=Nullable and it supportion in TypeHandler

Data/include/Poco/Data/Nullable.h

@@ -0,0 +1,220 @@
+//
+// Nullable.h
+//
+// $Id: //poco/Main/Data/include/Poco/Data/Nullable.h#1 $
+//
+// Library: Data
+// Package: DataCore
+// Module:  Nullable
+//
+// Definition of the Nullable class.
+//
+// Copyright (c) 2008, Applied Informatics Software Engineering GmbH.
+// and Contributors.
+//
+// Permission is hereby granted, free of charge, to any person or organization
+// obtaining a copy of the software and accompanying documentation covered by
+// this license (the "Software") to use, reproduce, display, distribute,
+// execute, and transmit the Software, and to prepare derivative works of the
+// Software, and to permit third-parties to whom the Software is furnished to
+// do so, all subject to the following:
+// 
+// The copyright notices in the Software and this entire statement, including
+// the above license grant, this restriction and the following disclaimer,
+// must be included in all copies of the Software, in whole or in part, and
+// all derivative works of the Software, unless such copies or derivative
+// works are solely in the form of machine-executable object code generated by
+// a source language processor.
+// 
+// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+// FITNESS FOR A PARTICULAR PURPOSE, TITLE AND NON-INFRINGEMENT. IN NO EVENT
+// SHALL THE COPYRIGHT HOLDERS OR ANYONE DISTRIBUTING THE SOFTWARE BE LIABLE
+// FOR ANY DAMAGES OR OTHER LIABILITY, WHETHER IN CONTRACT, TORT OR OTHERWISE,
+// ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
+// DEALINGS IN THE SOFTWARE.
+//
+
+
+#ifndef Data_Nullable_INCLUDED
+#define Data_Nullable_INCLUDED
+
+#include "Poco/Data/AbstractBinder.h"
+#include <iostream>
+
+//using namespace Poco::Data::Keywords;
+//using Poco::Data::NullData;
+   
+namespace Poco {
+namespace Data {
+           
+template <typename T>
+class Nullable {
+    /// Nullable class - template for field, that can be null
+public:
+    Nullable()
+        : _value(), _isNull(true) 
+        /// Creates the Nullable.
+    {
+    }
+
+    Nullable(const T& value)
+        : _value(value), _isNull(false) 
+        /// Creates the Nullable from value
+    {
+    }
+
+    Nullable(const NullData&)
+        : _value(), _isNull(true) 
+        /// Creates the Nullable from null
+    {
+    }
+
+    Nullable& operator=(const T& value)
+        /// Assigns new value to Nullable
+    {
+        _isNull = false;
+        _value = value;
+        return *this;
+    }
+
+    Nullable& operator=(const Nullable<T>& other)
+        /// Assigns other Nullable to Nullable
+    {
+        _isNull = other._isNull;
+        _value = other._value;
+        return *this;
+    }
+
+    Nullable& operator=(const NullData&)
+        /// Assigns null to Nullable
+    {
+        _isNull = true;
+        return *this;
+    }
+
+    bool operator==(const Nullable<T>& other) const
+        /// Compares two Nullable
+    {
+        return (_isNull && other._isNull) || (_isNull == other._isNull && _value == other._value);
+    }
+
+    bool operator==(const T& value) const
+        /// Compares Nullable with value
+    {
+        return (!_isNull && _value == value);
+    }
+
+    bool operator==(const NullData&) const
+        /// Compares Nullable with null
+    {
+        return _isNull;
+    }
+
+    bool operator!=(const NullData&) const
+        /// Compares Nullable for non null
+    {
+        return !_isNull;
+    }
+
+    bool operator!=(const T& value) const
+        /// Compares Nullable with value for non equal
+    {
+        return (_isNull || _value != value);
+    }
+
+    bool operator < (const Nullable<T>& other) const
+        /// Compares two Nullable 
+    {
+        if (_isNull < other._isNull)
+            return true;
+        return (_value < other._value);
+    }
+
+    operator T& ()
+        /// Get referens to value
+    {
+        return _value;
+    }
+
+    operator const T& () const
+        /// Get const referens to value
+    {
+        return _value;
+    }
+
+    bool isNull() const
+        /// Test Nullable for null
+    { 
+        return _isNull; 
+    }
+
+    void setNull(bool isNull)
+        /// Change Nullable "isNull" sign
+    {
+        _isNull = isNull; 
+    }
+
+    const T& getValue() const
+        /// Get value
+    { 
+        return _value; 
+    }
+
+    void setValue(const T& value)
+        /// Set value
+    { 
+        _isNull = false; _value = value; 
+    }
+
+private:
+
+    T _value;
+    bool _isNull;
+};
+
+//
+// operators
+//
+
+template <typename T>
+bool operator == (const T& value, const Nullable<T>& nValue) 
+{
+    return (!nValue.isNull() && value == nValue.getValue());
+}
+
+template <typename T>
+bool operator != (const T& value, const Nullable<T>& nValue) 
+{
+    return (nValue.isNull() || value != nValue.getValue());
+}
+
+template <typename T>
+bool operator == (const NullData&, const Nullable<T>& nValue) 
+{
+    return nValue.isNull();
+}
+
+template <typename T>
+bool operator != (const NullData&, const Nullable<T>& nValue) 
+{
+    return !nValue.isNull();
+}
+
+template <typename T>
+std::ostream& operator<<(std::ostream& out, const Nullable<T>& obj) 
+{
+    if (obj.isNull()) 
+    {
+        out << "NULL";
+    }
+    else 
+    {
+        out << obj.getValue();
+    }
+    return out;
+}
+  
+} } // namespace Poco::Data
+
+#endif // Data_Nullable_INCLUDED