Catch exception while initializing static final variable

Question

I have following code:

public class LoadProperty
{
public static final String property_file_location = System.getProperty("app.vmargs.propertyfile");
public static final String application-startup_mode = System.getProperty("app.vmargs.startupmode");
}

It reads from 'VM arguments' and assigns to variables.

Since static final variable is only initialized at class load, how can I catch exception in case some one forgets to pass parameter.

As of now, when I am using 'property_file_location' variable, exception is encountered in following cases:

If value is present, and location is wrong, FileNotFound exception comes.
If it is not initialized properly(value is null), it throws NullPointerException.

I need to handle second case at time of initialization only.

Similiar is case of second variable.

Whole idea is

To initialize application configuration parameters.
If successfully initialized, continue.
If not, alert user and terminate application.

morgano · Accepted Answer · 2013-07-26 06:14:54Z

5

You can catch it this way:

public class LoadProperty
{
    public static final String property_file_location;

    static {
        String myTempValue = MY_DEFAULT_VALUE;
        try {
            myTempValue = System.getProperty("app.vmargs.propertyfile");
        } catch(Exception e) {
            myTempValue = MY_DEFAULT_VALUE;
        }
        property_file_location = myTempValue;
    }
}

answered Jul 26, 2013 at 6:14

morgano

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1 Comment

dpinya Over a year ago

The last asignation property_file_location = myTempValue;must be inside a finally block

c.s. · Accepted Answer · 2013-07-26 06:30:43Z

2

You can use a static initializer block as suggested by the rest of the answers. Even better move this functionality to a static utility class so you can still use them as an one-liner. You could then even provide default values e.g.

// PropertyUtils is a new class that you implement
// DEFAULT_FILE_LOCATION could e.g. out.log in current folder
public static final String property_file_location = PropertyUtils.getProperty("app.vmargs.propertyfile", DEFAULT_FILE_LOCATION);

However if those properties are not expected to exist all the time, I would suggest to not initialize them as static variables but read them during normal execution.

// in the place where you will first need the file location
String fileLocation = PropertyUtils.getProperty("app.vmargs.propertyfile");
if (fileLocation == null) {
    // handle the error here
}

answered Jul 26, 2013 at 6:30

c.s.

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1 Comment

Learn More Over a year ago

Above parameters were subset of actual. I have parameters which I am using all the time. This aproach should work for me. PropertyUtils.getProperty(), will give me way to do exception handling. I will try.

Michael Laffargue · Accepted Answer · 2013-07-26 06:16:05Z

0

You may want to use a static bloc :

public static final property_file_location;
static {
  try {
    property_file_location = System.getProperty("app.vmargs.propertyfile");
  } catch (xxx){//...}
}

answered Jul 26, 2013 at 6:16

Michael Laffargue

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2 Comments

Michael Laffargue Over a year ago

That's because if it fails your final variable isn't set. so you could add a finally {proeprty_file_location = null};

morgano Over a year ago

Even with a finally clause, have a try and compile it.

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