C# Application Server - a.k.a. SharpBoss (WIP)

A simple C# Application Server inspired on Redhat JBoss Project.

Features

So far we have:

• Working HTTP Server
• Hot-Deploy / Un-deploy Assemblies
• Log support
• Multiple Applications
• Exception Handling support with Debug Symbols Support (if provided on the app folder)
• JSON Serializer for Object Return in REST calls
• Custom Exception Handlers
• Argument Deserialization for REST calls
• Dependency Injection with Inject attribute

TODO

• REST Path Param support (WIP)
• Better threading for multiple apps
• NHibernate Services Support with Automatic Session Open / Close / Exception Handler
• Unit Tests to ensure everything is OK

How it works

If you have ever used Redhat JBoss, it is pretty similar but for .NET. So basically you create a Library Project that uses the ASAttrib REST attributes to make REST Endpoint calls.

The output .dll file should be put inside apps/YOUR_APP_FOLDER to be deployed. It can either be before executing the AppServer or after it (Hot-Deploy). The assemblies will be automatically copied to a folder called deployed to avoid filesystem locking issues. In this way, you can also update the .dll assembly anytime, and the AppServer will be automatically reload it.

The AppServer handles unhandled exceptions by logging and returning the StackTrace of the exception. If a .pdb file is available, it will also shows the source file and line number of the crash.

How to use REST Attributes

This is actually pretty simple. Just create a Class and put the REST("/mypath") attribute on it to mark it as a REST Endpoint Class. In the methods of that class you can anotate with GET("/endpoint"), POST("/endpoint"), PUT("/endpoint"), DELETE("/endpoint"). The method should receive a RestRequest object that contains the Request Parameters and can return either string or a object that will be JSON serialized. The method can also throw an exception to indicate an error. The AppServer will return a HTTP Status Code 500 with the StackTrace as message.

The SampleApp Example:

namespace SampleApp {
  [Rest("/hue")]
  public class MyRestSample {
    [Inject]
    private TestProc myInjectedProc;
    
    [GET("/inject-test")]
    public string injTest() {
      return myInjectedProc.myName();
    }

    [POST("/inject-test")]
    public TestModel injTestPost(TestModel model) {
      return myInjectedProc.addCount(model, 20);
    }

    [GET("/test")]
    public string hueTest([QueryParam] string param0, [QueryParam] float param1) {
      return "GET TO HUEHUE with param: Param0(" + param0 + "), Param1(" + param1 +")";
    }
    
    [POST("/test")]
    public TestModel hueTest2(TestModel model) {
      model.count += 100;
      return model;
    }

    [GET("/exception-test")]
    public TestModel exceptionTest() {
      throw new NullReferenceException("Test of an Exception");
    }

    [GET("/custom-exception-test")]
    public TestModel customExceptionTest() {
      throw new CustomException("NOOOOOOOOOOOOOOOOOOOOO!");
    }
  }
}

This will create the endpoints that will be described in the next section.

How to use Custom Exception Handler

Also it is very simple. Just create a class that implements the interface IRestExceptionHandler and put a attribute [RestExceptionHandler(typeof(TheExceptionYouWantToHandle))] on it and you're good to go. Example:

namespace SampleApp {
  [RestExceptionHandler(typeof(CustomException))]
  public class MyCustomExceptionHandler : IRestExceptionHandler {
    public RestResult handleException(Exception e) {
      CustomException ce = (CustomException)e;    //  The Custom Exception handler will only be called with the correct type of exception

      RestResult result = new RestResult();
      result.ContentType = "text/plain";
      result.StatusCode = System.Net.HttpStatusCode.NotAcceptable;
      result.Result = Encoding.UTF8.GetBytes("Handling CustomException that has a message: " + ce.Message);

      return result;
    }
  }
}

Testing locally

1. Compile the Solution
2. Create a folder apps in the AppServer.exe folder.
3. Create a folder sampleapp in apps folder
4. Copy the SampleApp.dll and SampleApp.pdb file from the SampleApp project to apps/sampleapp folder.
5. Run AppServer.exe

You will have some endpoints available:

• GET /sampleapp/hue/test?param0=SomeString&param1=30,5
  • This will return a string "GET TO HUEHUE with param: Param0(SomeString), Param1(30,5)" as text/plain
• POST /sampleapp/hue/test
  • Post with a JSON like this:

    {
      "name":"Lucas",
      "count":10,
      "test":"HUEHUE"
    }

  • The response will be this:

  {
    "name":"Lucas",
    "count":110,
    "test":"HUEHUE"
  }

• GET /sampleapp/hue/exception-test
  • This will throw a test NullReferenceException with the message Test of an Exception
• GET /sampleapp/hue/custom-exception-test
  • This will throw a test CustomException that will be handled by MyCustomExceptionHandler and will output Handling CustomException that has a message: NOOOOOOOOOOOOOOOOOOOOO!