我对使用控制台应用程序时如何避免服务定位器感到有些困惑
程序
public static int Main(string[] args)
{
// Configuration
var configuration = new ConfigurationBuilder().AddJsonFile("appsettings.json").AddEnvironmentVariables().Build();
// DI container
var services = new ServiceCollection();
ConfigureServices(services, configuration);
var serviceProvider = services.BuildServiceProvider();
// Do I pass along the serviceProvider?
// Can resolve using locator pattern do I just use this in my classes?
// var exampleRepository = _serviceProvider.GetService<IExampleRepository>();
// Execute the correct command based on args
return CommandLineOptions.Execute(args);
}
private static void ConfigureServices(IServiceCollection services, IConfiguration configuration)
{
services.AddScoped<ApplicationDbContext>((s) => new ApplicationDbContext(configuration.GetSection("Data:DefaultConnection:ConnectionString").Value));
services.AddScoped<IExampleRepository, ExampleRepository>();
}
CommandLineOptions
public static class CommandLineOptions
{
public static int Execute(string[] args, IServiceProvider serviceProvider)
{
try
{
var app = new CommandLineApplication
{
Name = "dnx abc",
FullName = "Abc Commands",
Description = "ABC",
};
app.VersionOption("--version", PlatformServices.Default.Application.ApplicationVersion);
app.HelpOption("-?|-h|--help");
app.OnExecute(() =>
{
//ShowLogo();
app.ShowHelp();
return 2;
});
app.Command(
"task",
task=>
{
task.Name = "Task1";
task.FullName = "Task1";
task.Description = "Tasks";
task.HelpOption("-?|-h|--help");
task.OnExecute(() => { task.ShowHelp(); return 0; });
task.Command(
"task1",
data =>
{
data.FullName = "Task1 command";
data.Description = "Task1";
data.OnExecute(() =>
{
// Need to inject
var p = new Task1();
p.Process()
return 0;
});
我需要将IExampleRepository注入新的Task1（）
任务1
public class Task1
{
public Task1()
{
}
private readonly IExampleRepository _exampleRepository;
public Task1(IExampleRepository exampleRepository)
{
_exampleRepository = exampleRepository;
}
public void Process() {
....
}
所以基本上我的理解是我注册了我的依赖项，然后我应该能够在我的课程中注入它们。我不确定是否需要通过我的serviceProvider？
我相信在MVC中有魔术可以实现这一目标。如何在不使用服务定位器模式的情况下进行注入？
答案 0 :(得分：1)
基本上，您不希望将IServiceProvider传递给除引导程序（Startup）或工厂方法/类之外的任何类，因为这会将您的类绑定到特定的IoC容器。 / p>
您可以做的是将依赖项添加到CommandLineApplication类并在Main方法中解决它，然后从这里开始依赖注入链。只要您需要/想要立即解决所有依赖项，这将有效。
当你遇到只需要加载它的一个子集的情况时（即在传递某个参数时使用不同的服务或程序逻辑），你需要一种工厂（工厂是一个瘦的包装器，它在传递之前创建和配置一个对象，在IoC的情况下它也解析了依赖关系）。
在工厂实现中，如果需要，可以引用容器（您需要作用域依赖关系或每个对象创建的瞬态解析）。如果您需要多个Task1实例，则还需要工厂。
有两种方法。对于非常简单的工厂，您可以使用工厂方法，可以在进行IServiceCollection注册时直接使用。
services.AddTransient<Task1>();
services.AddTransient<Func<Task1>>( (serviceProvider) => {
return () => serviceProvider.GetService<Task1>();
});
然后注入您的依赖项。
public class MyTaskApplication
{
private readonly Func<Task> taskFactory;
public MyApplicationService(Func<Task> taskFactory)
{
this.taskFactory = taskFactory;
}
public void Run()
{
var task1 = taskFactory(); // one instance
var task2 = taskFactory(); // another instance, because its registered as Transient
}
}
如果您需要更复杂的配置或运行时参数，那么创建工厂类可能更有意义。
public class TaskFactory : ITaskFactory
{
private readonly IServiceProvider services;
public TaskFactory(IServiceProvider services)
{
this.services = services;
}
public Task1 CreateNewTask()
{
// get default task service, which is transient as before
// so you get a new instance per call
return services.GetService<Task1>();
}
public Task1 CreateNewTask(string connectionString)
{
// i.e. when having multiple tenants and you want to
// to the task on a database which is only determined at
// runtime. connectionString is not know at compile time because
// the user may choose which one he wants to process
var dbContext = MyDbContext(connectionString);
var repository = new ExampleRepository(dbContext);
return new Task1(repository);
}
}
用法
public class MyTaskApplication
{
private readonly ITaskFactory taskFactory;
public MyApplicationService(ITaskFactory taskFactory)
{
this.taskFactory = taskFactory;
}
public void Run()
{
// Default instance with default connectionString from appsettings.json
var task1 = taskFactory.CreateNewTask();
// Tenant configuration you pass in as string
var task2 = taskFactory.CreateNewTask(tenantConnectionString);
}
}
答案 1 :(得分：0)
这是我尝试在测试应用中使用您的代码，但我不确定我是否正确地执行了此操作。
我也不确定如何传入MyTaskApplication中的方法的连接字符串CreateNewTask（connectionString）
是否需要将其作为属性或MyTaskApplication的构造函数或替代方法的一部分传递？
public class Program
{
public static void Main(string[] args)
{
var services = new ServiceCollection();
services.AddScoped<Task1>();
services.AddScoped<MyTaskApplication>();
services.AddTransient<ITaskFactory, TaskFactory>();
var serviceProvider = services.BuildServiceProvider();
var m = serviceProvider.GetService<MyTaskApplication>();
m.Run();
}
}
public class TaskFactory : ITaskFactory
{
private readonly IServiceProvider services;
public TaskFactory(IServiceProvider services)
{
this.services = services;
}
public Task1 CreateNewTask()
{
// get default task service, which is transient as before
// so you get a new instance per call
return services.GetService<Task1>();
}
public Task1 CreateNewTask(string connectionString)
{
// i.e. when having multiple tenants and you want to
// to the task on a database which is only determined at
// runtime. connectionString is not know at compile time because
// the user may choose which one he wants to process
//var dbContext = MyDbContext(connectionString);
//var repository = new ExampleRepository(dbContext);
return new Task1(connectionString);
}
}
public interface ITaskFactory
{
Task1 CreateNewTask();
Task1 CreateNewTask(string connectionString);
}
public class MyTaskApplication
{
private readonly ITaskFactory taskFactory;
private string tenantConnectionString;
public MyTaskApplication(ITaskFactory taskFactory)
{
this.taskFactory = taskFactory;
}
public void Run()
{
// Default instance with default connectionString from appsettings.json
var task1 = taskFactory.CreateNewTask();
task1.Process();
// Tenant configuration you pass in as string
var task2 = taskFactory.CreateNewTask(tenantConnectionString);
task2.Process();
Console.WriteLine("Running");
}
}
public class Task1
{
private string _repositoryText;
public Task1()
{
_repositoryText = String.Empty;
}
public Task1(string repositoryText)
{
_repositoryText = repositoryText;
}
public void Process()
{
Console.WriteLine("process: " + _repositoryText);
}
}