README.md

BootstrapperLoader

A simple library to load and execute bootstrapper classes in referenced dlls by convention

CodeProject article

My article on CodeProject on design and implementation of this library: https://www.codeproject.com/Articles/1162975/Bootstrapper-Loader-for-Layered-Architecture

Installation

Install-Package Sharpenter.BootstrapperLoader

Usage Example

This library should be configured and called during the application starts up.

Let's assume following solution structure in a typical ASP.NET/Core layered architecture:

MyCoolProject.UI
    - Startup.cs
MyCoolProject.Model
    - ISomeRepository
    - Other model classes
MyCoolProject.Repository
    - SomeRepository: implementation of ISomeRepository
    - EF/NHibernate mapping to database

Ideally UI project should have reference to only Model project, but not Repository project, and the dependency direction will be:

UI -> Model <- Repository

But if your project is using IoC container, the UI project will either need to reference Repository project to register dependencies to IoC container, or UI project will need to reference another Bootstrapper project which knows about all projects in the solution.

To solve this dependency issue, the library provides a BootstrapperLoader that can load Bootstrapper classes in dlls based on convention.

To get started, let's add a Bootstrapper class to MyCoolProject.Repository that does registration to IoC container by itself (in this case it's Autofac):

public class Bootstrapper
{
    public void ConfigureContainer(IContainerBuilder builder)
    {
        builder.RegisterType<SomeRepository>().As<ISomeRepository>();
    }

    //Configure can have any number of dependencies injected, as long as those dependencies are already registered with IoC container
    public void Configure(ISomeDependency dependency)
    {
        //Any initialization
    }
}

In Startup.cs in MyCoolProject.UI:

public class Startup
{
    private BootstrapperLoader _bootstrapperLoader;

    public Startup(IHostingEnvironment env)
    {
        //...

        _bootstrapperLoader = new LoaderBuilder()
                    .Use(new FileSystemAssemblyProvider(Directory.GetCurrentDirectory(), "MyCoolProject*.dll")) //Look into current directory, grabs all dlls starting with MyCoolProject
                    .Build();
    }

    public void ConfigureServices(IServiceCollection services)
    {
        //Config Autofac to use with ASP.NET Core
        _containerBuilder = new ContainerBuilder();
        //...

        _bootstrapperLoader.TriggerConfigureContainer(_containerBuilder);

        //...
    }

    public void Configure()
    {
        //Use Resolve() from Autofac container as service locator
        _bootstrapperLoader.TriggerConfigure(_containerBuilder.Build().Resolve);
    }
}

Configuration

Default Configuration

By default, BootstrapperLoader has following settings:

• use FileSystemAssemblyProvider to look for all *.dll in current folder (Directory.GetCurrentDirectory())
• BootstrapperLoader.TriggerConfigure looks for Configure() method in any class with name Bootstrapper in dlls found above
• BootstrapperLoader.TriggerConfigureContainer looks for ConfigureContainer() method in any class with name Bootstrapper in dlls found above

Configure LoaderBuilder

• WithName("SomeBootstrapper"): look for class with name SomeBootstrapper instead of Bootstrapper

  Example:

  _bootstrapperLoader = new LoaderBuilder()
                      .ForClass()
                          .WithName("SomeBootstrapper")
                      .Build();
  

• HasConstructorParameter<ISomeDependency>(): when creating Bootstrapper instance, use constructor that takes ISomeDependency parameter

  Example:

  _bootstrapperLoader = new LoaderBuilder()
                      .ForClass()
                          .HasConstructorParameter<ISomeDependency>(new SomeDependency())
                      .Build();
  

• When(condition).CallConfigure("SomeConfigure"): when calling BootstrapperLoader.TriggerConfigure(), if condition invocation is evaluated to true, call SomeConfigure() method in Bootstrapper classes in addition to Configure()

  Example:

  _bootstrapperLoader = new LoaderBuilder()
                      .ForClass()
                          .When(env.IsDevelopment)
                              .CallConfigure("SomeConfigure")
                      .Build();
  

• When(condition).CallConfigureContainer("SomeConfigureContainer"): when calling BootstrapperLoader.TriggerConfigureContainer(), if condition invocation is evaluated to true, call SomeConfigureContainer() method in Bootstrapper classes in addition to ConfigureContainer()

  Example:

  _bootstrapperLoader = new LoaderBuilder()
                      .ForClass()
                          .When(env.IsDevelopment)
                              .CallConfigureContainer("SomeConfigureContainer")
                      .Build();
  

• When(condition).AddMethodNameConvention("Development"): when calling BootstrapperLoader.TriggerConfigure()/ BootstrapperLoader.TriggerConfigureContainer(), if condition invocation is evaluated to true, call SomeConfigure()/SomeConfigureContainer() method in Bootstrapper classes in addition to Configure()/ConfigureContainer()

  Example:

  _bootstrapperLoader = new LoaderBuilder()
                      .ForClass()
                          .When(env.IsDevelopment)
                              .AddMethodNameConvention("Development")
                      .Build();
  

• Use(): specify an alternative assembly provider:

  Example:

  _bootstrapperLoader = new LoaderBuilder()
                          .Use(new FileSystemAssemblyProvider(Directory.GetCurrentDirectory(), "MyCoolProject*.dll")) //Look into current directory, grabs all dlls starting with MyCoolProject
                          .Build();
  

You can also create new Assembly Provider class, to customize the source of assemblies provided to the loader. At the moment, there are 2 classes provided:

- FileSystemAssemblyProvider
- InMemoryAssemblyProvider

Trigger bootstrapper from root project

BootstrapperLoader provides 3 methods to trigger methods in sub-projects Bootstrapper class:

• TriggerConfigureContainer<TArg>(TArg parameter)

This method should be used when root project is doing IoC registration. Its parameter is usually IoC container or container builder. This method will look for ConfigureContainer method in Bootstrapper classes and pass in the parameter, allow Bootstrapper classes to register child projects' dependencies to IoC container

• TriggerConfigure(Func<Type, object> serviceLocator = null)

This method should be used when it's the right time to do any non-IoC configuration/initialization (.e.g. AutoMapper setting up). It can be called with or without serviceLocator parameter

This method takes Func<Type, object> as its parameter to allow Configure method in Bootstrapper classes to take in any number of dependencies (as long as those dependencies can be resolved using serviceLocator func). It works in the same way with Startup.Configure in ASP.NET Core

Func<Type, object> is used here to ensure this library is not dependent on any specific IoC container. Most IoC container should support a method with this signature (.e.g. in Autofac, it's Resolve() method)

When it's called without serviceLocator parameter, it will look for only Configure() method (without any parameter) in Bootstrapper classes

• Trigger<TArg>(string methodName, TArg parameter)

When this method is called, it will look for methods with specified name in Bootstrapper classes in sub-projects and invoke those, passing in provided parameter. This method is for any other situation where your project cannot use above 2 methods.