使用Roslyn的源生成器生成DTO
前言
源生成器的好处很多, 通过在编译时生成代码，可以减少运行时的反射和动态代码生成，从而提高应用程序的性能, 有时候需要对程序AOT以及裁剪编译的dll也是需要用SG来处理的。
我们开发程序应该都绕不过Mapper对象映射,用的比较多的库可能就是AutoMapper,Maspter之内的三方库吧;这些库很强大但是因为内部实现存在反射,因此开发的程序就没办法AOT了,因此如果程序不是很复杂但是又有很特殊的需求,建议使用SG来实现Mapper
功能演示
这里我演示下自己开发的AutoDto生成DTO功能:
比如我们有一个User的类,需要生成UserDto
public class User
{
public string Id { get; set; } = null!;
public string FirstName { get; set; } = null!;
public string LastName { get; set; } = null!;
public int? Age { get; set; }
public string? FullName => $"{FirstName} {LastName}";
}
定义UserDto并标注特性:
[AutoDto<User>(nameof(User.Id))]//这里我们假设排除Id属性
public partial record UserDto;
就这样,源生成器将自动为我们生成对应的Dto:
partial record class UserDto
{
/// <inheritdoc cref = "User.FirstName"/>
public string FirstName { get; set; }
/// <inheritdoc cref = "User.LastName"/>
public string LastName { get; set; }
/// <inheritdoc cref = "User.Age"/>
public int? Age { get; set; }
}
并同时为我们生成一个简单的Mapper扩展方法:
public static partial class UserToUserDtoExtentions
{
/// <summary>
/// mapper to UserDto
/// </summary>
/// <returns></returns>
public static UserDto MapperToUserDto(this User model)
{
return new UserDto()
{
FirstName = model.FirstName,
LastName = model.LastName,
Age = model.Age,
FullName = model.FullName,
};
}
}
实现代码
static void GENDTO(Compilation compilation, ImmutableArray<SyntaxNode> nodes, SourceProductionContext context)
{
if (nodes.Length == 0) return;
StringBuilder envStringBuilder = new();
envStringBuilder.AppendLine("// <auto-generated />");
envStringBuilder.AppendLine("using System;");
envStringBuilder.AppendLine("using System.Collections.Generic;");
envStringBuilder.AppendLine("using System.Text;");
envStringBuilder.AppendLine("using System.Threading.Tasks;");
envStringBuilder.AppendLine("#pragma warning disable");
foreach (var nodeSyntax in nodes.AsEnumerable())
{
//Cast<ClassDeclarationSyntax>()
//Cast<RecordDeclarationSyntax>()
if (nodeSyntax is not TypeDeclarationSyntax node)
{
continue;
}
//如果是Record类
var isRecord = nodeSyntax is RecordDeclarationSyntax;
//如果不含partial关键字,则不生成
if (!node.Modifiers.Any(x => x.IsKind(SyntaxKind.PartialKeyword)))
{
continue;
}
AttributeSyntax? attributeSyntax = null;
foreach (var attr in node.AttributeLists.AsEnumerable())
{
var attrName = attr.Attributes.FirstOrDefault()?.Name.ToString();
if (attrName?.IndexOf(AttributeValueMetadataNameDto, System.StringComparison.Ordinal) == 0)
{
attributeSyntax = attr.Attributes.First(x => x.Name.ToString().IndexOf(AttributeValueMetadataNameDto, System.StringComparison.Ordinal) == 0);
break;
}
}
if (attributeSyntax == null)
{
continue;
}
//转译的Entity类名
var entityName = string.Empty;
string pattern = @"(?<=<)(?<type>\w+)(?=>)";
var match = Regex.Match(attributeSyntax.ToString(), pattern);
if (match.Success)
{
entityName = match.Groups["type"].Value.Split(['.']).Last();
}
else
{
continue;
}
var sb = new StringBuilder();
sb.AppendLine();
sb.AppendLine($"//generate {entityName}-{node.Identifier.ValueText}");
sb.AppendLine();
sb.AppendLine("namespace $ni");
sb.AppendLine("{");
sb.AppendLine("$namespace");
sb.AppendLine("$classes");
sb.AppendLine("}");
// sb.AppendLine("#pragma warning restore");
string classTemp = $"partial $isRecord $className {{ $body }}";
classTemp = classTemp.Replace("$isRecord", isRecord ? "record class" : "class");
{
// 排除的属性
List<string> excapes = [];
if (attributeSyntax.ArgumentList != null)
{
for (var i = 0; i < attributeSyntax.ArgumentList!.Arguments.Count; i++)
{
var expressionSyntax = attributeSyntax.ArgumentList.Arguments[i].Expression;
if (expressionSyntax.IsKind(SyntaxKind.InvocationExpression))
{
var name = (expressionSyntax as InvocationExpressionSyntax)!.ArgumentList.DescendantNodes().First().ToString();
excapes.Add(name.Split(['.']).Last());
}
else if (expressionSyntax.IsKind(SyntaxKind.StringLiteralExpression))
{
var name = (expressionSyntax as LiteralExpressionSyntax)!.Token.ValueText;
excapes.Add(name);
}
}
}
var className = node.Identifier.ValueText;
var rootNamespace = string.Empty;
//获取文件范围的命名空间
var filescopeNamespace = node.AncestorsAndSelf().OfType<FileScopedNamespaceDeclarationSyntax>().FirstOrDefault();
if (filescopeNamespace != null)
{
rootNamespace = filescopeNamespace.Name.ToString();
}
else
{
rootNamespace = node.AncestorsAndSelf().OfType<NamespaceDeclarationSyntax>().Single().Name.ToString();
}
StringBuilder bodyBuilder = new();
List<string> namespaces = [];
StringBuilder bodyInnerBuilder = new();
StringBuilder mapperBodyBuilder = new();
bodyInnerBuilder.AppendLine();
List<string> haveProps = [];
// 生成属性
void GenProperty(TypeSyntax @type)
{
var symbols = compilation.GetSymbolsWithName(@type.ToString(), SymbolFilter.Type);
foreach (ITypeSymbol symbol in symbols.Cast<ITypeSymbol>())
{
var fullNameSpace = symbol.ContainingNamespace.ToDisplayString();
// 命名空间
if (!namespaces.Contains(fullNameSpace))
{
namespaces.Add(fullNameSpace);
}
symbol.GetMembers().OfType<IPropertySymbol>().ToList().ForEach(prop =>
{
if (!excapes.Contains(prop.Name))
{
// 如果存在同名属性,则不生成
if (haveProps.Contains(prop.Name))
{
return;
}
haveProps.Add(prop.Name);
//如果是泛型属性,则不生成
if (prop.ContainingType.TypeParameters.Any(x => x.Name == prop.Type.Name))
{
return;
}
// prop:
var raw = $"public {prop.Type.ToDisplayString()} {prop.Name} {{get;set;}}";
// body:
bodyInnerBuilder.AppendLine($"/// <inheritdoc cref=\"{@type}.{prop.Name}\" />");
bodyInnerBuilder.AppendLine($"{raw}");
// mapper:
// 只有public的属性才能赋值
if (prop.GetMethod?.DeclaredAccessibility == Accessibility.Public)
{
mapperBodyBuilder.AppendLine($"{prop.Name} = model.{prop.Name},");
}
}
});
}
}
// 生成属性:
var symbols = compilation.GetSymbolsWithName(entityName, SymbolFilter.Type);
var symbol = symbols.Cast<ITypeSymbol>().FirstOrDefault();
//引用了其他库.
if (symbol is null)
continue;
GenProperty(SyntaxFactory.ParseTypeName(symbol.MetadataName));
// 生成父类的属性:
INamedTypeSymbol? baseType = symbol.BaseType;
while (baseType != null)
{
GenProperty(SyntaxFactory.ParseTypeName(baseType.MetadataName));
baseType = baseType.BaseType;
}
var rawClass = classTemp.Replace("$className", className);
rawClass = rawClass.Replace("$body", bodyInnerBuilder.ToString());
// append:
bodyBuilder.AppendLine(rawClass);
string rawNamespace = string.Empty;
namespaces.ForEach(ns => rawNamespace += $"using {ns};\r\n");
var source = sb.ToString();
source = source.Replace("$namespace", rawNamespace);
source = source.Replace("$classes", bodyBuilder.ToString());
source = source.Replace("$ni", rootNamespace);
// 生成Mapper
var mapperSource = MapperTemplate.Replace("$namespace", namespaces.First());
mapperSource = mapperSource.Replace("$ns", rootNamespace);
mapperSource = mapperSource.Replace("$baseclass", entityName);
mapperSource = mapperSource.Replace("$dtoclass", className);
mapperSource = mapperSource.Replace("$body", mapperBodyBuilder.ToString());
// 合并
source = $"{source}\r\n{mapperSource}";
envStringBuilder.AppendLine(source);
}
}
envStringBuilder.AppendLine("#pragma warning restore");
var envSource = envStringBuilder.ToString();
// format:
envSource = envSource.FormatContent();
context.AddSource($"Biwen.AutoClassGenDtoG.g.cs", SourceText.From(envSource, Encoding.UTF8));
}
const string MapperTemplate = $@"
namespace $namespace
{{
using $ns ;
public static partial class $baseclassTo$dtoclassExtentions
{{
/// <summary>
/// mapper to $dtoclass
/// </summary>
/// <returns></returns>
public static $dtoclass MapperTo$dtoclass(this $baseclass model)
{{
return new $dtoclass()
{{
$body
}};
}}
}}
}}
";
最后
以上代码就完成了整个源生成步骤,最后你可以使用我发布的nuget包体验:
<ItemGroup>
<PackageReference Include="Biwen.AutoClassGen.Attributes" Version="1.3.6" />
<PackageReference Include="Biwen.AutoClassGen" Version="1.5.2" PrivateAssets="all" />
</ItemGroup>
当然如果你对完整的实现感兴趣可以移步我的GitHub仓储,欢迎star https://github.com/vipwan/Biwen.AutoClassGen
