Is it good architecture of an application if,
I am using multiple technologies leveraging strong points of each.
for example:
Encryption in python,
integration of services in java etc.
or should I stick to one technology like Java as I am comfortable with it?
Also the reason for this question is I am thinking of developing a new application in which speed is a major concern, I am targeting to attain.
Also Database that I am preferring for now is MongoDb.
Any suggestions on the Technologies apart from these technologies?
Also will this approach help in speeding up the application?
Writing the main application in one language only is a easier approach than dividing your application and attempting to write pieces in each language that is best suited for the task, unless you are fluent in a few languages and the ones chosen are particularly suited to specific groups of tasks that make up parts of the functionality.
Because MongoDB has a Java Driver there's nothing wrong with writing your main application in Java and relying on libraries written in other languages (MongoDB is written in C++, C and JavaScript).
As long as other works you need to rely on are well maintained there's no reason to switch from your preferred language to match what any of your libraries are using.
If you add artificial intelligence to your program in the future and part of the code is to run on a GPU you are forced to have a program that is a hybrid; learning a new language along with the details of the underlying algorithms is certainly more of a burden than learning the API.
Decide where to draw the line, what you will write in your preferred language and what will be written by others. It's certainly better to choose libraries and programs that you interface with written in languages you understand (assuming that they are open source). If what you interface with has no source available it becomes a 'black box' which simply must work, there are occasions when that is acceptable and occasional when there is no choice.
Related
Each time I create a software at some point I wish to provide a way for users to control it programatically.
So far I explored the following paths:
Implement the core of it as a library (dll/so, jar, TCL package...)
Embed a scripting engine (tried TCL)
Implement the core of it as a server using socket programming
The library approach does not cost much extra effort for the developer but is not exactly user friendly for "small" tasks.
The scripting engine approach is user friendly as long as you picked his favorite language. It may be rather slow and in any case has some impact on the software architecture, build flow, distribution... in the end I think it is the one which requires the most efforts for the developer.
The server option has the benefit of letting the user choose his favorite language and has the greatest decoupling with the user code.
First question is "are there other approaches ?"
Second question is about performances: I am wondering how the server approach compares with scripting engines. I understand that this is dependent on which scripting engine is considered as well as which OS, that's why I ask SO rather than just bench-marking on my computer at home...
I'm a fairly advanced hobby programmer. I consider myself capable at Objective-C, Java, some straight C, Python, and general MVC design.
I've written quite a few programs but they have all been relatively self-contained, using external libraries occasionally.
When reading about larger projects, and/or more complicated programs, I hear a lot of language thrown around about "Writing one part in X, and writing this part in Y."
Since I have a lack of experience with this, I was wondering if someone could point me in the right direction. What general designs/mechanisms are employed for applications or projects written in more than one language? What is involved in a "scriptable" design?
Thanks for any guidance on the topic!
-Chase
There is no single "right way". A multitude of approaches exist, including the .NET-way, where all the languages are hosted inside a common runtime environment with well-specified interoperability constraints, and a good old Unix-way, where all the components are supposed to communicate via pipes or sockets, using simple text-based protocols.
For the latter you can read a classic book: http://en.wikipedia.org/wiki/The_Unix_Programming_Environment
Depends on what you need to do. For example if you want to build a poker game online then, most probably you would use java for the application and flash/flex for the interface. Java has the power of the libraries and the flash/flex are quite generally available and offer a rich interface.
If you have a software that receives input from an online application and offers output on a specific output (label printer for example) then your online-ready software (Java/PHP/Python) would best communicate with a specially designed program on the target computer. A program for which I'd use C++ for it's technical power, rigurosity and speed compared to java.
The idea is to identify the languages that suit your purpose best. In my opinion it is ideal that you use one language to do all the stuff, that is why I like java as it seems to fit everything although it has a more or less bad renown for slowness.
I see things in a kind of this way:
1. Engineered, machine oriented stuff then it is C++ (and languages of it's kind)
2. Mobile multifunctional stuff (middle-ware mainly) Java
3. Online , browser based stuff PHP especially for B2C(people oriented) applications
4. Python,Ruby etc are from my point of view somewhere between java and PHP but I never really worked with them so I can not give an exact opinion
You can link them together depending on your needs.
For alot of the tasks I have to do I find myself having to choose between making the program using a Shell Script in Linux or a programming language such as Java or Groovy. Does anyone havce any experience about how I should choose one over the other and why?
Shell scripts are excellent for concise filesystem operations and scripting the combination of existing functionality in filters and command line tools via pipes.
When your needs are greater - whether in functionality, robustness, performance, efficiency etc - then you can move to a more full-featured language. They tend to offer some combination of:
type safety
more advanced containers
better control over variable lifetimes and memory usage
threading
advanced IPC like shared memory and TCP/IP
full binary I/O capabilities, memory mapped file access etc.
access to OS APIs and myriad powerful libraries
better readability and maintainability as the project size increases
support for more advanced programming paradigms: Object Orientation, Functional Programming, Generative Programming etc.
better error-checking before your program starts running, hence less dependent on test case coverage
#Tony provides an excellent list of pros and cons. I would add one more general point - shell scripts, because they are so handy, risk displaying the "there is nothing more lasting than a temporary solution" characteristic with all the attendant problems of maintenance when somebody else needs to use it.
Shell script is the most intuitive way to have a "glue" on your system. However, it does not have some useful concepts, like inheritance and modularization, that languages like Python (which is very used to "glue" systems too) have.
True, the use of language depends basically on the task you are trying to do. For the most cases I've worked, shell script worked well, although I'm using a lot of Python to accomplish system related tasks. I don't think that Java would be an alternative in this case. Probably Groovy would be, but not Java (I mean Java as a language, not Java as platform.)
In a sysadmin view, I think Python and Ruby are awesome languages. Not only because of dynamic typing and the lack of need to be compiled, but because tools like Fabric, Capistrano, Puppet, and a lot of others which makes a sysadmin's life a lot easier :-)
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I'm part of a group that starts a new development project from scratch.
Currently it is on hobby-basis but we aim to make it our living
in the time frame of 1-2 years.
We are senior developers coming from a multitude of languages and techniques
with much of the focus on Java for the last few years.
Now, we're thinking of choice of toolsets and languages (the future is
bright when starting from scratch).
We want to be able to use modern architectures efficiently and have
good experience in Java and other JRE-based techniques.
The project is in short a lot of I/O, databases and a decent UI that probably
needs to be web-based and feel quite efficient.
One route to go is classic Java and build UI using GWT (or layers on top of GWT),
another is Scala + lift.
Then there are other techniques based on Ruby, Groovy and so on.
My question is then: What would you select as tools for a new long-term
project given the above. Is Scala here to stay for instance or is one
of those with only temporary hype?
What other techniques do you consider for larger projects from scratch?
Possibly your biggest binary choice is whether you decide to stay on the Java Virtual Machine (JVM) via either Java or one of the other languages which compile into bytecode, or to move onto some other platform, possibly Ruby or Python (with the complications of working with different architectures/operating systems that this may entail). Personally, I decided that I very much wanted to stick with the JVM and hence your language choices would be...
Scala
All I can give is my own experiences coming from a Java background: migrating to scala was made easy by its natural integration into the Java ecosystem and the ability to continue to use pretty much the same toolset in the same way.
By this last point I mean that the statically-typed nature of scala means that all the refactoring and code-navigation opportunities are still available to the developer but scala's type inference means that this comes without the unnecessary verbosity of type declarations littered throughout your code.
I can still use my favourite stuff like Spring, ant, IDEA and I can still use all the libraries I've ever written in Java (this is an argument for picking a language which integrates with Java over a completely new one like Ruby, Smalltalk or Python).
From the perspective of whether scala is here to stay as a JVM language, this is what concerned me most. But consider how many questions on SO have been tagged Jython (161), JRuby (176), clojure (388) and Groovy (661), assuming you wish to stay on the JVM. Not only is scala now well ahead of these (815) but it is growing at quite a rate.
Lastly, although I have not used Lift, a colleague has been extremely impressed with it (and I would probably look at it if I were writing a web application). The fat-client alternative (scala swing) I have found to be more than useable (better than raw swing at any rate!).
Groovy
It's worth noting that the creator of Groovy recently said that had he known of the existence of Scala, he would never have bothered to create Groovy!
JRuby / Jython
I have lumped these two languages together because they both represent an attempt to port the syntax of a dynamic language onto the JVM. Unless that syntax is already familiar to you, why would you bother to go down this route? I must say, the SO stats (above) do not indicate that these have the momentum at the moment.
I would also opine that moving from a statically-compiled to a dynamic language is a big step and you might be surprised by what you miss (in terms of refactoring and development aides etc.) - you may also care about the fact that the interpreted nature of these languages makes them over an order of magnitude slower than Scala.
Clojure
I have no real opinions on clojure other than to say that with an imperative background, its syntax is scary and its flow extremely unfamiliar. I am becoming more impressed by the functional paradigm but I felt that clojure was a step too far for me; I would be a fish out of water in the language, having no previous experience of LISP/Scheme.
The choice of language implies a lot of other choices, which collectively can be more important than the language choice itself. More specifically, when you choose a language, you're also choosing that language's web framework, ORM, IDE, build tool, etc.
For example, if you choose Groovy, you're implicitly also choosing the Grails web framework, if you choose Scala you're choosing Lift, etc. Although you can use Eclipse/Netbeans/IntelliJ for almost any JVM language, the experience varies quite a bit depending on which language you're using. Eclipse is a great IDE for Java development, but a pretty crappy one for Groovy/Grails development.
The problem with this kind of question is that if you ask a guy who uses language X, he'll tell you to choose X, then list all the reasons why X is so great and a few shallow reasons not to use the other languages. Examples of such shallow criticisms include:
Scala
poor tool support
functional programming is esoteric to typical OO developers
Groovy
dynamic languages are unsuitable for large projects
dynamic languages perform poorly
Jython
whitespace indendation as code block delimiters sucks
dynamic langages (see above)
JRuby
reputation for bad performance
funky syntax (from the POV of a Java developer, at least)
Clojure
very funky syntax (from the POV of almost everyone)
very immature
I should emphasise that I don't necessarily believe any of the statements above to be true,
the point I'm trying to make is that it's very easy to dismiss languages without any real experience of them (I only really know one of the languages above). So I wouldn't put too much faith in what people say against a particular language, unless you're sure they've really used it.
If I was faced with your choice I would use Groovy/Grails, because I find it to be an extremely productive and enjoyable technology to work with for building web apps, with good tool support. Are there other choices that might be even better? Sure, but Groovy/Grails is good enough for me (for now).
If you all have strong Java background and no functional and/or dynamic languages background, then you are likely to do well by keeping to Java or migrating to Scala.
I don't mean to disparage any of the other languages here, but Scala will be more familiar to you, and you can put your Java familiarity to good use. Whether you should jump to Scala or not -- that's another question. If you do, however, take notice that you need not be stuck with Lift. Not only there are other web frameworks in Scala, but people have had success combining Scala with traditional Java frameworks such as Wicket.
I worked a lot with Scala, Groovy and JRuby and I can share my experience
Scala
This language was designed in a very in a professional way. You can see it in every aspect of it.
No performance issues because it is a static typed language.
Interesting to learn and play with because of its functional nature.
BUT:
It is very complicated. You can't spend an evening to write a hello world program. You should spend at least a weekend)) Dmitry Jemerov (one of the creators of IntelliJ) said that Scala is much more complex than C++.
Lack of a good tool support. I believe that IDEs for Groovy and Ruby is much superior.
Not well integrated into java ecosystem. Of course you can use java libraries but you will dance a lot of all conversions from one collection to another e.t.c.
Lack of pure Scala libs. You always have to write a small wrapper over a java lib.
Groovy
Has shortcuts for most java boilerplate code.
Great IDE integration.
Interactions with Java are so natural and easy. It is not important whether you use a java class or a groovy class, it just works.
Great for writing DSLs
BUT:
It is a slow language (But I think that it is not an issue in most cases)
As the integration with java is the main goal of Groovy there are some unnatural aspects of the language.
JRuby
One of the best designed languages I've ever seen.
There are a lot of cool libs that can be used.
The best language for writing internal DSLs
Easy to learn.
BUT:
The integration with java sucks.
In my opinion it is too early to use Scala in production systems. It is just too hard because of the lack of tools and libraries. I used Groovy in many big projects quite successfully so it may be the best tool from these 3 languages.
With the information given you can choose any language proposed. They will all still be here in 5 years.
If you cannot decide which tool to pick for your requirements we can't help you. The information given is just to vague to decide. Start building some prototypes for all language/framework and see what fits best. Maybe the requirements are more clear afterwards.
Have you tried Jython -- Python working on JVM? I use it quite often to do various database tasks and it works quite well with such databases as Oracle, PostgreSQL and Informix. I do not create classic UI apps, but I have read that well known Python Web frameworks like web2py or django work with Jython.
If you have experience using dynamic languages, and are able to write the unit tests to support them, go that way. The development speed should be greater than what you can achieve from a static language. However, as the project will get bigger, it may become harder & harder to mantain ( it may only be me, but compile time checks help you a great deal ).
If however, you have Scala experience, I'd choose that instead. I find Scala to be a nice mix between Java and Ruby.
Good luck!
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I would like some practical guidance on when I should use a Domain Specific Language. I have found resources about advantages and disadvantages, but what kind of project would warrant its use?
It seems like there is a big investment in time to create and maintain a DSL, so in what application space would I get a productivity return on my time investment?
Edit: It seems the most common use of DSL is for file formats for persisting data state, what about using a DSL for program logic and structure(perhaps code generation)? When is this feasible?
Edit #2 I am mainly asking about when is creating a specific DSL worthwhile. Of course we should use existing DSLs as much as possible to save time.
There are very few good reasons for creating yet another DSL. The world is fat with special-purpose languages.
Think along with these lines.
Solve the problem with a general-purpose language such as Python, Java, C++.. whatever.
Optimize that solution to factor out the common features and build a really nice, really elegant, really extensible class library.
Optimize that class library to emphasize "orthogonality". Make sure all features work well together, without any problems.
If you need simplification of the syntax only, create a scripting wrapper around your nice class library. This is your DSL. For Python, this is easy -- it's already a dynamic language. For Java, there are things you can leverage. For C++ it can be a bit of work to build this flexible scripting environment.
If you still need further optimization, consider writing a compiler for your DSL.
The ACM Computing Surveys article When and How to Develop Domain-Specific Languages provides advice on just this topic, as does Martin Fowler's 2010 book Domain-Specific Languages.
Firstly, I would use a DSL when the problem domain your developing against is a widely well known domain, and some business experts of that domain have already went through great lengths to build such a DSL so that you wouldn't have to go through the lengths yourself to solve all the problems they have already figured out.
If you're thinking of creating a DSL, I would consider doing so if your business is done in a very particular area, and you spend the majority of your time focusing in a specific problem domain. If you bounce around doing applications for multiple problem domains, then I wouldn't advise taking that approach.
For example, if your business is soley in building tax applications, it might be a good idea to build a tax system DSL. This would allow your language not only to be useable by you in your various tax applications, but it would also be marketeable (useable) by other businesses in your industry that want to do similar things that you're accomplishing.
Of course, you have to weight the costs/benefits of building a DSL vs a framework on top of an already existing language.
One situation that comes to mind is when the requirements requires a very high or improbable level of customization/configuration. So you would provide a kind of scripting model against a DSL instead.
Takes a car assembly "arm" for example, providing a configuration model to support various factory configurations would be impossible. (detect this, don't detect that, when this happens do this ... etc.)
But compiling a new application with specialized logic for each customer is probably not a good way to go. So in this case, you create a little framework that would becomes a kind of DSL, and then for each robotic arm you sells, you write a little app in your DSL and save it along with the core software that would compiles and runs your DSL scripts instead. Or better yet, tools to program the DSL are included along with the robotic arm so your customer can "program" the arm themselves in the DSL you created.
One real world examples that comes to mind is Yahoo Pipes (you could think of it as a DSL) or the robots.txt directive for automated web crawler for example. They may not be a full-blown DSL but they demonstrate where DSL might be useful.
Well, someone has to say it, so here goes:
Lisp is regarded by some as the domain specific language for any domain. A well-supported and very extensible DSL at that.
In some cases, fashioning a DSL from Lisp (or a similar language such as Haskell) could actually provide a lot of power with minimal effort, and thus would be quite worthwhile. DSLs do not always need to be big maintenance burdens.
The most obvious is you should definitely use them when the language already exists and is well-supported. The prime examples of this are UIL for Motif-based GUI development and make for software builds.
If you have to make your own, I'd say to look for domains a large amount of effort is in just specifying things properly, and where your compiler can't really find most errors, but a domain-specific compiler could. GUIs are a great example, as most of the work is in setting up the layout, and there are generally lots of ways to make syntacticly valid C++ calls that make no sense whatsoever to your underlying GUI system (EG: trying to embed an entire dialog widget inside a button).
I find UIL particularly a huge gain for GUI development because a UIL compiler can find errors in a GUI specification that just look like nice normal compilable code to a C++ compilter. The fact that it is well-supported means that the code is easy to port between platforms, and even GUI builders.