cyranoVR's Journal: Java: A Verbose Acronym

Can you spot the error?

import some.imaginary.package.MyService;
 
public class MyServiceFactory {
 
    private static MyService instance;
 
    String factoryName;
 
    public MyServiceFactory(String factoryName) {
        this.factoryName = factoryName;
    }
 
    public Object getService() {
// create if null...
    synchronized(this) {
            if(MyServiceFactory.instance == null) {
            MyServiceFactory.instance = new MyService();
            }
    }
    return MyServiceFactory.instance;
    }
 
    public static void main(String args[]) {
        Thread a = new Thread() {
            public void run() {
                MyService service = new MyServiceFactory("a").getService();
        service.doStuff();
        }
    };
 
    Thread a = new Thread() {
            public void run() {
                MyService service = new MyServiceFactory("b").getService();
        service.doStuff();
            }
        };
 
    a.start();
    b.start();
    }
}

The error is not a syntax one, so if I'm missing a semi-colon or something, please assume that's unintentional.

Found one

[Com2Kid]

if(MyServiceFactory.instance == null)
{
SomeObjectFactory.instance = new MyService();
}

Shouldn't it be MyServiceFactory.instance?

public void run()
{
MyService service = new MyServiceFactory("a").getService();
service.doStuff();
}

Should this be MyServiceFactory("a").getObject(); ?

WTF why even have a factory here? Why not just go MyService service = new MyService(); You lose track of that MyServiceFactory("a") right outside th

Re:Found one

[cyranoVR]

Those are typos, which I will fix.

My shot at it....

[jawtheshark]

It's been a while I did Java, so I may be way off.

The signature of getService(), specifies that it returns an Object. Okay, but further in the code you find the following lines:

MyService service = new MyServiceFactory("a").getService();
MyService service = new MyServiceFactory("b").getService();

Since, getService() returns an Object and this Object is assigned to a more specialized class, it should be cast to said class.

The second thing that I find strange is the staticness of "instance". Why? Q

Re:My shot at it....

[cyranoVR]

Hint:

http://java.sun.com/j2se/1.4.2/docs/api/javax/nami ng/spi/ObjectFactory.html/ [sun.com]

This is a cornerstone of J2EE

Corrected link

[cyranoVR]

http://java.sun.com/j2se/1.4.2/docs/api/javax/nami ng/spi/ObjectFactory.html [sun.com]

Jaw is right

[Com2Kid]

After spending another 10 seconds thinking about it last night, the instance variable thing is it. You only have 1 instance total.

I still say the other idiocy is using a factory class at all! Factory classes are good when you have complication associated with creating an object that goes beyond just a constructor. Have the object implement runnable and be done with it.

Re:Jaw is right

[cyranoVR]

What if your service has to be a singleton, but you want to make it availble via JNDI?

Hint: concurrency.

Re:Jaw is right

[Com2Kid]

Then just declare a static object some where and make sure the damn thing has locks on it. Use POSIX threads in whatever program is calling it, since the Java5 threading model maps closly to POSIX threads anyway.

Honestly, never had to fart around with JNDI, just heard bad things about it. :)

Ignore this post, tired.

Re:Jaw is right

[cyranoVR]

Read these two links when you have time:

http://www.javaworld.com/javaworld/jw-04-2003/jw-0 425-designpatterns.html [javaworld.com]

http://tomcat.apache.org/tomcat-5.0-doc/jndi-resou rces-howto.html [apache.org]