { { 1, new User { Id = 1, Name = "Jxj" } } };
UserDTO[] result = PocoEmit.Mapper.Default.Convert<Dictionary<int, User>, UserDTO[]>(source);

Dictionary<int, User> source = new() { { 1, new User { Id = 1, Name = "Jxj" } } };
Dictionary<int, UserDTO> result = PocoEmit.Mapper.Default.Convert<Dictionary<int, User>, Dictionary<int, UserDTO>>(source);

3.启用集合后集合成员互转无需配置

var source = new UserArray { Name = "VIP", Users = [new User { Id = 1, Name = "Jxj" }, new User { Id = 2, Name = "张三" }] };
UserDTOArray result = PocoEmit.Mapper.Default.Convert<UserArray, UserDTOArray>(source);

四、自定义配置

1. Mapper全局配置

  • 全局配置对所有Mapper适用
  • 全局配置应在使用所有Mapper实例之前配置,对已经完成初始化的Mapper实例无效

1.1 全局配置映射规则

PocoEmit.Mapper.GlobalConfigure(mapper => {
    mapper.ConfigureMap<User, UserDTO>()
    .Source
    .Ignore(nameof(User.Name));
});

1.2 全局配置内部缓存字典大小

  • 配置适当大小可以减少内存占用和扩容
PocoEmit.Mapper.GlobalOptions(options => {
    // 转化器数量
    options.ConverterCapacity = 100;
});

2. 配置单个Mapper

PocoEmit.Mapper.Default.ConfigureMap<User, UserDTO>()
    .Source
    .Ignore(nameof(User.Name));

3. 哪些需要配置

3.1 属性名前、后缀

  • AddPrefix设置前缀
  • AddSuffix设置后缀
  • ClearPrefix清空前缀
public class UserCustomDTO(string userName)
{
    public int? UId { get; set; }
    public string UName { get; } = userName;
}
3.1.1 源类型设置前缀
IMapper mapper = Mapper.Create();
mapper.ConfigureMap<UserCustomDTO, User>()
    .Source
    .AddPrefix("U");
var source = new UserCustomDTO("Jxj2") { UId = 222 };
var converter = mapper.GetConverter<UserCustomDTO, User>();
User result = converter.Convert(source);
3.1.2 目标类型设置前缀
IMapper mapper = Mapper.Create();
mapper.ConfigureMap<User, UserCustomDTO>()
    .Dest
    .AddPrefix("U");
var source = new User { Id = 222, Name = "Jxj2" };
var result = mapper.Convert<User, UserCustomDTO>(source);
3.1.3 默认前缀
  • ConfigureMap会默认把源类型名作为目标类型前缀
  • ConfigureMap会默认把目标类型名作为源类型前缀
  • 如果默认前缀干扰到正常匹配,可以调用ClearPrefix清空前缀
public class AutoUserDTO
{
    public string UserId { get; set; }
    public string UserName { get; set; }
}
IMapper mapper = Mapper.Create();
mapper.ConfigureMap<AutoUserDTO, User>();
var source = new AutoUserDTO{ UserId = "222", UserName = "Jxj"  };
var converter = mapper.GetConverter<AutoUserDTO, User>();
User result = converter.Convert(source);

3.2 属性一对一配置

3.2.1 通过Source配置
  • 直接MapTo或ForMember
IMapper mapper = Mapper.Create();
mapper.ConfigureMap<User, UserCustomDTO>()
    .Source
    .MapTo(nameof(User.Id), nameof(UserCustomDTO.UId))
    .MapTo(nameof(User.Name), nameof(UserCustomDTO.UName));
var source = new User { Id = 222, Name = "Jxj2" };
var converter = mapper.GetConverter<User, UserCustomDTO>();
UserCustomDTO result = converter.Convert(source);

IMapper mapper = Mapper.Create();
mapper.ConfigureMap<User, UserCustomDTO>()
    .Source
    .ForMember(nameof(User.Id)).MapTo(nameof(UserCustomDTO.UId))
    .ForMember(nameof(User.Name)).MapTo(nameof(UserCustomDTO.UName));
var source = new User { Id = 222, Name = "Jxj2" };
var converter = mapper.GetConverter<User, UserCustomDTO>();
UserCustomDTO result = converter.Convert(source);
3.2.2 通过Dest配置
  • 直接MapFrom或ForMember
IMapper mapper = Mapper.Create();
mapper.ConfigureMap<UserCustomDTO, User>()
    .Dest
    .MapFrom(nameof(User.Id), nameof(UserCustomDTO.UId))
    .MapFrom(nameof(User.Name), nameof(UserCustomDTO.UName));
var source = new UserCustomDTO("Jxj2") { UId = 222 };
var converter = mapper.GetConverter<UserCustomDTO, User>();
User result = converter.Convert(source);

IMapper mapper = Mapper.Create();
mapper.ConfigureMap<UserCustomDTO, User>()
    .Dest
    .ForMember(nameof(User.Id)).MapFrom(nameof(UserCustomDTO.UId))
    .ForMember(nameof(User.Name)).MapFrom(nameof(UserCustomDTO.UName));
var source = new UserCustomDTO("Jxj2") { UId = 222 };
var converter = mapper.GetConverter<UserCustomDTO, User>();
User result = converter.Convert(source);

3.3 忽略成员

3.3.1 被忽略的源类型成员不参与映射

IMapper mapper = Mapper.Create();
mapper.ConfigureMap<User, UserDTO>()
    .Source
    .Ignore(nameof(User.Name));
var source = new User { Id = 111, Name = "Jxj" };
var converter = mapper.GetConverter<User, UserDTO>();
// result.Name == null
UserDTO result = converter.Convert(source);

3.3.2 被忽略的目标类型成员不会被匹配

IMapper mapper = Mapper.Create();
mapper.ConfigureMap<User, UserDTO>()
    .Dest
    .Ignore(nameof(UserDTO.Name));
var source = new User { Id = 111, Name = "Jxj" };
var converter = mapper.GetConverter<User, UserDTO>();
// result.Name == null
UserDTO result = converter.Convert(source);

3.4 指定转化函数

  • 通过UseConvertFunc指定函数直接转化
IMapper mapper = Mapper.Create();
mapper.ConfigureMap<UserDTO, User>()
    .UseConvertFunc(source => new User { Id= source.Id, Name = source.Name });
var source = new UserDTO { Id = 111, Name = "Jxj" };
var converter = mapper.GetConverter<UserDTO, User>();
var result = converter.Convert(source);

3.5 指定构造函数

  • 通过UseActivator指定构造函数
  • 执行完构造函数还会尝试匹配与UseConvertFunc是不同的
IMapper mapper = Mapper.Create();
mapper.ConfigureMap<User, UserCustomDTO>()
    .UseActivator(u => new UserCustomDTO(u.Name) { UId = u.Id })
    .Source
    .MapTo(nameof(User.Id), nameof(UserCustomDTO.UId));
var source = new User { Id = userId, Name = "Jxj2" };
var converter = mapper.GetConverter<User, UserCustomDTO>();
var result = converter.Convert(source);

3.6 指定默认值

3.6.1 指定固定默认值
IMapper mapper = Mapper.Create()
    .UseDefault(Repository);
var dto = new UserDTO { Id = 1, Name = "Jxj" };
UserDomain user = mapper.Convert<UserDTO, UserDomain>(dto);

class UserDomain(UserRepository repository, int id, string name)
{
    private readonly UserRepository _repository = repository;
    public UserRepository Repository
        => _repository;
    public int Id { get; } = id;
    public string Name { get; } = name;
    // ...
}
static readonly UserRepository Repository = new();
class UserRepository
{
    void Add(UserDomain user) { }
    void Update(UserDomain entity) { }
    void Remove(UserDomain entity) { }
}
  • 注: 如果不指定UserRepository的默认值,以上转化会报异常
  • 注: 以上例子示例给领域模型注入仓储
3.6.2 默认值指定工厂方法
IMapper mapper = Mapper.Create()
    .UseDefault(() => MessageId.NewId());
var dto = new MessageDto { Message = "Hello UseDefault" };
MessageDomain message = mapper.Convert<MessageDto, MessageDomain>(dto);

class MessageDto
{
    public string Message { get; set; }
}
class MessageDomain(MessageId id, string message)
{
    public MessageId Id { get; } = id;
    public string Message { get; } = message;
    // ...
}
class MessageId(int id)
{
    private static int seed = 1;
    public int Id { get; } = id;
    public static MessageId NewId()
        => new(seed++);
}
  • 注: 以上例子示例给领域模型注入自增Id
  • 注: 实际项目这里建议调用雪花Id

3.7 转化后补刀

  • 使用UseCheckAction配置转化检查逻辑用来补刀
  • 对于实在不方便配置映射规则的遗留属性进行补刀
static void ConvertAddressCity(Customer customer, CustomerDTO dto)
{
    dto.AddressCity = customer.Address.City;
}
var mapper = PocoEmit.Mapper.Default;
mapper.ConfigureMap<Customer, CustomerDTO>()
    .UseCheckAction(ConvertAddressCity);
CustomerDTO result = mapper.Convert<Customer, CustomerDTO>(source);

五、PocoEmit的“继承”和“多态”

1. PocoEmit的“继承”

  • 通过全局配置实现类似继承的效果
  • 前面已经介绍了PocoEmit的全局配置

2. PocoEmit的“多态”

  • 对某些Mapper对象覆盖配置实现与其他Mapper不同的效果
  • 可以用不同的serviceKey注入容器,使用的时候就可以做到无感

2.1 举个发布平台需要“多态”的例子

  • 需要发布时间字段,平台内时间格式很好统一
  • 如果需要接入第三方数据,特别是国外的数据,格式很可能不一样
  • 牺牲性能用复杂逻辑去兼容也不是不可以
  • 这里建议提供多个Mapper的方案,不同渠道用不同的Mapper,每个Mapper只有极少的配置不同
  • 这就是PocoEmit“多态”的应用

2.2 再举个VIP的例子更明显

  • VIP客户提出各种格式化无关痛痒的问题
  • 一般就写if特殊处理了
  • 这类情况也适用PocoEmit“多态”

六、PocoEmit配合容器使用

1、容器注册转化器

1.1 默认注册

通过容器中默认的IMapper对象或Mapper.Global构造转化器

services.UseConverter();

1.2 指定IPoco对象注册

services.UseConverter(PocoEmit.Mapper.Global);

注: PocoEmit.Mapper.Global继承IPoco接口

1.3 隔离注册

指定IPoco和serviceKey注册

IPoco poco = specialMapper;
services.UseConverter(poco, "special");

1.4 通过IPocoConverter注入

通过构造函数参数、属性等方式注入

public sealed class Mapper(IPocoConverter<User, UserListDTO> converter)
    : Mapper<Request, Response, IEnumerable<User>>
{
    // ...
}

2、容器注册复制器

2.1 默认注册

通过容器中默认的IMapper对象或Mapper.Global构造复制器

services.UseCopier();

2.2 指定IMapper对象注册

services.UseCopier(PocoEmit.Mapper.Global);

注: PocoEmit.Mapper.Global继承IMapper接口

2.3 隔离注册

指定IPoco和serviceKey注册

IPoco poco = specialMapper;
services.UseCopier(poco, "special");

2.4 通过IPocoCopier注入

通过构造函数参数、属性等方式注入

public sealed class Mapper(IPocoCopier<User, UserListDTO> copier)
    : Mapper<Request, Response, IEnumerable<User>>
{
    // ...
}

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

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