从Oracle数据库，利用递归方法，读取 n级菜单，jdbc+jndi

package com.next.ebuy.test;

import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;
import java.text.ParseException;
import java.util.ArrayList;
import java.util.List;

import com.next.ebuy.entity.ProductType;

//测试方法
public class Test {
 private Connection con=null;
 private Statement stmt = null;
 private ResultSet rs =null;

 /**
  * @param Oracle数据库
  * @throws ParseException 

//main方法测试
  */
 public static void main(String[] args)  {
  //getConnection();
  Test t = new Test();
  List<ProductType> list = t.getList(0);
  t.print(list, 0, "--");
 }
//JDBC技术，获得数据库 连接
 public  Connection getConnection (){
  try {
   Class.forName("oracle.jdbc.OracleDriver");
   con = DriverManager.getConnection("jdbc:oracle:thin:@localhost:1521:orcl","Ebuy","t09");
  } catch (ClassNotFoundException e) {
   e.printStackTrace();
  } catch (SQLException e) {
   e.printStackTrace();
  }
  return con;
 }

//遍历数据库，拿到所有元素集合
 public  List<ProductType> getList(int id){
  getConnection();
  List<ProductType> list = new ArrayList<ProductType>();
  String sql ;
  if(id==0){
   sql="select * from t_product_type where p_id is null";
  }else{
   sql="select * from t_product_type where p_id ="+id;
  }
  try {
   stmt = con.createStatement();
   rs = stmt.executeQuery(sql);
   while(rs.next()){
    ProductType p = new ProductType();
    p.setId(rs.getInt("protype_id"));
    p.setName(rs.getString("name"));
    p.setP_id(rs.getInt("p_id"));
    list.add(p);
   }
   for(ProductType p:list){

//开始递归
    List<ProductType> childrenList = getList(p.getId());
    p.setChildren(childrenList);
   }
  } catch (SQLException e) {
   e.printStackTrace();
  }finally{
   try {
    rs.close();
   } catch (SQLException e) {
    e.printStackTrace();
   }
   try {
    stmt.close();
   } catch (SQLException e) {
    e.printStackTrace();
   }
   try {
    con.close();
   } catch (SQLException e) {
    e.printStackTrace();
   }
  }
  return list;
 }

//在控制台打印有层次的菜单
 public  void print(List<ProductType> list,int n,String s){
  String sp="";
  for(int i=0;i<n;i++){
   sp =sp+" ";
  }
  String ps =sp+s;
  for(ProductType p:list){
   System.out.println(ps+p.getName());
   if(p.getChildren().size()>0){

//递归打印
    print(p.getChildren(),n+2,s);
   }
  }
 }
} 

//实体类,get,set方法自己添上

//打印效果如下

数据库结构如下