Java Ajax implementation cascade drop-down box

CopyCode The Code is as follows: Package com. ajaxlab. Ajax;
Import java. util. arraylist;
Import java. util. collection;
Import java. util. iterator;
Import org. JDOM. Document;
Import org. JDOM. element;
Import org. JDOM. Input. saxbuilder;
Import com. ajaxlab. Ajax. productclass;

Public class classservice ...{
Private document Dom;
Public classservice ()...{
Try ...{
Saxbuilder builder = new saxbuilder ();
This. DOM = builder. Build (classservice. Class. getresource ("product. xml "));
} Catch (exception e )...{
E. printstacktrace ();
}
}
Public productclass [] getallclass1 ()...{
Collection products = new arraylist ();
Iterator = This. Dom. getrootelement (). getchildren (). iterator ();
Do ...{
Element element = (element) iterator. Next ();
Productclass Product = new productclass (element. getattributevalue ("ID "),
Element. getattributevalue ("classname "));
Products. Add (product );
} While (iterator. hasnext ());
Return (productclass []) products. toarray (New productclass [0]);

}

Public productclass [] getallclass2byid (string class1id )...{
Collection products = new arraylist ();
Element classelement = NULL;
Iterator = This. Dom. getrootelement (). getchildren (). iterator ();
Do ...{
Element element = (element) iterator. Next ();
If (class1id. inclusignorecase (element. getattributevalue ("ID ")))...{
Classelement = element;
Break;
}
} While (iterator. hasnext ());

If (classelement! = NULL )...{
Iterator iter = classelement. getchildren (). iterator ();
Do ...{
Element element = (element) ITER. Next ();
Productclass Product = new productclass (element. getattributevalue ("ID "),
Element. getattributevalue ("classname "));
Products. Add (product );
} While (ITER. hasnext ());
Return (productclass []) products. toarray (New productclass [0]);
}
Else ...{
Return NULL;
}
}

Public productclass [] getallclass3byid (string class1id, string class2id )...{
Collection products = new arraylist ();
Element class1element = NULL;
Element class2element = NULL;

Iterator = This. Dom. getrootelement (). getchildren (). iterator ();
Do ...{
Element element = (element) iterator. Next ();
If (class1id. inclusignorecase (element. getattributevalue ("ID ")))...{
Class1element = element;
Break;
}
} While (iterator. hasnext ());

If (class1element! = NULL )...{
Iterator iter = class1element. getchildren (). iterator ();
Do ...{
Element element = (element) ITER. Next ();
If (class2id. inclusignorecase (element. getattributevalue ("ID ")))...{
Class2element = element;
Break;
}
} While (ITER. hasnext ());

If (class2element! = NULL )... {
iterator iter2 = class2element. getchildren (). iterator ();
do... {
element = (element) iter2.next ();
productclass Product = new productclass (element. getattributevalue ("ID"), element. getattributevalue ("classname");
products. add (product);
}while (iter2.hasnext ();
}< br> return (productclass []) products. toarray (New productclass [0]);
}< br> else return NULL;
}< BR >}

JSP:
(1) getclass. JSP acts as the business layer for Ajax calls
<% @ page contenttype = "text/html; charset = gb2312" %>
<% @ page import = "com. ajaxlab. ajax. * "%>
<%
string class1id = request. getparameter ("class1id");
string class2id = request. getparameter ("class2id");
If ("". equals (class1id) class1id = NULL;
If ("". equals (class2id) class2id = NULL;
classservice service = new classservice ();
If (Class1id! = NULL) & (class2id = NULL)... {
productclass [] classes = service. getallclass2byid (class1id);
If (classes! = NULL )... {
for (INT I = 0; I out. print (classes [I]. GETID () + "," + classes [I]. getclassname () + "|");
}< BR >}< br>
else if (class1id! = NULL) & (class1id! = NULL)... {
productclass [] classes = service. getallclass3byid (class1id, class2id);
If (classes! = NULL )... {
for (INT I = 0; I out. print (classes [I]. GETID () + "," + classes [I]. getclassname () + "|");
}< BR >%>

(2) divmenu. JSP
<% @ page contenttype = "text/html; charset = gb2312" %>
<% @ page import = "com. ajaxlab. ajax. * "%>

Function dochange ()...{
VaR F = Document. Forms [0];
Send_request ("get", "getclass. jsp? Class1id = "+ F. select11.value +" & class2id = ", null," text ", populateclass2 );
}
Function dochange2 ()...{
VaR F = Document. Forms [0];
Send_request ("get", "getclass. jsp? Class1id = "+ F. select11.value +" & class2id = "+ F. select12.value, null," text ", populateclass3 );
}
Function populateclass2 ()...{
VaR F = Document. Forms [0];
If (http_request.readystate = 4 )...{
If (http_request.status = 200 )...{
VaR list = http_request.responsetext;
VaR classlist = List. Split ("| ");
F. select12.options. Length = 1;
For (VAR I = 0; I <classlist. Length-1; I ++ )...{
VaR temp = trim (classlist [I]). Split (",");
F. select12.add (New Option (temp [1], temp [0]);
}
}
}
}

Function populateclass3 ()...{
VaR F = Document. Forms [0];
If (http_request.readystate = 4 )...{
If (http_request.status = 200 )...{
VaR list = http_request.responsetext;
VaR classlist = List. Split ("| ");
F. select13.options. Length = 1;
For (VAR I = 0; I <classlist. Length-1; I ++ )...{
VaR temp = trim (classlist [I]). Split (",");
F. select13.add (New Option (temp [1], temp [0]);
}
}
}
}
Function ltrim (STR)
...{
VaR whitespace = new string ("");
VaR S = new string (STR );
If (whitespace. indexof (S. charat (0 ))! =-1)
...{
VaR J = 0, I = S. length;
While (j <I & whitespace. indexof (S. charat (j ))! =-1)
...{
J ++;
}
S = S. substring (J, I );
}
Return S;
}
Function rtrim (STR)
...{
VaR whitespace = new string ("");
VaR S = new string (STR );
If (whitespace. indexof (S. charat (S. Length-1 ))! =-1)
...{
VaR I = S. Length-1;
While (I> = 0 & whitespace. indexof (S. charat (I ))! =-1)
...{
I --;
}
S = S. substring (0, I + 1 );
}
Return S;
}
Function trim (STR)
...{
Return rtrim (ltrim (STR ));
}
</SCRIPT>
<%
Classservice service = new classservice ();
Productclass [] classes = service. getallclass1 ();
%>
<Meta http-equiv = "Content-Type" content = "text/html; charset = ISO-8859-1">
<Title> insert title here </title>
</Head>
<Body> <center>
<Form name = "classform" method = "Post" Action = "">
<Select name = "select11" id = "select11" onchange = "dochange (this. Value)">
<Option value = ""> select category 1 </option>
<%
For (INT I = 0; I <classes. length; I ++ )...{
Out. println ("<option value = '" + classes [I]. GETID () + "'>" + classes [I]. getclassname () + "</option> ");
}
%>
</SELECT>

<Select name = "select12" id = "select12" onchange = "dochange2 (this. Value)">
<Option value = ""> select category 2 </option>
</SELECT>

<Select name = "select13" id = "select13">
<Option value = ""> select category 3 </option>
</SELECT>
</Form>
</Center> </body>
</Html>