ServiceComposer.AspNetCore

Composition requests filters

Available starting with v2.3.0

Composition requests filters allow intercepting composition requests to specific composition handlers. Contrary to endpoint filters that are generic HTTP filters, composition filters sit right in front of the composition handlers they are configured to intercept.

Defining composition requests filters

Composition requests filter can be defined as attributes or as classes.

Defining composition requests filters as attributes

Create an attribute that inherites from CompositionRequestFilterAttribute like in the following snippet:

public class SampleCompositionFilterAttribute : CompositionRequestFilterAttribute
{
    public override ValueTask<object> InvokeAsync(CompositionRequestFilterContext context, CompositionRequestFilterDelegate next)
    {
        return next(context);
    }
}

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[!NOTE] The InvokeAsync implementation is responsible to invoke the next filter in the pipeline.

Apply the attribute to the composition handlers to intercept:

public class SampleHandler : ICompositionRequestsHandler
{
    [SampleCompositionFilter]
    [HttpGet("/sample/{id}")]
    public Task Handle(HttpRequest request)
    {
        return Task.CompletedTask;
    }
}

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Defining composition requests filters as classes

Create a class te implements the ICompositionRequestFilter<T> interface, where the generic T parameter is the composition handler type to intercept:

public class SampleCompositionFilter : ICompositionRequestFilter<SampleHandler>
{
    public ValueTask<object> InvokeAsync(CompositionRequestFilterContext context, CompositionRequestFilterDelegate next)
    {
        return next(context);
    }
}

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The above snippet defines a filter intercepting requests to the SampleHandler composition handler.

[!NOTE] Filters defined as classes implementing the ICompositionRequestFilter<T> interface will be automatically registered in DI as transiten, and can use DI to resolve dependencies.

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