WCF4.0 -- RESTful WCF Services 错误处理 (Error Handling)

REST WCF 的错误处理可用于从 WCF Web HTTP 服务返回指定 HTTP 状态代码的错误，并且返回的错误详细信息使用与操作相同的格式（如 XML 或 JSON）。在WCF 4.0中增加了WebFaultException<T>异常类，我们可以更加方便的处理错误，并能给予客户端详细的错误提示。

服务端代码：

//当查不到User时，抛出WebFaultException，并提示NotFound及错误信息
[WebGet(UriTemplate="/Users/{name}")]
public User GetUser(string name)
{
    var user = Users.FirstOrDefault(u => u.Name == name);
    if (user == null)
        throw new WebFaultException<string>(
           string.Format("There is no user with the userName '{0}'.", name),
           HttpStatusCode.NotFound);
    else
        return user;
}

//当查不到User时，抛出WebFaultException，并提示NotFound及错误信息 [WebGet(UriTemplate="/Users/{name}")] public User GetUser(string name) { var user = Users.FirstOrDefault(u => u.Name == name); if (user == null) throw new WebFaultException<string>( string.Format("There is no user with the userName '{0}'.", name), HttpStatusCode.NotFound); else return user; }
客户端代码：
1. 先包装 HttpWebRequest 的Get方法便于演示：

static string RequestGet(string url)
{
    var req = HttpWebRequest.Create(url);
    using (var resp = req.GetResponse())
    {
        using (var stream = resp.GetResponseStream())
        {
            using (var sr = new StreamReader(stream))
            {
                return sr.ReadToEnd();
            }
        }
    }
}

static string RequestGet(string url) { var req = HttpWebRequest.Create(url); using (var resp = req.GetResponse()) { using (var stream = resp.GetResponseStream()) { using (var sr = new StreamReader(stream)) { return sr.ReadToEnd(); } } } }
2. 客户端请求REST服务，这里传给服务端一个错误名字:errorname，服务端查不到抛出异常。

var resp = RequestGet("http://localhost:52402/Service1/Users/errorname");
Console.WriteLine(resp);

var resp = RequestGet("http://localhost:52402/Service1/Users/errorname"); Console.WriteLine(resp);
3. 当Response.StatusCode 不等于 200(成功) 的时候，GetResponse() 方法会抛出 WebException，我们通过捕获它获得异常的详细内容：(WebException.Response 可以获得出错时的Response，服务端的错误内容写在Response Body里)

try
{
    // Request ...
}
catch (WebException ex)
{
    var errResp = ex.Response as HttpWebResponse;
    Console.WriteLine("StatusCode:{0}({1})", errResp.StatusCode, (int)errResp.StatusCode);
    using (var stream = errResp.GetResponseStream())
    {
        using (var sr =  new StreamReader(stream))
        {
            Console.WriteLine("Content:{0}", sr.ReadToEnd());
        }
    }
}

try { // Request ... } catch (WebException ex) { var errResp = ex.Response as HttpWebResponse; Console.WriteLine("StatusCode:{0}({1})", errResp.StatusCode, (int)errResp.StatusCode); using (var stream = errResp.GetResponseStream()) { using (var sr = new StreamReader(stream)) { Console.WriteLine("Content:{0}", sr.ReadToEnd()); } } }
运行结果：


WebFaultException<T> 还支持返回复杂的“错误”对象，我们在服务端定义一个复杂的错误类：

public class ComplexError
{
    public string ErrorCode { get; set; }
    public string ErrorMessage { get; set; }
}

public class ComplexError { public string ErrorCode { get; set; } public string ErrorMessage { get; set; } }
在服务中抛出这个复杂错误：

[WebGet(UriTemplate = "/Users2/{name}")]
public User GetUser2(string name)
{
    var user = Users.FirstOrDefault(u => u.Name == name);
    if (user == null)
        throw new WebFaultException<ComplexError>(
           new ComplexError
           {
               ErrorCode = "E001",
               ErrorMessage = string.Format("There is no user with the userName '{0}'.", name)
           },
           HttpStatusCode.NotFound);
    else
        return user;
}

[WebGet(UriTemplate = "/Users2/{name}")] public User GetUser2(string name) { var user = Users.FirstOrDefault(u => u.Name == name); if (user == null) throw new WebFaultException<ComplexError>( new ComplexError { ErrorCode = "E001", ErrorMessage = string.Format("There is no user with the userName '{0}'.", name) }, HttpStatusCode.NotFound); else return user; }
服务端会按照既定的ResponseFormat返回错误信息。
运行结果：


PS: 如果使用 WCF REST Starter Kit 的 HttpClient 处理的话，需要自己判断 StatusCode。

var client = new HttpClient();
var resp = client.Get("http://localhost:52402/Service1/Users/errorname");
Console.WriteLine("StatusCode:{0}({1})", resp.StatusCode, (int)resp.StatusCode);
var result = resp.Content.ReadAsString();
Console.WriteLine("Content:{0}", result);