asp.net mvc源码分析Route的GetRouteData

我知道Route这里东西应该算路由，这里把它放到mvc里面有些不怎么合适，但是我想大家多数遇到路由都是在mvc的时候吧.首先我们还是来看看GetRouteData方法吧

public override RouteData GetRouteData(HttpContextBase httpContext)
{
    string virtualPath = httpContext.Request.AppRelativeCurrentExecutionFilePath.Substring(2) + httpContext.Request.PathInfo;
    RouteValueDictionary values = this._parsedRoute.Match(virtualPath, this.Defaults);
    if (values == null)
    {
        return null;
    }
    RouteData data = new RouteData(this, this.RouteHandler);
    if (!this.ProcessConstraints(httpContext, values, RouteDirection.IncomingRequest))
    {
        return null;
    }
    foreach (KeyValuePair<string, object> pair in values)
    {
        data.Values.Add(pair.Key, pair.Value);
    }
    if (this.DataTokens != null)
    {
        foreach (KeyValuePair<string, object> pair2 in this.DataTokens)
        {
            data.DataTokens[pair2.Key] = pair2.Value;
        }
    }
    return data;
}

 我还是沿用以前的思路，已一个demo来便说明吧，现在假设我的路由信息是：

   routes.IgnoreRoute("{resource}.axd/{*pathInfo}");
            routes.IgnoreRoute("{*favicon}", new { favicon = @"(.*/)?favicon.ico(/.*)?" });
            routes.MapRoute(
                "Default", // 路由名称
                "{controller}/{action}/{id}", // 带有参数的 URL
                new { controller = "Home", action = "Index", id = UrlParameter.Optional }, // 参数默认值
                new { controller="([A-Za-z])*" },
                new string[] { "MvcApp.Controllers" }
            );
   请求路径： http://localhost:7503/Home/index
我们知道httpContext.Request.AppRelativeCurrentExecutionFilePath的返回值都是以~/打头的，这里httpContext.Request.PathInfo为空，多数情况下该属性也是空的，所以这里的virtualPath=Home/index。

有关MapRoute的代码可以参照

  public static Route MapRoute(this RouteCollection routes, string name, string url, object defaults, object constraints, string[] namespaces) {
            if (routes == null) {
                throw new ArgumentNullException("routes");
            }
            if (url == null) {
                throw new ArgumentNullException("url");
            }

            Route route = new Route(url, new MvcRouteHandler()) {
                Defaults = new RouteValueDictionary(defaults),
                Constraints = new RouteValueDictionary(constraints),
                DataTokens = new RouteValueDictionary()
            };

            if ((namespaces != null) && (namespaces.Length > 0)) {
                route.DataTokens["Namespaces"] = namespaces;
            }

            routes.Add(name, route);

            return route;
        }

首先调用_parsedRoute.Match(virtualPath, this.Defaults)获取一个RouteValueDictionary ，至于这个方法的具体实现放到后面来说，然后实例化一个RouteData ，并且把先前的RouteValueDictionary的值添加到先前实例化的  RouteData中，如果DataTokens有元素的话也加入到RouteData的DataTokens中来。不过这个过程有个约束的处理

 if (!this.ProcessConstraints(httpContext, values, RouteDirection.IncomingRequest))
    {
        return null;
    }

其中RouteDirection的定义如下：
    public enum RouteDirection
{
    IncomingRequest,
    UrlGeneration
}
约束检查失败而返回null，现在我们来看看ProcessConstraints方法：

private bool ProcessConstraints(HttpContextBase httpContext, RouteValueDictionary values, RouteDirection routeDirection)
{
    if (this.Constraints != null)
    {
        foreach (KeyValuePair<string, object> pair in this.Constraints)
        {
            if (!this.ProcessConstraint(httpContext, pair.Value, pair.Key, values, routeDirection))
            {
                return false;
            }
        }
    }
    return true;
}

如果Constraints有元素，依次检查每个成员，检查方法主要是调用ProcessConstraint方法，

protected virtual bool ProcessConstraint(HttpContextBase httpContext, object constraint, string parameterName, RouteValueDictionary values, RouteDirection routeDirection)
{
    object obj2;
    IRouteConstraint constraint2 = constraint as IRouteConstraint;
    if (constraint2 != null)
    {
        return constraint2.Match(httpContext, this, parameterName, values, routeDirection);
    }
    string str = constraint as string;
    if (str == null)
    {
        throw new InvalidOperationException(string.Format(CultureInfo.CurrentUICulture, SR.GetString("Route_ValidationMustBeStringOrCustomConstraint"), new object[] { parameterName, this.Url }));
    }
    values.TryGetValue(parameterName, out obj2);
    string input = Convert.ToString(obj2, CultureInfo.InvariantCulture);
    string pattern = "^(" + str + ")$";
    return Regex.IsMatch(input, pattern, RegexOptions.CultureInvariant | RegexOptions.Compiled | RegexOptions.IgnoreCase);
}

 这里首先检查我们的约束类型，如果它是IRouteConstraint那么就直接调用它的Match方法，约束不是IRouteConstraint那 么就转化为字符串，再把约束验证的值从RouteValueDictionary 中取出来转化为字符串，最后在用正则表达式来验证我们的值是否通过。
好，现在让我们来看看this._parsedRoute.Match(virtualPath, this.Defaults);这个方法是然后获取RouteValueDictionary的：

public RouteValueDictionary Match(string virtualPath, RouteValueDictionary defaultValues)
{
    IList<string> source = RouteParser.SplitUrlToPathSegmentStrings(virtualPath);
    if (defaultValues == null)
    {
        defaultValues = new RouteValueDictionary();
    }
    RouteValueDictionary matchedValues = new RouteValueDictionary();
    bool flag = false;
    bool flag2 = false;
    for (int i = 0; i < this.PathSegments.Count; i++)
    {
        PathSegment segment = this.PathSegments[i];
        if (source.Count <= i)
        {
            flag = true;
        }
        string a = flag ? null : source[i];
        if (segment is SeparatorPathSegment)
        {
            if (!flag && !string.Equals(a, "/", StringComparison.Ordinal))
            {
                return null;
            }
        }
        else
        {
            ContentPathSegment contentPathSegment = segment as ContentPathSegment;
            if (contentPathSegment != null)
            {
                if (contentPathSegment.IsCatchAll)
                {
                    this.MatchCatchAll(contentPathSegment, source.Skip<string>(i), defaultValues, matchedValues);
                    flag2 = true;
                }
                else if (!this.MatchContentPathSegment(contentPathSegment, a, defaultValues, matchedValues))
                {
                    return null;
                }
            }
        }
    }
    if (!flag2 && (this.PathSegments.Count < source.Count))
    {
        for (int j = this.PathSegments.Count; j < source.Count; j++)
        {
            if (!RouteParser.IsSeparator(source[j]))
            {
                return null;
            }
        }
    }
    if (defaultValues != null)
    {
        foreach (KeyValuePair<string, object> pair in defaultValues)
        {
            if (!matchedValues.ContainsKey(pair.Key))
            {
                matchedValues.Add(pair.Key, pair.Value);
            }
        }
    }
    return matchedValues;
}

 这里RouteParser的SplitUrlToPathSegmentStrings方法很简单，就是把url字符串按照”/“来分割

internal static IList<string> SplitUrlToPathSegmentStrings(string url)
{
    List<string> list = new List<string>();
    if (!string.IsNullOrEmpty(url))
    {
        int index;
        for (int i = 0; i < url.Length; i = index + 1)
        {
            index = url.IndexOf('/', i);
            if (index == -1)
            {
                string str = url.Substring(i);
                if (str.Length > 0)
                {
                    list.Add(str);
                }
                return list;
            }
            string item = url.Substring(i, index - i);
            if (item.Length > 0)
            {
                list.Add(item);
            }
            list.Add("/");
        }
    }
    return list;
}

 所以Match方法中的source 是成员是很好明白的，我的示例中它的值是：

在ParsedRoute的Match方法中用到了一个PathSegments属性。该属性定义为：private IList<PathSegment> PathSegments { get; set; }真正该改属性复制的是ParsedRoute的构造函数。而Route中的_parsedRoute的获取是在Url属性中

   public string Url
    {
        get
        {
            return (this._url ?? string.Empty);
        }
        set
        {
            this._parsedRoute = RouteParser.Parse(value);
            this._url = value;
        }
    }

在我们这个例子中url的value={controller}/{action}/{id}。
其中RouteParser的Parse方法如下：

public static ParsedRoute Parse(string routeUrl)
{
    if (routeUrl == null)
    {
        routeUrl = string.Empty;
    }
    if ((routeUrl.StartsWith("~", StringComparison.Ordinal) || routeUrl.StartsWith("/", StringComparison.Ordinal)) || (routeUrl.IndexOf('?') != -1))
    {
        throw new ArgumentException(SR.GetString("Route_InvalidRouteUrl"), "routeUrl");
    }
    IList<string> pathSegments = SplitUrlToPathSegmentStrings(routeUrl);
    Exception exception = ValidateUrlParts(pathSegments);
    if (exception != null)
    {
        throw exception;
    }
    return new ParsedRoute(SplitUrlToPathSegments(pathSegments));
}

 在这里我们知道url不能以~ /打头，也不能含有？。这里的pathSegments也很好理解，其值：

这里的ValidateUrlParts主要就是验证这里的pathSegments集合，ValidateUrlParts这里的具体是怎么验证的很是复杂，这里就忽略了它吧。

有关SplitUrlToPathSegments的方法比较复杂，分为两部分，把urlParts中的"/" 变成SeparatorPathSegment对象作为站位，像{controller}这样转换为ContentPathSegment对象，其中它的 subsegments是一个List<PathSubsegment>实例，

private static IList<PathSegment> SplitUrlToPathSegments(IList<string> urlParts)
{
    List<PathSegment> list = new List<PathSegment>();
    foreach (string str in urlParts)
    {
        if (IsSeparator(str))
        {
            list.Add(new SeparatorPathSegment());
        }
        else
        {
            Exception exception;
            IList<PathSubsegment> subsegments = ParseUrlSegment(str, out exception);
            list.Add(new ContentPathSegment(subsegments));
        }
    }
    return list;
}

internal static bool IsSeparator(string s)
{
    return string.Equals(s, "/", StringComparison.Ordinal);
}

 private static IList<PathSubsegment> ParseUrlSegment(string segment, out Exception exception)
{
    int startIndex = 0;
    List<PathSubsegment> list = new List<PathSubsegment>();
    while (startIndex < segment.Length)
    {
        int num2 = IndexOfFirstOpenParameter(segment, startIndex);
        if (num2 == -1)
        {
            string str = GetLiteral(segment.Substring(startIndex));
            if (str == null)
            {
                exception = new ArgumentException(string.Format(CultureInfo.CurrentUICulture, SR.GetString("Route_MismatchedParameter"), new object[] { segment }), "routeUrl");
                return null;
            }
            if (str.Length > 0)
            {
                list.Add(new LiteralSubsegment(str));
            }
            break;
        }
        int index = segment.IndexOf('}', num2 + 1);
        if (index == -1)
        {
            exception = new ArgumentException(string.Format(CultureInfo.CurrentUICulture, SR.GetString("Route_MismatchedParameter"), new object[] { segment }), "routeUrl");
            return null;
        }
        string literal = GetLiteral(segment.Substring(startIndex, num2 - startIndex));
        if (literal == null)
        {
            exception = new ArgumentException(string.Format(CultureInfo.CurrentUICulture, SR.GetString("Route_MismatchedParameter"), new object[] { segment }), "routeUrl");
            return null;
        }
        if (literal.Length > 0)
        {
            list.Add(new LiteralSubsegment(literal));
        }
        string parameterName = segment.Substring(num2 + 1, (index - num2) - 1);
        list.Add(new ParameterSubsegment(parameterName));
        startIndex = index + 1;
    }
    exception = null;
    return list;
}

private static int IndexOfFirstOpenParameter(string segment, int startIndex)
{
    while (true)
    {
        startIndex = segment.IndexOf('{', startIndex);
        if (startIndex == -1)
        {
            return -1;
        }
        if (((startIndex + 1) == segment.Length) || (((startIndex + 1) < segment.Length) && (segment[startIndex + 1] != '{')))
        {
            return startIndex;
        }
        startIndex += 2;
    }
}

 private static string GetLiteral(string segmentLiteral)
{
    string str = segmentLiteral.Replace("{{", "").Replace("}}", "");
    if (!str.Contains("{") && !str.Contains("}"))
    {
        return segmentLiteral.Replace("{{", "{").Replace("}}", "}");
    }
    return null;
}

 internal sealed class LiteralSubsegment : PathSubsegment
{
    // Methods
    public LiteralSubsegment(string literal)
    {
        this.Literal = literal;
    }

    // Properties
    public string Literal { get; private set; }
}
internal sealed class ParameterSubsegment : PathSubsegment
{
    // Methods
    public ParameterSubsegment(string parameterName)
    {
        if (parameterName.StartsWith("*", StringComparison.Ordinal))
        {
            this.ParameterName = parameterName.Substring(1);
            this.IsCatchAll = true;
        }
        else
        {
            this.ParameterName = parameterName;
        }
    }

    // Properties
    public bool IsCatchAll { get; private set; }

    public string ParameterName { get; private set; }
}
    internal sealed class ContentPathSegment : PathSegment
    {
        // Methods
        public ContentPathSegment(IList<PathSubsegment> subsegments)
        {
            this.Subsegments = subsegments;
        }

        // Properties
        public bool IsCatchAll
        {
            get
            {
                return this.Subsegments.Any<PathSubsegment>(seg => ((seg is ParameterSubsegment) && ((ParameterSubsegment)seg).IsCatchAll));
            }
        }

        public IList<PathSubsegment> Subsegments { get; private set; }
    }

 ParseUrlSegment方法主要就是获取代码是：

string parameterName = segment.Substring(num2 + 1, (index - num2) - 1);
        list.Add(new ParameterSubsegment(parameterName));

例如我们传进来的字符串是{controller}，那么这里parameterName就会处理为controller。如果传入的参数没有{、}如Channel，那么ParseUrlSegment将处理为

   if (str.Length > 0)
                    {
                        list.Add(new LiteralSubsegment(str));
                    }
                    break;

现在是时候回到ParsedRoute的Match方法了，首先我们来看看这个方法用到的PathSegments是个什么东东，我的url是{controller}/{action}/{id}它对应的PathSegments如图：

着了我们看看几次循环的主要变量取值：

当前ContentPathSegment的IsCatchAll为false。那么我们现在主要关心的是MatchContentPathSegment方法了。

private bool MatchContentPathSegment(ContentPathSegment routeSegment, string requestPathSegment, RouteValueDictionary defaultValues, RouteValueDictionary matchedValues)
{
    if (string.IsNullOrEmpty(requestPathSegment))
    {
        if (routeSegment.Subsegments.Count <= 1)
        {
            object obj2;
            ParameterSubsegment subsegment = routeSegment.Subsegments[0] as ParameterSubsegment;
            if (subsegment == null)
            {
                return false;
            }
            if (defaultValues.TryGetValue(subsegment.ParameterName, out obj2))
            {
                matchedValues.Add(subsegment.ParameterName, obj2);
                return true;
            }
        }
        return false;
    }
    int length = requestPathSegment.Length;
    int num2 = routeSegment.Subsegments.Count - 1;
    ParameterSubsegment subsegment2 = null;
    LiteralSubsegment subsegment3 = null;
    while (num2 >= 0)
    {
        int num3 = length;
        ParameterSubsegment subsegment4 = routeSegment.Subsegments[num2] as ParameterSubsegment;
        if (subsegment4 != null)
        {
            subsegment2 = subsegment4;
        }
        else
        {
            LiteralSubsegment subsegment5 = routeSegment.Subsegments[num2] as LiteralSubsegment;
            if (subsegment5 != null)
            {
                subsegment3 = subsegment5;
                int startIndex = length - 1;
                if (subsegment2 != null)
                {
                    startIndex--;
                }
                if (startIndex < 0)
                {
                    return false;
                }
                int num5 = requestPathSegment.LastIndexOf(subsegment5.Literal, startIndex, StringComparison.OrdinalIgnoreCase);
                if (num5 == -1)
                {
                    return false;
                }
                if ((num2 == (routeSegment.Subsegments.Count - 1)) && ((num5 + subsegment5.Literal.Length) != requestPathSegment.Length))
                {
                    return false;
                }
                num3 = num5;
            }
        }
        if ((subsegment2 != null) && (((subsegment3 != null) && (subsegment4 == null)) || (num2 == 0)))
        {
            int num6;
            int num7;
            if (subsegment3 == null)
            {
                if (num2 == 0)
                {
                    num6 = 0;
                }
                else
                {
                    num6 = num3 + subsegment3.Literal.Length;
                }
                num7 = length;
            }
            else if ((num2 == 0) && (subsegment4 != null))
            {
                num6 = 0;
                num7 = length;
            }
            else
            {
                num6 = num3 + subsegment3.Literal.Length;
                num7 = length - num6;
            }
            string str = requestPathSegment.Substring(num6, num7);
            if (string.IsNullOrEmpty(str))
            {
                return false;
            }
            matchedValues.Add(subsegment2.ParameterName, str);
            subsegment2 = null;
            subsegment3 = null;
        }
        length = num3;
        num2--;
    }
    if (length != 0)
    {
        return (routeSegment.Subsegments[0] is ParameterSubsegment);
    }
    return true;
}

 这个方法就是真正把路由参数和路由的值给关联起来，如果参数requestPathSegment为null则参数值从defaultValues中获取，

 if (defaultValues.TryGetValue(subsegment.ParameterName, out obj2))
            {
                matchedValues.Add(subsegment.ParameterName, obj2);
                return true;
            }

否则从我们传递进来的requestPathSegment获取。

   string str = requestPathSegment.Substring(num6, num7);
            if (string.IsNullOrEmpty(str))
            {
                return false;
            }
            matchedValues.Add(subsegment2.ParameterName, str);

Match方法在结束之前会检查我们的defaultValues字典，把defaultValues中的key（matchedValues不存 在对应的key）加到matchedValues中来。整个match方法及结束了，结合前面的东西我们也就可以明白Route类的 GetRouteData方法了。
为了跟好的理解上面个方法，我这里再举一个demo：

 路由信息： routes.MapRoute("Default", "{ChannelName}/{action}", new { controller = "Home", action = "Index" });

请求路径：http://localhost:7503/men/index

调用Match方法的  virtualPath=men/index，

source取值：

PathSegments取值：

至于Match方法中的有一种路径是调用MatchCatchAll方法，

private void MatchCatchAll(ContentPathSegment contentPathSegment, IEnumerable<string> remainingRequestSegments, RouteValueDictionary defaultValues, RouteValueDictionary matchedValues)
{
    object obj2;
    string str = string.Join(string.Empty, remainingRequestSegments.ToArray<string>());
    ParameterSubsegment subsegment = contentPathSegment.Subsegments[0] as ParameterSubsegment;
    if (str.Length > 0)
    {
        obj2 = str;
    }
    else
    {
        defaultValues.TryGetValue(subsegment.ParameterName, out obj2);
    }
    matchedValues.Add(subsegment.ParameterName, obj2);
}

它要求contentPathSegment.IsCatchAll为true。从 ParameterSubsegment类的定义可以知道当且仅当传进来parameterName以*打头才是True。parameterName是从url中来的，也就是说url中要含有*，IsCatchAll才为true。在前面提到的ValidateUrlParts方法会验证url的，其主要代码如下：

private static Exception ValidateUrlParts(IList<string> pathSegments)
{
    HashSet<string> usedParameterNames = new HashSet<string>(StringComparer.OrdinalIgnoreCase);
    bool? nullable = null;
    bool flag = false;
    foreach (string str in pathSegments)
    {
        bool flag2;
        if (flag)
        {
            return new ArgumentException(string.Format(CultureInfo.CurrentUICulture, SR.GetString("Route_CatchAllMustBeLast"), new object[0]), "routeUrl");
        }
 
        if (!flag2)
        {
            Exception exception;
            IList<PathSubsegment> pathSubsegments = ParseUrlSegment(str, out exception);
 
            flag = pathSubsegments.Any<PathSubsegment>(seg => (seg is ParameterSubsegment) && ((ParameterSubsegment) seg).IsCatchAll);
        }
    }
    return null;
}
所以以上的那个MatchCatchAll执行的条件也很明显就是url中带有*号，并且是最后一个参数带有*，希望大家注意一下。大家看到这里相信对Route类的GetRouteData方法有个大致的了解了吧。