JSP树形菜单的实现(转载)(2009-04-20 15:21:03)转载标签：分类：技术讲解杂谈1。

原理简介dtree是一个免费的javascript脚本，只需定义有限的几个参数，就可以做出漂亮的树型菜单。

下载目录：/javascripts/tree/以下是dtree的用法示例：1）初始化菜单<script type="text/javascript"><!--var Tree = new Array; Tree[0] = "1|0|Page 1|#";Tree[1] = "2|1|Page 1.1|#";Tree[2] = "3|1|Page 1.2|#";Tree[3] = "4|3|Page 1.2.1|#";</script>2）调用函数<div class="tree"><script type="text/javascript"><!--createTree(Tree,1,7); // starts the tree at the top and open it at node nr. 7//--></script></div>显然，如果用动态的脚本来初始化菜单数组（asp,jsp均可），那就可以很方便的实现动态的树型菜单了。

2。

jsp动态实现分以下步骤实现动态的树型菜单：1）在数据库建tree_info表，有nodeId，parentNodeId，nodeName，nodeUrl四个字段，来存储节点信息。

2）编写java类，用于从数据库找出节点信息，并且生成javascript脚本。

3）编写tag类。

用于封装逻辑，简化jsp的开发。

4）建一个web程序进行测试。

3。

详细过程1）在数据库建表，脚本如下：CREATE TABLE `test`.`tree_info` (`node_id` INTEGER UNSIGNED NOT NULL DEFAULT -1,`parent_id` INTEGER UNSIGNED NOT NULL DEFAULT -1,`node_name` VARCHAR(45) NOT NULL,`ref_url` VARCHAR(45) NOT NULL,PRIMARY KEY(`node_id`))我使用mysql数据库，如果脚本细节有出入，请自行修改按照上面的dTree示例插入数据2）编写TreeInfo.java，这个类用于封装节点信息package com.diegoyun.web.tree;public class TreeInfo {private int nodeId = -1;//node idprivate int parentId = -1;//parentIdprivate String nodeName = null;//node nameprivate String url = null;//url referencespublic int getNodeId() {return nodeId;}public void setNodeId(int nodeId) {this.nodeId = nodeId;}public int getParentId() {return parentId;}public void setParentId(int parentId) {this.parentId = parentId;}public String getNodeName() {return nodeName;}public void setNodeName(String nodeName) { this.nodeName = nodeName;}public String getUrl() {return url;}public void setUrl(String url) {this.url = url;}}编写TreeUtil.java，用于从数据库得到节点信息，封装到TreeInfo对象，并生成javascript 脚本TreeUtil.javapackage com.diegoyun.web.tree;import java.util.Collection;import java.util.ArrayList;import java.util.Iterator;import java.util.List;import java.sql.PreparedStatement;import java.sql.ResultSet;import java.sql.Connection;import java.sql.DriverManager;public class TreeUtil {public static List retrieveNodeInfos(){List coll = new ArrayList();String driverName = "com.mysql.jdbc.Driver";String host = "localhost";String port = ":3306";String serverID = "test";String userName = "root";String userPwd = "root";String url = "jdbc:mysql://" + host + port + "/" + serverID ;Connection conn = null ;PreparedStatement ps = null;ResultSet rs = null;try{Class.forName(driverName).newInstance();conn = DriverManager.getConnection(url , userName , userPwd); String sql = "select * from tree_info";ps = conn.prepareStatement(sql);rs = ps.executeQuery();TreeInfo info = null;while(rs!=null && rs.next()){info = new TreeInfo();info.setNodeId(rs.getInt(1));info.setParentId(rs.getInt(2));info.setNodeName(rs.getString(3));info.setUrl(rs.getString(4));coll.add(info);}// if(rs!=null){// rs.close();// rs=null;// }// if(ps!=null){// ps.close();// ps=null;// }}catch(Exception e){System.out.println(e);}return coll;}public static String createTreeInfo(List alist){StringBuffer contents = new StringBuffer();contents.append("<!--\n");contents.append("var Tree = new Array;");//create a array in javascript TreeInfo info =null;for(int max = alist.size(),i=0;i<max;i++){info = (TreeInfo)alist.get(i);//define elements of arraycontents.append("Tree[");contents.append(i);contents.append("]=\"");contents.append(info.getNodeId());contents.append("|");contents.append(info.getParentId());contents.append("|");contents.append(info.getNodeName());contents.append("|");contents.append(info.getUrl());contents.append("\";");}contents.append("docment.writer(Tree);");contents.append("//-->");return contents.toString();}public static void main(String[]args){List alist = TreeUtil.retrieveNodeInfos();// TreeInfo info = null;// for(Iterator i = c.iterator();i.hasNext();){// info = (TreeInfo)i.next();// System.out.println("*****" + info.getNodeName());// }System.out.println(TreeUtil.createTreeInfo(alist));}}3)编写标签类InitTreeTag.javapackage com.diegoyun.web.taglibs;import com.diegoyun.web.tree.TreeUtil;import javax.servlet.jsp.tagext.TagSupport;import javax.servlet.jsp.JspException;import java.io.IOException;public class InitTreeTag extends TagSupport{public int doEndTag() throws JspException {StringBuffer tree = new StringBuffer();tree.append("<script type=\"text/javascript\">\n");tree.append(TreeUtil.createTreeInfo(TreeUtil.retrieveNodeInfos())); tree.append("</script>\n");try{pageContext.getOut().println(tree.toString());}catch(IOException ioe){ioe.printStackTrace();}return super.doEndTag();}}ShowTreeTag.java :package com.diegoyun.web.taglibs;import javax.servlet.jsp.tagext.TagSupport;import javax.servlet.jsp.JspException;import java.io.IOException;public class ShowTreeTag extends TagSupport{ public int doEndTag() throws JspException {StringBuffer buffer = showTree();try {pageContext.getOut().println(buffer.toString()); }catch (IOException ioe) {ioe.printStackTrace();}return super.doEndTag();}private StringBuffer showTree(){StringBuffer sb = new StringBuffer();sb.append("<div class=\"tree\">\n");sb.append("<script type=\"text/javascript\">\n"); sb.append("<!--\n");sb.append("createTree(Tree);\n");sb.append("//-->\n");sb.append("</script>\n");sb.append("</div>\n");return sb;}}标签的tld如下：<?xml version="1.0" encoding="ISO-8859-1" ?><!DOCTYPE taglibPUBLIC "-//Sun Microsystems, Inc.//DTD JSP Tag Library 1.2//EN" "/dtd/web-jsptaglibrary_1_2.dtd"><taglib><tlib-version>1.0</tlib-version><jsp-version>1.2</jsp-version><short-name>tree</short-name><!--initTreeTag--><tag><name>init</name><tag-class>com.diegoyun.web.taglibs.InitTreeTag</tag-class><body-content>empty</body-content></tag><!--ShowTreeTag--><tag><name>show</name><tag-class>com.diegoyun.web.taglibs.ShowTreeTag</tag-class><body-content>empty</body-content></tag></taglib>4）建立web过程，编写jsp进行测试。