webmsgdao.java

新闻,新闻类别管理,批量删除,不同的用户登陆

package cn.edu.zucc.news.model;

import java.sql.*;
import java.util.*;

public class WebMsgDAO {
	private Connection conn = null;
    private Statement st = null;
    public WebMsgDAO() {
        try {
            Class.forName("com.microsoft.jdbc.sqlserver.SQLServerDriver");
            conn = DriverManager
                    .getConnection(
                            "jdbc:microsoft:sqlserver://localhost:1433;DatabaseName=j2ee_news",
                            "sa", "123456");
            st = conn.createStatement();
        } catch (Exception ex) {
            ex.printStackTrace();
        }
    }

    public synchronized void release() {
        if (st != null) {
            try {
                st.close();
            } catch (Exception e) {
            }
        }
        if (conn != null) {
            try {
                conn.close();
            } catch (Exception e) {
            }
        }
    }

    public synchronized List loadAllMsgs() throws Exception{
        List result = new ArrayList();
        try {
            ResultSet rs = st.executeQuery("select * from tb_msg");
            while (rs.next()) {
                WebMsg msg=new WebMsg();
                msg.setMsg_id(rs.getInt("msg_id"));
                msg.setUserid(rs.getString("userid"));
                msg.setMsg(rs.getString("msg"));
                msg.setSend_time(rs.getDate("send_time"));
                result.add(msg);
            }
        } catch (Exception ex) {
            ex.printStackTrace();
            throw new Exception("数据库查询错误");
        }
        return result;
    }
    public synchronized void addMsg(String userid,String msgs) throws Exception{
        try {
            String sql="insert into tb_msg(userid,msg,send_time) values('"+userid+"','"+msgs+"',getDate())";
            st.execute(sql);
        } catch (SQLException ex) {
            ex.printStackTrace();
            throw new Exception("数据库错误");
        }
        
    }
 
    public synchronized void delMsg(int msg_id) throws Exception{
        try {
            ResultSet rs = st.executeQuery("select * from tb_msg where msg_id='"+msg_id+"'");
            if (!rs.next()) {
                throw new Exception("留言不存在");
            }
            String sql="delete from tb_msg where msg_id='"+msg_id+"'";
            st.execute(sql);
        } catch (SQLException ex) {
            ex.printStackTrace();
            throw new Exception("数据库错误");
        }
    }
    public synchronized WebMsg readMsg(int msg_id) throws Exception{
        WebMsg result=null;
        try {
            ResultSet rs = st.executeQuery("select * from tb_msg where msg_id='"+msg_id+"'");
            if (rs.next()) {
                result=new WebMsg();
                result.setMsg_id(rs.getInt("msg_id"));
                result.setUserid(rs.getString("userid"));
                result.setMsg(rs.getString("msg"));
                result.setSend_time(rs.getDate("send_time"));
            }
        } catch (Exception ex) {
            ex.printStackTrace();
            throw new Exception("数据库查询错误");
        }        
        return result;
    }
}