jquery Ajax two-level linkage

First implementation of jquery Ajax two-level linkage to download a jquery.js I'm not ready here. Baidu Download

Background: Through the Department ID to find all the classes under the Department

I realize the two-level linkage of the idea is: First query all departments displayed on the page as shown:

Second, the Click event in the Drop-down box gets the ID of the department, and then the department's ID is used to find the class.

Paste Code

Foreground JSP:

	<select id= "department" name= "DepartmentID" onchange= "Findclass ()" >
		<option value= "0" > Please select </ option>
		<c:foreach items= "${departmentall}" var= "D" >
			<option value= "${d.departmentid}" >${ d.departmentname}</option>
		</c:forEach>
	</select>
	<select id= "classId" Name= " ClassId ">
		<option value=" 0 "> Please select </option>
	</select>

Ajax:

	function Findclass () {
		var DepartmentID = $ ("#department"). attr ("value");
		$.ajax ({
			URL: "${pagecontext.request.contextpath}/student/findclass",
			type: "Get",
			timeout: "1000",
			Data:{departmentid:departmentid},
			success:function (data) {
				$ ("#classId option"). Remove ();
				$ ("#classId"). Append ("<option value= ' 0 ' > Please select </option>");
				if (data!= 0) {for
					(var i = 0; i < data.length; i++) {
						var classId = data[i].classid;
						var className = data[i].classname;
						$ ("#classId"). Append ("
								<option value=" +classid+ ">"
										+ className + "</option>");
					}
				}
			,
			error:function (xmlresponse) {
				alert (xmlresponse.responsetext);}}
		);
	

This is the code for the background controller:

Inquiry Department:

		Modelandview modelandview=new Modelandview ();
		list<department> Departmentall = Departmentservice.finddepartmentall ();
		Modelandview.setviewname ("Student/add");
		Modelandview.addobject ("Departmentall", Departmentall);
		return modelandview;

Inquiry class:

	@RequestMapping (value= "Findclass") public
	String Findclass (httpservletrequest reuqest,httpservletresponse Response) throws exception{
		Response.setcontenttype ("Text/json; Charset=utf-8 ");
		Gets the department id
		String departmentid = Reuqest.getparameter ("DepartmentID");
		Integer id = integer.parseint (departmentid);
		PrintWriter out = null;
		try{out
			= Response.getwriter ();
		} catch (Exception e) {
			e.printstacktrace ();
		}
		Jsonarray array = new Jsonarray ();
		Jsonobject member = NULL;
		try{
			//According to Department ID to find all classes under the Department
			list<classes> classeslist = Classesservice.findclassbydepartmentid (ID);
			for (Classes classes:classeslist) {member
				= new Jsonobject ();
				Member.put ("ClassId", Classes.getclassid ());
				Member.put ("ClassName", Classes.getclassname ());
				Array.put (member);
			}
		catch (Exception e) {
			e.printstacktrace ();
		}
		Out.print (Array.tostring ());
		return null;
	}

Effect chart