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>();
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