可以使用HTTP模块捕获Web服务方法引发的异常消息、堆栈跟踪和异常类型。
首先是一些背景…
-
如果Web服务方法引发异常,则HTTP响应的状态代码为500。
-
如果关闭自定义错误,则Web
服务将返回异常
到客户端的消息和堆栈跟踪
作为JSON。例如:
{"Message":"Exception
message","StackTrace":" at
WebApplication.HelloService.HelloWorld()
in C:\Projects\Stackoverflow
Examples\WebApplication\WebApplication\HelloService.asmx.cs:line
22","ExceptionType":"System.ApplicationException"}
-
当启用自定义错误时,
Web服务返回默认消息
到客户端并移除堆栈
跟踪和异常类型:
{"Message":"There was an error processing the request.","StackTrace":"","ExceptionType":""}
因此,我们需要为Web服务设置自定义错误,并插入一个HTTP模块:
-
检查请求是否为Web服务方法
-
检查是否引发异常-即返回状态代码500
-
如果1)和2)为真,则获取将发送到客户机的原始JSON,并将其替换为默认JSON。
下面的代码是执行此操作的HTTP模块的示例:
using System;
using System.Collections.Generic;
using System.IO;
using System.Text;
using System.Web;
public class ErrorHandlerModule : IHttpModule {
public void Init(HttpApplication context) {
context.PostRequestHandlerExecute += OnPostRequestHandlerExecute;
context.EndRequest += OnEndRequest;
}
static void OnPostRequestHandlerExecute(object sender, EventArgs e) {
HttpApplication context = (HttpApplication) sender;
// TODO: Update with the correct check for your application
if (context.Request.Path.StartsWith("/HelloService.asmx")
&& context.Response.StatusCode == 500) {
context.Response.Filter =
new ErrorHandlerFilter(context.Response.Filter);
context.EndRequest += OnEndRequest;
}
}
static void OnEndRequest(object sender, EventArgs e) {
HttpApplication context = (HttpApplication) sender;
ErrorHandlerFilter errorHandlerFilter =
context.Response.Filter as ErrorHandlerFilter;
if (errorHandlerFilter == null) {
return;
}
string originalContent =
Encoding.UTF8.GetString(
errorHandlerFilter.OriginalBytesWritten.ToArray());
// If customErrors are Off then originalContent will contain JSON with
// the original exception message, stack trace and exception type.
// TODO: log the exception
}
public void Dispose() { }
}
此模块使用以下筛选器覆盖发送到客户端的内容并存储原始字节(包含异常消息、堆栈跟踪和异常类型):
public class ErrorHandlerFilter : Stream {
private readonly Stream _responseFilter;
public List OriginalBytesWritten { get; private set; }
private const string Content =
"{\"Message\":\"There was an error processing the request.\"" +
",\"StackTrace\":\"\",\"ExceptionType\":\"\"}";
public ErrorHandlerFilter(Stream responseFilter) {
_responseFilter = responseFilter;
OriginalBytesWritten = new List();
}
public override void Flush() {
byte[] bytes = Encoding.UTF8.GetBytes(Content);
_responseFilter.Write(bytes, 0, bytes.Length);
_responseFilter.Flush();
}
public override long Seek(long offset, SeekOrigin origin) {
return _responseFilter.Seek(offset, origin);
}
public override void SetLength(long value) {
_responseFilter.SetLength(value);
}
public override int Read(byte[] buffer, int offset, int count) {
return _responseFilter.Read(buffer, offset, count);
}
public override void Write(byte[] buffer, int offset, int count) {
for (int i = offset; i < offset + count; i++) {
OriginalBytesWritten.Add(buffer[i]);
}
}
public override bool CanRead {
get { return _responseFilter.CanRead; }
}
public override bool CanSeek {
get { return _responseFilter.CanSeek; }
}
public override bool CanWrite {
get { return _responseFilter.CanWrite; }
}
public override long Length {
get { return _responseFilter.Length; }
}
public override long Position {
get { return _responseFilter.Position; }
set { _responseFilter.Position = value; }
}
}
此方法要求关闭Web服务的自定义错误。您可能希望为应用程序的其余部分保留自定义错误,以便将Web服务放在子目录中。只能使用覆盖父设置的web.config关闭该目录中的自定义错误。
