/// <summary>
/// 初始化服务容器
/// </summary>
/// <param name="serviceName"> 服务约定名称 </param>
/// <param name="serviceType"> 服务约定基类或接口类型 </param>
/// <param name="typeComparer"> 比较2个类型服务的优先级 </param>
/// <param name="logger"> 日志记录器 </param>
/// <exception cref="ArgumentNullException">
/// <paramref name="serviceName" /> and <paramref name="serviceType" /> is all
/// <see langword="null" />.
/// </exception>
/// <exception cref="OverflowException"> 匹配插件数量超过字典的最大容量 (<see cref="F:System.Int32.MaxValue" />)。 </exception>
protected ServiceContainer(string serviceName, Type serviceType, IComparer<Type> typeComparer, TraceSource logger = null)
{
TypeComparer = typeComparer;
_logger = logger ?? LogServices.Logger;
_items = new ConcurrentDictionary<Type, ServiceItem>();
_logger?.Write(TraceEventType.Start, $"开始扫描服务插件 serviceName={serviceName},serviceType={serviceType}");
foreach (var p in MEF.PlugIns.GetPlugIns(serviceName, serviceType).OrderByDescending(p => p.Priority))
{
var value = p.GetValue(serviceType);
if (value == null)
{
continue;
}
var type = GetServiceType(p, value);
if (type == null)
{
continue;
}
var item = new ServiceItem(this, type, value, p);
item.MakeSystem(); //默认为系统插件
if (_items.TryAdd(type, item) == false)
{
_logger?.Write(TraceEventType.Verbose, $"服务插件({value.GetType().FullName})因优先级({p.Priority})过低被抛弃");
}
else
{
_logger?.Write(TraceEventType.Verbose, $"服务插件({value.GetType().FullName}),优先级({p.Priority})装载完成");
}
}
_logger?.Write(TraceEventType.Stop, $"服务插件装载完成,有效服务 {Count} 个");
}
/// <summary>
/// 获取指定类型的服务对象。
/// </summary>
/// <returns>
/// <paramref name="serviceType" /> 类型的服务对象。- 或 -如果没有 <paramref name="serviceType" /> 类型的服务对象，则为 null。
/// </returns>
/// <param name="serviceType"> 一个对象，它指定要获取的服务对象的类型。 </param>
/// <exception cref="Exception"> 构造函数中传入的 value 为 <seealso cref="ServiceCreatorCallback" /> 类型,且执行中出现异常. </exception>
/// <exception cref="ArgumentException"><see cref="serviceType"/> 为 <seealso cref="ServiceItem"/> 类型.</exception>
public ServiceItem GetServiceItem(Type serviceType)
{
if (serviceType == typeof(ServiceItem))
{
throw new ArgumentException($"{nameof(serviceType)}不能是{nameof(ServiceItem)}类型");
}
var child = (Value as IServiceProvider)?.GetService(serviceType); //生成新的服务
if (child == null)
{
return null;
}
var item = new ServiceItem(Container, serviceType, child, PlugIn);
if (IsSystem) //生成服务与当前服务(依赖服务)属性必须一致
{
item.MakeSystem();
}
PropertyChanged += item.ParentPropertyChanged; //当当前服务(依赖服务)发生属性变化时需要通知生成服务
return item;
}