如果想要做ORM,将数据映射为对象,则基本的数据类型转换是必要的功能,而Java似乎未提供该功能,只有自己下手来完成该功能.
完成该功能的目标如下:
1: 提供基本的数据转换
2: 考虑转换的性能.
下面是我的具体实现:
1: 接口:
public static <T> T Cast(Class<T> t, Object value)
2: 依赖:需要依赖与获得数据默认值,因为在很多情况下,如果要转换的数据为null,调用者期望的是返回默认值.
系统自动提供的默认值不能满足我们的需求,例如int的默认值为0,但是在sql查询中,如果查询失败,我们期望的是小于0的值,例如Select Count(1) from table1这样的操作.
3: 实现:
/** * 类型转换 * @param t * @param value * @return */ @SuppressWarnings("unchecked") public static <T> T Cast(Class<T> t, Object value) { if (value == null) { return GetDefault(t); } if (t == Object.class) { return (T)value; } try { return Cast_i(t, value); } catch(Exception ex) { ex.printStackTrace(); return GetDefault(t); } } private static String GetStr(Class<?> t, Object value) { if (value == null) { return ""; } if (t == String.class){ return (String)value; }else { return value.toString(); } } @SuppressWarnings("unchecked") private static <T> T Cast_i(Class<T> t, Object value) { Class<?> objClass = value.getClass(); if (t == String.class) { return (T)GetStr(objClass, value); } if (t == int.class) { if (objClass == int.class) { return (T)value; } String text = GetStr(objClass, value); Object ret = Integer.parseInt(text); return (T)ret; } if (t == Integer.class) { if (objClass == Integer.class) { return (T)value; } if (objClass == int.class) { return (T)value; } String text = GetStr(objClass, value); Object ret = Integer.parseInt(text); return (T)ret; } if (t == short.class) { if (objClass == int.class) { return (T)value; } String text = GetStr(objClass, value); Object ret = Short.parseShort(text); return (T)ret; } if (t == boolean.class || t == Boolean.class) { if (objClass == int.class) { Object ret = (int)value >= 1? true:false; return (T)ret; } if (objClass == Integer.class) { Object ret = (Integer)value >= 1? true:false; return (T)ret; } String text = GetStr(objClass, value); Object ret = Integer.parseInt(text); ret = (int)ret >= 1? true:false; return (T)ret; } if (t == long.class) { if (objClass == long.class) { return (T)value; } String text = GetStr(objClass, value); Object ret = Long.parseLong(text); return (T)ret; } if (t == byte.class) { if (objClass == byte.class) { return (T)value; } String text = GetStr(objClass, value); Object ret = Byte.parseByte(text); return (T)ret; } if (t == double.class) { if (objClass == double.class) { return (T)value; } String text = GetStr(objClass, value); Object ret = Double.parseDouble(text); return (T)ret; } if (t == float.class) { if (objClass == float.class) { return (T)value; } String text = GetStr(objClass, value); Object ret = Float.parseFloat(text); return (T)ret; } if (t == BigDecimal.class) { if (objClass == BigDecimal.class) { return (T)value; } String text = GetStr(objClass, value); return (T)new BigDecimal(text); } if (t == java.util.Date.class){ if (objClass == java.util.Date.class) { return (T)value; } String text = GetStr(objClass, value); return (T)HiTypeHelper.Convert2Date(text); } if (t == java.sql.Date.class){ if (objClass == java.sql.Date.class) { return (T)value; } String text = GetStr(objClass, value); return (T)HiTypeHelper.Convert2SqlDate(text); } if (t == Time.class) { if (objClass == Time.class) { return (T)value; } String text = GetStr(objClass, value); Object ret = HiTypeHelper.Convert2Date(text).getTime(); return (T)ret; } if (t == Timestamp.class) { if (objClass == Timestamp.class) { return (T)value; } String text = GetStr(objClass, value); return (T)Timestamp.valueOf(text); } return (T)value; } |