如何将额外的依赖项/配置注入装饰器 class

Question

我有一个 IRepository<> 和一些 Setting 实体。我知道对于这个实体，我需要一个缓存存储库，所以我想创建一个 ICachedRepository<Setting> 装饰器并使用 Simple Injector 注册它。

问题是我有额外的配置需要以某种方式传递到缓存的存储库，例如过期时间跨度、预取策略等

CachedRepository(IRepository repository, CachedRepositoryConfiguration configuration)
{
   ...
}

我该怎么做？（这些配置对于不同的存储库当然可以不同，例如一个 30 分钟，另一个 1 小时）

Answer 1

Simple Injector 不允许您轻松配置装饰器的构造函数值（尽管这可以通过 implementing a custom IDependencyInjectionBehavior - 或 v2 中的 IConstructorInjectionBehavior 完成）。

解决此问题的最简单方法是回退到属性注入并为每个装饰器注册一个初始化程序：

public class CachingRepositoryDecorator<TEntity> : IRepository<TEntity>
{
    private readonly IRepository<TEntity> decoratee;
    public CachingRepositoryDecorator(IRepository<TEntity> decoratee) {
        this.decoratee = decoratee;
        this.Configuration = CachedRepositoryConfiguration.NoCaching;
    }

    public CachedRepositoryConfiguration Configuration { get; set; }

    // IRepository<T> methods here.
}

container.RegisterDecorator(typeof(IRepository<>), 
    typeof(CachingRepositoryDecorator<>));

container.RegisterInitializer<CachingRepositoryDecorator<Setting>>(decorator => {
   decorator.Configuration = 
       CachedRepositoryConfiguration.AbsoluteExpiration(TimeSpan.FromMinutes(30));
});

另一种选择是使用 Context Based injection。使用文档中给出的扩展方法，您可以执行以下操作：

public class CachingRepositoryDecorator<TEntity> : IRepository<TEntity>
{
    private readonly IRepository<TEntity> decoratee;
    private readonly CachedRepositoryConfiguration configuration;
    public CachingRepositoryDecorator(IRepository<TEntity> decoratee,
        CachedRepositoryConfiguration configuration) {
        this.decoratee = decoratee;
        this.configuration = configuration;
    }

    // IRepository<T> methods here.
}

container.RegisterDecorator(typeof(IRepository<>), 
    typeof(CachingRepositoryDecorator<>));

container.RegisterWithContext<CachedRepositoryConfiguration>(context => {
    if (context.ImplementationType == typeof(CachingRepositoryDecorator<Setting>)) {
        return CachedRepositoryConfiguration.AbsExpiration(TimeSpan.FromMinutes(30));
    } else {
        CachedRepositoryConfiguration.NoCaching;
    }
});

第三个选项是使配置对象通用，如下所示：

public class CachingRepositoryDecorator<TEntity> : IRepository<TEntity>
{
    private readonly IRepository<TEntity> decoratee;
    private readonly CachedRepositoryConfiguration<TEntity> configuration;
    public CachingRepositoryDecorator(IRepository<TEntity> decoratee,
        CachedRepositoryConfiguration<TEntity> configuration) {
        this.decoratee = decoratee;
        this.configuration = configuration;
    }

    // IRepository<T> methods here.
}

container.RegisterDecorator(typeof(IRepository<>), 
    typeof(CachingRepositoryDecorator<>));

container.RegisterSingleton<CachedRepositoryConfiguration<Setting>>(
    CachedRepositoryConfiguration<Setting>.Absolute(TimeSpan.FromMinutes(30)));

container.RegisterSingleton<CachedRepositoryConfiguration<Customer>>(
    CachedRepositoryConfiguration<Customer>.Sliding(TimeSpan.FromMinutes(5)));

// Register the 'no caching' configuration as fallback
container.Register(
    typeof(CachedRepositoryConfiguration<>),
    typeof(NoCachingCachedRepositoryConfiguration<>).
    Lifestyle.Singleton);

public sealed class NoCachingCachedRepositoryConfiguration<T>
    : CachedRepositoryConfiguration<T>
{
    public NoCachingCachedRepositoryConfiguration() : base(cache: false) { }
}

第三个选项允许您完全删除有条件的注册。

如何将额外的依赖项/配置注入装饰器 class

How to inject additional dependencies / configuration into a decorated class

.net

c#

dependency-injection

simple-injector