SQL递归查询-——java.lang.StackOverflowError，求解！
目前在练习尚学堂马士兵BBS项目，在Eclipse中运行Tomcat,连接Mysql,在做树状结构展现时（jsp文件）发生java.lang.StackOverflowError。
在网上看了这个异常的发生原因，一种是递归程序陷入死循环，内存耗尽；一种是JVM内存过小，递归过度消耗内存。
对照视频中的代码，没发现我的代码有什么错误；检查Eclipse的eclipse.ini的配置文件，“Xms40m-Xmx512m”，内存也不小。
下面我把SQL语句和JSP代码贴出来，希望大家能帮我分析下原因，万分感谢。
SQL部分：
create database bbs;
use bbs;
create table article
(
id int primary key auto_increment, //帖子id
pid int, //回复帖子的id,0代表主题帖
rootid int,
title varchar(255),
cont text,
pdate datetime,
isleaf int //叶子节点,0表示叶子结点，1表示非叶子结点
);
use bbs;
insert into article values(null,0,1,"蚂蚁大战大象","蚂蚁大战大象",now(),1);
insert into article values(null,1,1,"大象被打趴下了","大象被打趴下了",now(),1);
insert into article values(null,2,1,"蚂蚁也不好过","蚂蚁也不好过",now(),0);
insert into article values(null,2,1,"瞎说","瞎说",now(),1);
insert into article values(null,4,1,"没有瞎说","没有瞎说",now(),0);
insert into article values(null,1,1,"怎么可能","怎么可能",now(),1);
insert into article values(null,6,1,"怎么没有可能","怎么没有可能",now(),0);
insert into article values(null,6,1,"可能性是很大的","可能性是很大的",now(),0);
insert into article values(null,2,1,"大象进医院了","大象进医院了",now(),1);
insert into article values(null,9,1,"护士是蚂蚁","护士是蚂蚁",now(),0);
<%@ page language="java" contentType="text/html; charset=gbk"
pageEncoding="gbk"%>
<%@ page import="java.sql.*" %>
<%!
String str = "";
private void tree(Connection conn,int id,int level) {
Statement stmt = null;
ResultSet rs = null;
String preStr = ""; //前缀字符
for(int i=0;i<level;i++) {
preStr += "----";
}
try {
String sql = "select * from article where pid=" + id;
stmt = conn.createStatement();
rs = stmt.executeQuery(sql);
while(rs.next()) {
str += "<tr><td>" + rs.getInt("id") + "</td><td>" +
preStr + rs.getString("title") + "</td></tr>";
if(rs.getInt("isleaf") != 0) { //不是叶子节点
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();
}
}
}
%>
<%
Class.forName("com.mysql.jdbc.Driver");
String url = "jdbc:mysql://localhost:3306/bbs?user=root&password=123";
Connection conn = DriverManager.getConnection(url);
Statement stmt = conn.createStatement();
ResultSet rs = stmt.executeQuery("select * from article where pid= 0");//主题帖结果集
while(rs.next()) { //展现主题贴下的回复帖
str += "<tr><td>" + rs.getInt("id") + "</td><td>" +
rs.getString("title") + "</td></tr>";
if(rs.getInt("isleaf") != 0) {
tree(conn,rs.getInt("id"),1);
}
}
rs.close();
stmt.close();
conn.close();
%>
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=gbk">
<title>Insert title here</title>
</head>
<body>
<table border="1">
<%= str %>
</table>
</body>
</html>
????????stmt?=?conn.createStatement();
????????rs?=?stmt.executeQuery(sql);
????????while(rs.next())?{
????????????str?+=?"<tr><td>"?+?rs.getInt("id")?+?"</td><td>"?+
???????????????????preStr?+?rs.getString("title")?+?"</td></tr>";
????????????if(rs.getInt("isleaf")?!=?0)?{???????//不是叶子节点
????????????????tree(conn,rs.getInt(id),level+1);
????????????}
????????}
????}?catch(SQLException?e)?{
没加引号
