[英]Return generic types from an sql query method
I am trying to return generic types from a sql query method but I am stuck on assigning the value from database to the generic type: 我正在尝试从sql查询方法返回泛型类型,但我坚持将数据库中的值分配给泛型类型:
public static <T extends Comparable<T>> T selectQuery(Connection conn, String sql, T[] parameters) {
T value = null;
try {
PreparedStatement ps = conn.prepareStatement(sql);
List<T> list = Arrays.asList(parameters);
for (T param : list) {
if (param instanceof String) {
ps.setString(list.indexOf(param), (String) param);
} else if (param instanceof Integer) {
ps.setInt(list.indexOf(param), (Integer) param);
} else if (param instanceof Double) {
ps.setDouble(list.indexOf(param), (Double) param);
}
}
ResultSet rs = ps.executeQuery();
while (rs.next()) {
//AM STUCK RIGHT HERE************
}
Conn.closeConn(conn);
} catch (Exception asd) {
System.out.println(asd.getMessage());
}
return value;
}
Please help me with suggestions to this challenge. 请帮助我提供有关此挑战的建议。
int i=0;
while (rs.next())
{
int type=rs.getMetaData().getColumnTypeName(i);
if(type ==Types.INTEGER)
value = (T) rs.getInt();
else if(type ==Types.DOUBLE)
value = (T) rs.getDouble();
else if(type ==Types.FLOAT)
value = (T) rs.getFloat();
else if(type ==Types.VARCHAR)
value = (T) rs.getString();
else if(type ==Types.LONG)
value = (T) rs.getLong();
}
For further reference on Types in sql 有关sql中的类型的更多参考
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