ASP.NET Core中的对象池化技术详解

目录

• 写在前面
• 代码实现
• 调用示例

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PooledObjectPolicybuilder.Services.TryAddSingleton(); builder.Services.TryAddSingleton<ObjectPool>(serviceProvider =>{    var provider = serviceProvider.GetRequiredService();    var policy = new DefaultPooledObjectPolicy();    return provider.Create(policy);}); builder.Services.TryAddSingleton<ObjectPool>(serviceProvider => {    var provider = serviceProvider.GetRequiredService();    var policy = new PersonPoolPolicy();    return provider.Create(policy);}); builder.Services.TryAddSingleton<ObjectPool>(serviceProvider =>{    var provider = serviceProvider.GetRequiredService();    var policy = new StringBuilderPooledObjectPolicy();    return provider.Create(policy);}); var app = builder.Build(); // config middlewareapp.UseMiddleware(); app.MapGet("/", () => "Hello rjcql!"); // return the SHA256 hash of a word http://localhost:5128/hash/xxxxapp.MapGet("/hash/{word}", (string word, ObjectPool 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 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 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{    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;    }} /// 
/// 创建中间件/// 
public class BirthdayMiddleware{    private readonly RequestDelegate _next;     public BirthdayMiddleware(RequestDelegate next)    {        _next = next;    }     public async Task InvokeAsync(HttpContext context, ObjectPool 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。

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