购买网页，myeclipse实现SQL的添加

网页代码

    		<tr align=center>
    			<td colspan=3><a style="color:red;font-size=16px">所有物品:</a></td>
    		</tr>
    		<tr align=center>
	    		<td>物品</td>
	    		<td>价格</td>
	    		<td>购买</td>
    		</tr>
    		<tr align=center>
			<%	caipin n=new caipin();
			ArrayList msg1=n.retrieveAll();
			for(int i=msg1.size()-1;i>=0;i--){
				tuijian nn=(tuijian)msg1.get(i);%>
				<tr align=center>
				<td><%=nn.getCaiming()%></td>
				<td><%=nn.getJiage()%></td>
				<td><a href="add.jsp?jiage=<%=nn.getJiage() %>&caiming=<%=nn.getCaiming()%>&username=<%=check.getUsername()%>" >购买</a></td>
	    		</tr>
			<%}%>

实现对数据库的添加
<%

	String username =request.getParameter("username");
	String caiming = request.getParameter("caiming");
	int jiage =Integer.parseInt(request.getParameter("jiage"));
	Connection conn = null;
	PreparedStatement pstmt = null;
	ResultSet rs = null;
	try{
    	Class.forName("com.microsoft.sqlserver.jdbc.SQLServerDriver");
		conn=DriverManager.getConnection("jdbc:sqlserver://127.0.0.1:1433;DatabaseName=Dinner","sa","sa");
		String sql="select jiage from caipin where caiming=?";
		pstmt=conn.prepareStatement(sql);
		pstmt.setString(1,caiming);
		rs = pstmt.executeQuery();
		if(rs.next()){
			String sql2="insert into yonghudiancan values(?,?,?)";
			pstmt=conn.prepareStatement(sql2);
			pstmt.setString(1,username);
			pstmt.setString(2,caiming);
			pstmt.setInt(3,jiage);
			response.sendRedirect("shopcar.jsp");
			pstmt.executeUpdate();
		}
		else{
			out.println("购买的物品不存在。");
		}
		
		rs.close();
		pstmt.close();
		conn.close();}
	catch(ClassNotFoundException e){
		e.printStackTrace();
	}
	catch(SQLException e){
		e.printStackTrace();
	}
%>