SQL递归查询-——java.lang.StackOverflowError，求解！

a673921712 2013-08-15 12:26:29

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);

JSP部分：



<%@ 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>

...全文

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末日哥 2013-08-15

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拿到的是列的索引号。。不是列名

a673921712 2013-08-15

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引用 2 楼 abstruct 的回复:

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) { 没加引号

太感谢您了，找了一整天都没发现问题。

安特矮油 2013-08-15

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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) { 没加引号