dbhelper.java~24~

一个java

package bookstore.util;

import bookstore.ejb.*;

import java.sql.*;
import javax.sql.*;

/**
 * This class contains helper methods for components
 * that access Cloudscape databases.
 */

public final class DBHelper
{

    // The getNext<name>Id methods retrieve the next unique
    // primary key.

    public static final String getNextCustomerID(Connection con)
        throws SQLException
    {
        String customerID;
        int i;
        System.out.println("DBHelper getNextAccountId");
        customerID=getNextId(con, "CustomerID");
        i=8-customerID.length();//设定ID长度为10,"CT" 已经占去两位,还有8位,减去整数部分的长度,
                                //位数全填零剩下的
        while(i>0)
        {
          customerID="0"+customerID;
          i=i-1;
        }//while
        customerID="CT"+customerID;
        return customerID;
    } // getNextCustomerId

    public static final String getNextBasketID(Connection con)
        throws SQLException
    {
        String basketID;
        int i;
        System.out.println("DBHelper getNextBasketID");
        basketID=getNextId(con, "BasketID");
        i=8-basketID.length();//设定ID长度为10,"CT" 已经占去两位,还有8位,减去整数部分的长度,
                                //位数全填零剩下的
        while(i>0)
        {
          basketID="0"+basketID;
          i=i-1;
        }//while
        basketID="BK"+basketID;
        return basketID;
    } // getNextBasketId

    public static final String getNextCommentID(Connection con)
            throws SQLException
        {
            String commentID;
            int i;
            System.out.println("DBHelper getNextCommentID");
            commentID=getNextId(con, "CommentID");
            i=8-commentID.length();//设定ID长度为10,"CT" 已经占去两位,还有8位,减去整数部分的长度,
                                    //位数全填零剩下的
            while(i>0)
            {
              commentID="0"+commentID;
              i=i-1;
            }//while
            commentID="CM"+commentID;
            return commentID;
        } // getNextCommentId

        public static final String getNextManagerID(Connection con)
                throws SQLException
            {
                String managerID;
                int i;
                System.out.println("DBHelper getNextmanagerID");
                managerID=getNextId(con, "managerID");
                i=8-managerID.length();//设定ID长度为10,"CT" 已经占去两位,还有8位,减去整数部分的长度,
                                        //位数全填零剩下的
                while(i>0)
                {
                  managerID="0"+managerID;
                  i=i-1;
                }//while
                managerID="MG"+managerID;
                return managerID;
            } // getNextmanagerId



    private static final String getNextId(Connection con, String field)
        throws SQLException
    {

        System.out.println("DBHelper getNextId");

        String selectStatement =
                "select "+field+" from MaxIDs";
        System.out.println(selectStatement);
        String updateStatement =
                "update MaxIDs " +
                "set "+ field + " = "+ field + " +1 ";
        System.out.println(updateStatement);

        PreparedStatement prepSelect =
                con.prepareStatement(selectStatement);
        PreparedStatement prepUpdate =
                con.prepareStatement(updateStatement);

        prepUpdate.executeUpdate();
        ResultSet rs = prepSelect.executeQuery();
        rs.next();
        int i = rs.getInt(1);
        rs.close();
        prepSelect.close();
        prepUpdate.close();

        if (i <= 0) {
            throw new SQLException
            ("Field "+field+" in table MaxIDs is empty.");
        }

        return Integer.toString(i);

    } // getNextId

} // class