递归显示数据库目录树

1.数据库： 

SET FOREIGN_KEY_CHECKS=0; 
-- ---------------------------- 
-- Table structure for article 
-- ---------------------------- 
CREATE TABLE `article` ( 
  `id` int(11) NOT NULL auto_increment, 
  `pid` int(11) default NULL, 
  `rootid` int(11) default NULL, 
  `title` varchar(255) default NULL, 
  `cont` text, 
  `pdate` datetime default NULL, 
  `isleaf` int(11) default NULL, 
  PRIMARY KEY  (`id`) 
) ENGINE=InnoDB AUTO_INCREMENT=27 DEFAULT CHARSET=utf8; 

-- ---------------------------- 
-- Records 
-- ---------------------------- 
INSERT INTO `article` VALUES ('1', '0', '1', '蚂蚁大战大象', '蚂蚁大战大象', '2009-07-27 01:44:54', '1'); 
INSERT INTO `article` VALUES ('2', '1', '1', '大象被打趴下了', '大象被打趴下了', '2009-07-27 01:44:54', '1'); 
INSERT INTO `article` VALUES ('3', '2', '1', '蚂蚁也不好过', '蚂蚁也不好过', '2009-07-27 01:44:54', '0'); 
INSERT INTO `article` VALUES ('4', '2', '1', '瞎说', '瞎说', '2009-07-27 01:44:54', '1'); 
INSERT INTO `article` VALUES ('5', '4', '1', '没有瞎说', '没有瞎说', '2009-07-27 01:44:54', '0'); 
INSERT INTO `article` VALUES ('6', '1', '1', '怎么可能', '怎么可能', '2009-07-27 01:44:54', '1'); 
INSERT INTO `article` VALUES ('7', '6', '1', '怎么没有可能', '怎么没有可能', '2009-07-27 01:44:54', '0'); 
INSERT INTO `article` VALUES ('8', '6', '1', '可能性是很大的', '可能性是很大的', '2009-07-27 01:44:54', '0'); 
INSERT INTO `article` VALUES ('9', '2', '1', '大象进医院了', '大象进医院了', '2009-07-27 01:44:54', '1'); 
INSERT INTO `article` VALUES ('10', '9', '1', '护士是蚂蚁', '护士是蚂蚁', '2009-07-27 01:44:54', '0'); 

2.源代码： 

 package com.bjtu.jdbc;

 import java.sql.*;

 public class ArticleTree {
     public static void main(String[] args) {
         new ArticleTree().show();
     }

     public void show() {
         Connection conn = null;
         Statement stmt = null;
         ResultSet rs = null;
         try {
             Class.forName("com.mysql.jdbc.Driver");
             conn = DriverManager
                     .getConnection("jdbc:mysql://localhost/bbs?user=root&password=admin");
             stmt = conn.createStatement();
             rs = stmt.executeQuery("select * from article where pid = 0"); //根节点
             while(rs.next()){
                 System.out.println(rs.getString("cont"));
                 tree(conn, rs.getInt("id"), 1);
             }
         } catch(ClassNotFoundException e) {
             e.printStackTrace();
         } catch (SQLException e) {
             e.printStackTrace();
         } finally {
             try {
                 if(rs != null) {
                     rs.close();
                     rs = null;
                 }
                 if(stmt != null) {
                     stmt.close();
                     stmt = null;
                 }
                 if(conn != null) {
                     conn.close();
                     conn = null;
                 }
             } catch (SQLException e) {
                 e.printStackTrace();
             }
         }
     }

     private void tree(Connection conn, int id, int level) {
         Statement stmt = null;
         ResultSet rs = null;

         StringBuffer strPre = new StringBuffer("");
         for(int i=0; i<level; i++) {
             strPre.append("    ");
         }

         try {
             stmt = conn.createStatement();
             String sql = "select * from article where pid = " + id;//父节点ID
             rs = stmt.executeQuery(sql);
             while(rs.next()) {
                 System.out.println(strPre + rs.getString("cont"));
                 if(rs.getInt("isleaf") != 0)
                     tree(conn, rs.getInt("id"), level + 1);
             }

         } catch (SQLException e) {
             e.printStackTrace();
         } finally {
             try {
                 if(rs != null) {
                     rs.close();
                     rs = null;
                 }
                 if(stmt != null) {
                     stmt.close();
                     stmt = null;
                 }
             } catch (SQLException e) {
                 e.printStackTrace();
             }
         }
     }
 }

3.运行结果： 

 蚂蚁大战大象
     大象被打趴下了
         蚂蚁也不好过
         瞎说
             没有瞎说
         大象进医院了
             护士是蚂蚁
     怎么可能
         怎么没有可能
         可能性是很大的