bookdbbean.java

自己写的基于JSP+servlet+Javabean的bookshop源代码

package beans;

import java.io.Serializable;
import java.util.ArrayList;
import java.util.Collection;
import java.util.Iterator;
import java.sql.*;
import javax.sql.DataSource;
import javax.naming.Context;
import javax.naming.InitialContext;
import javax.naming.NamingException;

public class BookDBBean implements Serializable
{
    private DataSource ds=null;
    
    public BookDBBean() throws NamingException
    {
        Context ctx = new InitialContext();
        ds = (DataSource) ctx.lookup("java:comp/env/jdbc/bookstore");
    }
    
    /**
    * 得到数据库连接。
    */
    public Connection getConnection() throws SQLException
    {
       return ds.getConnection();
    }
    
    /**
    * 关闭连接对象。
    */
    protected void closeConnection(Connection conn)
    {
        if(conn!=null)
        {
            try
            {
                conn.close();
                conn=null;
            }
            catch (SQLException ex)
            {
                ex.printStackTrace();
            }
        }
    }
    
    /**
    * 关闭Statement对象。
    */
    protected void closeStatement(Statement stmt)
    {
        if(stmt!=null)
        {
            try
            {
                stmt.close();
                stmt=null;
            }
            catch (SQLException ex)
            {
                ex.printStackTrace();
            }
        }
    }
    
    /**
    * 关闭PreparedStatement对象。
    */
    protected void closePreparedStatement(PreparedStatement pstmt)
    {
        if(pstmt!=null)
        {
            try
            {
                pstmt.close();
                pstmt=null;
            }
            catch (SQLException ex)
            {
                ex.printStackTrace();
            }
        }
    }
    
    /**
    * 关闭ResultSet对象。
    */
    protected void closeResultSet(ResultSet rs)
    {
        if(rs!=null)
        {
            try
            {
                rs.close();
                rs=null;
            }
            catch (SQLException ex)
            {
                ex.printStackTrace();
            }
        }
    }
    
    /**
    * 得到数据库中所有的图书信息。
    */
    public Collection<BookBean> getBooks() throws SQLException
    {
        Connection conn=null;
        Statement stmt=null;
        ResultSet rs=null;
        ArrayList<BookBean> bookList=new ArrayList<BookBean>();
        
        try
        {
            conn = getConnection();
            stmt = conn.createStatement();
            rs = stmt.executeQuery("select * from bookinfo");
            while (rs.next())
            {
            
                BookBean book = new BookBean(rs.getInt(1), rs.getString(2), rs.getString(3),
                                             rs.getString(4), rs.getString(5),
                                             rs.getFloat(6), rs.getInt(7),
                                             rs.getString(8));
                 bookList.add(book);
            }
            return bookList;
        }
        finally
        {
            closeResultSet(rs);
            closeStatement(stmt);
            closeConnection(conn);
        }
    }
    
    /**
    *得到选择的图书信息。
    */
    public BookBean getBook(int bookId) throws SQLException
    {
        Connection conn=null;
        PreparedStatement pstmt=null;
        ResultSet rs=null;
        
        try
        {
            conn = getConnection();
            pstmt = conn.prepareStatement("select * from bookinfo where id = ?");
            pstmt.setInt(1,bookId);
            rs=pstmt.executeQuery();
            BookBean book=null;
            if(rs.next())
            {
                 book= new BookBean(rs.getInt(1), rs.getString(2), rs.getString(3),
                                    rs.getString(4), rs.getString(5),
                                    rs.getFloat(6), rs.getInt(7),
                                    rs.getString(8));
            }
            return book;
        }
        finally
        {
            closeResultSet(rs);
            closePreparedStatement(pstmt);
            closeConnection(conn);
        }
    }
    
    /**
    * 通过关键字搜索图书的信息。
    */
    public Collection<BookBean> searchBook(String keyword) throws SQLException
    {
        Connection conn=null;
        Statement stmt=null;
        ResultSet rs=null;
        
        ArrayList<BookBean> bookList=new ArrayList<BookBean>();
        try
        {
            conn=getConnection();
            stmt=conn.createStatement();
            String sql="select * from bookinfo where title like '%"+keyword+"%'";
            rs=stmt.executeQuery(sql);
            
            while (rs.next())
            {
            
                BookBean book = new BookBean(rs.getInt(1), rs.getString(2), rs.getString(3),
                                             rs.getString(4), rs.getString(5),
                                             rs.getFloat(6), rs.getInt(7),
                                             rs.getString(8));
                bookList.add(book);
            }
            return bookList;
        }
        finally
        {
            closeResultSet(rs);
            closeStatement(stmt);
            closeConnection(conn);
        }
    }
    
    /**
    * 判断剩余的图书的数量是否大于客户购买的数量。
    */
    public boolean isAmountEnough(int bookId, int quantity) throws SQLException
    {
        Connection conn=null;
        Statement stmt=null;
        ResultSet rs=null;
        boolean bEnough=false;
        try
        {
            conn=getConnection();
            stmt=conn.createStatement();
            rs=stmt.executeQuery("select amount from bookinfo where id = "+bookId);
            while(rs.next())
            {
                int amount=rs.getInt(1);
                if(amount >= quantity)
                    bEnough=true;
            }
        }
        finally
        {
            closeResultSet(rs);
            closeStatement(stmt);
            closeConnection(conn);
        }
        return bEnough;
    }
    
    /**
    * 购买购物车中所有的图书。
    */
    public synchronized void buyBooks(CartBean cart) throws SQLException
    {
        Connection conn=null;
        PreparedStatement pstmt=null;
        Iterator<CartItemBean> it=cart.getItems().iterator();
        try
        {
            conn=getConnection();
            String sql="update bookinfo set amount = amount - ? where id = ?";
            pstmt=conn.prepareStatement(sql);
            
            while(it.hasNext())
            {
                CartItemBean item=(CartItemBean)it.next();
                BookBean book=item.getBook();
                int bookId=book.getId();
                int quantity=item.getQuantity();
                
                pstmt.setInt(1,quantity);
                pstmt.setInt(2,bookId);
                
                pstmt.addBatch();
            }
            
            pstmt.executeBatch();
        }
        finally
        {
        	closePreparedStatement(pstmt);
            closeConnection(conn);
        }
    }
}