JAVA-DAO實現批量刪除

表結構

CREATE TABLE `user` (
  `u_id` int(11) NOT NULL AUTO_INCREMENT,
  `u_name` varchar(255) NOT NULL,
  `u_password` varchar(255) NOT NULL,
  `u_realname` varchar(255) NOT NULL,
  `u_email` varchar(255) DEFAULT NULL,
  `u_r_id` int(10) NOT NULL,
  `u_status` int(11) NOT NULL,
  PRIMARY KEY (`u_id`),
  KEY `ur_fk` (`u_r_id`),
  CONSTRAINT `ur_fk` FOREIGN KEY (`u_r_id`) REFERENCES `role` (`role_id`)
) ENGINE=InnoDB AUTO_INCREMENT=6 DEFAULT CHARSET=utf8

DAO層

//方法一:拼接sql語句
//刪除多個user ,需要傳入一個userid 數組，userid 必須是主鍵
//sql語句： delete  from `user` where u_id in (1，2，3);
public int deleteMultiUser(String[] userids) {
        this.getConn();
        String sql = "delete  from `user` where u_id in (?";
        StringBuffer sqlbuf = new StringBuffer(sql);
        try {
        //拼接sqlbuf，兩種情況 
            if (userids.length == 1) {
            //有1條時， 直接加 "）"結束
                sqlbuf.append(")");
            }else{
            //有多條時候，拼接length-1 次，因爲初始sql語句已經有一次了。"delete  from `user` where u_id in (? "
                for (int i = 0; i < userids.length-1; i++) {
                    sqlbuf.append(",?");

                }
                //最後拼接" )"  圓滿完成拼接sql
                sqlbuf.append(")");
            }
            System.out.println(sqlbuf.toString());
            this.ps = conn.prepareStatement(sqlbuf.toString());
            if (userids.length == 1) {
                ps.setString(1, userids[0]);
            }else{

                for (int i = 1; i <= userids.length; i++) {
                    ps.setString(i, userids[i-1]);
                    //userids[i-1] 因爲數據下標從0 開始。     
                }
            }
            return st.executeUpdate();

        } catch (SQLException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        } finally {
            this.close(conn, st, res);
        }
        return 0;
    }

//方法二：批處理
//返回1 爲成功，0 爲失敗
public int deleteMultiUser(String[] userids) {
        this.getConn();
        String sql = "delete  from `user` where u_id = ?";
        try {
            ps = conn.prepareStatement(sql);
            for (String userid : userids) {
                ps.setString(1, userid);
                ps.addBatch();
            }
            ps.executeBatch();
            return 1;
        } catch (SQLException e) {
            e.printStackTrace();
        } finally {
            this.close(conn, st, res);
        }
        return 0;
    }