树形目录的递归实现数据库+jsp+javabean

树形目录的递归实现(一)数据库+jsp+javabean

<%@ page contentType="text/html; charset=gb2312" language="java" import="java.sql.*" errorPage="" %>

<%!//方便起见这里就不写成javabean了
class cn {//连接数据库，这里以MS-SQL为例
String jdbcDriver="com.microsoft.jdbc.sqlserver.SQLServerDriver";//jdbc驱动
String connectionString="jdbc:microsoft:sqlserver://localhost:1433;DatabaseName=test";//数据库连接字符串
String user="sa";//数据库用户名
String pass="";//数据库密码
Connection conn=null;
ResultSet rs=null;

public cn() {
try {
 Class.forName(jdbcDriver);
} catch(ClassNotFoundException e) {
 System.err.println(e.toString());
}
}

public ResultSet executeQuery(String sql) {
rs=null;
try {
conn=DriverManager.getConnection(connectionString,user,pass);
Statement stmt=conn.createStatement(ResultSet.TYPE_SCROLL_SENSITIVE,ResultSet.CONCUR_UPDATABLE);
rs=stmt.executeQuery(sql);
}
catch(SQLException e) {
System.err.println(e.toString());
}
return rs;
}

public void executeUpdate(String sql) {
try {
conn=DriverManager.getConnection(connectionString,user,pass);
Statement stmt=conn.createStatement(ResultSet.TYPE_SCROLL_SENSITIVE,ResultSet.CONCUR_UPDATABLE);
stmt.executeUpdate(sql);
}
catch(SQLException e) {
System.err.println(e.toString());
}
}
}

class tree {
cn conn=new cn();
public void init(javax.servlet.jsp.JspWriter out,javax.servlet.http.HttpServletRequest request) throws Exception {
 out.println("");
 dowith(request);
 buildTree(out,0,0);//初始调用
}

private void dowith(javax.servlet.http.HttpServletRequest request) {
if(request.getParameter("parentid")==null||request.getParameter("parentid").equals(""))return;
String action=request.getParameter("action");
if(action.equals("add"))
 conn.executeUpdate("insert into tree(parentid,message) values('"+request.getParameter("parentid")+"','"+request.getParameter("message")+"')");
else if(action.equals("delete"))
 conn.executeUpdate("delete from tree where id="+request.getParameter("parentid")+" or parentid="+request.getParameter("parentid"));
}

public void buildTree(javax.servlet.jsp.JspWriter out,int parentid,int level) throws Exception {
 level++;
 ResultSet rs=conn.executeQuery("select * from tree where parentid="+parentid+" order by id");
 while(rs.next()) {
  out.println("");
  for(int i=0;i   out.print(" ");
  if(has_child(rs.getInt("id"))) {
   out.print(" ");
   out.print(""+rs.getString("message")+" id="+rs.getInt("id")+"");
   out.println("");
   buildTree(out,rs.getInt("id"),level);//递归调用
   out.println("<>");
  } else
   out.print(" "+rs.getString("message")+" id="+rs.getInt("id")+"");
  out.println("<>");
 }
 rs.close();
 rs=null;
}

private boolean has_child(int parentid) throws Exception {
 ResultSet rs=conn.executeQuery("select * from tree where parentid="+parentid+" order by id");
 return rs.next();
}

public String getOption() throws Exception {
 String option="";
 ResultSet rs=conn.executeQuery("select * from tree order by id");
 while(rs.next())
  option+=""+rs.getInt("id")+" ";
 return option;
}
}
%>