實現論壇樹型結構的具體算法
2020-07-27 21:49:05
供稿：網友
實現論壇樹型結構的算法很多，具體你可以去www.chinaasp.com的全文搜索中查詢。我現在的JSP論壇采用的也是當中的一種：不用遞歸實現樹型結構的算法，現在我將論壇樹型結構的具體算法和大家介紹一下，和大家一起交流。
1。演示表的結構：
表名：mybbslist
字段
數據類型
說明
BBSID 自動編號
RootID Int 根帖ID，本身為根帖則RootID = ID
FID Int 父帖ID，上一層帖子的ID，如是根帖則FID = 0
DEPTH Int 根帖Level=0，其他依據回復的深度遞增
BBSSubject Char 主題
2。創建表：
create table mybbslist (
forumID int(20) not null,
bbsID int auto_increment primary key,
rootid int(20) not null,
fid int(20) not null,
depth int(20) not null,
userID int(20) not null,
bbsUser varchar(24) not null,
bbsSubject varchar(100) not null,
bbsContent text,
bbsTime varchar(30),
bbsRead int(20),
bbsReply int(20),
INDEX forumID (forumID))
3。連接MYSQL數據庫的BEAN
package netzero;
import java.sql.*;
public class mydb
{
String driverName = "org.gjt.mm.mysql.Driver";
Connection conn = null;
Statement stmt = null;
ResultSet rs = null;
String connURL= "jdbc:mysql://localhost/mybbs?user=root&password=how&useUnicode=true&characterEncode=8859_1";
//String connURL= "jdbc:mysql://localhost/netzerobbs?user=root&password=how";
public mydb()
{
try
{
Class.forName(driverName);
}
catch (java.lang.ClassNotFoundException e)
{
System.err.println("netzero(String): " + e.getMessage());
}
}
public ResultSet executeQuery(String sql) throws SQLException
{
conn = DriverManager.getConnection(connURL);
stmt = conn.createStatement();
rs = stmt.executeQuery(sql);
return rs;
}
public boolean closeConn()
{
try
{
if (rs!=null) rs.close();
if (stmt!=null) stmt.close();
if (conn!=null) conn.close();
return true;
}
catch ( SQLException ex )
{
System.err.println("closeConn: " + ex.getMessage());
return false;
}
}
}
4。顯示論壇的JSP程序
<jsp:useBean id="mybbs" scope="session" class="netzero.mydb" />
<%@ page contentType="text/html;charset=gb2312" %>
<%@ page import="java.io.*" %>
<%@ page import="java.sql.*" %>
<%
int intRowCount;
out.print("顯示論壇樹形結構");
out.print("<br><br>");
try {
String sql="select * from mybbslist order by rootid desc,depth,fid,bbsid";
ResultSet rs = mybbs.executeQuery(sql);
if (rs.next())
{
rs.last();
intRowCount=rs.getRow();
out.print("論壇樹中有");
out.print(intRowCount);
out.print("個葉子節點");
rs.first();
int j=0;
int Depth = 0;
out.print("<ul>");
while(j<intRowCount)
{
int rsDepth=rs.getInt("Depth");
if (rsDepth<Depth)
{
for(int i=1;i<Depth+1;i=i+1)
{
out.print("</ul>");
}
}
rsDepth=rs.getInt("Depth");
if (rsDepth>Depth)
{
out.print("<ul>");
}
out.print("<li>");
String bbssubject=rs.getString("bbssubject");
out.print(bbssubject);
out.print("</li>");
Depth = rs.getInt("Depth");
j=j+1;
rs.next();
}
out.print("</ul>");
}
else
{
out.print("數據庫中無記錄");
}
}catch (SQLException E) {
out.println("SQLException: " + E.getMessage());
out.println("SQLState: " + E.getSQLState());
out.println("VendorError: " + E.getErrorCode());
}
%>
<% //關閉mysql連接
try {
if(!mybbs.closeConn());
} catch (Exception ex) {
System.err.println("closeConn: " + ex.getMessage());
}
%>
算法參考：http://www.chinaasp.com/sqlbbs/showEssence.asp?id=4783
