探索设计模式的魅力：了解Object Pool（对象池）

最编程 2024-08-06 13:08:28

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1 namespace ObjectPoolPattern.Implementation1 2 { 3 public abstract class ObjectPool<T> 4 { 5 private TimeSpan _expirationTime; 6 private Dictionary<T, DateTime> _unlocked; 7 private Dictionary<T, DateTime> _locked; 8 private readonly object _sync = new object(); 9 10 public ObjectPool() 11 { 12 _expirationTime = TimeSpan.FromSeconds(30); 13 _locked = new Dictionary<T, DateTime>(); 14 _unlocked = new Dictionary<T, DateTime>(); 15 } 16 17 public ObjectPool(TimeSpan expirationTime) 18 : this() 19 { 20 _expirationTime = expirationTime; 21 } 22 23 protected abstract T Create(); 24 25 public abstract bool Validate(T reusable); 26 27 public abstract void Expire(T reusable); 28 29 public T CheckOut() 30 { 31 lock (_sync) 32 { 33 T reusable = default(T); 34 35 if (_unlocked.Count > 0) 36 { 37 foreach (var item in _unlocked) 38 { 39 if ((DateTime.UtcNow - item.Value) > _expirationTime) 40 { 41 // object has expired 42 _unlocked.Remove(item.Key); 43 Expire(item.Key); 44 } 45 else 46 { 47 if (Validate(item.Key)) 48 { 49 // find a reusable object 50 _unlocked.Remove(item.Key); 51 _locked.Add(item.Key, DateTime.UtcNow); 52 reusable = item.Key; 53 break; 54 } 55 else 56 { 57 // object failed validation 58 _unlocked.Remove(item.Key); 59 Expire(item.Key); 60 } 61 } 62 } 63 } 64 65 // no object available, create a new one 66 if (reusable == null) 67 { 68 reusable = Create(); 69 _locked.Add(reusable, DateTime.UtcNow); 70 } 71 72 return reusable; 73 } 74 } 75 76 public void CheckIn(T reusable) 77 { 78 lock (_sync) 79 { 80 _locked.Remove(reusable); 81 _unlocked.Add(reusable, DateTime.UtcNow); 82 } 83 } 84 } 85 86 public class DatabaseConnection : IDisposable 87 { 88 // do some heavy works 89 public DatabaseConnection(string connectionString) 90 { 91 } 92 93 public bool IsOpen { get; set; } 94 95 // release something 96 public void Dispose() 97 { 98 } 99 } 100 101 public class DatabaseConnectionPool : ObjectPool<DatabaseConnection> 102 { 103 private string _connectionString; 104 105 public DatabaseConnectionPool(string connectionString) 106 : base(TimeSpan.FromMinutes(1)) 107 { 108 this._connectionString = connectionString; 109 } 110 111 protected override DatabaseConnection Create() 112 { 113 return new DatabaseConnection(_connectionString); 114 } 115 116 public override void Expire(DatabaseConnection connection) 117 { 118 connection.Dispose(); 119 } 120 121 public override bool Validate(DatabaseConnection connection) 122 { 123 return connection.IsOpen; 124 } 125 } 126 127 public class Client 128 { 129 public static void TestCase1() 130 { 131 // Create the ConnectionPool: 132 DatabaseConnectionPool pool = new DatabaseConnectionPool( 133 "Data Source=DENNIS;Initial Catalog=TESTDB;Integrated Security=True;"); 134 135 // Get a connection: 136 DatabaseConnection connection = pool.CheckOut(); 137 138 // Use the connection 139 140 // Return the connection: 141 pool.CheckIn(connection); 142 } 143 } 144 }

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