reinventing the wheel : connection pool

As a learning experience I am in the process of creating sort of an jdbc connection pool class for my java/jsf application. It's just to play around. I'm sure there are much more sophisticated ways to handle this.

@ManagedBean(name = "pooltje", eager = true)
@ApplicationScoped
public class pooltje {

    private Integer max_connecties = 10;
    private connectie[] pool = new connectie[max_connecties];

    public pooltje() {
        for (Integer teller = 0; teller < max_connecties; teller++) {
            pool[teller] = new connectie();
        }
    }

    public Synchronzed Connection borrow() {
        Connection ret_con = null;
        while (ret_con == null) {
            for (Integer t = 0; t < max_connecties; t++) {
                if (pool[t].getUsed() == Boolean.FALSE && ret_con == null) {
                    ret_con = pool[t].getConn();
                    pool[t].setUsed(Boolean.TRUE);
                }
            }
        }
        return ret_con;
    }

    public synchronized void giveback(Connection terug) {
        for (Integer t = 0; t < max_connecties; t++) {
            if (pool[t].getConn() == terug) {
                pool[t].setUsed(Boolean.FALSE);
            }
        }
    }
}

I made the class a managed bean with application scope, so I开发者_开发百科 know it will be instantiated only once at startup of the application.

My actual question is, how can I call the borrow and giveback method. For the method borrow() I found the following:

FacesContext fc2 = FacesContext.getCurrentInstance();
Application app = fc2.getApplication();

Connection conn = (Connection) app.evaluateExpressionGet(fc2, "#{pooltje.borrow()}", Connection.class);

This works fine, however I feel that it should/could be easier. At least I do get a connection passed back.

For the method giveback() I have to pass a variable (the connection not to use anymore). How can I accomplish this?

The connection pool approach aside (or I would totally waste time doing a writeup along with detailed examples :/ ), you could just access other managed beans from inside a managed bean by injecting them as @ManagedProperty.

@ManagedBean
@RequestScoped
public class ArbitraryBean {

    @ManagedProperty("pooltje")
    private Pooltje pooltje;

    // ... Add at least a setter for it.
}

This way you can just access it in your @PostConstruct or action methods whenever necessary:

public void doSomething() {
    Connection connection = pooltje.borrow();
    // ...
}

But really, a connection pool shouldn't be a JSF managed bean, and also not be designed that way. I basically entered this answer with my jaw wide open all the time .. I recommend to explore some existing open source connection pool libraries, such as BoneCP, if your sole purpose is to learn by example/exercise.