查詢操作:
只查詢一條記錄
Sys_user getSys_userById(Integer userid);
@Override
public Sys_user getSys_userById(Integer userid) {
// TODO Auto-generated method stub
Sys_user s = null;
try(Connection conn = JdbcUtil.getConnections();
PreparedStatement ps = conn.prepareStatement(sql_selectOne)){
ps.setInt(1, userid);
ResultSet rs =ps.executeQuery();
if(rs.next()) {
s = new Sys_user();
s.setUserid(rs.getInt(1));
s.setUsername(rs.getString(2));
s.setRemain(rs.getInt(3));
}
} catch (SQLException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
return s;
}
查詢多條記錄:
List繼承了Collection,是有序的列表。
實現類有ArrayList、LinkedList、Vector、Stack等
1.ArrayList是基於數組實現的,是一個數組隊列。可以動態的增加容量!
2.LinkedList是基於鏈表實現的,是一個雙向循環列表。可以被當做堆棧使用!
3.Vector是基於數組實現的,是一個矢量隊列,是線程安全的!
4.Stack是基於數組實現的,是棧,它繼承與Vector,特性是FILO(先進後出)
public List<Sys_user> getAll() {
// TODO Auto-generated method stub
List<Sys_user> list= new ArrayList<Sys_user>();
try(Connection conn = JdbcUtil.getConnections();
PreparedStatement ps = conn.prepareStatement(sql_selectTwo);
ResultSet rs = ps.executeQuery()){
Sys_user s = new Sys_user();
while(rs.next())
{
s.setUserid(rs.getInt(1));
s.setUsername(rs.getString(2));
s.setRemain(rs.getInt(3));
list.add(s);
}
} catch (SQLException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
return list;
}