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

[qq744056399]

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。
检查Eclipse的eclipse.ini的配置文件，“Xms256m-Xmx1024m”，内存也不小。
下面我把java代码贴出来，希望大家能帮我分析下原因，万分感谢。

package com.MSG2.servlet;
import java.io.IOException;
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.http.HttpSession;
public class QueryMessageServlet extends HttpServlet {
	protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
		doPost(req, resp);
	}
	private static final long serialVersionUID = 6370397999953861485L;
	private List<Map<String,Object>> query(String serial,Connection conn) throws SQLException {
		if(conn != null){
			conn.close();
		}
		String URL = "jdbc:mysql://localhost:3306/test3?useUnicode=true&characterEncoding=utf-8";
		String USER = "root";
		String PWD = "123456";
		conn = null;
			try {
			Class.forName("com.mysql.jdbc.Driver");
			conn = DriverManager.getConnection(URL, USER, PWD);
			String sql1 = "SELECT Message,number,messa,user,Raply FROM reply WHERE Message=?";
			PreparedStatement pst = conn.prepareStatement(sql1);
			pst.setString(1, serial);
			ResultSet rs = pst.executeQuery();
			if (rs != null){
				List<Map<String,Object>> list1 = new ArrayList<Map<String,Object>>();
				while (rs.next()) {
					Map<String, Object> map1 = new HashMap<String,Object>();
					String Message = rs.getString("Message");
					map1.put("Message",Message);
					map1.put("number",rs.getString("number"));
					map1.put("messa",rs.getString("messa"));
					map1.put("user",rs.getString("user"));
					map1.put("Raply",rs.getString("Raply"));
					List<Map<String,Object>> l = query(Message, conn);
					map1.put("replys", l);
					list1.add(map1);
				}
				return list1;
			}
		} catch (ClassNotFoundException e){
				e.printStackTrace();
		} catch (SQLException e) {
				e.printStackTrace();
			} finally {
				if (conn != null) {
					try {
						conn.close();
					} catch (SQLException e) {

						e.printStackTrace();
					}
				}
			}
		return null;
	}
	protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
		String URL = "jdbc:mysql://localhost:3306/test3?useUnicode=true&characterEncoding=utf-8";
		String USER = "root";
		String PWD = "123456";
		Connection conn = null;
		try {
			Class.forName("com.mysql.jdbc.Driver");
			conn = DriverManager.getConnection(URL, USER, PWD);
			String sql = "SELECT serial,username,content FROM message";
			PreparedStatement pre = conn.prepareStatement(sql);
			ResultSet re = pre.executeQuery();
			List<Map<String, Object>> list = new ArrayList<Map<String, Object>>();
			if (re != null) {
				while (re.next()) {
					Map<String, Object> map = new HashMap<String, Object>();
					int serial1 = re.getInt("serial");
					String serial = "" + serial1;
					map.put("serial", serial);
					map.put("username", re.getString("username"));
					map.put("content", re.getString("content"));
					List<Map<String,Object>> l = query(serial, conn);
					map.put("replys", l);
					list.add(map);
				}
			} else {
				System.out.println("还未留言");
			}
			HttpSession session = req.getSession();
			session.setAttribute("list",list);
			resp.sendRedirect(req.getContextPath() + "/list.jsp");
		} catch (ClassNotFoundException e) {
			e.printStackTrace();
		} catch (SQLException e) {
			e.printStackTrace();
		} finally {
			if (conn != null) {
				try {
					conn.close();
				} catch (SQLException e) {

					e.printStackTrace();
				}
			}
		}

	}

}

[qq744056399]

谢谢大神哈！不过我还没学映射呢！ 问题我已经找到了 是因为Message的值与serial相等了所有才会报错。 不过大神你可以给我说说怎么用映射吗？

[浮云若水]

异常信息呢？你的内存损耗是在 List<Map<String,Object>> l = query(Message, conn); List<Map<String,Object>> l = query(serial, conn); 这两行代码 每一条记录你都要去数据库再找一遍 多麻烦 hibernate提供list映射的