Re: [PLUG] Educational Languages

[Fred Stluka <fred@bristle.com>]

PLUG folks,

I got a direct e-mail query about Java in response to my previous
posting, but it and my reply may be of general interest.  If so,
read on.  If not, you know what to do...

> Since you seem knowledgeable/experienced with Java, I was wondering if
> you would mind if I followed up with you directly with a question or
> two about that programming language?
>
> My current situation with Java is this:  At $DAYJOB, I work full time
> as a PHP programmer, and have for the last 8 years.  While I agree
> with the comments on the PLUG mailing list that PHP should not be
> taught to beginners, I enjoy writing code in the language and find it
> easy to program in.
>
> That being said, I've tried researching Java a few times, specifically
> in terms of web development, but didn't have much luck.  It seemed
> like there were so many different technologies for solving the same
> set of problems. (EJB, Struts, Tomcat, JSP, Servlets, JDBC, Web
> containers, etc. etc.)  I had a really hard time trying to figure out
> the bare minimum that I needed to install just to do a "hello world".
>
> Now, when it comes to new technologies, I have no problem learning
> them on my own.  All I need is a way to "bootstrap" myself (usually by
> downloading an interpreter) and I'm set.
>
> So, assuming I haven't bored you by now, my question about Java would
> be: what's the best/minimal way for me to get started doing web
> development with Java?
>
> If you could help point me in the right direction, I would really
> appreciate it. :-)
>
> Thanks for your time, 


I suggest you start at the Getting Started section of the Java Tips
page at my web site.  The links I posted to the PLUG list are complete
examples of Hello World as an application, applet, and servlet, plus a
slightly more complex JSP example.  Each article is very short (1-2
screens of text) but contains the source code for a complete example,
plus instructions on how to download and install any tools (Java
compiler, Tomcat web server, etc.) you might need:
   http://bristle.com/Tips/Java.htm#applications
   http://bristle.com/Tips/Java.htm#applets
   http://bristle.com/Tips/Java.htm#servlets
   http://bristle.com/Tips/Java.htm#jsp_intro

Yes, Java is very modular.  Instead of having everything built into
one massive monolithic hulk, there are modules you can pick and
choose from to do what you need to do, without carrying along all the
other baggage.  They all work smoothly together, but you don't
necessarily need all of them.

Don't try to take it all on at once.  Why bother?  Just use what you
need.  It's easy to get started, and easy to add more later.  Don't
bother to dive into technologies that you haven't yet found a need for.
I don't believe in using technologies just because they exist.  Many
of the latest fads you hear about are just "solutions looking for a
problem to solve" -- useless!  Java makes it very easy to use what you
need and leave the rest behind.

If someone challenges you, asking why you are not using some particular
feature, get them to give you a detailed list of benefits, and decide
whether any of them matter to your project.  Again, you will find lots
of people trying to sell you solutions for problems you don't have.
Use what you need, and leave the rest.

Learn Java in the same way that you read this e-mail message -- a piece
at a time.  Both are written very incrementally, and very modularly.
If you start getting bored, you must have hit a solution that doesn't
fit any of your current problems.  Not of interest right now, so skip
to the next paragraph, or stop reading entirely.  Don't bother with
things you don't need yet.  Just be aware that there is more out there
when you need it.

Since you want to do Web development, start by just using Java servlets,
until you see that it is tedious to wrap all of your HTML in print
statements.  Then add JSP pages to the mix, replacing those servlets
that were mostly generating simple HTML, but continuing to use servlets
for more complex things.  For a concrete example of this, see:
   http://bristle.com/Tips/Java.htm#jsp_intro

Then, perhaps learn some of the additional power of JSP.  It does not
do anything a servlet can't do, but it is often easier.  JSTL is another
step in the same direction.  Nothing you couldn't do with a servlet or
with JSP, but some things are again much easier.  For JSP and JSTL info,
see the series of short articles and summary sheets at:
   http://bristle.com/Tips/Java.htm#jsp
   http://bristle.com/Tips/Java.htm#jsp_directives
   http://bristle.com/Tips/Java.htm#jsp_scripting_elements
   http://bristle.com/Tips/Java.htm#jsp_and_jstl_actions
   http://bristle.com/Tips/Java.htm#jsp_and_jstl_implicit_objects
   
http://bristle.com/Tips/Java.htm#accessing_properties_of_objects_in_jsp_and_el
   http://bristle.com/Tips/Java.htm#el_convenience_objects
   http://bristle.com/Tips/Java.htm#enabling_el_expression_evaluation
   http://bristle.com/Tips/Java.htm#looping_through_cookies_in_jsp_and_el
   
http://bristle.com/Tips/Java.htm#looping_through_parameters_in_jsp_and_el
   http://bristle.com/Tips/Java.htm#looping_through_headers_in_jsp_and_el

If you need to access a relational database, start using the JDBC classes:
   http://bristle.com/Tips/Java.htm#jdbc

Along the way, you'll start to hear about Java Beans.  Stop to read the
two-pager:
   http://bristle.com/Tips/Java.htm#java_beans
and learn that you have been writing Java Beans all along.  They are not
huge complex things like Microsoft ActiveX objects.  In fact, the following
is the complete source code for a trivial JavaBean:
   public class BeanWithNoProperties {}
They are just as powerful as ActiveX objects, but much simpler, since all
of the "discoverability" is already built in to the Java language.  All you
have to do is follow a couple of simple conventions about how you name your
methods.

At some point, you'll want to automatically generate your API documentation
from your code, producing docs like:
   http://bristle.com/Tips/javadocs/index.html
Want to generate such a set of docs with minimal effort?  The javadoc tool
comes for free with the free Java compiler, so it is already installed and
ready go on your computer.  Just type:
   javadoc *.java
as described in:
   http://bristle.com/Tips/Java.htm#javadoc_intro
For a description of the layout and contents of the generated docs, see:
   http://bristle.com/Tips/Java.htm#javadoc_default
Want more detailed docs, based on the comments in your Java code, not just
on your Java code itself?  See:
   http://bristle.com/Tips/Java.htm#javadoc_comments
Want the docs to contain even more detail about each method (descriptions
instead of just names of each parameter, return value and exception)?  See:
   http://bristle.com/Tips/Java.htm#javadoc_tags
For a complete small example, see:
   http://bristle.com/Tips/Java.htm#javadoc_example
Want more control over which portions of the docs are included/omitted,
or the format of the generated pages?  See:
   http://bristle.com/Tips/Java.htm#javadoc_cli
   http://bristle.com/Tips/Java.htm#javadoc_formatting
   http://bristle.com/Tips/Java.htm#javadoc_doclet

If you:
- Are planning a large Web application and want the benefit of a formal
 Model-View-Controller architecture to separate your user interface
 from your business logic, or
- Find it tedious and clunky to have each JSP page or servlet hardcoded
 to know the name of the next JSP page or servlet in your workflow, or
- Want a way to separate the presentation tier (JSP pages) from the
 business logic so that human factors people can do one and Java
 programmers can do the other, or
- Are just getting tired of writing lots of tedious repetitive code to
 check user input fields for errors and show error messages to the user
you may want to look into the Struts library.  See links to lots of Struts
info at my links page:
   http://bristle.com/~fred/#java_struts

If you want a more object-oriented, less HTML-centric user interface,
consider JavaServer Faces (JSF, not just JSP).  See my links at:
   http://bristle.com/~fred/#java_jsf

If you are writing a lot of JDBC code for database access, you may prefer
to use Hibernate:
   http://www.hibernate.org/
or EJBs (Enterprise JavaBeans):
   http://bristle.com/~fred/#java_ejb

If you are writing a huge application that has to manage thousands of
instances of each object in memory at the same time, and run on multiple
Web and application servers in a server farm, that's another reason to
look into EJBs.

If you want a more lightweight architecture, but still want the benefits
of an "inversion of control" framework to automatically instantiate your
Java Beans, and offering dependency injection, service abstractions, and
aspect oriented programming (AOP), you may want to look into the Spring
framework:
   http://www.springframework.org/

Each of these increments is compatible with all of the others.  Mix and
match as you like.  Use what you need and leave the rest.

You also mentioned Tomcat and web containers.  If you are going to write
a Java web app, you're going to be writing servlets and/or JSPs, so you're
going to need a "servlet container" (a Web server that knows how to run
Java servlets and JSPs).  Tomcat is the official reference implementation
of such a container, and is free.  Download it, unzip it, and run it. 
No install required.

BTW, if you want some personal one-on-one tutoring in any of these areas,
I am available at an hourly rate.  Again, incremental -- pay for one hour
and then decide if you got enough value to justify paying for another
hour.  When you don't need any more, stop.  Use what you need and leave
the rest.

--Fred
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Fred Stluka -- mailto:fred@bristle.com -- http://bristle.com/~fred/
Bristle Software, Inc -- http://bristle.com -- "Glad to be of service!"
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