Common Maven Errors

When you encounter such an error just change JBoss repository URL in pom.xml or settings.xml to "https://repository.jboss.org/nexus/content/groups/public" from whatever it is. (JBOSS changed their maven repository url) Failed to execute goal on project XXXX: Could not resolve dependencies for project XXXX: Failed to collect dependencies for .......: Failed to read artifact descriptor for ....... Could not transfer artifact ...... from/to jboss.org (http://repository.jboss.org/maven2/): Access denied to .... Error code 403, Forbidden -> [Help 1]

Sun Certified Java Programmer (SCJP) Exam

Merhabalar,

SCJP sınavı için, "Sun Certified Programmer for Java 6 Study Guide" kitabına çalışmanızı öneririm.
Ondan sonra da bol bol soru çözün. Sonuç %99 başarı olacaktır.

Kitaptaki çoğu konu için kimilerimiz "Bu konu basit, zaten hergün kullanıyorum" diye düşünebilir. Yanılıyorsunuz, ben yanıldığımı gördüm en azından. Çünkü her başlık altında bir-kaç tane de olsa bilmediğiniz detaylar bulacaksınız. Bu detaylar hem sınav için, hem de profösyönel java yazılımcılığı için çok önemli diye düşünüyorum.

Ha unutmadan, önceleri sertifika ne de olsa Türkiye'de çok da önemsenmiyor almasam da olur diyep düşünüp bugüne kadar ilgilenmedim. Çok yanlış yapmışım. Aynı yanlışı siz yapmayın. Hangi alanda çalışıyorsanız çalışın mutlaka o alanla ilgili sertifikaları toplamaya gayret edin...

Beni dinlediğiniz için teşekkürler...

Blogger Buzz: Blogger integrates with Amazon Associates

Blogger Buzz: Blogger integrates with Amazon Associates

Blogger Buzz: Blogger integrates with Amazon Associates

Blogger Buzz: Blogger integrates with Amazon Associates

Java HotSpot VM: -server vs -client

You can find a lot of web-sites about Java HotSpot VM. As you may know there are two binary-distributions of JVM: Server JVM and Client JVM.
Differences between them is, Server JVM is best suited for long running server-side applications, and tuned for maximizing operating speed. On the other hand Client JVM is tuned for client-side applications and more memory-friendly. Until now everything is ok.

I have a question. On which side xml – data is process more? On server side or client side? I guess you will reply as “of course in server side”.

However, although server-side applications are processing xml-data more often than client-side applications, and although Server JVM is claimed to be more suitable for server-side applications, Client JVM performing two times better than Server JVM in xml processing. Surprising isn’t it?

You can check what I am claiming by running following code with two jmv options: -server, -client:


import org.dom4j.Document;
import org.dom4j.DocumentException;
import org.dom4j.DocumentHelper;

public class Test {

public static void main(String[] args) throws InterruptedException {
String xmlData = //read from file

int count = 999;
long start, stop;

start = System.currentTimeMillis();
for(int i=0; i newDocument(xmlData );
}
stop = System.currentTimeMillis();
System.out.println
("\n-- Elapsed Time for echo1: " + (stop - start));

}

public static Document newDocument(String message) {
Document doc = null;
try {
doc = DocumentHelper.parseText(message);
} catch (DocumentException e) {
e.printStackTrace();
}
return doc;
}
}

Thanks for reading
Aydın Karaman

How to parse xml strings or files faster?

Xml-data processing involves two phases:
1. Parsing phase (identifying infosets in an xml-source, such as xml-string)
2. Processing phase (retrieving and modifying infosets)

For these purposes, there are basically two parsing & processing models.
1. Tree-Based parsers (DOM implementations such as DOM4j)
2. Event-Based parsers (STREAMING implementations such as SAX, StAX)
a. Streaming Pull parsers (SAX)
b. Streaming Push parsers (StAX)

There are advantages and disadvantages of all xml-parsing models. Depending on your project needs, you may prefer one to others. But before making a decision, it will be helpful to think that you don’t need to use the same parser for both phases mentioned above. That is, you may use a SAX implementation for Parsing-Phase and a DOM implementation for Processing-Phase.

You are right to say, in event-based parsers two phases are running in parallel. That is; you must process xml-infosets at the time you parse them. So it is not suitable to use Event-Based parsers for only “Processing-Phase”. But on the other hand, you can use Event-Based parsers for reading phase and Tree-Based parsers for processing phase in order to benefit from advantages of DOM parsers.

You must be wondering why should I use a STREAMING parser for the first phase, if I would process xml-infosets by DOM parsers. Here is the answer: For better PERFORMANCE!!!

DOM implementations, actually I tried it only with DOM4j, is not good at parsing phase. They are two times slower than Event-Based parsers. You can check performances of both parsers by running two functions I gave below in a loop.

//DOM example
public static Document newDocument(String message) {
Document doc = null;
try {
doc = DocumentHelper.parseText(message);
} catch (DocumentException e) {
e.printStackTrace();
}
return doc;
}

//STREAMING example
public static void newDocumentByString message) {
XMLReader parser = null;
try {
parser = XMLReaderFactory.createXMLReader();
// parser.setContentHandler(new NodeCounter());
InputSource in = new InputSource(new ByteArrayInputStream(message.getBytes()));
parser.parse(in);
}
catch (Exception e) {
System.err.println(e.toString());
}
}


If for your project a DOM parser is more suitable, for performance reasons use StAX or SAX parser for Parsing-Phase and create a Document object as a result. The code-snapshot that is doing that is below:

public static Document newDocumentByStax(String message) {
XMLInputFactory inputFactory = XMLInputFactory.newInstance();
InputStream input = new ByteArrayInputStream(message.getBytes());
XMLStreamReader parser;
Document doc = null;
try {
parser = inputFactory.createXMLStreamReader(input);
doc = process(parser);

} catch (XMLStreamException e1) {
e1.printStackTrace();
}
return doc;
}

private static Document process(XMLStreamReader reader)
throws XMLStreamException {

Document doc = newDocument();
Element current = null;
Stack elements = new Stack();

while (reader.hasNext()) {
int eventType = reader.getEventType();
switch (eventType) {
case XMLStreamConstants.START_ELEMENT:
Element element = new DOMElement(reader.getLocalName());
if (current == null) {
current = element;
doc.setRootElement(current);
} else {
current.add(element);
}
elements.add(current);
current = element;
break;

case XMLStreamConstants.END_ELEMENT:
current = elements.pop();
break;

case XMLStreamConstants.CHARACTERS:
current.setText(reader.getText());
break;
default:
break;
}
reader.next();
}
return doc;
}

Thanks For Reading
Aydın Karaman