写在前面
Microsoft.Extensions.ObjectPool 是 ASP.NET Core 基础结构的一部分，当对象的初始化成本较高，并且可能被频繁使用时，才适合采用对象池技术；被ObjectPool管理的对象不会进入垃圾回收，使用时通过由实例对象实现的Get()方法，从对象池中借出对象，用完之后调用Return(T obj)方法，将对象还回去。也可以在Return(T obj)方法中设置判断条件，仅允许特定的对象进入对象池。
通过NuGet 获取 Microsoft.Extensions.ObjectPool 类库
代码实现
using Microsoft.Extensions.DependencyInjection.Extensions;
using Microsoft.Extensions.ObjectPool;
using System.Security.Cryptography;
using System.Text;
var builder = WebApplication.CreateBuilder(args);
// DefaultPooledObjectPolicy: 默认的策略，继承抽象类PooledObjectPolicy
builder.Services.TryAddSingleton<ObjectPoolProvider, DefaultObjectPoolProvider>();
builder.Services.TryAddSingleton<ObjectPool<ReusableBuffer>>(serviceProvider =>
{
var provider = serviceProvider.GetRequiredService<ObjectPoolProvider>();
var policy = new DefaultPooledObjectPolicy<ReusableBuffer>();
return provider.Create(policy);
});
builder.Services.TryAddSingleton<ObjectPool<Person>>(serviceProvider => {
var provider = serviceProvider.GetRequiredService<ObjectPoolProvider>();
var policy = new PersonPoolPolicy();
return provider.Create(policy);
});
builder.Services.TryAddSingleton<ObjectPool<StringBuilder>>(serviceProvider =>
{
var provider = serviceProvider.GetRequiredService<ObjectPoolProvider>();
var policy = new StringBuilderPooledObjectPolicy();
return provider.Create(policy);
});
var app = builder.Build();
// config middleware
app.UseMiddleware<BirthdayMiddleware>();
app.MapGet("/", () => "Hello rjcql!");
// return the SHA256 hash of a word
http://localhost:5128/hash/xxxx
app.MapGet("/hash/{word}", (string word, ObjectPool<ReusableBuffer> bufferPool) =>
{
var buffer = bufferPool.Get();
try
{
// Set the buffer data to the ASCII values of a word
for (var i = 0; i < word.Length; i++)
{
buffer.Data[i] = (byte)word[i];
}
Span<byte> hash = stackalloc byte[32];
SHA256.HashData(buffer.Data.AsSpan(0, word.Length), hash);
return "Hash: " + Convert.ToHexString(hash);
}
finally
{
// Data is automatically reset because this type implemented IResettable
bufferPool.Return(buffer);
}
});
app.MapGet("/create/{name}", (string name, ObjectPool<Person> personPool) =>
{
var person = personPool.Get();
try
{
person.Id = Guid.NewGuid().ToString("N");
var lastName = person.Name; // 这个是上一个对象的值
person.Name = name;
return $"{person.Id}:{person.Name}, {lastName}";
}
finally
{
// 根据条件回收
personPool.Return(person);
}
});
app.Run();
public class ReusableBuffer : IResettable
{
public byte[] Data { get; } = new byte[1024 * 1024]; // 1 MB
public bool TryReset()
{
Array.Clear(Data);
return true;
}
}
public class Person
{
public string Id { get; set; }
public string Name { get; set; }
}
public class PersonPoolPolicy : PooledObjectPolicy<Person>
{
public override Person Create()
{
return new Person { Id = "", Name = "rjcql" };
}
public override bool Return(Person p)
{
if (p.Name != "rjcql")
{
// 不允许其他名称的对象放入对象池
return false;
}
return true;
}
}
/// <summary>
/// 创建中间件
/// </summary>
public class BirthdayMiddleware
{
private readonly RequestDelegate _next;
public BirthdayMiddleware(RequestDelegate next)
{
_next = next;
}
public async Task InvokeAsync(HttpContext context, ObjectPool<StringBuilder> builderPool)
{
var stringBuilder = builderPool.Get();
try
{
stringBuilder.Append("Hi");
// 在中间干点啥别的
// await context.Response.WriteAsync(stringBuilder.ToString());
await _next.Invoke(context);
}
finally // 即使出错也要保证归还对象
{
builderPool.Return(stringBuilder);
}
}
}
调用示例
因为设置了回收条件，所以只有名字为rjcql的对象才会被回收，所以每次调用都先把rjcql对象取出。
