Question

为创建调整大小的图像的本地磁盘缓存，我试图弄清楚如何在运行时创建URL重写。

类似这样的东西：

[Route("(images/{id}.jpg")]
public IActionResult ResizeImage(int id, int height, int width)
{
    string webRoot = _env.ContentRootPath;
    var file = System.IO.Path.Combine(webRoot, $"resizedimage{id}.jpg");
    //Pseudocode:
    UrlRewriter.DoMagic($"images/{id}.jpg?height={height}&width={width}", "/resizedimage{id}.jpg")
    return File(file, "image/jpeg");
}

客户请求/images/123.jpg?height=100&width=100 ...

我可以创建一个静态URL重写，将/images/123.jpg?height=100&width=100重写为/images/resizedimage.jpg（磁盘上已调整大小的图像），绕过操作方法（大概）。 >

如何使用上面的伪代码即时执行相同的操作？

注意：

我不在乎第一个请求，该请求将命中该操作方法，并通过文件结果（如上所示）将图像提供给图像，仅后续请求发送到相同的url。
我知道在启动时创建动态url重写的方法，但在运行时（我问的不是）
是的，我可以将重定向返回到图像文件，这也非常有效-但它仍然是来自客户端的两个同步请求。
需要ASP.Net Core 2 +

Answer 1

最简单的方法是将RewriteOptions注入控制器，然后向其中添加规则，但是RewriteOptions.Rules不是线程安全的。

您需要自定义规则和线程安全集合。这样的事情应该起作用：

启动：

public void ConfigureServices(IServiceCollection services)
{
    services.AddSingleton<ImageRewriteCollection>();
    // ...
}

public void Configure(IApplicationBuilder app, IHostingEnvironment env)
{
    app.UseRewriter(new RewriteOptions().Add(new ImageRewriteRule(app.ApplicationServices.GetService<ImageRewriteCollection>())));
    // ...
}

ImageRewriteCollection：

public class ImageRewriteCollection
{
    private ConcurrentDictionary<(int id, int width, int height), string> imageRewrites
        = new ConcurrentDictionary<(int id, int width, int height), string>();

    public bool TryAdd(int id, int width, int height, string path)
        => imageRewrites.TryAdd((id, width, height), path);

    public bool TryGetValue(int id, int width, int height, out string path)
        => imageRewrites.TryGetValue((id, width, height), out path);
}

ImageRewriteRule：

public class ImageRewriteRule : IRule
{
    private readonly ImageRewriteCollection rewriteCollection;
    private readonly Regex pathRegex = new Regex("^/images/(\\d+).jpg");

    public ImageRewriteRule(ImageRewriteCollection rewriteCollection)
    {
        this.rewriteCollection = rewriteCollection;
    }

    public void ApplyRule(RewriteContext context)
    {
        var request = context.HttpContext.Request;
        var pathMatch = pathRegex.Match(request.Path.Value);
        if (pathMatch.Success)
        {
            bool isValidPath = true;
            int id = int.Parse(pathMatch.Groups[1].Value);

            int width = 0;
            int height = 0;
            string widthQuery = request.Query["width"];
            string heightQuery = request.Query["height"];

            if (widthQuery == null || !int.TryParse(widthQuery, out width))
                isValidPath = false;

            if (heightQuery == null || !int.TryParse(heightQuery, out height))
                isValidPath = false;

            if (isValidPath && rewriteCollection.TryGetValue(id, width, height, out string path))
            {
                request.Path = path;
                context.Result = RuleResult.SkipRemainingRules;
            }
        }
    }
}

控制器：

private readonly ImageRewriteCollection rewriteCollection;

public HomeController(ImageRewriteCollection rewriteCollection)
{
    this.rewriteCollection = rewriteCollection;
}

[Route("images/{id}.jpg")]
public IActionResult ResizeImage(int id, int width, int height)
{
    rewriteCollection.TryAdd(id, width, height, "/resizedimagepath...");
    return File();
}

Answer 2

您需要编写中间件来进行重写-https://docs.microsoft.com/en-us/aspnet/core/fundamentals/url-rewriting?view=aspnetcore-2.2

如何在运行时在ASP.Net Core中创建URL重写？

2 个答案: