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PONinject Conventions and Interception
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  1. PONinject Conventions and Interception
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    copied!<p>I want to decorate my services with attributes for interception, and then have conventions based binding set the interceptors up for me. I don't want my attributes to inherit from the interception attributes... if I can avoid it.</p> <p>For example, I have the following class:</p> <pre><code>[Log] public class SomeClassToLog { public void DoSomething() { ... } } </code></pre> <p>I understand I can bind this as follows:</p> <pre><code>var kernel = new StandardKernel(); kernel.Bind(x =&gt; x.FromAssembliesMatching("SomeProject.*") .SelectAllClasses() .WithAttribute(typeof(LogAttribute)) .BindToSelf().Configure(syntax =&gt; syntax.Intercept().With(LogInterceptor))); </code></pre> <p>How can I do this with different combinations of attributes and interceptors? For example:</p> <p>If I have Log and Authorize attributes I would have to configure 3 sets of bindings? (1 for log without authorize, 1 for authorize without log and one for both log and authorize).</p> <p><strong>Updated:</strong> While I couldn't find a solution based on my original question parameters, I did stumble upon a similar question which lead me to the solution I ended up going with. Here is the source code:</p> <p><strong>Notes:</strong> <em>Common.Interception.Interceptors</em> namespace is in an assembly which has a reference to Ninject.Extensions.Interception (and all of its required dependencies). My attributes are defined in a separate assembly with no dependencies of their own.</p> <p><strong>MiscExtensions.cs</strong></p> <pre><code>using System; using System.Collections.Generic; using System.Linq; using System.Reflection; using System.Text; using System.Threading.Tasks; namespace Common.Interception.Interceptors { // TODO: Remove the dependence on these eventually /// &lt;summary&gt; /// A bundle of extension methods which I needed to borrow from ninject source since they were internal: /// Ninject.Extensions.Interception.Infrastructure.Language /// ExtensionsForIEnumerable /// ExtensionsForMethodInfo /// ExtensionsForICustomAttributeProvider /// &lt;/summary&gt; internal static class MiscExtensions { /// &lt;summary&gt; /// Converts all of the items in the specified series using the specified converter. /// &lt;/summary&gt; /// &lt;typeparam name="TInput"&gt;The type of items contained in the input list.&lt;/typeparam&gt; /// &lt;typeparam name="TOutput"&gt;The type of items to return.&lt;/typeparam&gt; /// &lt;param name="items"&gt;The series of items to convert.&lt;/param&gt; /// &lt;param name="converter"&gt;The converter to use to convert the items.&lt;/param&gt; /// &lt;returns&gt;A list of the converted items.&lt;/returns&gt; public static IEnumerable&lt;TOutput&gt; Convert&lt;TInput, TOutput&gt;(this IEnumerable&lt;TInput&gt; items, Func&lt;TInput, TOutput&gt; converter) { return items.Select(converter); } /// &lt;summary&gt; /// Skips the last items where the count of skipped items is given by count. /// &lt;/summary&gt; /// &lt;typeparam name="T"&gt;The type of the enumerable.&lt;/typeparam&gt; /// &lt;param name="source"&gt;The source.&lt;/param&gt; /// &lt;param name="count"&gt;The count of skipped items.&lt;/param&gt; /// &lt;returns&gt;An enumerable that skippes the last items from the source enumerable.&lt;/returns&gt; public static IEnumerable&lt;T&gt; SkipLast&lt;T&gt;(this IEnumerable&lt;T&gt; source, int count) { var enumerator = source.GetEnumerator(); var items = new Queue&lt;T&gt;(); while (enumerator.MoveNext()) { if (count-- &lt;= 0) { yield return items.Dequeue(); } items.Enqueue(enumerator.Current); } } private const BindingFlags DefaultBindingFlags = BindingFlags.Public | BindingFlags.NonPublic | BindingFlags.Instance; public static PropertyInfo GetPropertyFromMethod(this MethodInfo method, Type implementingType) { if (!method.IsSpecialName) { return null; } var isGetMethod = method.Name.Substring(0, 3) == "get"; var returnType = isGetMethod ? method.ReturnType : method.GetParameterTypes().Last(); var indexerTypes = isGetMethod ? method.GetParameterTypes() : method.GetParameterTypes().SkipLast(1); return implementingType.GetProperty(method.Name.Substring(4), DefaultBindingFlags, null, returnType, indexerTypes.ToArray(), null); } public static PropertyInfo GetPropertyFromMethod(this MethodInfo method) { if (!method.IsSpecialName) { return null; } return method.DeclaringType.GetProperty(method.Name.Substring(4), DefaultBindingFlags); } /// &lt;summary&gt; /// Gets the types of the parameters of the method. /// &lt;/summary&gt; /// &lt;param name="method"&gt;The method in question.&lt;/param&gt; /// &lt;returns&gt;An array containing the types of the method's parameters.&lt;/returns&gt; public static IEnumerable&lt;Type&gt; GetParameterTypes(this MethodBase method) { return method.GetParameters().Convert(p =&gt; p.ParameterType); } /// &lt;summary&gt; /// Gets the method handle of either the method or its generic type definition, if it is /// a generic method. /// &lt;/summary&gt; /// &lt;param name="method"&gt;The method in question.&lt;/param&gt; /// &lt;returns&gt;The runtime method handle for the method or its generic type definition.&lt;/returns&gt; public static RuntimeMethodHandle GetMethodHandle(this MethodBase method) { var mi = method as MethodInfo; if (mi != null &amp;&amp; mi.IsGenericMethod) { return mi.GetGenericMethodDefinition().MethodHandle; } return method.MethodHandle; } /// &lt;summary&gt; /// Gets the first attribute of a specified type that decorates the member. /// &lt;/summary&gt; /// &lt;typeparam name="T"&gt;The type of attribute to search for.&lt;/typeparam&gt; /// &lt;param name="member"&gt;The member to examine.&lt;/param&gt; /// &lt;returns&gt;The first attribute matching the specified type.&lt;/returns&gt; public static T GetOneAttribute&lt;T&gt;(this ICustomAttributeProvider member) where T : Attribute { var attributes = member.GetCustomAttributes(typeof(T), true) as T[]; return (attributes == null) || (attributes.Length == 0) ? null : attributes[0]; } /// &lt;summary&gt; /// Gets the first attribute of a specified type that decorates the member. /// &lt;/summary&gt; /// &lt;param name="member"&gt;The member to examine.&lt;/param&gt; /// &lt;param name="type"&gt;The type of attribute to search for.&lt;/param&gt; /// &lt;returns&gt;The first attribute matching the specified type.&lt;/returns&gt; public static object GetOneAttribute(this ICustomAttributeProvider member, Type type) { object[] attributes = member.GetCustomAttributes(type, true); return (attributes == null) || (attributes.Length == 0) ? null : attributes[0]; } /// &lt;summary&gt; /// Gets an array of attributes matching the specified type that decorate the member. /// &lt;/summary&gt; /// &lt;typeparam name="T"&gt;The type of attribute to search for.&lt;/typeparam&gt; /// &lt;param name="member"&gt;The member to examine.&lt;/param&gt; /// &lt;returns&gt;An array of attributes matching the specified type.&lt;/returns&gt; public static T[] GetAllAttributes&lt;T&gt;(this ICustomAttributeProvider member) where T : Attribute { return member.GetCustomAttributes(typeof(T), true) as T[]; } /// &lt;summary&gt; /// Gets an array of attributes matching the specified type that decorate the member. /// &lt;/summary&gt; /// &lt;param name="member"&gt;The member to examine.&lt;/param&gt; /// &lt;param name="type"&gt;The type of attribute to search for.&lt;/param&gt; /// &lt;returns&gt;An array of attributes matching the specified type.&lt;/returns&gt; public static object[] GetAllAttributes(this ICustomAttributeProvider member, Type type) { return member.GetCustomAttributes(type, true); } /// &lt;summary&gt; /// Determines whether the member is decorated with one or more attributes of the specified type. /// &lt;/summary&gt; /// &lt;typeparam name="T"&gt;The type of attribute to search for.&lt;/typeparam&gt; /// &lt;param name="member"&gt;The member to examine.&lt;/param&gt; /// &lt;returns&gt;&lt;see langword="True"/&gt; if the member is decorated with one or more attributes of the type, otherwise &lt;see langword="false"/&gt;.&lt;/returns&gt; public static bool HasAttribute&lt;T&gt;(this ICustomAttributeProvider member) where T : Attribute { return member.IsDefined(typeof(T), true); } /// &lt;summary&gt; /// Determines whether the member is decorated with one or more attributes of the specified type. /// &lt;/summary&gt; /// &lt;param name="member"&gt;The member to examine.&lt;/param&gt; /// &lt;param name="type"&gt;The type of attribute to search for.&lt;/param&gt; /// &lt;returns&gt;&lt;see langword="True"/&gt; if the member is decorated with one or more attributes of the type, otherwise &lt;see langword="false"/&gt;.&lt;/returns&gt; public static bool HasAttribute(this ICustomAttributeProvider member, Type type) { return member.IsDefined(type, true); } /// &lt;summary&gt; /// Determines whether the member is decorated with an attribute that matches the one provided. /// &lt;/summary&gt; /// &lt;typeparam name="T"&gt;The type of attribute to search for.&lt;/typeparam&gt; /// &lt;param name="member"&gt;The member to examine.&lt;/param&gt; /// &lt;param name="attributeToMatch"&gt;The attribute to match against.&lt;/param&gt; /// &lt;returns&gt;&lt;see langword="True"/&gt; if the member is decorated with a matching attribute, otherwise &lt;see langword="false"/&gt;.&lt;/returns&gt; public static bool HasMatchingAttribute&lt;T&gt;(this ICustomAttributeProvider member, T attributeToMatch) where T : Attribute { T[] attributes = member.GetAllAttributes&lt;T&gt;(); if ((attributes == null) || (attributes.Length == 0)) { return false; } return attributes.Any(attribute =&gt; attribute.Match(attributeToMatch)); } } } </code></pre> <p><strong>AlternateInterceptorRegistrationStrategy.cs</strong></p> <pre><code>using System; using System.Collections.Generic; using System.Linq; using System.Reflection; using Ninject; using Ninject.Components; using Ninject.Extensions.Interception; using Ninject.Extensions.Interception.Advice; using Ninject.Extensions.Interception.Planning.Directives; using Ninject.Extensions.Interception.Registry; using Ninject.Planning; using Ninject.Planning.Strategies; namespace Common.Interception.Interceptors { /// &lt;summary&gt; /// This is a derivation of InterceptorRegistrationStrategy from Ninject.Extensions.Interception.Planning.Strategies, merged with /// http://stackoverflow.com/questions/6386461/ninject-intercept-any-method-with-certain-attribute /// &lt;/summary&gt; public class AlternateInterceptorRegistrationStrategy&lt;TAttribute, TInterceptor&gt; : NinjectComponent, IPlanningStrategy where TAttribute : Attribute where TInterceptor : IInterceptor { protected const BindingFlags DefaultBindingFlags = BindingFlags.Public | BindingFlags.NonPublic | BindingFlags.Instance; public AlternateInterceptorRegistrationStrategy(IAdviceFactory adviceFactory, IAdviceRegistry adviceRegistry, IKernel kernel) { AdviceFactory = adviceFactory; AdviceRegistry = adviceRegistry; Kernel = kernel; } public IKernel Kernel { get; set; } public IAdviceFactory AdviceFactory { get; set; } public IAdviceRegistry AdviceRegistry { get; set; } public virtual void Execute(IPlan plan) { IEnumerable&lt;MethodInfo&gt; candidates = GetCandidateMethods(plan.Type); RegisterClassInterceptors(plan.Type, plan, candidates); foreach (MethodInfo method in candidates) { PropertyInfo property = method.GetPropertyFromMethod(plan.Type); ICustomAttributeProvider provider = (ICustomAttributeProvider)property ?? method; TAttribute[] attributes = provider.GetAllAttributes&lt;TAttribute&gt;(); if (attributes.Length == 0) { continue; } RegisterMethodInterceptor(plan.Type, method); // Indicate that instances of the type should be proxied. if (!plan.Has&lt;ProxyDirective&gt;()) { plan.Add(new ProxyDirective()); } } } protected virtual void RegisterClassInterceptors(Type type, IPlan plan, IEnumerable&lt;MethodInfo&gt; candidates) { var attributes = type.GetAllAttributes&lt;TAttribute&gt;(); if (attributes.Length == 0) { return; } foreach (MethodInfo method in candidates) { PropertyInfo property = method.GetPropertyFromMethod(type); ICustomAttributeProvider provider = (ICustomAttributeProvider) property ?? method; var config = Kernel.Get&lt;IInterceptorConfig&gt;(); if (config.DoNotInterceptAttribute == null) { // A "do not intercept" attribute wasn't defined in the config, so go ahead and register RegisterMethodInterceptor(type, method); } else if (!provider.IsDefined(config.DoNotInterceptAttribute, true)) { // The method wasn't decorated with the "do not intercept" attribute, so go ahead and register RegisterMethodInterceptor(type, method); } } if (!plan.Has&lt;ProxyDirective&gt;()) { plan.Add(new ProxyDirective()); } } protected virtual void RegisterMethodInterceptor(Type type, MethodInfo method) { IAdvice advice = AdviceFactory.Create(method); advice.Callback = request =&gt; request.Context.Kernel.Get&lt;TInterceptor&gt;(); var config = Kernel.TryGet&lt;IInterceptorConfig&gt;(); if (config != null) { advice.Order = config.GetOrder&lt;TInterceptor&gt;(); } AdviceRegistry.Register(advice); } protected virtual IEnumerable&lt;MethodInfo&gt; GetCandidateMethods(Type type) { MethodInfo[] methods = type.GetMethods(DefaultBindingFlags); return methods.Where(ShouldIntercept); } protected virtual bool ShouldIntercept(MethodInfo methodInfo) { return methodInfo.DeclaringType != typeof(object) &amp;&amp; !methodInfo.IsPrivate;// &amp;&amp; //!methodInfo.IsFinal; } } } </code></pre> <p><strong>IInterceptorConfig.cs</strong></p> <pre><code>using System; using System.Collections.Generic; using System.Linq; using System.Text; using System.Threading.Tasks; using Ninject.Extensions.Interception; namespace Common.Interception.Interceptors { public interface IInterceptorConfig { IInterceptorConfig SpecifyOrder&lt;TInterceptor&gt;(int order) where TInterceptor : IInterceptor; IInterceptorConfig SpecifyDoNotInterceptAttribute&lt;TAttribute&gt;() where TAttribute : Attribute; int GetOrder&lt;TInterceptor&gt;() where TInterceptor : IInterceptor; Type DoNotInterceptAttribute { get; } } } </code></pre> <p><strong>InterceptorConfig.cs</strong></p> <pre><code>using System; using System.Collections.Generic; using System.Linq; using System.Text; using System.Threading.Tasks; using Ninject.Extensions.Interception; namespace Common.Interception.Interceptors { public class InterceptorConfig : IInterceptorConfig { private readonly Dictionary&lt;Type, int&gt; _orderDictionary = new Dictionary&lt;Type, int&gt;(); public IInterceptorConfig SpecifyOrder&lt;TInterceptor&gt;(int order) where TInterceptor : IInterceptor { _orderDictionary.Add(typeof(TInterceptor), order); return this; } public IInterceptorConfig SpecifyDoNotInterceptAttribute&lt;TAttribute&gt;() where TAttribute : Attribute { DoNotInterceptAttribute = typeof(TAttribute); return this; } public int GetOrder&lt;TInterceptor&gt;() where TInterceptor : IInterceptor { return _orderDictionary[typeof(TInterceptor)]; } public Type DoNotInterceptAttribute { get; private set; } } } </code></pre> <p><strong>TraceInterceptor.cs</strong> - just a sample interceptor</p> <pre><code>using System; using System.Collections.Generic; using System.Linq; using System.Text; using System.Threading.Tasks; using Ninject.Extensions.Interception; namespace Common.Interception.Interceptors { public class TraceInterceptor : IInterceptor { public void Intercept(IInvocation invocation) { Console.WriteLine("Enter Method"); invocation.Proceed(); Console.WriteLine("Exit Method"); } } } </code></pre> <p><strong>Notes:</strong> Here is a simple console app that shows how to wire up the attributes/interceptors. This has dependencies on both Ninject.Extensions.Interception.DynamicProxy and Ninject.Extensions.Conventions (and all their required dependencies)</p> <pre><code>using System; using System.Collections.Generic; using System.Linq; using System.Reflection; using System.Text; using System.Threading.Tasks; using Common.Interception.Attributes; using Common.Interception.Interceptors; using Ninject; using Ninject.Extensions.Conventions; using Ninject.Planning.Strategies; using SomeProject.Infrastructure; namespace SomeProject.ConsoleApp { class Program { static void Main(string[] args) { var kernel = new StandardKernel(); kernel.Components.Add&lt;IPlanningStrategy, AlternateInterceptorRegistrationStrategy&lt;TraceAttribute, TraceInterceptor&gt;&gt;(); kernel.Components.Add&lt;IPlanningStrategy, AlternateInterceptorRegistrationStrategy&lt;AuthorizeAttribute, AuthorizeInterceptor&gt;&gt;(); // I needed a way to specify execution order and "DoNotIntercept" without deriving from attributes that would force ninject references all over my domain // not 100% confident this is the best way - but it works kernel.Bind&lt;IInterceptorConfig&gt;().ToConstant(new InterceptorConfig() .SpecifyOrder&lt;TraceInterceptor&gt;(1) .SpecifyOrder&lt;AuthorizeInterceptor&gt;(0) .SpecifyDoNotInterceptAttribute&lt;DoNotInterceptAttribute&gt;()); // SomeProject.Infrastructure contains my service classes decorated with my custom attributes kernel.Bind(x =&gt; x.FromAssembliesMatching("SomeProject.Infrastructure") .SelectAllClasses() .BindToSelf()); var a = kernel.Get&lt;SomeServiceA&gt;(); var b = kernel.Get&lt;SomeServiceB&gt;(); Console.WriteLine("Calling a.DoSomeStuff()..."); a.DoSomeStuff(); Console.WriteLine("Calling b.DoMyThing()..."); b.DoMyThing(); Console.WriteLine("Calling b.NowTraceThis()..."); b.NowTraceThis(); Console.ReadLine(); } } } </code></pre>
 

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