basedao.java

是一个简单的在线投票系统

package votetool;
import java.sql.*;
import java.util.*;
public class BaseDao {
    //建立连接
    public Connection getConn(){
        Connection conn=null;
    try {
        Class.forName("com.microsoft.jdbc.sqlserver.SQLServerDriver");
        try {
             conn = DriverManager.getConnection(
                    "jdbc:microsoft:sqlserver://localhost:1433;DataBaseName=votedb",
                    "sa", "sa");
        } catch (SQLException ex1) {
            ex1.printStackTrace();
        }
    } catch (ClassNotFoundException ex) {
        ex.printStackTrace();
    }
        return conn;
    }
    //关闭连接
    public void closeAll(Connection conn,Statement st,ResultSet rs){
        if(rs!=null){
            try {
                rs.close();
            } catch (SQLException ex) {
            }
        }
        if(st!=null){
            try {
                st.close();
            } catch (SQLException ex1) {
            }
        }
        if(conn!=null){
            try {
                conn.close();
            } catch (SQLException ex2) {
            }
        }
    }
    //插入数据
    public int update(String str){
        Connection conn=null;
        Statement st=null;
        int num=0;
        String sql="insert into votetool values('"+str+"')";
        conn=this.getConn();
        try {
            st = conn.createStatement();
            try{
                 num=st.executeUpdate(sql);
            }catch(Exception ex3){
                System.out.println("未选中任何一项！");
            }
        } catch (SQLException ex) {
            ex.printStackTrace();
        }
        finally{
        this.closeAll(conn,st,null);
    }
        return num;
    }
    //查询
    public ArrayList getTicket(){
        Connection conn=null;
        Statement st=null;
        ResultSet rs=null;
        conn=this.getConn();
        ArrayList ls=new ArrayList();
        try {
            st = conn.createStatement();
            rs=st.executeQuery("select * from votetool");

            while(rs.next()){
                Ticket tk=new Ticket();
                tk.setId(rs.getInt(1));
                tk.setItem(rs.getString(2));
                ls.add(tk);
            }
        } catch (SQLException ex) {
            ex.printStackTrace();
        }
        return ls;
    }

    public int getCount(String str){
       Connection conn=null;
       Statement st=null;
       ResultSet rs=null;
       conn=this.getConn();
       int num=0;
       try {
           st = conn.createStatement();
           rs=st.executeQuery("select count(*) from votetool where item='"+str+"'");

           while(rs.next()){
               num=rs.getInt(1);
           }
       } catch (SQLException ex) {
           ex.printStackTrace();
       }
       return num;
   }
   public static void main(String[] args){
       BaseDao db=new BaseDao();
       System.out.println(db.getCount("B"));
   }
}