如何实现树形目录的递归功能？
<%@ page contentType="text/html; charset=gb2312" language="java" import="java.sql.*" errorPage="" %>
<!-- 数据库结构： 库名：test 表名：tree CREATE TABLE [dbo].[tree] ( [id] [int] IDENTITY (1, 1) NOT NULL , [parentid] [int] NOT NULL , [message] [varchar] (50) COLLATE Chinese_PRC_CI_AS NULL ) 为了达到比较好的效果，这里准备了五张小图片 加号：plus.gif 减号：minus.gif 打开的文件夹：openfold.gif 关闭的文件夹：closedfold.gif 白板：white.gif --> <%!//方便起见这里就不写成javabean了 class cn {//连接数据库，这里以MS-SQL为例 String jdbcDriver="com.microsoft.jdbc.sqlserver.SQLServerDriver";//jdbc驱动 String connectionString="jdbc:microsoft:sqlserver://localhost:1433;DatabaseName=test";//数据库连接字符串 String user="sa";//数据库用户名 String pass="";//数据库密码 Connection conn=null; ResultSet rs=null;public cn() {
try { Class.forName(jdbcDriver); } catch(ClassNotFoundException e) { System.err.println(e.toString()); } }public ResultSet executeQuery(String sql) {
rs=null; try { conn=DriverManager.getConnection(connectionString,user,pass); Statement stmt=conn.createStatement(ResultSet.TYPE_SCROLL_SENSITIVE,ResultSet.CONCUR_UPDATABLE); rs=stmt.executeQuery(sql); } catch(SQLException e) { System.err.println(e.toString()); } return rs; }public void executeUpdate(String sql) {
try { conn=DriverManager.getConnection(connectionString,user,pass); Statement stmt=conn.createStatement(ResultSet.TYPE_SCROLL_SENSITIVE,ResultSet.CONCUR_UPDATABLE); stmt.executeUpdate(sql); } catch(SQLException e) { System.err.println(e.toString()); } } }class tree {
cn conn=new cn(); public void init(javax.servlet.jsp.JspWriter out,javax.servlet.http.HttpServletRequest request) throws Exception { out.println("<title>用jsp种树</title>"); dowith(request); buildTree(out,0,0);//初始调用 }private void dowith(javax.servlet.http.HttpServletRequest request) {
if(request.getParameter("parentid")==null||request.getParameter("parentid").equals(""))return; String action=request.getParameter("action"); if(action.equals("add")) conn.executeUpdate("insert into tree(parentid,message) values('"+request.getParameter("parentid")+"','"+request.getParameter("message")+"')"); else if(action.equals("delete")) conn.executeUpdate("delete from tree where id="+request.getParameter("parentid")+" or parentid="+request.getParameter("parentid")); }public void buildTree(javax.servlet.jsp.JspWriter out,int parentid,int level) throws Exception {
level++; ResultSet rs=conn.executeQuery("select * from tree where parentid="+parentid+" order by id"); while(rs.next()) { out.println("<div>"); for(int i=0;i<level-1;i++) out.print("<img src=/"white.gif/"> "); if(has_child(rs.getInt("id"))) { out.print("<img alt=/"展开/" style=/"cursor:hand;/" onclick=/"myClick('"+rs.getInt("id")+"');/" id=/"img"+rs.getInt("id")+"/" src=/"plus.gif/"> <img id=/"im"+rs.getInt("id")+"/" src=/"closedfold.gif/"> "); out.print("<span onclick=/"myClick1('"+rs.getInt("id")+"');/" style=/"cursor:default;/" id=/"span"+rs.getInt("id")+"/">"+rs.getString("message")+" id="+rs.getInt("id")+"</span>"); out.println("<div style=/"display:none;/" id=/"div"+rs.getInt("id")+"/">"); buildTree(out,rs.getInt("id"),level);//递归调用 out.println("</div>"); } else out.print("<img src=/"minus.gif/"> <img src=/"openfold.gif/"> <span onclick=/"myClick1('"+rs.getInt("id")+"');/" style=/"cursor:default;/" id=/"span"+rs.getInt("id")+"/">"+rs.getString("message")+" id="+rs.getInt("id")+"</span>"); out.println("</div>"); } rs.close(); rs=null; }private boolean has_child(int parentid) throws Exception {
ResultSet rs=conn.executeQuery("select * from tree where parentid="+parentid+" order by id"); return rs.next(); }public String getOption() throws Exception {
String option=""; ResultSet rs=conn.executeQuery("select * from tree order by id"); while(rs.next()) option+="<option value=/""+rs.getInt("id")+"/">"+rs.getInt("id")+"</option>/n"; return option; } } %> <!--以上代码可以写成javabean--> <script language="JavaScript"><!--这段js为了实现树的展开和关闭的效果--> <!-- function myClick(id) { eval("var div=div"+id); eval("var img=img"+id); eval("var im=im"+id); div.style.display=div.style.display!="none"?"none":"block"; img.src=div.style.display!="none"?"minus.gif":"plus.gif"; im.src=div.style.display!="none"?"openfold.gif":"closedfold.gif"; img.alt=div.style.display!="none"?"关闭":"展开"; } function myClick1(id) { document.form1.parentid.value=id; } //--> </script> <table> <tr><td height="300" valign="top"> <% tree myTree=new tree(); myTree.init(out,request); %> </td></tr> <tr><td valign="top"> <% if(myTree.getOption().equals("")) { %> <form name="form1" action="" method="get"> parentid:0-表示根节点 message:<input type="text" name="message"> <input type="hidden" name="parentid" value="0"> <input type="submit" name="action" value="add"> </form> <%} else {%> <form name="form1" action="" method="get"> parentid:<select name="parentid"><%=myTree.getOption()%></select> message:<input type="text" name="message"> <input type="submit" name="action" value="add"> <input type="submit" name="action" value="delete"> </form> <%}%> </td></tr></table>