Optional Resources in Spring.Net

Question

How to include Spring configuration files optionally? I think about something simular to this:

  <spring>
    <context>
      <resource uri="file:///Objects/RequiredObjects.xml" />
      <resource uri="file:///Objects/OptionalObjects.xml" required="false" />
    </context>

This way I could provide developers the possibility to override some configuration parts (e.g. for a local speed improvement or automatism during app startup) without affecting the app.config and the problem that a developer could checkin his modified file when it is not really his intent to change the config for all.

Answer 1

Not as simple as in AutoFac (because there is already a builtin way) but possible to achieve something similar with a little coding:

using System.IO;
using System.Xml;

using Spring.Core.IO;

    public class OptionalFileSystemResource : FileSystemResource
    {
        public OptionalFileSystemResource(string uri)
            : base(uri)
        {
        }

        public override Stream InputStream
        {
            get
            {
                if (System.IO.File.Exists(this.Uri.LocalPath))
                {
                    return base.InputStream;
                }

                return CreateEmptyStream();
            }
        }

        private static Stream CreateEmptyStream()
        {
            var xml = new XmlDocument();
            xml.LoadXml("<objects />");
            var stream = new MemoryStream();
            xml.Save(stream);
            stream.Position = 0;

            return stream;
        }
    }

Register a section handler:

<sectionGroup name="spring">
     ...
      <section name="resourceHandlers" type="Spring.Context.Support.ResourceHandlersSectionHandler, Spring.Core"/>
     ...
</sectionGroup>

...

<spring>
  <resourceHandlers>
    <handler protocol="optionalfile" type="MyCoolStuff.OptionalFileSystemResource, MyCoolStuff" />
  </resourceHandlers>

  ...

<context>
  <resource uri="file://Config/MyMandatoryFile.xml" />
  <resource uri="optionalfile://Config/MyOptionalFile.xml" />
  ...

You'll find more information about resources and resource handlers in the Spring.Net documentation.