Using Spreadsheet JSP Tag

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Using Spreadsheet JSP Tag




Available in ZK Spreadsheet EE only


Overview

In this section, we will demonstrate how to make a HTML element like a button interact with Spreadsheet in a JSP by AJAX request. We suppose you know some basics about JQuery.

The example application is a simple page to request for leave. A user fills the required field in cells and click "OK" button to submit his request for leave. Or he can clicks "Reset" button to reset what he inputs to default value. The screenshot below shows a request of a user "John":

Essentials-jsp-app.png

We use Spreadsheet to make the application form and two buttons are just ordinary HTML buttons.


Interaction between JSP and Spreadsheet

The sequence diagram displays the overall handling process of a AJAX request when a user clicks a button in app4l.jsp.

Essentials-jsp-interaction.png

The app4l.jsp is the main page with the form for leave. The ForLeaveServlet is a servlet we implement for the example to handle AJAX requests from app4l.jsp. JsonUpdateBridge is a utility class that provides access to ZK desktop and starts an execution in foreign AJAX channel. We should access components like spreadsheet in its process() method and it will generate corresponding AU response for us.

Firstly, app4l.jsp sends AJAX request with required parameter such as desktop ID, spreadsheet UUID, and application related data to ForLeaveServlet. The servlet extracts necessary parameters to create JsonUpdateBridge object and call its process() handle AJAX request. Then response the JSON object which contains ZK AU response to the client. Then we use a Javascript utility object zssjsp provided by Spreadsheet to process ZK AU response and process other data of the JSON response according to our business logic.

Using Spreadsheet Tag

Using Spreadsheet JSP tag is like using other JSP custom tag library. You have to declare a tag library with <%@taglib %> first and write Spreadsheet JSP tag with specified prefix.

app4l.jsp

<%@page language="java" contentType="text/html; charset=UTF-8" pageEncoding="UTF-8"%>
<%@taglib prefix="zssjsp" uri="http://www.zkoss.org/jsp/zss"%>
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html>
	<head>
		<meta http-equiv="Content-Type" content="text/html; charset=UTF-8"/>
		<title>Application for Leave</title>
		<zssjsp:head/>
	</head>
<body>
	<div>
		<zssjsp:spreadsheet id="myzss" 
			bookProvider="org.zkoss.zss.jspdemo.DemoBookProvider"
			width="800px" height="500px" 
			maxrows="100" maxcolumns="20"
			showToolbar="true" showFormulabar="true" showContextMenu="true"/>
	</div>
	<button id="resetBtn">Reset</button>
	<button id="checkBtn">OK</button>
	...
</body>
  • Line 2, 8: Basic steps to use spreadsheet JSP tag.
  • Line 13: A special attribute of spreadsheet JSP tag which should be specified as a book provider class name, and we will explain it later.


Book Provider

The line 13 in previous code, app4l.jsp, has a special attribute which contains a book provider class name org.zkoss.zss.jspdemo.DemoBookProvider. The class implements an interface, BookProvider, which is used to load a book model programmatically in JSP or in a servlet. This provider is called when creating a Spreadsheet in ZK context. The returned book model will be set to a Spreadsheet.

public class DemoBookProvider implements BookProvider{

	public Book loadBook(ServletContext servletContext, HttpServletRequest request, HttpServletResponse res) {
		
		Book book;
		try {
			URL bookUrl = servletContext.getResource("/WEB-INF/books/application_for_leave.xlsx");
			book = Importers.getImporter().imports(bookUrl, "app4leave");
		} catch (Exception e) {
			e.printStackTrace();
			return null;
		}

		//initialize the book model
		...
		return book;
	}
}

Send AJAX Request

The scenario is clicking a button to send an AJAX request, so we have to bind event listeners on buttons. To send AJAX request with JQuery in JSP doesn't require any ZK knowledge, but the servlet needs desktop ID and spreadsheet's UUID to retrieve ZK desktop and spreadsheet component. We can use a Javascript object zssjsp provided by Spreadsheet to get it.

Javascript in app4l.jsp

	//jq is jquery name in zk, which version is 1.6.4 in sparedsheet 3.0.0 (zk 6.5.3 and later) 
	jq(document).ready(function(){
		//register client event on button by jquery api 
		jq("#checkBtn").click(function(){
			postAjax("check");
		});
		jq("#resetBtn").click(function(){
			postAjax("reset");
		});
	});
	
	function postAjax(action){
		//get the necessary zk ids form zssjsp[component_id] 
		//'myzss' is the sparedhseet id that you gaved in sparedsheet tag 
		var desktopId = zssjsp['myzss'].desktopId; 
		var zssUuid = zssjsp['myzss'].uuid;
		
		
		//use jquery api to post ajax to your servlet (in this demo, it is AjaxBookServlet),
		//provide desktop id and spreadsheet uuid to access zk component data in your servlet 
		jq.ajax({url:"app4l",//the servlet url to handle ajax request 
			data:{desktopId:desktopId,zssUuid:zssUuid,action:action},
			type:'POST',dataType:'json'}).done(handleAjaxResult);
	}
...
  • Line 4: The jq is a variable that equals to $ of JQuery.
  • Line 15,16 : Use Javascript object zssjsp provided by Spreadsheet to get desktop ID and spreadsheet's UUID with spreadsheet's component ID, "myzss".
  • Line : You can refer to JQuery API documenation about AJAX for details.

Handle AJAX Request and Response

The ForLeaveServlet is a servlet we implement to handle AJAX requests from app4l.jsp. It extracts necessary parameters from AJAX request to create JsonUpdateBridge object and call its process() handle AJAX request. Then response the JSON object which contains ZK AU response to the client.

We should override JsonUpdateBridge's process() to access spreadsheet component and implement our business logic and JsonUpdateBridge will generate corresponding AU response for us.

public class ForLeaveServlet extends HttpServlet{

	@Override
	protected void doPost(HttpServletRequest req, HttpServletResponse resp)
			throws ServletException, IOException {
		...
		
		//parameter from ajax request, you have to pass it in AJAX request
		//necessary parameter to get ZK server side desktop
		final String desktopId = req.getParameter("desktopId");
		//necessary parameter to get ZK server side spreadsheet
		final String zssUuid = req.getParameter("zssUuid");
		
		final String action = req.getParameter("action");
		
		// prepare a json result object, it can contain your ajax result and
		// also the necessary zk component update result
		final JSONObject result = new JSONObject();
		// set back for client to check action result, it depends on your logic.
		result.put("action", action);
		
		// use utility class to wrap zk in servlet request and
		// get access and response result
		JsonUpdateBridge bridge = new JsonUpdateBridge(getServletContext(), req, resp,
				desktopId) {
			@Override
			protected void process(Desktop desktop) {
				Spreadsheet ss = (Spreadsheet)desktop.getComponentByUuidIfAny(zssUuid);
				Book book = ss.getBook();
				Sheet sheet = book.getSheetAt(0);
				
				if("reset".equals(action)){
					handleReset(sheet,result);
				}else if("check".equals(action)){
					handleCheck(sheet,result);
				}
			}
		};
		
		/*
		 * Generate ZK update result in given JSON object. An AJAX response
		 * handler at client side, zssjsp, will 'eval' this result to update ZK
		 * components.
		 */
		bridge.process(result);

		Writer w = resp.getWriter();
		w.append(result.toJSONString());	
	}
...
}
  • Line 10,12: Get desktop ID and spreadsheet UUID for they will be used in JsonUpdateBridge
  • Line 27: Override process() to implement your business logic and access components.
  • Line 45: Invoke JsonUpdateBridge to handle AJAX request
  • Line 48: Convert result to JSON string and response to client.


Reset Cells

The method handleReset() impelement the business logic to clear user input back to default value. It uses Range API we mentioned in previous sections.

public class ForLeaveServlet extends HttpServlet{
...
	//reset cells to default value
	private void handleReset(Sheet sheet, JSONObject result) {
		final String dateFormat =  "yyyy/MM/dd";
		//you can use a cell reference to get a range
		Range from = Ranges.range(sheet,"E5");//Ranges.range(sheet,"From");
		//or you can use a name to get a range (the named range has to be set in Excel);
		from.setCellEditText(DateUtil.tomorrow(0,dateFormat));
		
		//set other cells...
	}


Check Cells

The method handleReset() impelement the business logic to validate user input and back to default value. It uses Range API we mentioned in previous sections

public class ForLeaveServlet extends HttpServlet{
...
	//validate cell data of user input and return a JSONObject
	private void handleCheck(Sheet sheet, JSONObject result) {
		Date from = Ranges.rangeByName(sheet,"From").getCellData().getDateValue();
		Date to = Ranges.rangeByName(sheet,"To").getCellData().getDateValue();
		String reason = Ranges.rangeByName(sheet,"Reason").getCellData().getStringValue();
		Double total = Ranges.rangeByName(sheet,"Total").getCellData().getDoubleValue();
		String applicant = Ranges.rangeByName(sheet,"Applicant").getCellData().getStringValue();
		Date requestDate = Ranges.rangeByName(sheet,"RequestDate").getCellData().getDateValue();
		
		if(from == null){
			result.put("message", "FROM is empty");
		}else if(to == null){
			result.put("message", "TO is empty");
		}else if(total==null || total.intValue()<0){
			result.put("message", "TOTAL small than 1");
		}else if(reason == null){
			result.put("message", "REASON is empty");
		}else if(applicant == null){
			result.put("message", "APPLICANT is empty");
		}else if(requestDate == null){
			result.put("message", "REQUEST DATE is empty");
		}else{
			//Option 1:
			//You can handle your business logic here and return a final result for user directly
			
			
			
			//Or option 2: return necessary form data, 
			//so client can process it by submitting that can be handled by Spring MVC or Struts
			result.put("valid", true);
			JSONObject form = new JSONObject();
			result.put("form", form);

			form.put("from", from.getTime());//can't pass as data, use long for time
			form.put("to", to.getTime());//can't pass as data, use long for time
			form.put("reason", reason);
			form.put("total", total.intValue());//we just need int
			form.put("applicant", applicant);
			form.put("requestDate", requestDate.getTime());
			
			...
		}
	}
...
}
  • Line 13: The result is a JSONObject that will be sent back to client. You can put any data you like according to your business requirement because you can get it in app4l.jsp and handle by yourself. In our case, we put a validation message in order and show it with Javascript.

Process AJAX Response

After the servlet sending the response, there is a segment of Javascript code which is responsible for handling response. This segment of code will perform some business logic according to the data in JSON object like showing validation message or submitting a form.

Javascript in app4l.jsp

	function postAjax(action){
		...
		jq.ajax({url:"app4l",//the servlet url to handle ajax request 
			data:{desktopId:desktopId,zssUuid:zssUuid,action:action},
			type:'POST',dataType:'json'}).done(handleAjaxResult);
	}

	//the method to handle ajax result from your servlet 
	function handleAjaxResult(result){
		//process the json result that contains zk client update information 
		zssjsp.processJson(result);
		
		//use your way to hanlde you ajax message or error 
		if(result.message){
			alert(result.message);
		};
		
		//use your way handle your ajax action result 
		if(result.action == "check" && result.valid){
			if(result.form){
				//create a form dynamically to submit the form data 
				var field,form = jq("<form action='submitted.jsp' method='post'/>").appendTo('body');
				for(var nm in result.form){
					field = jq("<input type='hidden' name='"+nm+"' />").appendTo(form);
					field.val(result.form[nm]);
				}
				form.submit();
			}
		};
	}
  • Line 5: Specify AJAX response handling method with handleAjaxResult when we send AJAX request.
  • Line 11: Use zssjsp to process ZK AU response in responsed JSON object, e.g. reset data in cells.
  • Line 14: Display a validation message if it exists.
  • Line 27: Submit a form whose data comes from JSON object. This technique can be used to trigger another controller of Spring MVC's or Struts.