How to Integrate Prism, Unity, and Enterprise Library - prism

I'm building a WPF application. I'm using Prism 4, and Unity. I want to add two Enterprise Library 5 blocks to the application, Logging and Exception Handling. I have a singleton LoggerFacadeCustom.cs in my Infrastructure class that supports the ILoggerFacade and I've created it in my bootstrapper, and it is generating log files. It "news" up a unity container in its constructor (second code block)
Where do I add the container.resolve for ExceptionManager? How do I connect the Exception handling block to ILoggerFacade in my bootstrapper? How do I get all the exceptions to come out in the same log? Here is my existing bootstrapper.cs
public class Bootstrapper : UnityBootstrapper {
protected override ILoggerFacade CreateLogger() {
return LoggerFacadeCustom.Instance;
}
protected override DependencyObject CreateShell() {
return Container.Resolve<Shell>();
}
protected override void InitializeShell() {
base.InitializeShell();
App.Current.MainWindow = (Window)Shell;
App.Current.MainWindow.Show();
//Other shell stuff...
}
protected override IModuleCatalog CreateModuleCatalog() {
var catalog = new ModuleCatalog();
//These primary modules must register their own services as if they were acting independantly
catalog.AddModule(typeof(XmlCommentMergeModule));
//These support modules require at least one primary module above to be added first
catalog.AddModule(typeof(ToolboxHeaderModule));
catalog.AddModule(typeof(ToolboxFooterModule));
catalog.AddModule(typeof(ToolboxStartModule));
return catalog;
}
}
LoggerFacadeCustom:
public class LoggerFacadeCustom : ILoggerFacade {
private static readonly LoggerFacadeCustom _instance = new LoggerFacadeCustom();
public static LoggerFacadeCustom Instance { get { return _instance; } }
private LoggerFacadeCustom() {
var container = new UnityContainer();
container.AddNewExtension<EnterpriseLibraryCoreExtension>();
_logWriter = container.Resolve<LogWriter>();
}
private readonly LogWriter _logWriter;
public void Write(string message) { Write(message, null); }
public void Write(string message, string category, int priority) {
_logWriter.Write(message, category, priority);
}
public void Write(string message, Dictionary<string, object> properties) {
_logWriter.Write(message, LiteralString.LogCategoryProcess, properties);
}
#region ILoggerFacade Members
public void Log(string message, Category category, Priority priority) {
throw new NotImplementedException();
}
#endregion
}

Your bootstrapper is the Composition Root of your application. You should register all dependencies there. And only there. You should never reference the container directly outside the composition root.
If your classes have a dependency you should inject that dependency using a pattern like constructor injection.
Don't use static classes. Static kills dependency injection and testability and it hides dependencies to a point where everything is referenced from everywhere.
Make your logger facade a constructor parameter. You can do the same with the error handling block.
Don't use the container as a ServiceLocator. That is considered an anti-pattern in modern software architecture.

Related

Replace default IoC container in MvvmCross

Since MvvmCross v7 sticks on its own IoC container, I would like to replace it with the .NET Core one in order to have an easier life when registering third party libraries such as IHttpClientFactory, Polly, Automapper, etc. through already built-in extensions methods.
To achieve this, I've successfully created a class that implementas MvxSingleton<IMvxIoCProvider> described as follow:
public class HostingAdapter : MvxSingleton<IMvxIoCProvider>, IMvxIoCProvider
{
private IServiceProvider ServiceProvider;
private IServiceCollection ServiceCollection;
public HostingAdapter()
{
var host = Host
.ConfigureServices((context, serviceCollection) =>
{
// Configure local services
ConfigureServices(context, serviceCollection);
ServiceCollection = serviceCollection;
ServiceProvider = ServiceCollection.BuildServiceProvider();
})
.Build();
}
public void RegisterType<TFrom, TTo>() where TFrom : class where TTo : class, TFrom
{
ServiceCollection.AddTransient<TFrom, TTo>();
ServiceProvider = ServiceCollection.BuildServiceProvider();
}
public T GetSingleton<T>() where T : class
{
return ServiceProvider.GetRequiredService<T>();
}
public object GetSingleton(Type type)
{
return ServiceProvider.GetRequiredService(type);
}
.. and all the required methods requested by the interface.
Then on the platform specific side I override the IoC creation as follow:
protected override IMvxIoCProvider CreateIocProvider()
{
var hostingAdapter = new HostingAdapter();
return hostingAdapter;
}
The code seems to work but as soon as the app starts Mvx registers its own "extra" services such as the IMvxLoggerProvider, IMvxSettings and so on. And here issues come:
ServiceProvider = ServiceCollection.BuildServiceProvider(); is called during the Host initialization but Mvx still continue to register services after that. This means IServiceProvider is not 'in sync' with IServiceCollection and a new ServiceCollection.BuildServiceProvider(); call is needed. I temporarily solved updating the provider at each collection registration (like the code above) but I'm aware this affects performances. Anyone knows how to workaround this?
There are plenty of Mvx services that are not registered so the app fails to start. These are the IMvxLogProvider, IMvxAndroidLifetimeMonitor, IIMvxSettings, IMvxStart, etc. I just wonder, why? How can let Mvx handle the registration in my container of all what it needs to start? I partially solved some of them such as the logger thing replacing the default with a custom one, but other callbacks like InitializeLifetimeMonitor are called too late for being registered.
Do I need to change anything in my MvxApplication than the most standard implementation?
Am I really forced to replace the standard IoC container? How can I handle the IServiceCollection's extension methods that 3rd party libraries expose like services.AddHttpClient();?
If it needs, I am on Xamarin classic using the Droid platform. Thanks
Deliberately inspired by Unity.Microsoft.DependencyInjection repository I've workarounded this approaching the problem the other way round: instead of replacing the default IoC container, I manually initialize an IServiceCollection instance and I add it to the Mvx's IoC provider.
To achieve this, I've used the following code:
public class App : MvxApplication
{
public override void Initialize()
{
base.Initialize();
InitializeServiceCollection();
CreatableTypes()
.EndingWith("Service")
.AsInterfaces()
.RegisterAsLazySingleton();
RegisterAppStart<HomeViewModel>();
}
private static void InitializeServiceCollection()
{
IServiceCollection serviceCollection = new ServiceCollection();
ConfigureServices(serviceCollection);
IServiceProvider serviceProvider = serviceCollection.BuildServiceProvider();
MapServiceCollectionToMvx(serviceProvider, serviceCollection);
}
private static void ConfigureServices(IServiceCollection serviceCollection)
{
serviceCollection.AddHttpClient();
}
private static void MapServiceCollectionToMvx(IServiceProvider serviceProvider,
IServiceCollection serviceCollection)
{
foreach (var serviceDescriptor in serviceCollection)
{
if (serviceDescriptor.ImplementationType != null)
{
Mvx.IoCProvider.RegisterType(serviceDescriptor.ServiceType, serviceDescriptor.ImplementationType);
}
else if (serviceDescriptor.ImplementationFactory != null)
{
var instance = serviceDescriptor.ImplementationFactory(serviceProvider);
Mvx.IoCProvider.RegisterSingleton(serviceDescriptor.ServiceType, instance);
}
else if (serviceDescriptor.ImplementationInstance != null)
{
Mvx.IoCProvider.RegisterSingleton(serviceDescriptor.ServiceType, serviceDescriptor.ImplementationInstance);
}
else
{
throw new InvalidOperationException("Unsupported registration type");
}
}
}
}

Using FluentScheduler - ASP.NET Core MVC

I currently have a simple website setup with ASP.NET Core MVC (.NET 4.6.1), and I would like to periodically do some processes like automatically send emails at the end of every day to the registered members.
After doing some searching, I came across two common solutions - Quartz.NET and FluentScheduler.
Based on this SO thread, I found the approach of using FluentScheduler more easier to digest and use for my simple task. After quickly implementing the following lines of code into my Program.cs class, I had the emails going out successfully every minute (for testing purposes).
public class Program
{
public static void Main(string[] args)
{
var host = new WebHostBuilder()
.UseKestrel()
.UseContentRoot(Directory.GetCurrentDirectory())
.UseIISIntegration()
.UseStartup<Startup>()
.Build();
var registry = new Registry();
JobManager.Initialize(registry);
JobManager.AddJob(() => MyEmailService.SendEmail(), s => s
.ToRunEvery(1)
.Minutes());
host.Run();
}
}
However, now apart from sending emails I also need to do some back-end processing for e.g. updating the user records in the DB when mails are being sent out. For this, I normally inject my Entity Framework Context into the constructor of my controllers and use it to get/update SQL records.
My question is, since I cannot really inject these services into the main method, where would be the appropriate place to initialize the registry and add jobs for scheduling?
Thanks for the help, I am a little new to this so a little guidance would be much appreciated!
Instead of Program's Main function, I initialized the same in Startup.cs before app.UseMvc..
public void Configure(...., IDependencyObject dependencyObject)
{
....
JobManager.Initialize(new MyRegistry(dependencyObject));
app.UseMvc(routes =>
{
routes.MapRoute(
name: "default",
template: "api/{controller}/{action}/{id?}");
});
}
My registry class looks like this:
public class MyRegistry: Registry
{
public MyRegistry(IDependencyObject dependencyObject)
{
Schedule(() => new SyncUpJob(dependencyObject)).ToRunNow().AndEvery(10).Seconds();
}
}
My Job class looks like this:
public class SyncUpJob: IJob
{
public SyncUpJob(IDependencyObject dependencyObject)
{
DependencyObject= dependencyObject;
}
public IDependencyObject DependencyObject{ get; set; }
public void Execute()
{
// call the method to run weekly here
}
}
You can define all your jobs and their schedules, by subclassing from FluentScheduler Registry class. something like:
public class JobRegistry : Registry {
public JobRegistry() {
Schedule<EmailJob>().ToRunEvery(1).Days();
Schedule<SomeOtherJob>().ToRunEvery(1).Seconds();
}
}
public class EmailJob : IJob {
public DbContext Context { get; } // we need this dependency, right?!
public EmailJob(DbContext context) //constructor injection
{
Context = context;
}
public void Execute()
{
//Job implementation code: send emails to users and update database
}
}
For injecting dependencies into jobs, you need to implement FluentScheduler IJobFactory interface. GetJobIntance method is called by FluentScheduler for creating job instances. Here you can use any DI library you want; In this sample implementation, I'm going to assume that you use Ninject:
public class MyNinjectModule : NinjectModule {
public override void Load()
{
Bind<DbContext>().To<MyDbContextImplemenation>();
}
}
public class JobFactory : IJobFactory {
private IKernel Kernel { get; }
public JobFactory(IKernel kernel)
{
Kernel = kernel;
}
public IJob GetJobInstance<T>() where T : IJob
{
return Kernel.Get<T>();
}
}
Now you can start your jobs in main method by calling:
JobManager.JobFactory = new JobFactory(new StandardKernel(new MyNinjectModule()));
JobManager.Initialize(new JobRegistry());

Reading an OSGi config value

I've got some code like this to read a value that could be set either with a sling:OsgiConfig node or after being set in the Felix UI...
#Component(immediate = true, metatype = true, label = "Dummy Service")
public class DummyService {
#Property(label = "Dummy Service Value")
public static final String DUMMY_VALUE = "dummyValue";
private static String m_strDummyValue = "default value";
public static String getDummyValue(){
return m_strDummyValue;
}
#Activate
protected void activate(ComponentContext context) {
configure(context.getProperties());
}
#Deactivate
protected void deactivate(ComponentContext context) {
}
#Modified
protected void modified(ComponentContext componentContext) {
configure(componentContext.getProperties());
}
public void updated(Dictionary properties) throws ConfigurationException {
configure(properties);
}
private void configure(Dictionary properties) {
m_strDummyValue = OsgiUtil.toString(properties.get(DUMMY_VALUE), null);
}
}
And could be called in any consuming class as
DummyService.getDummyValue();
This is currently working in our development environment. It's also very similar to some code that another vendor wrote and is currently in production in the client environment, and seems to be working. However, I ran across this post OSGi component configurable via Apache Felix... which recommends against using a static accessor like this. Are there potential problems where getDummyValue() could return an incorrect value, or is the recommendation more about being philosophically consistent with OSGi's patterns?
Generally statics are frowned upon especially in OSGi as it involves a tight code coupling. It would be better to have DummySerivce be an interface and your class implement it with the component being a service. Then others would reference your component's service. Once injected with the service, they can call the service's methods.
You shouldn't do this for one major reason: there is no guarantee that DummyService has been configured when you access the static method - in contrast with a service reference.

How can I access previously set fields in a seam #Observer method?

My current setup is JBoss Seam 2.2 on JBoss 4.2.3.GA.
I have two Beans like so:
#Name("mailingManager")
#Scope(ScopeType.PAGE)
public class MailingMgr {
private Mailing selectedMailing;
#Observer("mailing.letter.success")
public void recordSuccess(final Object arg) {
if (null != selectedMailing) { // store arg }
}
public void send() {
selectedMailing = new Mailing();
if ('EMAIL' == determineType()) {
EmailSender mailer = (EmailSender) Component.getInstance(EmailSender.class);
mailer.send(getAddresses());
}
// ... more options
}
}
#Name("emailSender")
#Scope(ScopeType.PAGE)
public class EmailSender {
public void send(final Set<String> addresses) {
for (String addr : addresses) {
// ... create a mail
Events.instance().raiseEvent("mailing.letter.success", getGeneratedMail());
}
}
}
The problem is that when recordSuccess() is called selectedMailing is always null.
As a workaround I'm setting selectedMailing in the conversation context manually before calling any code that could potentially trigger my events, and then annotate my field with #In(required=false) to inject it again before recordSuccess is called. But is there a more elegant solution (keeping the decoupling intact)? And why isn't the calling bean reused to handle the event?

Nhibernate with windows form

I have a asp.net application with Nihbernate setup, now I want to convert it to Windows form application.
Here is the code which have been setup in the Global.asax.cs. Can anyone give me some code sample how to do this in Windows form?
protected void Application_BeginRequest(object sender, EventArgs e)
{
ManagedWebSessionContext.Bind(HttpContext.Current, SessionManager.SessionFactory.OpenSession());
}
protected void Application_EndRequest(object sender, EventArgs e)
{
ISession session = ManagedWebSessionContext.Unbind(HttpContext.Current, SessionManager.SessionFactory);
if (session != null)
{
try
{
if (session.Transaction != null && session.Transaction.IsActive)
{
session.Transaction.Rollback();
}
else
{
session.Flush();
}
}
finally
{
session.Close();
}
}
}
Well, there are several methods for accessing ISessionFactory in statefull application (and a desktop application is that kind of application), among them:
Singleton
You could build the session factory once during the startup of your program and access it through a static singleton class.
This would force the application to use only one instance of the session factory.
example:
public sealed class NHibernateHelper
{
private static ISessionFactory SessionFactory;
private static readonly Configuration NhibernateConfig;
// ....
static NHibernateHelper()
{
NhibernateConfig = new Configuration().Configure();
SessionFactory = NhibernateConfig.BuildSessionFactory();
}
public static ISessionFactory GetSessionFactory()
{
return SessionFactory;
}
// ....
}
... and access the session factory through GetSessionFactory method all over the application.
Context Object and/or Dependency Injection
You could build the session factory from configuration and pass it through a context object all over the application.
example:
during startup:
// here you configure NHibernate.
ISessionFactory _sessionFactory = BuildMySessionFactory();
// ...
ObjectFactory.Initialize(x =>
{
x.For<IPatientRepository>()
.Use<StandardPatientRepository>()
.Ctor<ISessionFactory>().Is(_sessionFactory);
// ... initialize the rest of your repositories...
});
then:
public class StandardPatientRepository : IPatientRepository
{
private readonly ISessionFactory _sessionFactory;
public StandardPatientRepository(ISessionFactory sessionFactory)
{
if (sessionFactory == null)
throw new ArgumentNullException("sessionFactory");
_sessionFactory = sessionFactory;
}
public virtual Patient Get(Guid id)
{
using (IStatelessSession session =
_sessionFactory.OpenStatelessSession())
{
return session.Get<Patient>(id);
}
}
// the rest of data-access methods.
}
then in your classes that will make use of the data (ie. use the repositories) you will use:
Patient = ObjectFactory.GetInstance<IPatientRepository>().Get(patient);
In my opinion the second method is better as I think that singleton in most cases is an anti-pattern. The second approach will give you more control over your data layer, you will know who and when is accessing it.
Here is a well done and extensive sample application using NHibernate in a desktop application:
Building a Desktop To-Do Application with NHibernate
Managing the NHibernate session in a desktop application tends to be a lot more involved than managing the NHibernate session in a web application.

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