Dynamic Loading of tree in extjs

After several days of hard work, I finally got it done. I dynamically connected the database to load the node in the tree ticket. I also checked a lot of information on the Internet. Unfortunately, I basically reprinted it all. It looks very troublesome. At first glance, I felt dizzy and did nothing. I finally found a simple method, but it was still not easy to use and I had to rely on myself. Finally I put them Code For a comprehensive reference, It's okay after sorting it out, although it's a bit messy.
Database Table Design
Drop table treenode;
Create Table treenode (
TID int not null primary key,
Parentid int,
Text char (16) not null,
Href char (32)
);
Insert into treenode (TID, parentid, text, href) values (-100, -100,'01', 'hello.html ');
Insert into treenode (TID, parentid, text, href) values (1, -100,'01', 'hello.html ')
Insert into treenode (TID, parentid, text, href) values (2,-100, '02', 'hello.html ')
Insert into treenode (TID, parentid, text, href) values (3,-100, '03', 'hello.html ')
Insert into treenode (TID, parentid, text, href) values (4, '04', 'hello.html ')
Insert into treenode (TID, parentid, text, href) values (5, 1, '05', 'hello.html ')
Insert into treenode (TID, parentid, text, href) values (6, 2, '02-01', 'hello.html ')
Insert into treenode (TID, parentid, text, href) values (7, 2, '02-01 ', 'hello.html ')
Insert into treenode (TID, parentid, text, href) values (8, 3,'03-01', 'hello.html ')
Insert into treenode (TID, parentid, text, href) values (9, 3,'03-02', 'hello.html ')
Insert into treenode (TID, parentid, text, href) values (10, 3, '03-03', 'hello.html ')
Extjs code:
Ext. onready (function (){
VaR tree = ext. tree;
VaR treeloader = new tree. treeloader ({dataurl: 'servlet/treeaction? Tid =-100 '});
// Define the nodes of the tree
VaR root = new Ext. Tree. asynctreenode ({
ID: "-100", // root node ID
Draggable: false,
Expanded: True,
Text: "background management"
});

// Generate a tree panel
VaR tree = new Ext. Tree. treepanel ({
Renderto: 'tree ',
Root: Root, // locate the root node
Width: 150,
Height: 300,
Animate: True, // enable the animation effect
Enabledd: false, // sub-nodes cannot be dragged.
Autoscroll: True,
Loader: treeloader
// Border: false, // no border
// Rootvisible: false // if it is set to false, the root node is hidden,
});

Tree. setrootnode (Root );
Tree. On ('beforeload ',
Function (node ){
Tree. loader. dataurl = 'servlet/treeaction? Tid = '+ node. ID; // defines the loader of the child node
});
Tree. Render ();
Root. Expand ();

});
Java code:

// Return the ID of the parent node from the database
String SQL = "select parentid from treenode where parentid> 0 group by parentid order by parentid ";
Stringbuilder S = new stringbuilder ();
Preparedstatement PST = NULL;
Resultset rs = NULL;
Try {
Pst = conn. preparestatement (SQL );
Rs = pst.exe cutequery ();

While (Rs. Next ())
{
S. append ('| ');
S. append (Rs. getint ("parentid "));
}
} Catch (sqlexception e ){
E. printstacktrace ();
}
Return S;
}
// Return the jsonarray String object class from the database
Stringbuilder S = This. getresulsetrow (conn );
Arraylist Al = new arraylist ();
Stringbuilder node = new stringbuilder ("[");
String SQL = "select * From treenode where parentid =" + PID + "order by TID ";
Statement PST = NULL;
Resultset rs = NULL;
Try {
Pst = conn. createstatement (resultset. type_scroll_insensitive, resultset. concur_read_only );
Rs = pst.exe cutequery (SQL );
Rs. Last ();
Int I = Rs. getrow ();
System. Out. println (I );
Rs. First ();
While (Rs. Next ())
{

String P = string. valueof (Rs. getint ("TID "));
Node. append ("{ID: '" + P + "', text: '" + Rs. getstring ("text "). trim () + "', href:'" + Rs. getstring ("href "). trim () + "',");
// The set and get methods are not used. It seems that they are not easy to use. Here I use my own method,
// Treenode TD = new treenode ();
// TD. settid (Rs. getint ("TID "));
// TD. settext (Rs. getstring ("text"). Trim ());
// TD. sethref (Rs. getstring ("href"). Trim ());
If (S. indexof ("|" + P + "| ")! =-1 ){
Node. append ("CLS: 'folder', leaf:" + false + "}");
// TD. setcls ("folder ");
// TD. setleaf (false );

} Else {

Node. append ("CLS: 'file', leaf:" + true + "}");
// TD. setcls ("file ");
// TD. setleaf (true );
}
Int ROW = Rs. getrow ();
System. Out. println (ROW );
If (row <I ){
Node. append (",");

}

// Al. Add (TD );
}

} Catch (sqlexception e ){
E. printstacktrace ();
}
Node. append ("]");
Return node;