programming – Page 11

Comparing PHP and ASP

PHP and ASP (Active Server Pages) have many ideas in common, and I tend to lump both in to the same category: page-based server-side web scripting tools. I use that category for small to medium sized application; I usually don’t choose it for large or complex web applications.

Here are a few points of comparison between the two:

PHP is more seamless across platforms. I can develop on my Windows box and deploy on Linux. (I know about ChiliSoft’s ASP implementation for Unix, but I don’t see much point in bringing my ASP code, which tends to use COM objects, over to Linux.)
PHP has a great number of functions that a web developer needs “in the box” – read through the manual to see the list. I found that I had to go looking around to third parties and COM objects to get some things in ASP which
were already there in PHP. For example, the htmlentities() function.
PHP is very often available on external web hosts, if they use Unix/Linux servers, at very low cost.
ASP is not tied to one language. It uses the same infrastructure to work with VBScript, JScript, PerlScript, PyhonScript, and more! This is an excellent approach, and Microsoft should be applauded for it.
In ASP, the dominant model for DB access is to use ADO, which provides a degree of database independence; PHP has seperate functions for each database type, and requires an additional layer to acheive that degree of independence.
Code modules in a COM object can be plugged in to ASP or 100 other places.
Code modules in C with appropriate PHP linkage are only for PHP, and are potentially more difficult to write.
ASP is almost always available on external web hosts, if they use Windows servers. Windows-based hosting tends to cost a bit more than Linux-based hosting, especially with SQL Server is provided.

Update (2007): PHP and ASP (now ASP.NET) have changed considerably since I wrote this; I suggest looking around for a more current comparison if you need to select between them now.

Improving Delphi Object Pascal

In a conversation between me and others in a newsgroup thread a while
back, I made some comment about not caring for the Object Pascal syntax
in some way. Someone asked:

> If you dislike Pascal so much, please explain what you like and
why.

This is a slightly more detailed answer to the question than I presented
at the time:

I actually like Delphi / OP, just not as much as I could. In case
you are interested, here are some things I wish were different:

I find the begin and end keywords to be needlessly verbose.
Control structures could have matching, non-optional blocks… like
Modula-2 or (!) VB. if .. then .. endif would be more concise than "if
.. then begin .. end", and make it easier to read code and prevent
bugs. The whole begin/end thing really belies Pascal’s origin as a teaching
language. When you write 2-page programs, it doesn’t matter if begin/end
is verbose.
Case insensitivity permits sloppy coding.
Now that I’ve used Java quite extensively, I am really sold on garbage
collection as a Very Good Thing for large-scale projects.
I wish there was a more effective structure for handling large amounts
of code, other than the flat module structure. Java packages are nice.
I wish the RTTI covered everything about the class, not just published
properties.
Why do we have to do:

  try
    try
      // yada
    except
      // yada
    end;
  finally
    // yada
  end;

rather than

  try
    // yada
  except
    // yada
  finally
    // yada
  end;

Borland could easily allow the latter, short and clear syntax.

The underlying point to all of this is that Object Pascal is Borland’s language;
they can do anything they want with it. The things above are within their
power to change; it’s not like that are complying with a standard.

But do I really want them to change all this? Probably not. Would I choose
OP for my code if it weren’t for the great stuff around it (the IDE, VCL,
weatlh of third party components, etc.)? Definately not.

In my opinion, the core strength of Delphi is not the language. It’s the IDE, VCL,
lightning-fast compiler, linker, and overall environment which have made it possible for Delphi to have
a vast array of available plugin components. Delphi has attracted a remarkable
number of vendors of high quality components. Using those components as well
as Delphi’s (object-oriented) core features, it is often possible to build a working solution in Delphi
much sooner than would be possible with another tool… and that is what I
like most about Delphi.

Web Services

There has been a lot of buzz recently about "Web Services". A short examination shows that essentially a web services is an RPC (remote procedure call), generally across the internet, using SOAP/XML over HTTP.

RPCs are nothing new – so why all the excitement? Here are some reasons:

Web services work over the internet, through firewalls. Getting other RPC technologied to do this can be challenging.
Web services carry "WSDL" service descriptions, which will make it possible for software development tools to greatly automate the process of using them.
Web services are truly language-neutral; many other technologies carry baggage that belies their origin in one primary language.
Web services are text-based; the protocol is human readable and hence much more debuggable than (for example) IIOP, DCOM, RMI, etc.

Borland has made it near-trivial to expose functionality as a web service, or call web service functionity in Delphi 6. With just a few clicks the needed client or server side "stub" code is automatically generated, allowing you to use a web services as easily as any local function/procedure.

Many publicly accessible web services are listed at http://www.xmethods.net/

Refactoring

Here is a common situation where refactoring can be used:

Problem:

You have a body of code which exposes and API (set of entry points). You want this code to have a different API.

Non-refactoring based solution:

Take the old code apart. From the pieces, write new code that has the desired API. The problem with this is that it’s a big leap… with little confidence along the way that the code will work.

Refactoring based solution:

Create a empty implementation of the desired API. Use the old code’s API to implement these functions – create a wrapper around the old code. Verify (with unit tests) that the code does what you want, using the desired API.

Now, consider the “wrapper” and the old code as a body of code to be refactored… incrementally change it to improve the design, maintainability, etc.

Alternatively, if the code is “throw-away” code not of long term important, you have the option to stp – just leave the code wrappered and un-refactored.

Right now, most refactoring is happening “manually” – but in the future, a direction that IDEs can add more value is by automating the process. Imagine right-clicking a method and selecting “refactor up to superclass”. You can take a look at this idea with a tool that “adds-in” refactoring to your existing IDE, like TransMorgify. A new Java IDE, IntelliJ IDEA offers a limited set of refactoring tools, built in to the IDE.

Under The Hood – PHP and MySQL

(This introductory article was written in 2001 to help explain to clients why LAMP (Linux, Apache, PHP and MySQL) were chosen as the infrastructure for for certain kinds of web sites. We generally choose other tools now.)

Many of our dynamic web sites are built using PHP and MySQL. Although these products are frequently used together, they do not have to be, and each plays a separate role in the dynamic web content generation process. The two major components needed for that process are:

A database system to hold the dynamic web site’s data. Although it is possible to build small sites on flat-file storage systems, a database server is a much more scalable, reliable foundation for a dynamic web site. The database server is not web-specific per se, although it does need to potentially support a heavy load of queries, slanted heavily towards “SELECT” (data reading) queries rather than data updating queries.
A web-database integration tool (scripting language or equivalent) for dynamically generating HTML pages, email messages, etc. based on data stored in the database, and processing user interactions to update that database.

Often for the database, we choose MySQL for several reasons:

Reliability – based on reading comments from many users, MySQL appears to be a reliable product. We have experienced no MySQL failures of any kind ourselves.
Price – MySQL is free, keeping the budget to a minimum for smaller sites.
Speed – MySQL is designed to operate very quickly and efficiently for simple SELECT statements, at the expense of lacking some features that “heavier” databases have, such as transaction support, stored procedure, correlated subqueries, etc. Although these are very valuable features, most dynamic web sites do not need these features because of the nature of the features they provide.

We are also familiar with a number of other database choices for other projects:

Microsoft SQL Server – this product, in it’s 7.0 and higher versions, is a very nice database server with excellent integration (of course) in to the Windows NT environment. It would be an obvious choice to consider when working on a project which was required to be NT-based.
Oracle – Oracle is the market leading for large database servers, and runs behind the scenes and many of the internet’s busiest web sites. It has a mildly painful but extremely powerful stored procedure capability, and can be tuned for high performance under extreme load, if you can find a sufficiently skilled DBA. We are happy to bulid an Oracle-based solution where it is appropriate. Oracle is however quite expensive and require much more hardware to run well than MySQL, for example.
PostgreSQL – This is the “other” free database server out there. It has only recently begun to approach the stability and speed of MySQL, and it offer a much richer set of features, more similar to the top-tier commercial database servers.
Interbase – Released as one point as open source from Borland, Interbase is also very fully featured. It seems to not be as fast as MySQL for simple SELECTs (the most common case in web apps), but can handle complex tasks effectively and does not require much DBA attention.
Various others.

For our programming / web-database integration tool, we are using PHP, a web-specific scripting language. There are literally hundreds of web-database tools to choose from, so not surprisingly there are many excellent choices. Some of the reasons we use PHP are:

Tight integration with Apache, the most popular web server on the internet.
Good performance, because of that tight integration. PHP is an excellent compromise between power and efficiency; it provide a flexible, expressive language yet it is simple enough to teach to new team member quickly
A very rich array of built-in features. In particular, PHP has many capabilities “in the box” that have to be added on to other popular solutions like ASP.
Built in database access, with connection pooling.
It is Open Source, and under very active development; any bugs that appear get fixed quickly.
There are commercial performance enhancement mechanisms available if needed.

PHP is not without weaknesses, however. For example, its basic design encourages mixing the scripts in with the site’s HTML. This works well for small sites, but becomes very troublesome on large site where different people are responsible for the HTML and the programming. Another weakness is that the language relies mostly on programming technique to remain manageable and structured; it has almost no support for modularization. Some other web-database integration tools that address these issues and others are:

Java Servlets, which leverage the increasingly dominant Java language.
a Java-based application server, such as WebLogic, WebSphere, etc. These can be used to build systems which include servlets, JSPs,EJB, JMS, and other powerful Java technologies.
mod_perl integrates the remarkably expressive Perl language into Apache, and the wide array of accompanying Perl modules can implement isolation between the application code and HTML if desired.
Zope, an application server based on the Python language, has a strong following and provide the desired seperation between logic and HTML. It also offers total web-based management, scalability, and a vibrant developer community.

We are pleased and satisfied with the usability and performance of PHP and MySQL. They are an excellent combination for small to medium-scale read-intensive web application projects.

Windows Clients, Java Servers

Problem / Scenario:

You have server code in Java implementing business logic, or you want to have such code. Java is your strategic choice.

But… you have a need for a client application that will be a native Windows application, for whatever reason. Sample reasons: (1) they need to run quickly and smoothly on a factory floor full of Pentium 150 or slower machines with limited RAM. (2) they need to work in disconnected mode, or talk to local hardware, so a web application won’t work.

How do you write server code in Java (in EJBs, for example) but access it easily from a native Windows clients, for example a Delphi application?

Possible Solutions:

Solution #1: Talk JRMP from Delphi

Implement the Java RMI JRMP protocol in Delphi. This will be nearly impossible, since it is built on Java object serialization. So there are various approaches you could take.

Solution #2: Java on the Client, use JNI

Run Java on the client as well, and use JNI to communicate between Delphi and Java, then Java to do the client side RMI. This defeated the goal of keeping the client lean, though… a Delphi thin client can run well on an old, slow machine with 32 meg of RAM, Java can’t.

Solution #3: RMI-IIOP / CORBA

Some Java application servers can seamlessly (?) expose Java services (like EJBs) as CORBA objects. Borland has CORBA support available for Delphi. This will avoid the overhead of Java on the client, but is too vendor-specific for my tastes.

Solution #4: Your own Proxy on the server

Use a non-RMI way to communicate between the Delphi client and an extra “tier” at the server; this piece of middleware would communicate with Delphi using any of a number of methods, including DCOM. Then use JNI or other means to access the Java services on the same (server) machine.

Solution #5: ASTA-Java

ASTA has a product (though I don’t know if it’s in development, or ready to go) that provide an generic mechanism for invoking EJB operations, from a Delphi client. The challenge here is how to send and receive complex types, which are defined by Java classes.

Solution #6: Web Services with SOAP

Expose the server-side services as web services via SOAP. Choose an application server which will automatically expose your EJBs this way, if possible. Then use any available way to make a Delphi client talk SOAP. PureSOAP and Microsoft’s SOAP support are two possible ways. (This is really the most appealing choice to me, as of 2001.)

Solution #7: Homegrown web services

It’s really not all that hard to write wrapper code that exposes your server services via HTTP requests with parameters, via XML strings, etc. Such a thing would not be language specific, so the server could be on one language, the client in another. This solution has some appeal in cases where you want the pieces to be tightly “wrapped up” and not exposes in anything as standard as SOAP for some reason.

There many, many paths to use to get from point A to point B… if you have a different scenariou in mind, tell me about it and I will try to expand this page to cover it.

Need to do this for your own project? Consulting services are available.