RE: Source Evaluation?

["Joe Teff" <JoeTeff@xxxxxxxxxxxxx>]

You can use instance variable as long as you don't update
them. That's the thread exposure. The init() is the proper
place to initialize them as it is called prior to servicing
any requests.

One comment I was going to make about Brad's code is to
place your jdbc values in a file and then load them into
a Properties object. Very easy to do. I do that because
I'll test on my home PC using Access and switch to the
AS/400 for production. I have a database.properties file
on both machines, so I don't have to change my code to
switch.

The file is plain ascii text that has key=value pairs.
So I would have entries in my file like:

   driver=com.ibm.as400.access.AS400JDBCDriver
   url=jdbc:as400://web400
   user=jdbc
   password=jdbc

The Properties class extends Hashtable. To create my
Properties object from my file I use:

   Properties prop = new Properties();
   prop.load(new FileInputStream("database.properties"));

I then use the getProperty() method that takes the key
as a String and returns the value as a String.

   Class.forName(prop.getProprty("driver"));
   con  = DriverManager.getConnection(prop.getProperty("url"),
          prop.getProperty("user"), prop.getProperty("password"));

Joe

-----Original Message-----
From: owner-java400-l@midrange.com
[mailto:owner-java400-l@midrange.com]On Behalf Of Larry Loen
Sent: Friday, February 09, 2001 12:03 PM
To: JAVA400-L@midrange.com
Subject: RE: Source Evaluation?



Paul Clapham wrote:

>But in my (limited) experience, I've found that
>most of my servlets don't require an init() method.

Well, strictly speaking, you are correct.  However,
this is an interesting topic.  Either a static class initializer or the
init
method is a good place to stick read-only kinds of objects, especially
those that are fairly expensive to construct.

As I understand the servlet rules, you can't really use regular "instance"
variables on grounds that architecturally, multiple threads can
simultaneously
use the same servlet object.  This means modification raises thread safety
issues.  However, you can put instance variables in them that are
what Java calls "immutable" -- don't change after they are constructed.
These are thread safe by design and definition.

Still, an init method can in the end include a lot of stuff, the kind
of stuff that starts out in .ini files and are configuration specific, such
as
the www.whateversystemthisis.com prefix  and like things.

I must admit, I tend to use the static class initializer because most of
this
stuff only needs to be done once and can fit in class-wide variables.  But
if I thought about it longer, I could probably find examples that made
sense for
init as well.
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