如何使用PocoEmit.Mapper替代AutoMapper

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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