Back from JavaOne China 2013

JavaOne China

JavaOne China

I just get back from JavaOne China that was held in Shanghai 22-25 July 2013. JavaOne China is one of the biggest Java Conferences in Asia. The conference organization was good and there were a lot of attendees in the conference sessions.

JavaOne China

JavaOne China

I had the chance to present “Efficient JavaScript Unit Testing” in 23 July, the room of the session was full of attendees and I was really amazed by the energy, enthusiasm, and responsiveness of the attendees during the session.

Photo with Chinese Developers

Photo with Chinese Developers

The session went great and I was glad to give a free copy of my JavaScript Unit Testing book to one of the attendees who answered a JavaScript quiz at the end of the session.

I uploaded my session below:

Aside from the conference, Shanghai is a modern city that has many good places to visit, I had the chance to visit three places there:
1. Yuyuan Garden and Old Town Area:
Yuyuan Garden Photos

2. Jing Temple:
Jingle Temple Photos

3. Oriental Pearl TV Tower:
Oriental Pearl TV Tower Photos

Dojo Ajaxified multi-file upload (including IE7)

One of the most common requirements of business applications is to develop Ajaxified multi-file upload. Thanks to Dojo 1.6 (and later), you can achieve this requirement, however, there are some tricks that you need to do in order to have this feature developed across all the browsers including IE. Let’s start to see the code.

The following listing shows the HTML code part of the file uploader.

<%@ page language="java" contentType="text/html; charset=ISO-8859-1"
    pageEncoding="ISO-8859-1"%>
<!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=ISO-8859-1">
	<title>File Upload POC</title>
	
	<script type="text/javascript" src="//ajax.googleapis.com/ajax/libs/dojo/1.7.2/dojo/dojo.js">
	</script>
</head>
<body>
	<script type="text/javascript" src="${pageContext.request.contextPath}/js/fileUploader.js"></script>
	<div id="container">
		<form method="post" id="myForm" enctype="multipart/form-data">
		    <fieldset>
		        <legend>Form Files Test</legend>
		        
		        <input id="clearBtn" type="button" value="Clear"></input><br/><br/>
				<div id="uploader"></div><br/>
				<div id="uploaderStatus"></div>
      					
		        <input id="uploadBtn" type="button" value="Submit"></input>
		    </fieldset>
		</form>
	</div>
</body>
</html>

As shown the file upload HTML, the form’s enctype needs to be set to “multipart/form-data”. The form contains “uploader” div that represents the Ajaxified file upload component and “uploaderStatus” div that represents the status panel of the selected files and finally it contains the upload button that will be used for uploading.

Now, Let’s look at the JavaScript file (fileUploader.js) which uses the dojos/form/Uploader module.

require([
        "dojo/parser", "dojox/form/Uploader", "dojo/dom", "dojo/on", "dojo/has", 
        "dojox/form/uploader/FileList", "dojox/form/uploader/plugins/IFrame", 
        "dojo/domReady!"], 
function(parser, Uploader, dom, on, has) {    
    parser.parse(document.getElementById("container"));
    
    var uploaderDIV = document.getElementById("uploader");
    
    var up = new dojox.form.Uploader({
        label: 'Select files',
        style : 'background-color: #ddddff; border: solid 1px;', //Externalize ...
        multiple: true,
        url: "/multifile-ajax-poc/UploaderServlet"
    }).placeAt(uploaderDIV);
    
    on (dom.byId("uploadBtn"), "click", function(evt) {
    	
    	//You can put some validations here ...
        up.submit();
    });  

    on (dom.byId("clearBtn"), "click", function(evt) {
        dom.byId("uploaderStatus").innerHTML = "";
        up.reset();
    });
    
    dojo.connect(up, "onComplete", function(dataArray) {
        var i = 0;
        
        dom.byId("uploaderStatus").innerHTML = "";
        
        if (!dataArray.error) {
            for (i = 0; i < dataArray.length; ++i) {
            	dom.byId("uploaderStatus").innerHTML += "File ID is: " + dataArray[i].id + " is uploaded" + "<br/>";
            }
        } else {
        	dom.byId("uploaderStatus").innerHTML = "Unable to upload the file(s)";
        }
    });    
    
    dojo.connect(up, "onChange", function(evt) {
        var i = 0;
        var content = "";
        var dataArray = up.getFileList();
        
        for (i = 0; i < dataArray.length; ++i) {
            content += dataArray[i].name + "<br/>";
        }
        
        dom.byId("uploaderStatus").innerHTML = content;
    });    
    
    up.startup();     
}
);

As shown in the code, the Dojo Ajaxified file uploader is created using dojox.form.Uploader constructor with specifying the main important attributes:
1. label.
2. multiple attribute is set to true in order to support multi-file uploading.
3. url attribute is set to the Java Servlet which handles the file uploading.

In order to get the uploader working fine, you need to call startup() method of the component.

There are important methods that are needed to be considered:
1. submit() method which allows submitting the selected files to the Java Servlet specified in the url attribute.
2. reset() method which is used to clear the selected files. Note that one of the limitations of this component is that it does not allow removing the selected files individually so the only option you have is ti clear all the files and select them again.
3. getFileList() method which is used to get the list of selected files that you can display for example in the “on change” event of the component as shown by the example.

One important thing to note is dojox/form/uploader/plugins/IFrame plugin which is essential for non-HTML5 browser in order to perform Ajaxified file uploads. Using this plugin will allow file uploading to be done through iframe for poor browsers like IE7.

Finally, let’s come to the most important trick of Ajaxified file uploading which is the server side part. The following code listing shows UploaderServlet Java Servlet.

package servlets;

import java.io.IOException;
import java.io.PrintWriter;
import java.util.Iterator;
import java.util.List;
import java.util.Random;

import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

import org.apache.commons.fileupload.FileItem;
import org.apache.commons.fileupload.FileUploadException;
import org.apache.commons.fileupload.disk.DiskFileItemFactory;
import org.apache.commons.fileupload.servlet.ServletFileUpload;

@WebServlet("/UploaderServlet")
public class UploaderServlet extends HttpServlet {
	private static final long serialVersionUID = 1809724554045451657L;

	protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
		DiskFileItemFactory factory = new DiskFileItemFactory();
		ServletFileUpload upload = new ServletFileUpload(factory);
		String result = "";
		
		try {
			List<FileItem> items = upload.parseRequest(request);
			Iterator<FileItem> iter = items.iterator();
			int index = 0;

			result += "[";
			
			while (iter.hasNext()) {
			    FileItem item = iter.next();

			    if (!item.isFormField()) {
				    if (index != 0) {
				    	result += ", ";
				    }
				    
			        String feedback = processUploadedFile(item);
			        
			        //Handle IE7 ugly uploading bug
			        if (feedback == null) {
			        	continue;
			        } else {
			        	result += feedback;
			        }
			        
				    ++index;
				    
				    System.out.println(index);
			    }
			}
			
			result += "]";
			
			System.out.println(result);
			
		} catch (FileUploadException e) {
			result = "{'error':'" + e.getLocalizedMessage() + "'}";
			e.printStackTrace();
		}
		
		respondToClient(request, response, result);
	}

	private String processUploadedFile(FileItem item) {
		byte[] data = item.get();
	    String fileName = item.getName();
	    String contentType = item.getContentType();
	    
	    // Handle IE7 file uploading ugly bug ...
	    if (fileName.equals("")) {
	    	return null; //ignore
	    }
	    
		System.out.println(fileName + ", " + contentType + ", " + data.length);	    
	    
	    return "{'fileName':'" + fileName + "', " + 
	    		"'contentType':'" + contentType + "', " + 
	    		"'size':" + data.length + ", " + 
	    		"'id':" + (System.currentTimeMillis() + new Random().nextInt(100)) + "}";
	}
	
	private void respondToClient(HttpServletRequest request, HttpServletResponse response, String result) throws IOException {
        response.setContentType("text/html");
		PrintWriter writer = response.getWriter();		
		String browser = request.getHeader("User-Agent");
		
		if (browser.indexOf("MSIE 9") &gt; 0 || browser.indexOf("MSIE 8") &gt; 0 || browser.indexOf("MSIE 7") &gt; 0 ) {
			
			// For IE 9, 8, and 7 browser, render JSON object inside text area ...
			//String sampleOutput = "<textarea>[{'success':'true', 'id':'123456789'}]</textarea>";
			writer.write("<textarea>" + result + "</textarea>");
		} else {
			
			//For non-IE browsers, render normal JSON objects.
			//String sampleOutput = "[{\"success\":\"true\", \"id\":\"123456789\"}]";
			writer.write(result.replace("'", "\""));
		}		

		writer.flush();		
	}
}

Our UploaderServlet main purpose is to receive the files and if it succeeds to process the files, then it returns a simple array with the basic information of the files that are successfully uploaded.

The most important thing to notice here is for IE7 and IE8 and IE9 (NOT IE 10), a special handling is needed to be taken into consideration in the Servlet response:
1. The response data must be wrapped into textarea field.
2. Do not use double quotes (“) inside the returned JSON array, instead use single quote (‘).

In other modern browsers (which support HTML5 file uploading), you do not need to wrap the content in textarea as it does not use iframe for uploading, and you can freely use the double quotes (“) in the JSON array.

There is an ugly bug that you need to take care about in IE 7 and 8 and also 9 with the Dojo file uploader component, this bug is about having a redundant file with non-name that is always sent in the request of the multiple-file Ajax uploading. In order to handle this bug, just ignore the file which does not have a name (Ugly problem and ugly fix :-)).

This is all about my experience in this component, I wish that it can be helpful to you.

Download the code sample

Creating JSF RESTful pages

In a web browser, a bookmark allows users to get back to a given web page at any time. Users can share bookmarkable pages with other users by just sharing a page URL (with its required parameters). Bookmarkable pages are also friends to search engines because they can be indexed by search crawlers. Sometimes you might want to create a bookmarkable page programmatically, with Java for instance. Here’s how to create bookmarkable pages in Java EE applications using the JavaServer Faces (JSF) framework.

Read the full article in Wazi

JavaScript Quiz #7

Assume that we have the following short JavaScript code:

<script>
    var result = typeof("Hello" instanceof String);
    alert(result); //What is the output of the alert? 
	
    result = typeof typeof("Hello" instanceof String);
    alert(result); //What is the output of the alert? 
	
    result = typeof typeof typeof("Hello" instanceof String);
    alert(result); //What is the output of the alert? 	
</script>

What is the output of each alert?

Know the complete answer

Back from JavaOne Russia 2013

I just get back from JavaOne Russia that was held in Moscow 23-24 April 2013. JavaOne Russia is the biggest Java Conferences in Eastern Europe. The conference organization was great and there were a lot of attendees in the conference sessions.
I had the chance to present “JSF Mashups in Action” in 24 April:

"JSF Mashups in Action" session

“JSF Mashups in Action” session

I would really like to thanks all the attendees of my session, they really made the session very interactive. I also appreciate the nice feedback that I got either verbally or from the tweets about the session:
Tweets

I uploaded my JavaOne Russia 2013 session in speakerdeck.com, It is attached below:

Have a nice time

Speaking in JavaOne Russia 2013

JavaOne Russia

JavaOne Russia

The next Wednesday, Apr 24, 16:45 – 17:45, I will be speaking in JavaOne Russia about [CON1112] JSF Mashups in Action. The session will be practical, I will talk about Mashup development, common Mashup scenarios, and the current challenges of developing Mashups. I will explain how to utilize the JSF powerful component-oriented architecture and its 2.x Ajax capabilities in order to overcome most of these challenges for creating rich Mashups. In the session, I will build many interactive Web 2.0 Mashups to show how it is possible to create rich Mashups in the JavaServer Faces world with the least required Java and JavaScript code. I wish that all of you will enjoy the session. My session will be held in San Francisco Hall, Crocus Expo International Exhibition Center, Moscow:
http://eng.crocus-expo.ru/exhibitioncenter/aboutcenter.php.

Personally, it is my first time to visit Moscow, beside enjoying technical stuff, I would like to visit some tourist places in Moscow such as kremlin and Moscow Red square and may be other interesting places, any suggestions 🙂 ?

I really wish to see all of you there in JavaOne Russia!

Resolving the virtual keyboard popup issue in Android 2.x browsers

One of the alarming issues of the Android 2.x browsers is that virtual keyboard sometimes becomes open even if the cursor is not focused on an editable field.
This symptom can be extended to a degree that the virtual keyboard can be still open in views other than the one that initially shows the keyboard.

After spending hours in trying to figure out a solution to this problem, I tried the following solutions and none of them worked with me:
1. Disabling the input elements in the form temperaroly.
2. Setting the input elements in the form to read-only temporarily.
3. Blurring the current focused editable field does not also work.

The only way that works with me is to send an enter key to one of the text fields in the form (or to any hidden field) after 1000 milliseconds before performing the transition to any other views, this can be done in Dojo mobile as follows:

window.setTimeout(function() {

    registry.byId("[your dojo/mobile/textbox id]")._onInput({ charOrCode: keys.ENTER });

}, 1000);

If you have a better solution for this issue, let me know.

JavaScript Quiz #5

This quiz covers some of the JavaScript operators in order to explain they can work together inside expressions. Assume that we have the following JavaScript code:

var object1 = {
    valueOf: function () {
	return 10;
    },
    toString: function () {
	return "object1";
    }
};

var object2 = {
    valueOf: function () {
	return 20;
    },
    toString: function () {
	return "object2";
    }
};

var object3 = {
    valueOf: function () {
	return 30;
    },
    toString: function () {
	return "object3";
    }
};

var result = (object2, object1, object3) + object1 +-- object1; 
alert(result);

What is the output of the alert?

Read the complete answer

JavaScript Quiz #4

Understanding JavaScript by example is useful for absorbing the different concepts of the language quickly. In this post, I will illustrate a JavaScript quiz in order to understand how JavaScript operators work together. Assume that we have the following JavaScript code:

var object1 = {
    valueOf: function () {
        return 1;
    },
    toString: function () {
        return "object1";
    }
};

var object2 = {
    valueOf: function () {
        return 2;
    },
    toString: function () {
        return "object2";
    }
};

alert((object2 > object1 +-- object1) + true); //What is the output of the alert?

What is the output of the alert?

Read the complete answer