如何将依赖项名称作为构造函数参数注入 [英] How to inject dependency name as a constructor parameter

问题描述

使用 Autofac，我可以注册一个类以使用属性注入来解析接口，使用以下代码:

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

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

但是，我的 Log4NetAdapter 类有一个构造函数参数，该参数需要调用类的名称.这样，我可以根据调用类的名称记录事件.

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.

public class Log4NetAdapter : ILogger
{
    private readonly ILog _logger;

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

    ...
}

如果每个依赖项都有自己的 Log4NetAdapter代码>实例?

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?

推荐答案

更新: 基于 LogInjectionModule 示例和 Autofac 如何进行属性注入，我扩展了该模块以进行构造函数和属性注入.

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

注意:我已经修复了在 OnComponentPreparing 中传递给 LogManager 的类型以使用声明类型.这使得例如Resolve> 使用正确的日志类型.

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.

    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);
            }
        }
    }

关于如何使用该模块，这里有一个示例:

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

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>();

这篇关于如何将依赖项名称作为构造函数参数注入的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！