关于servlet的链表操作，现在只剩下一个将链表存入mysql的函数（saveNode()）有毛病了，实在想不出来，大家帮看看，先谢谢了！
import java.util.Scanner;import java.io.*; import javax.servlet.*;import javax.servlet.http.*;import java.sql.*;class Node { public int BookStore; //图书库存量 public String BookNo; //图书编号 public String BookName; //图书名称 public int BookLend; //图书上架数量 public String BookPublishing;//图书出版社 public Node Next; //指向下一个Node对象的对象引用 public Node(){//只有一个节点 BookNo="000000"; BookName="书名未初始化"; BookLend=0; BookStore=0; BookPublishing="出版社未初始化"; Next = null; } public Node(Node eNext,Node t){//不止一个节点 BookNo=t.BookNo; BookName=t.BookName; BookLend=t.BookLend; BookStore=t.BookStore; BookPublishing=t.BookPublishing; Next = eNext; } public void setData(int eBookStore,int eBookLend,String eBookNo,String eBookName,String eBookPublishing){ //设置当前结点的值 BookNo = eBookNo; BookName = eBookName; BookPublishing = eBookPublishing; BookLend = eBookLend; BookStore = eBookStore; } public Node getData() {//获取当前节点的值 Node rNode =new Node(); rNode.BookNo=BookNo; rNode.BookName=BookName; rNode.BookPublishing=BookPublishing; rNode.BookLend=BookLend; rNode.BookStore=BookStore; rNode.Next=Next; return rNode; } public void setNext(Node dNext){ //设置当前节点的指针 Next = dNext; } //修改指针 public Node getNext() { //获取当前节点的指针 return Next; } //获得指向的对象引用}class LinkList {private Node firstNode;private Node headNode=firstNode;String htm="";public LinkList() { firstNode = null;}//建立空链表 public String visitAllNode(){//遍历表中每个结点，并串成一个字符串Node nextNode = firstNode; String s = "<table><tr><td>书号</td><td>书名</td><td>库存量</td><td>上架数量</td><td>出版社</td></tr>"; while (nextNode != null) { Node number = nextNode.getData(); s = s +"<tr>"; s = s +"<td>"+number.BookNo + "</td>"; s = s +"<td>"+number.BookName + "</td>"; s = s +"<td>"+number.BookStore + "</td>"; s = s +"<td>"+number.BookLend + "</td>"; s = s +"<td>"+number.BookPublishing + "</td></tr>"; nextNode = nextNode.getNext(); }s+="</table>";return s; }public String vN(){//遍历表中每个结点，并串成一个字符串Node nextNode = firstNode; String s = "<table><tr><td>书号</td><td>书名</td><td>库存量</td><td>上架数量</td><td>出版社</td></tr>";if(nextNode==null){ s="没有可供删除的结点！";}else{while (nextNode != null) { Node number = nextNode.getData(); s = s +"<tr>"; s = s +"<td>"+number.BookNo + "</td>"; s = s +"<td>"+number.BookName + "</td>"; s = s +"<td>"+number.BookStore + "</td>"; s = s +"<td>"+number.BookLend + "</td>"; s = s +"<td>"+number.BookPublishing + "</td>"; s = s +"<td><a href=\"DemoLink?menu=1&no="+number.BookNo+"\" target=\"_self\">删 除</a></td></tr>"; nextNode = nextNode.getNext();}s+="</table>";}return s; }public void insertAtEnd(Node tt) //在链表后插入结点{ firstNode = new Node(firstNode,tt);}public void deleteAtID(String data)//删除指定的节点{ int flag=0; Node tempNode = firstNode; Node headNode = tempNode; if(firstNode == null) htm="这是一个空链表,没有可供删除的结点!"; else { if(firstNode.BookNo.equals(data)) { firstNode=firstNode.getNext(); } else { while(firstNode!=null) { if(firstNode.BookNo.equals(data)) { tempNode.setNext(firstNode.getNext()); firstNode=headNode; flag=1; htm="<script language=\"javascript\"> self.location.href=\"DemoLink?menu=4\"</script>"; break; } else { tempNode=firstNode; firstNode=firstNode.getNext(); } } if(flag ==0 ) { htm="链表中没有你要删除的节点"; } } }}public void saveNode(){ String driver = "com.mysql.jdbc.Driver"; // 驱动程序名 String url = "jdbc:mysql://localhost/book"; // URL指向要访问的数据库名scutcs String user = "root"; // MySQL配置时的用户名 String password = "6868932"; // MySQL配置时的密码 String sql = ""; try { Class.forName(driver); // 加载驱动程序 Connection conn = DriverManager.getConnection(url, user, password);// 连续数据库 Statement statement = conn.createStatement(); // statement用来执行SQL语句 if(firstNode == null) htm="这是一个空链表,没有可供存储的结点!"; else { while(firstNode!=null) { sql="insert into book(BookNo,BookName,BookLend,BookStore,BookPublishing) values(firstNode.BookNo,firstNode.BookName,first.BookLend,first.BookStore,first.BookPublishing)"; statement.executeUpdate(sql); firstNode=firstNode.getNext(); } } } catch(ClassNotFoundException e) { htm= e.toString(); }catch(SQLException e) { htm= e.toString(); }catch(Exception e) { htm= e.toString(); }} public LinkList readNode(){Node h=new Node(); LinkList listNull = new LinkList(); h=firstNode; String driver = "com.mysql.jdbc.Driver"; // 驱动程序名 String url = "jdbc:mysql://localhost/book"; // URL指向要访问的数据库名scutcs String user = "root"; // MySQL配置时的用户名 String password = "6868932"; // MySQL配置时的密码 Node t1=new Node(); t1.Next=null; try { Class.forName(driver); // 加载驱动程序 Connection conn = DriverManager.getConnection(url, user, password);// 连续数据库 //if(!conn.isClosed()) // return htm="Succeeded connecting to the Database!"; Statement statement = conn.createStatement(); // statement用来执行SQL语句 String sql = "select * from book"; // 要执行的SQL语句 ResultSet rs = statement.executeQuery(sql); // 结果集 String BookNo = null; String BookName=null; String BookPublishing=null; while(rs.next()) { t1.BookNo = rs.getString("BookNo"); // 数据库编码为utf-8时的输出方式 // 数据库未使用utf-8时的输出方式：首先使用ISO-8859-1字符集将选定字段解码为字节序列并将结果存储新的字节数组中。 // 然后使用utf-8字符集解码指定的字节数组 //BookNo = new String(rs.getString("BookNo").getBytes("ISO-8859-1"),"utf-8"); t1.BookName = rs.getString("BookName"); //BookName = new String(rs.getString("BookName").getBytes("ISO-8859-1"),"utf-8"); t1.BookPublishing = rs.getString("BookPublishing"); //BookPublishing = new String(rs.getString("BookPublishing").getBytes("ISO-8859-1"),"utf-8"); t1.BookLend = rs.getInt("BookLend"); t1.BookStore= rs.getInt("BookStore"); listNull.insertAtEnd(t1); } //htm=listNull.showNode(); rs.close(); conn.close(); return listNull; } catch(ClassNotFoundException e) { htm= e.toString(); }catch(SQLException e) { htm= e.toString(); }catch(Exception e) { htm= e.toString(); } return listNull;}public String showNode(){ if(firstNode == null) return htm="这是一个空链表!"; else return htm=visitAllNode(); }}public class DemoLink extends HttpServlet{ String htm=""; LinkList listNull = new LinkList(); LinkList list = new LinkList(); public static void main(String args[]){ } public void doPost(HttpServletRequest req,HttpServletResponse resp) throws ServletException,IOException { resp.setContentType("text/html;charset=utf-8"); Node tt=new Node(); String BN=new String(req.getParameter("BookNo").getBytes("ISO-8859-1"),"utf-8"); String B =new String(req.getParameter("BookName").getBytes("ISO-8859-1"),"utf-8"); String BP=new String(req.getParameter("BookPublishing").getBytes("ISO-8859-1"),"utf-8"); int L =Integer.valueOf(req.getParameter("BookLend")).intValue(); int S =Integer.valueOf(req.getParameter("BookStore")).intValue(); tt.BookNo=BN; tt.BookName=B; tt.BookPublishing=BP; tt.BookLend=L; tt.BookStore=S; listNull.insertAtEnd(tt); resp.sendRedirect("DemoLink?menu=3"); } public void doGet(HttpServletRequest req,HttpServletResponse resp) throws ServletException,IOException { String menu=req.getParameter("menu"); resp.setContentType("text/html;charset=utf-8"); int xz=Integer.valueOf(menu).intValue(); switch(xz){ case 1: String delno=req.getParameter("no"); listNull.deleteAtID(delno); htm=listNull.showNode(); break; case 2: htm=listNull.showNode(); break; case 3: htm="<table><form method=\"post\" action=\"DemoLink\">"+ "<tr><td>图书编号：</td><td><input name=\"BookNo\" type=\"text\" /></td></tr>"+ "<tr><td>图书名称：</td><td><input name=\"BookName\" type=\"text\" /></td></tr>"+ "<tr><td>上架数量：</td><td><input name=\"BookLend\" type=\"text\" /></td></tr>"+ "<tr><td>库 存 量：</td><td><input name=\"BookStore\" type=\"text\" /></td></tr>"+ "<tr><td>出 版 社：</td><td><input name=\"BookPublishing\" type=\"text\" /></td></tr>"+ "<tr><td><input type=\"submit\" value=\"确 定\" /> <input value=\"重 置\" type=\"reset\" />"+ "</form></table>"; break; case 4: htm=listNull.vN(); break; case 5: listNull.saveNode(); //listNull=listNull.readNode(); htm=listNull.showNode(); break; case 6: listNull=listNull.readNode(); //list=listNull; htm=listNull.showNode(); break; default: htm="参数调用不合法！"; break; } PrintWriter out=resp.getWriter(); out.println("<html>"); out.println("<meta http-equiv=\"content-type\" content=\"text/html; charset=utf-8\">"); out.println("<head><title></title>"); out.println("<SCRIPT LANGUAGE=\"JavaScript\" type=\"text/javascript\" src=\"node.js\"></SCRIPT>"); out.println("</head><body>"); out.println(htm); out.println("</body></html>"); out.close(); }}