Top 10 Most Read Last Week On Javablogs.com, Week 19

First Steps With EhCache

static  {  
 //Create a CacheManager  using a specific  config file  
 cacheManager = CacheManager.create(TestClass.class.getResource( "/config/ehcache.xml"));
 cache = cacheManager.getCache("firstcache");
} 

/**
 * retrieves value  from cache if exists
 * if not  create it and add  it to cache */
public String doit(String key, String value) {
 //get an element  from cache by key
  Element e = cache.get(key);
 if (e != null)    {
   value  = (String)e.getValue();
   LOGGER.info("retrieved "+ value+" from cache ");
 }
  else   {
   value = "new value" ;
   cache.put(new Element(key, value));
 }
  return value;
}

/**
 * refresh value  for given key */
public void refresh(String key) { cache.remove(key); }

/**
 * to call eventually  when your application is  exiting  */
 public void shutdown() { cacheManager.shutdown(); } 

Null vs. Errors

Algorithms in Java (Third Edition) Book Review

public int hashCode() {

  int h = hash;

  if (h == 0) {

     int off = offset;

     char val[] = value;

     int len = count;

     for (int i = 0; i <  len; i++) h = 31*h + val[off ++];

     hash = h;

  }

  return h;

} 

Caching HTTP Responses in Java

Caching HTTP response can dramatically improve performance of your app if what you generate is in reality not very dynamic. There are many free caching frameworks in Java. Most popular seem to be ehcache, oscache, jcs and JBoss Cache.

ehcache is quite simple to use and its code is clean. They have a CachingFilter that you can put in your webapp server to cache transparently HTTP responses. However as the framework only allows you to store Objects (which makes sense for most uses), I was wondering how they cached the HttpResponse which is a stream. I was a bit disappointed by the answer, they just create a copy ByteArrayOutputStream and call toBytes() to store it in the cache. While this is optimal for a memory cache store (the whole response will anyway be in the cache, although I am not sure if they check for particularly big responses to avoid caching those or try to cache those) I don’t think it is that good for a disk cache store.

Ideally one would like the response to be stored using a buffer, to avoid having the whole response in memory. This would enable a much higher concurrent use. I think it is doable by writing your own CachingFilter and by using the concurrent utils Queue to block writing when the buffer is full.

I googled for this kind of stuff without success. I only found solutions similar to ehcache one (for example sun CachingResponseWrapper and CachingFilter or oscache CacheFilter (a bit more careful, but still a toBytes())) I wonder why it is not already done and public.

Javablogs.com 2005 Top 20

1. New in Hibernate 3: Criteria API enhancements (816): Projection, aggregation, subselects, detatched criterias - its all there in the Hibernate 3 Criteria API. Let me show you some examples, starting with the new projection API.… [read]


2. Hello, IDEA! (555): From the recent Java IDE discussions, it seems like there's a good portion of Java programmers who don't know IntelliJ IDEA, or simply haven't tried it yet. In this short screencast,… [read]


3. Hey Gosling: This is why we don’t use Java 5.0 yet! (461): Whenever there is a major JDK update everyone on the Sun Microsystems side seems to love to beat the drum of upgrading.… [read]


4. MSN7.5?? (450): ?????Google Talk????????????????????????????????????Google Talk???????? Google Talk????????????????????????????????????   [read]


5. The worst code I've ever seen. Yes, that's true. (422): I've been in this business for 25 years and have been programming since the mid seventies. Even when I was a young pup, full of bright ideas and hubris and those around me were at least as bad,… [read]


6. JSP is officially dead (407): Well, it looks like with the Final Draft of Java EE 5, the final nail has been placed in JSP's coffin.… [read]


7. My wife is hot and she can code, too (400): My wife Keri loves puzzle games--tetris, scrabble, crosswords, text twist--any game where you have to figure something out, she's on it. She has a degree in CS, and is employed as a UI specialist,… [read]


8. IBM announced SOMA - Service-Oriented Modelling and Architecture (396): [read]


9. G-mail runs on Tomcat???!!!!! (390): Well, hello guys and gals...haven't been in the Java blog scene recently, but am glad to know Java is going strong as ever (not that I ever doubted it,… [read]


10. Web Services articles (374): [read]


11. Bill Gates tries Firefox (362): Tim Weber of the BBC reporter rustles up Bill Gates quote of 2005: Bill Gates is one of the people with Firefox on his computer, so I asked him for his opinion. I played around with it a bit,… [read]


12. Language Oriented Programming: Everything is a Language (361): Some people don't 'get' Language Oriented Programming. It's a different perspective. Once you make the mental shift, everything starts to fall into place. Over the past few months,… [read]


13. The killer app for Web 2.0 has arrived (356): Time to throw in the towel, 37 Signals. The future has arrived: iClock (via flocksucks) [read]


14. New Search Engine Blows Google Away (356): After months of incredibly secret development, PreviewSeek Limited has launched the PreviewSeek search engine. My initial impression? It blows google away with its far more powerful searches. [read]


15. Death to Apache (356): So our Apache heros have now decided that it isn't quite enough to prove to the world that they are abysmal failures at producing a J2EE container,… [read]


16. WebSphere 6.0 System Management Enhancements (356): [read]


17. It's Official, Struts is History! (352): [read]


18. What Steve isn't telling us (348): So the rumors were true, Apple is really switching to Intel.  There are a lot of interesting things in Steve Jobs' keynote, as usual, but the most interesting part is,... [read]


19. RE: Why I Ditched Hibernate (346): I saw this post and couldn't help but respond. The post's author, Bruce, is ditching Hibernate and Spring b/c he wants to use a connection pool (configured in Tomcat) instead.… [read]

How To Use Java With Blogger: A Tutorial

private  HttpClient initHttpClient()
{
  HttpClient client  = new HttpClient();
  List authPrefs =  new ArrayList(2);
  authPrefs.add(AuthPolicy.DIGEST );
  authPrefs.add(AuthPolicy.BASIC);
  client.getParams().setParameter (AuthPolicy.AUTH_SCHEME_PRIORITY, authPrefs);
  client.getParams().setAuthenticationPreemptive(true);
  Credentials defaultcreds = new UsernamePasswordCredentials(user, password); 
  client.getState().setCredentials(new AuthScope( "www.blogger.com", 443, AuthScope.ANY_REALM), defaultcreds);
  return client;          
}

public Collection getPosts() throws  HttpException, IOException, ParserConfigurationException, SAXException, DocumentException 
{
  GetMethod get = new  GetMethod("https://www.blogger.com/atom" +"/"+blogId);
  int  statusCode = client.executeMethod(get);
  if   (statusCode !=  HttpStatus.SC_OK)
  {
    throw new RuntimeException(" Could not make HTTP  request properly: " +get.getStatusLine());
  }
  InputStream response  = get.getResponseBodyAsStream();
  SAXReader reader = new  SAXReader();
  Document doc = reader.read(response);
  Collection posts = new ArrayList();
  List entries  = doc.getRootElement().elements("entry");
  if (LOG.isDebugEnabled()) 
  {
    LOG.debug("found  "+entries.size()+"  entries");
  }
  for (int  i = 0; i <entries.size();i ++)
  {
    Element entry  = (Element) entries.get(i); 
    Map m = new  HashMap();
    for (Iterator it = entry.elementIterator();it. hasNext();)
    {
      Element detail =  (Element) it.next();
      String name = detail.getName();
      if (name.equals("link"))
      {
        m.put("link ",detail.attribute("href").getValue());
      }
      else if (name. equals("content"))
      {
        m.put("content",detail.asXML());
      }
      else
      { 
        m.put(name,detail.getTextTrim());
      } 
    }
    posts.add(m);                   
    if  (LOG.isDebugEnabled())
    {
      LOG.debug( "found="+m.get(" title")+", url= "+m.get("link")); 
    }
  }
  return  posts;
}

private String createXmlForCreatePost(String postTitle, String postContent) throws   IOException, DocumentException
{
  SAXReader xmlReader =  new SAXReader();
  xmlReader.setValidation(false );
  Document doc = DocumentHelper.createDocument();
  QName rootName  = DocumentHelper.createQName("entry", new  Namespace("", "http://purl.org/atom/ns# "));
  Element root = doc.addElement(rootName);
  Element title = root.addElement("title"); 
  title.addAttribute("mode"," escaped");
  title.addAttribute("type ","text/plain");
  title.setText (postTitle);
  Element generator = root.addElement("generator ");
  generator.addAttribute("url" , "http://31416.org");
  generator. setText("31416 Java Generator ");
  Element content = root.addElement("content ");
  content.addAttribute("type" , "application/xhtml+xml");
  //Element  div = content.addElement(DocumentHelper.createQName("div",new  Namespace("","http://www.w3.org/1999/xhtml")));
  //div.add(...); //YOUR XHTML HERE
  StringWriter result = new  StringWriter();
  XMLWriter writer = new XMLWriter (result);
  writer.write(doc);
  writer.close();
  return result.toString();
}

Last week Javablogs.com top 10

Web Services No Better Than CORBA?

Is your UML Composition French or American?

Si l'agrégat est détruit (ou copié), ses composants le sont aussi.

Composition [...] is exactly like Aggregation except that the lifetime of the 'part' is controlled by the 'whole'. This control may be direct or transitive. That is, the 'whole' may take direct responsibility for creating or destroying the 'part', or it may accept an already created part, and later pass it on to some other whole that assumes responsibility for it.