javaweb后端实例 dao

DAO层主要作用在  封装sql语句，并将sql语句获取到的结果存进do创建的集合里面  linklist  arraylist  等

代码实现如下

public class StationDao {
private final String query_sido_by_year = "select stn,wban,station_name,latitude,longitude"
        + " from station_info where end_date >=?";


// 查多个。方法以list开头
// 查一个。方法以get开头
// 如果有查询条件，listxxxByxxx,YYY为条件手段
public List<StationInfoDO> listSIDOByYear(int year) {
List<StationInfoDO> list = new LinkedList<StationInfoDO>();
Connection conn = null;
PreparedStatement ps = null;
ResultSet rs = null;


// 通过调用工具类的静态方法获取数据库的连接对象
try {
conn = JDBCUtils.getConnnection();
ps = conn.prepareStatement(query_sido_by_year);
ps.setString(1, year + "0101");
rs = ps.executeQuery();
int index = 0;
while (rs.next()) {
StationInfoDO SIDO = new StationInfoDO();// 用对象封装散装数据
SIDO.setStn(rs.getString("stn"));
SIDO.setWban(rs.getString("wban"));
SIDO.setStationName(rs.getString("station_name"));
SIDO.setLatitude(rs.getBigDecimal("latitude"));
SIDO.setLongitude(rs.getBigDecimal("longitude"));
list.add(SIDO);
index++;
}
System.out.println(index);
} catch (SQLException e) {
e.printStackTrace();
} finally {
releaseResource(conn, ps, rs);
}
return list;
}


public void releaseResource(Connection conn, PreparedStatement ps, ResultSet rs) {
if (conn != null) {
try {
conn.close();
} catch (SQLException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
;
if (ps != null) {
try {
ps.close();
} catch (SQLException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
if (rs != null) {
try {
rs.close();
} catch (SQLException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}


}
}