JAVA-DAO实现批量删除

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表结构

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层

//方法一:拼接sql语句//删除多个user ,需要传入一个userid 数组，userid 必须是主键//sql语句： 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，两种情况             if (userids.length == 1) {            //有1条时， 直接加 "）"结束                sqlbuf.append(")");            }else{            //有多条时候，拼接length-1 次，因为初始sql语句已经有一次了。"delete  from `user` where u_id in (? "                for (int i = 0; i < userids.length-1; i++) {                    sqlbuf.append(",?");                }                //最后拼接" )"  圆满完成拼接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] 因为数据下标从0 开始。                     }            }            return st.executeUpdate();        } catch (SQLException e) {            // TODO Auto-generated catch block            e.printStackTrace();        } finally {            this.close(conn, st, res);        }        return 0;    }

//方法二：批处理//返回1 为成功，0 为失败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;    }

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