DB.java

package wyf.hxl;
import java.sql.*;
import java.util.*;
import javax.sql.*;
import javax.naming.*;
public class DB
{
    private static int quantity=2;//初始页码数为2
    public static void setQuantity(int n)//修改页码
    {
        quantity=n;
    }
    public static int getQuantity()//获取yema
    {
        return quantity;
    }
    public static boolean selectMsg(String sql)//获取信息返回值为布尔型
    {
        boolean flag = false;
        Try//读取数据库配置文件，获取sql语句执行产生结果
        {   
            Context initial = new InitialContext();//初始化上下文  
            //其中mysql为数据源jndi名称         
            DataSource ds = (DataSource)initial.lookup("java:comp/env/jdbc/chaoshids");
            Connection con=ds.getConnection();//得到连接
            Statement st = con.createStatement();//声明语句
            ResultSet rs = st.executeQuery(sql); //执行语句得到结果集
            if(rs.next())
            {
                flag = true;
            }            
            rs.close();//关闭结果集
            st.close();//关闭语句
            con.close();//归还连接
        }
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