如何将依赖名作为构造函数参数注入

Using Autofac, I can register a class to resolve against an interface using property injection, using the following code:

使用Autofac，我可以使用以下代码注册一个类，通过属性注入来解析一个接口:

builder.RegisterType<Log4NetAdapter>()
       .As<ILogger>()
       .PropertiesAutowired()
       .InstancePerDependency();

However, my Log4NetAdapter class has a constructor parameter that requires the name of the calling class. This way, I can log events based upon the name of the calling class.

但是，我的Log4NetAdapter类有一个构造函数参数，它需要调用类的名称。通过这种方式，我可以基于调用类的名称来记录事件。

public class Log4NetAdapter : ILogger
{
    private readonly ILog _logger;

    public Log4NetAdapter(string logName)
    {
        _logger = LogManager.GetLogger(logName);
    }

    ...
}

How can I inject the name (i.e. typeof(dependency).Name) of the dependency into the property-injected class' constructor given that each dependency will have its own Log4NetAdapter instance?

如果每个依赖项都有自己的Log4NetAdapter实例，那么如何将依赖项的名称(即类型(dependency).Name)注入到属性注入类的构造函数中呢?

2 个解决方案

#1

Update: Building on the LogInjectionModule sample and how Autofac does property injection, I have extended the module to do both constructor and property injection.

更新:在LogInjectionModule示例和Autofac如何进行属性注入的基础上，我扩展了模块来完成构造函数和属性注入。

Note: I've fixed the type passed to LogManager in OnComponentPreparing to use the declaring type. This makes e.g. Resolve<Func<Service>> use the correct log type.

注意:我已经修复了在oncomponentprepareto中传递给LogManager的类型，准备使用声明类型。这使得Resolve >使用正确的日志类型。

    using System.Linq;
    using log4net;

    public class LogInjectionModule : Module
    {
        protected override void AttachToComponentRegistration(IComponentRegistry registry, IComponentRegistration registration)
        {
            registration.Preparing += OnComponentPreparing;
            registration.Activating += OnComponentActivating;
        }

        private static void OnComponentActivating(object sender, ActivatingEventArgs<object> e)
        {
            InjectLogProperties(e.Context, e.Instance, false);
        }

        private static void OnComponentPreparing(object sender, PreparingEventArgs e)
        {
            e.Parameters = e.Parameters.Union(new[]
                {
                    new ResolvedParameter(
                       (p, i) => p.ParameterType == typeof(ILog),
                       (p, i) => LogManager.GetLogger(p.Member.DeclaringType))
                });
        }

        private static void InjectLogProperties(IComponentContext context, object instance, bool overrideSetValues)
        {
            if (context == null) throw new ArgumentNullException("context");
            if (instance == null) throw new ArgumentNullException("instance");

            var instanceType = instance.GetType();
            var properties = instanceType
                .GetProperties(BindingFlags.Public | BindingFlags.Instance)
                .Where(pi => pi.CanWrite && pi.PropertyType == typeof(ILog));

            foreach (var property in properties)
            {
                if (property.GetIndexParameters().Length != 0)
                    continue;

                var accessors = property.GetAccessors(false);
                if (accessors.Length == 1 && accessors[0].ReturnType != typeof(void))
                    continue;

                if (!overrideSetValues &&
                    accessors.Length == 2 &&
                    (property.GetValue(instance, null) != null))
                    continue;

                ILog propertyValue = LogManager.GetLogger(instanceType);
                property.SetValue(instance, propertyValue, null);
            }
        }
    }

On how to use the module, here's a sample:

关于如何使用这个模块，这里有一个例子:

public class Service
{
    public Service(ILog log) { ... }
}

var cb = new ContainerBuilder();
cb.RegisterModule<LogInjectionModule>();
cb.RegisterType<Service>();
var c = cb.Build();

var service = c.Resolve<Service>();

#2

You only use logName to effectively resolve by name an ILog, so why not just inject an ILog?

您只使用logName来有效地解析ILog，那么为什么不直接注入ILog呢?

public class Log4NetAdapter : ILogger
{
    private readonly ILog _logger;

    public Log4NetAdapter(ILog logger)
    {
        _logger = logger;
    }

    ...
}

OK, so now I've just moved the problem a bit, but I've also made this less coupled to other classes, namely the LogManager.

好了，现在我把问题移了一点，但我也让它与其他类的耦合更小，也就是LogManager。

So if I was using unity, I would then do this to ensure I get the right logger:

如果我使用unity，我就会这样做，以确保我找到正确的日志记录器:

var childContainer = container.CreateChildContainer();
childContainer.RegisterInstance<ILog>(LogManager.GetLogger(logName));
var adaptor = childContainer.Resolve<Log4NetAdapter>();

The child container prevents any other code getting access to that ILog. You can do this as high up as you like, I don't know any more about your code.

子容器防止任何其他代码访问该ILog。你可以在你喜欢的高度做这个，我不知道你的代码。

#1