📄 mysort.java
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package tree;
import java.io.*;
import java.sql.*;
import java.util.*;
import javax.servlet.*;
import javax.servlet.http.*;
/**
* 实现无限级分类目录树的Servlet
* 完成数据库的连接
* 完成分类的查询，增加，删除等操作
* 编写日期：2007-10-05
* @author 何裕浩 *
*/
public class MySort extends HttpServlet{
public int Id;
public String name;
public int parentId;
private Connection conn;
private Statement stmt;
public ResultSet rs;
int level=0;
PrintWriter out;
/*覆盖doPost方法*/
public void doPost(HttpServletRequest request,HttpServletResponse response) throws ServletException,IOException{
String dsn=request.getParameter("dsn");
String user=request.getParameter("user");
String password=request.getParameter("password");
String sql=request.getParameter("sql");
request.setCharacterEncoding("gb2312");
response.setCharacterEncoding("gb2312");
out=response.getWriter();
OpenConn(dsn,user,password); //建立连接
show(sql,0);
closeConn();
}
//加载驱动程序，建立数据库的连接
public void OpenConn(String dsn,String user,String password){
try{
dsn = "jdbc:mysql:" + dsn;
Class.forName("com.mysql.jdbc.Driver");
conn = DriverManager.getConnection(dsn,user,password);
}catch(Exception e){
System.err.println("aq.executeQuery:"+e.getMessage());
}
}
//查询
public ResultSet executeQuery(String sql){
try{
stmt=null;
rs=null;
stmt=conn.createStatement();
rs=stmt.executeQuery(sql);
}catch(SQLException e){
System.err.println("aq.executeQuery:"+e.getMessage());
}
return rs;
}
//更新
public void executeUpdate(String sql){
try{
stmt=null;
stmt=conn.createStatement();
stmt.executeUpdate(sql);
}catch(SQLException e){
System.err.println("aq.executeUpdate:"+e.getMessage());
}
}
//用递归算法,获得某一个分类的等级,0为顶级分类
public int getLevel(String sql,int Id){
try{
String sql2=sql+" where Id="+Id;
ResultSet result=executeQuery(sql2);
while(result.next()){
parentId=result.getInt("parentId");
}
}catch(SQLException e){
System.err.println("aq.executeUpdate:"+e.getMessage());
}
while(parentId!=0){
level++; //level为全局变量,其他函数使用完后都应清零
getLevel(sql,parentId); ////递归
}
return level;
}
//检测当前分类是否为最底层的分类
public boolean isLast(String sql,int Id){
boolean last=false;
try{
String sql2=sql+" where parentId="+Id;
ResultSet result=executeQuery(sql2);
rs.next();
if(rs.getRow()==0)
last=true;
else
last=false;
}catch(SQLException e){
System.err.println("aq.executeUpdate:"+e.getMessage());
}
return last;
}
//用递归算法，显示分类之间的父子关系
public void show(String sql,int parentId){
int printCount=0;
String li="";
try{
String sql2=sql+" where parentId="+parentId;
ResultSet result=executeQuery(sql2);
while(result.next()){
Id=result.getInt("Id");
name=result.getString("name");
printCount=getLevel(sql,Id);
out.print("<html>\n<body>");
for(int i=0;i<printCount;i++)
out.print(" ");
if(level==0)
li="<img src=\"images/close.gif\"/>";
else if(isLast(sql,Id))
li="<img src=\"images/lastnodeline.gif\"/>";
else
li="<img src=\"images/midopenedfolder.gif\"/>";
out.println(li+"<a href=\"show.jsp?Id="+Id+"\" target=\"main\">"+name+"</a><br>");
out.print("\n</body>\n</html>");
level=0; //level为全局变量,其他函数使用完后都应清零
show(sql,Id); //递归
}
}catch(SQLException e){
System.err.println("aq.executeUpdate:"+e.getMessage());
}
}
//关闭连接
public void closeConn(){
try{
conn.close();
}catch(SQLException e){
System.err.println("aq.closeConn:"+e.getMessage());
}
}
/*覆盖doGet方法*/
public void doGet(HttpServletRequest request,HttpServletResponse response) throws ServletException,IOException{
doPost(request,response);
}
}
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