Lamia's Java Blog - A Pinoy Java Blog : Tomcat

Connection Pooling and Looking up an EJB through JNDI

lamia — Wed, 07 Nov 2007 06:04:00 GMT

While I was reading a tutorial in EJB today and I read a portion on how a Servlet uses an EJB through JNDI, it reminded me on how I did connection pooling in Tomcat before in one of my previous projects.

//Looking up an EJB , from RoseIndia example by Deepak Kumar

public void init(ServletConfig config) throws ServletException{
//Look up home interface
try {
       InitialContext ctx = new InitialContext();
       Object objref = ctx.lookup("TestSessionBean");
        testSessionBean = (TestSessionBeanHome)PortableRemoteObject.narrow(objref,

TestSessionBeanHome.class);
} catch (Exception NamingException) {
NamingException.printStackTrace();
}

//The way I did Connection pooling before

    public static Connection getConnectionFromPool()
    {
        ResourceBundle resourceManager = ResourceBundle.getBundle(RESOURCE_PROPERTIES);

        String dbResource = resourceManager.getString("dbresource");

        Connection conn = null;

        try
        {
            Context ctx = new InitialContext();
            DataSource dataSource = (DataSource)ctx.lookup("java:comp/env/" + dbResource);

            conn = dataSource.getConnection();
        }
        catch(NamingException nex)
        {
            //nex.printStackTrace();

            //conn = DataSourceManager.getConnection();
            ConnectionBrokerManager.init();
            conn = ConnectionBrokerManager.getConnection();
        }
        catch(SQLException sqlex)
        {
            sqlex.printStackTrace();
        }

        System.out.println("Got Connection: " + conn.toString() );

        return conn;
    }

I wasn't able to answer how I did connection pooling in one of my job interviews before. It amazes me how things like this is helping me to better understand things now. The name you specify in ctx.lookup() should be configured in your container. In tomcat, it's usually in web.xml or context.xml for your datasource. For EJB's there's ejb-jar.xml and an additional weblogic-ejb-jar.xml if you're using weblogic.

Additional Resources:

javax.naming.InitialContext

javax.naming.Context

Java is not slow on server-side!

lamia — Thu, 21 Sep 2006 08:34:00 GMT

I know I've been in the field for quite sometime now... However, over and over I get to ask myself the question how many servlet instance is created in the container? At first I thought that multiple instances are created for each user and then reused over and over again... I was wrong...

Only one instace of a Servlet is created but multiple threads are created for each user to access it.

Another question came into my mind... How about static fields?

Well unless an object is synchronized, I guess both static and non-static fields are not thread safe. I dunno what effect synchronizing an objet will have on the application... I'm really not that good with multithreading(yet, but I'm working on it).

So how can other people say that Java is slow as a server-side programming language when only one servlet instance is created? Well... I have to say... Blame it to those model 1 developers who code in straight JSP (you *@#$3#@424!!!). FYI, JSP's are compiled at runtime so putting the business logic in it will really make your app slooowww...

Hmmm... It was quite a relief having to know how my container works...

Virtual Hosting with Apache Tomcat

lamia — Tue, 01 Aug 2006 04:24:00 GMT

I don't know if this is the thing I've been looking for... But this looks promising to me. My company wants to host multiple applications on a single server. However, our hosting provider won't give us any support for Tomcat. What we need actually is like this

www.mysite1.com points to xxx.xxx.xxx.xxx:8080/application1

With the lack of experience to do this, I'm really starting to get frustrated. While browsing the forums at Javaranch, I encountered the term virtual hosting with Tomcat. Hmmmm... Rings a bell! So I googled and bumped into these two interesting sites:

http://tomcat.apache.org/connectors-doc-archive/jk2/jk2/vhosthowto.html
http://www.ex-parrot.com/~pete/tomcat-vhost.html

I haven't tried these yet. But I hope this works for me.