asp.net – 覆盖webapi odata链接的主机

var externalAddress = ConfigClient.Get().ExternalAddress;  // e.g. https://account-name.domain.com
var account = ConfigClient.Get().Id;  // e.g. AccountName
var uriToReplace = new Uri(new Uri("http://" + Request.RequestUri.Host),account);
string originalUri = Request.RequestUri.AbsoluteUri;
Request.RequestUri = new Uri(Request.RequestUri.AbsoluteUri.Replace(uriToReplace.AbsoluteUri,externalAddress));
string newUri = Request.RequestUri.AbsoluteUri;
this.GetLogger().Info($"Request URI was rewritten from {originalUri} to {newUri}");

重写RequestUri足以影响@ odata.nextLink值,因为 code that computes the next link直接依赖于RequestUri.其他@ odata.xxx链接是通过 UrlHelper计算的,它以某种方式引用原始请求URI的路径. (因此你在@ odata.context链接中看到的AccountName.我在我的代码中看到过这种行为,但是我无法找到缓存的URI路径的来源.)

我们可以通过创建CustomUrlHelper类来动态重写OData链接,而不是重写RequestUri.新的GetNextPageLink方法将处理@ odata.nextLink重写,而Link方法覆盖将处理所有其他重写.

public class CustomUrlHelper : System.Web.Http.Routing.UrlHelper
{
    public CustomUrlHelper(HttpRequestMessage request) : base(request)
    { }

    // Change these strings to suit your specific needs.
    private static readonly string ODataRouteName = "ODataRoute"; // Must be the same as used in api config
    private static readonly string TargetPrefix = "http://localhost:8080/somePathPrefix"; 
    private static readonly int TargetPrefixLength = TargetPrefix.Length;
    private static readonly string ReplacementPrefix = "http://www.contoso.com"; // Do not end with slash

    // Helper method.
    protected string ReplaceTargetPrefix(string link)
    {
        if (link.StartsWith(TargetPrefix))
        {
            if (link.Length == TargetPrefixLength)
            {
                link = ReplacementPrefix;
            }
            else if (link[TargetPrefixLength] == '/')
            {
                link = ReplacementPrefix + link.Substring(TargetPrefixLength);
            }
        }

        return link;
    }

    public override string Link(string routeName,IDictionary<string,object> routeValues)
    {
        var link = base.Link(routeName,routeValues);

        if (routeName == ODataRouteName)
        {
            link = this.ReplaceTargetPrefix(link);
        }

        return link;
    }

    public Uri GetNextPageLink(int pageSize)
    {
        return new Uri(this.ReplaceTargetPrefix(this.Request.GetNextPageLink(pageSize).ToString()));
    }
}

在基本控制器类的Initialize方法中连接CustomUrlHelper.

public abstract class BaSEODataController : ODataController
{
    protected abstract int DefaultPageSize { get; }

    protected override void Initialize(System.Web.Http.Controllers.HttpControllerContext controllerContext)
    {
        base.Initialize(controllerContext);

        var helper = new CustomUrlHelper(controllerContext.Request);
        controllerContext.RequestContext.Url = helper;
        controllerContext.Request.ODataProperties().NextLink = helper.GetNextPageLink(this.DefaultPageSize);
    }

请注意,在给定的控制器类中,页面大小对于所有操作都是相同的.您可以通过将ODataProperties().NextLink的赋值移动到特定操作方法的主体来解决此限制,如下所示：

var helper = this.RequestContext.Url as CustomUrlHelper;
this.Request.ODataProperties().NextLink = helper.GetNextPageLink(otherPageSize);