.net core 高性能对象转换
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2022-04-17 22:27:38
关于对象转换已经有不少*(AutoMapper,TinyMapper) .出于项目需要，手动造一个简单*。先贴代码 g>1.采用静态泛型类缓存，避免了拆箱装箱操作。 2.对于转换对象中有，字段名一样但是类型不一样的类时仍可以用 1 public static class Mapper
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关于对象转换已经有不少*(AutoMapper,TinyMapper) .出于项目需要，手动造一个简单*。先贴代码
g>1.采用静态泛型类缓存，避免了拆箱装箱操作。
2.对于转换对象中有，字段名一样但是类型不一样的类时仍可以用
1 public static class Mapper<TSource, TTarget> where TSource : class where TTarget : class
2 {
3 public readonly static Func<TSource, TTarget> Map;
4
5 static Mapper()
6 {
7 if (Map == null)
8 Map = GetMap();
9 }
10
11 private static Func<TSource, TTarget> GetMap()
12 {
13 var sourceType = typeof(TSource);
14 var targetType = typeof(TTarget);
15
16 var parameterExpression = Expression.Parameter(sourceType, "p");
17 var memberInitExpression = GetExpression(parameterExpression, sourceType, targetType);
18
19 var lambda = Expression.Lambda<Func<TSource, TTarget>>(memberInitExpression, parameterExpression);
20 return lambda.Compile();
21 }
22
23 /// <summary>
24 /// 根据转换源和目标获取表达式树
25 /// </summary>
26 /// <param name="parameterExpression">表达式参数p</param>
27 /// <param name="sourceType">转换源类型</param>
28 /// <param name="targetType">转换目标类型</param>
29 /// <returns></returns>
30 private static MemberInitExpression GetExpression(Expression parameterExpression, Type sourceType, Type targetType)
31 {
32 var memberBindings = new List<MemberBinding>();
33 foreach (var targetItem in targetType.GetProperties().Where(x => x.PropertyType.IsPublic && x.CanWrite))
34 {
35 var sourceItem = sourceType.GetProperty(targetItem.Name);
36
37 //判断实体的读写权限
38 if (sourceItem == null || !sourceItem.CanRead || sourceItem.PropertyType.IsNotPublic)
39 continue;
40
41 //标注NotMapped特性的属性忽略转换
42 if (sourceItem.GetCustomAttribute<NotMappedAttribute>() != null)
43 continue;
44
45 var propertyExpression = Expression.Property(parameterExpression, sourceItem);
46
47 //判断都是class 且类型不相同时
48 if (targetItem.PropertyType.IsClass && sourceItem.PropertyType.IsClass && targetItem.PropertyType != sourceItem.PropertyType)
49 {
50 if (targetItem.PropertyType != targetType)//防止出现自己引用自己无限递归
51 {
52 var memberInit = GetExpression(propertyExpression, sourceItem.PropertyType, targetItem.PropertyType);
53 memberBindings.Add(Expression.Bind(targetItem, memberInit));
54 continue;
55 }
56 }
57
58 if (targetItem.PropertyType != sourceItem.PropertyType)
59 continue;
60
61 memberBindings.Add(Expression.Bind(targetItem, propertyExpression));
62 }
63 return Expression.MemberInit(Expression.New(targetType), memberBindings);
64 }
65 }
3.调用方法如下
（1）构造样例类
public class A
{
public int Id { get; set; }
public string Name { get; set; }
public C User { get; set; }
/// <summary>
/// 标注为notmapped特性时，不转换赋值
/// </summary>
[System.ComponentModel.DataAnnotations.Schema.NotMapped]
public D UserA { get; set; }
}
public class B
{
public int Id { get; set; }
public string Name { get; set; }
public D User { get; set; }
public D UserA { get; set; }
}
public class C
{
public int Id { get; set; }
public string Name { get; set; }
}
public class D
{
public int Id { get; set; }
public string Name { get; set; }
}
(2) 调用
var a = new A
{
Id = 1,
Name = "张三",
User = new C
{
Id = 1,
Name = "李四"
}
};
B b = Mapper<A, B>.Map(a);//得到转换结果
4.性能测试
1 var length = 10000000;
2 var listA = new List<A>();
3 for (int i = 0; i < length; i++)
4 {
5 listA.Add(new A
6 {
7 Id = i,
8 Name = "张三",
9 User = new C
10 {
11 Id = i,
12 Name = "李四"
13 }
14 });
15 }
16
17 var sw = Stopwatch.StartNew();
18 for (int i = 0; i < length; i++)
19 {
20 var item = listA[i];
21 var b = new B
22 {
23 Id = item.Id,
24 Name = item.Name,
25 User = new D
26 {
27 Id = i,
28 Name = "李四",
29 }
30 };
31 }
32 sw.Stop();
33 Console.WriteLine($"原生的时间:{sw.ElapsedMilliseconds}ms");
34
35 //表达式
36 Mapper<A, B>.Map(listA[0]);//预先编译缓存
37 sw.Restart();
38 for (int i = 0; i < length; i++)
39 {
40 Mapper<A, B>.Map(listA[i]);
41 }
42 sw.Stop();
43 Console.WriteLine($"表达式的时间:{sw.ElapsedMilliseconds}ms");
44
45 //AutoMapper
46 AutoMapper.Mapper.Initialize(cfg => cfg.CreateMap<A, B>());
47 sw.Restart();
48 for (int i = 0; i < length; i++)
49 {
50 var b = AutoMapper.Mapper.Map<B>(listA[i]);
51 }
52 sw.Stop();
53 Console.WriteLine($"AutoMapper时间:{sw.ElapsedMilliseconds}ms");
54
55 //TinyMapper
56 TinyMapper.Bind<A, B>();
57 sw.Restart();
58 for (int i = 0; i < length; i++)
59 {
60 var b = TinyMapper.Map<B>(listA[i]);
61 }
62 sw.Stop();
63 Console.WriteLine($"TinyMapper时间:{sw.ElapsedMilliseconds}ms");
64
65 Console.ReadLine();
5. 1000万数据不带子类集结果
6. 1000万数据带子类集结果