Pakzilla » Java

From 1st September 10, Sun Certification titles will be changed to Oracle Certification

Tahir Akram — Tue, 31 Aug 2010 10:06:55 +0000

Just came to know from Oracle website that they have completely integrated Sun certifications with Oracle certification program. The title of certification has been changed. Now Sun Certified Java Programmer will be know as Oracle Certified Professional, Java Programmer.
From Oracle website:

Effective September 1, 2010, all Java, Oracle Solaris, MySQL, Open Office and Oracle Solaris Cluster certifications have been re-published and rebranded under the Oracle Certification Program. This change will not impact any of the exam objectives and with Oracle’s firm commitment to the growth of the program, these credentials will continue to be some of the highest recognized achievements in the industry.

Struts 2 Spring integration: a kickstart on using dependency injection

Tahir Akram — Thu, 12 Aug 2010 10:35:16 +0000

In this post you will find how we can integrate Spring with Struts2 through struts2-spring-plugin. And we will also see how we can use dependency injection. I assume that you are successfully running a Struts2 application. We will add our Spring integration code in that.

Lets take a scenario. You have an Interface DAO.java that has abstract methods. You have written separate implementation for it. Lets suppose for different databases. So we are going to use the implementation of this DAO in our Struts2 application.

DAO.java

package com.pakzilla;
public interface DAO {
public void save(Object o);
}

DAOOracle.java

package com.pakzilla;
public class DAOOracle implements DAO {

public void save(Object o) {
System.out.println("Oracle implementaion");
}
}

DAOMySQL.java

package com.pakzilla;
public class DAOMySQL implements DAO {

public void save(Object o) {
System.out.println("MySQL implementaion");
}
}

DAOService .java

package com.pakzilla;
public class DAOService {
private DAO dao;

public void setDao(DAO _dao){
this.dao = _dao;
}

public DAO getDao(){
return dao;
}

public void saveRecord(Object o){
dao.save(o);
}
}

applicationContext.xml. You will put this file in JavaSource. So it will become the part of your classpath.

Add following in web.xml. You see we are using classpath prefix with applicationContext.xml. Because this file will be in our classpaths. And on server startup web.xml will load it.



contextConfigLocation

classpath:applicationContext.xml




org.springframework.web.context.ContextLoaderListener

Somewhere in your Struts2 Action, where you want to insert the record.

ApplicationContext context =
       new ClassPathXmlApplicationContext("applicationContext.xml");
DAOService daoService = (DAOService) context.getBean("daoService");
daoService.saveRecord();

You must have following jars in your classpath.

antlr-runtime-3.0.jar
commons-fileupload-1.2.1.jar
commons-io-1.3.2.jar
commons-logging-1.1.jar
freemarker-2.3.13.jar
junit-3.8.1.jar
ognl-2.6.11.jar
org.springframework.asm-3.0.0.M3.jar
org.springframework.beans-3.0.0.M3.jar
org.springframework.context-3.0.0.M3.jar
org.springframework.core-3.0.0.M3.jar
org.springframework.expression-3.0.0.M3.jar
org.springframework.web-3.0.0.M3.jar
org.springframework.web.servlet-3.0.0.M3.jar
spring.jar
struts2-convention-plugin-2.1.6.jar
struts2-core-2.1.6.jar
struts2-spring-plugin-2.1.6.jar
xwork-2.1.2.jar

Accessing a selected row from h:dataTable

Div based UIs. Heaven or Hell for a developer?

Tahir Akram — Mon, 02 Aug 2010 22:06:23 +0000

At my work I have a large application that has all web pages in table based layout. The use of Div is just limited to hide and show some content area on web page. Same is the case with CSS. Using them for styling fonts and some formatting for tables. Like every developer (not designer) I am very comfortable in developing UIs by using tables. But quite impressed with Div based layouts, as its a fashion thing for web pages. I see how gracefully div is helping to manage contents instead of tr and tds. Whenever I visit some site that has some good layout. I hit the view source of that page to see whether the designer/developer has used tables. And almost all of time I find myself alone loving tables. And I know the cost to manage a big web page all developed in table. What happen if some td missed. And I need to do the debugging by enabling the border of tables. Ehh.

Its been several years people started developing UIs in Divs. Now no one is working on tables. But if you want to shift on developing UI in Div, you need a learning curve on CSS. So what happen here? It has increased the cost of your time to develop a web page. Unless you master yourself in CSS. Huh?

So being a Java developer, should I master myself in CSS things too. If I am an independent (solo performer) developer that want to develop some app. First thing that came in my mind is, what happen when people will hit view source button. And will it not increase my time to deliver a thing. What should I consider, the features in my application? or the fear of developing the web pages in divs?

New topics added in SCJP 6 Certification (CX-310-065)

Tahir Akram — Sat, 17 Jul 2010 09:29:44 +0000

Following are the points that are highlighted in Kathi Sierra and Bert Bates book on SCJP6.

1-   Console class.
2-   NavigableSet and NavigableMap.
3-   Lower(int) and higher(int) function are added in Treeset collection.
4-   Polling method in TreeSet and TreeMap.
5-   TreeSet.descendingSet() and TreeMap.descendingMap().

Thanks to Bilal for discussing these points with me.

Fetch Twitter friends or followers through REST API in Java

Tahir Akram — Fri, 16 Jul 2010 11:08:18 +0000

I was playing around with fetching Twitter followers and friends with Twitter4J. But it was taking time to do that. So I code it with using REST urls given by Twitter. It fetches all your friends or followers. Depending upon your application that you want one list or you want to use paging. But I did it in one go. Performance wise, it will be trouble of fetching say 2000 followers or friends.

I used JDOM to parse XML.

import java.io.ByteArrayInputStream;
import java.io.DataInputStream;
import java.net.URL;
import java.net.URLConnection;
import java.util.ArrayList;
import java.util.List;

import org.jdom.Document;
import org.jdom.Element;
import org.jdom.input.SAXBuilder;

public class Twt {

String urlFlwrs= "http://twitter.com/statuses/followers/YOUR_TWITTER_SCREEN_NAME.xml?cursor=";
String urlFrnds= "http://twitter.com/statuses/friends/YOUR_TWITTER_SCREEN_NAME.xml?cursor=";

List followers = new ArrayList();
long cursorCounter = -1;

public static void main(String[] args) {
long start = System.currentTimeMillis();
new Twt().readFollowFriends();
System.out.printf("Total Time: %d secs",
(System.currentTimeMillis() - start)/1000);
}

void readFollowFriends(){

try {
StringBuffer followersData = new StringBuffer();
// use urlFrnds as a parameter if you want to fetch friends
URL url = new URL(urlFlwrs+cursorCounter);
URLConnection urlConnection = url.openConnection();
DataInputStream dis = new DataInputStream(
urlConnection.getInputStream());
String inputLine;
while ((inputLine = dis.readLine()) != null) {
followersData.append(inputLine);
}

SAXBuilder builder = new SAXBuilder();
Document document = builder.build(new ByteArrayInputStream(
followersData.toString().getBytes()));

Element root = document.getRootElement();
Element usersElm = root.getChild("users");
Element nextCursor = root.getChild("next_cursor");
List users = usersElm.getChildren("user");

for (int c = 0; c < users.size(); c++) {
Element user = (Element) users.get(c);
Element name = user.getChild("name");
// now you have every thing, the information of a user
// here you can populate followers list
}

if (nextCursor != null){
cursorCounter = Long.parseLong(nextCursor.getText());

if (cursorCounter != 0)
readFollowFriends();
}
} catch (Exception e) {
e.printStackTrace();
}
}
}

But you will also get following HTTP 400 error. Due to API limits by Twitter. For this we want to whitelist ourself.

java.io.IOException: Server returned HTTP response code: 400 for URL: http://twitter.com/statuses/followers/YOUR_TWITTER_SCREEN_NAME.xml?cursor=-1
at sun.net.www.protocol.http.HttpURLConnection.getInputStream(HttpURLConnection.java:1133)
at Twt.readFollowFriends(Twt.java:32)
at Twt.main(Twt.java:22)
Total Time: 7 secs

Java certification voucher in $40 till 31st March 2010 for students

Tahir Akram — Sat, 20 Mar 2010 10:14:10 +0000

From a recent announcement from Oracle under Sun Academic Initiative program (SAI). Now students can get Java certification voucher in $40 till 31st March 2010. This is an excellent opportunity for students. After this date they will give 40% discount on the actual price of the exam fee.

How to use and retain Twitter4J OAuth access token

Tahir Akram — Sun, 28 Feb 2010 20:41:34 +0000

I was stuck in a problem that how to re use access token, once user has authenticated by Twitter (on call back URL). I got it working. There was problem in my understanding about request token vs access token. When user first time comes on call backed URL. I take request token and token secret from session and prepare the access token. Here the place where I was confused.

Now if user presses the refresh button or you want to get user information again from twitter any where in your application. You need to use the access token and this method twitter.setOAuthAccessToken(String1, String2). Because user has already been authenticated by Twitter. You can save this information in session.

HttpSession session = request.getSession();

twitter.setOAuthConsumer(Constants.CONSUMER_KEY,Constants.CONSUMER_SECRET);

if (session.getAttribute("aToken") == null){
	// request token
	String token = (String) session.getAttribute("token");
	String tokenSecret = (String)session.getAttribute("tokenSecret");
	AccessToken accessToken =
		twitter.getOAuthAccessToken(token, tokenSecret);
	twitter.setOAuthAccessToken(accessToken);

	// save the access token, that are different from request token
	session.setAttribute("aToken", accessToken.getToken());
	session.setAttribute("aTokenSecret", accessToken.getTokenSecret());

}else{
	// use the access token to authenticate user whenever you want
	twitter.setOAuthAccessToken((String)session.getAttribute("aToken"),
		(String)session.getAttribute("aTokenSecret"));
}
User user = twitter.verifyCredentials();

If you are also developing some app by using Twitter4J API on Google App Engine. Please give feedback on it.

Twitter4J Quick Tutorial: A quick tutorial on how to develop Twitter app by using Twitter4J on Google App Engine.

Sun.com is dead now

Tahir Akram — Sun, 31 Jan 2010 15:35:29 +0000

Just found that sun.com is now redirecting to oracle.com. Some days back I visited Sun’s original website. But it didn’t took long by Oracle to make it red. Well I am a regular visitor of Sun forums. And with this change, I am trying to adjust myself with this transition. As I am having some issue in finding contents.

After some browsing Oracle’s website I found they were some thing to say to Java developers community about continuing Sun Developer Network.

Sun.com now redirects to Oracle.com

FAQs for Sun Java developer community:

What will happen to Sun Developer Network, java.sun.com, and BigAdmin?

For the near future, all these sites will remain in their current form. We know that these resources are important, so you can continue to access them just as you always have at the same URLs and bookmarks. At some time, we foresee an integration of these sites into a newly redesigned and re-architected Oracle Technology Network, and we welcome your feedback about this process. We will make sure that any changes are communicated well in advance so that you will continue to have access to the tools and resources that you need.

And there are some other promises too about continuing Sun things.

I also found a Sun blogger saying good bye to blog.sun.com. Due to some Oracle policies that they can host only those blogs that targets to their products only not personal topics. You can read that blog post here.

I have started preparing for SCJP

Tahir Akram — Wed, 27 Jan 2010 12:01:03 +0000

Its been a year since I purchased the voucher for SCJP 5.0. But I cant concentrate to have time to prepare it. From last night I have taken the oath to finally make it done. I have started with the book SCJP Sun Certified Programmer for Java 5 Study Guide (Exam 310-055) by Kathy Sierra and Bert Bates.

A remarkable thing is I purchased the free retake voucher which is going to expire on June 2010. But I still didnt make even a single attempt. Ok thats all right. I am going to do it. I hope to appear for the successful first attempt in good marks.

I am not using any IDE for coding practice. I am using Notepad++ editor and command line Javac compilation. I want to get maximum of language fundamentals and want to think out of code completion feature.

Useful cheat sheets on Cloud Computing and Google App Engine for Java

Tahir Akram — Tue, 12 Jan 2010 09:49:13 +0000

Just read cheat sheets (Refcard) by Dzone on Cloud Computing and Google App Engine for Java. They contain a very jumped to the point and quick reference on these things. You can read to have a quick overview.

Read them here:

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