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I've already run several times into the issue of creating a desktop client app for working with some server, and every time I ended with ugly code, which becomes just impossible to support after couple of releases.
I have highlighted the following key points:
All operations must be asynchronous, without any dummy windows for relative fast operations (i.e. less than 30 seconds)
App has to periodically connect with the server and check, for example, user account
All heavy operations must be cancelable
But, most important, all of this must be "naturally" in code, without creating unnecessary difficulties (singletons, hacks, etc)... only really needed code with minimal overhead.
How would you design such kind of app? What pattern would you use? What open source project with good architecture you can recommend?
This seems a little too broad, but instead of flagging I'll try and give an answer as I find the question interesting. I invite you to add more details if they come to mind.
Even though your design concerns the design of the application, there are a number of languages, patterns and technologies that would suit your requirements.
Keeping it general,
If your want your operations to be asynchronous, you are going to
need multiple threads. Their implementation and use may vary
depending on the language that you are using, but the concept behind
is the same. So, just spawn a thread every time you need an
asynchronous task, and implement a way to be noticed when the task is
done (with or without errors). This can be done in a number of ways,
since you asked for pattern I suggest you have a look at
observer.
The second requirement is not completely clear to me, I assume you
want to periodically check that the client's data is aligned with the
server's, and maybe perform security checks ("Are session and
authentication credentials still valid?"). The first solution is to
actually ask the server every n seconds, again using another
thread. This kind of polling might not be the best option though: how
do you factor in the possibility of connectivity issues? Even if your
client cannot operate without a working connection to the server, it
might bother the user to be disconnected and lose his work just
because his Wi-Fi router rebooted. I would suggest you perform
alignment checks at I/O, perhaps distinguishing between critical and
non-critical ones. For example, if you decide the user's profile
has to be aligned, then you would retrieve updated data from the server upon viewing it. On the other hand, if your app offers the
user a list of cooking recipes and you don't care about him not
viewing the one that has been inserted on the server 10 minutes in
the past, you could simply cache these items and refresh them in a
background thread every minute, without even noticing the user in
case the update fails. Last but not least, if you are also
concerned with concurrent modifications of data, again based on your
requirements you can decide to implement locks on data being edited,
to performs checks on save operations to see if the data has
changed in the meanwhile, or to simply let the user overwrite the
data on the server no matter what. All in all, hoping I interpreted
your question correctly, this requirement is nontrivial and has to be
adjusted to your particular use case.
Assuming the data is eventually saved on some sort of database on
the server, one answer are transactions, which allow you to
treat even complex sequences of operations as "all or nothing",
atomic instructions. You might implement your own system to have the
same result, but I don't really see the point of not using this
powerful instrument when possible. Keep in mind one thing: I'm
assuming "cancelable" means "cancelable before some point in time,
and not after" (a sort of "undo"). If you're looking for complete
revertability of any operation of data, the requirement becomes far
more complex, and in general not possible to guarantee.
I believed I already answered in a way that helps you minimize "hacks" in code where possible. To recap:
You are going to need threads, and the observer pattern can help you
keep the code clean.
Again, you can use threads, or focus on check on I/O operations. In
the second case, you might consider an application layer
specifically for client-server synchronization, embed it in one or
more classes, and perform all your checks there. Have a look at the
proxy pattern.
Use transactions to revert operations, and issue a COMMIT only
when you are sure that the operation is confirmed, a ROLLBACK in
every other case. Encapsule this logic in your server's code so that
the client is not aware of the actual transaction system being used,
and your code should be quite clean.
Please comment if my answer is not satisfying or clear.
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I wanted to ask you, experienced programmers, a question that bothers me recently. I'm a second year student of the university of technology, where we spend a lot of time learning how to code. I found creating small but practical applications the best way to learn, and sometimes I would like to give them for free to someone else. And here the problem appears. If someone want to use it but is afraid that the app is not safe, I don't know any other way how to prove that it's not harmful but to show the source. It's not a big deal for me since those apps are not that big and complex, but I'm wondering if there is any way to show that the program is fully safe without sending the source code. It's basic stuff I guess, sorry if it sounds stupid an obvious.
Thanks.
Edit:
By "safe" I mean it's not a keylogger or anything like that.
Even if you strive hard to keep your app safe, when the underlying OS is vulnerable, it goes vain! So if you expect that trust, probably, if you have restrict your app to be in platforms, that you believe to be trustworthy.
For keyloggers you mean, show only virtual keyboard of your own app, donot use the system's default. Encrpyt evrything (data) you send from your app. Create a checksum value for you app, and when someone tampers it, make sure , your app recognises it and makes it unusable, till reinstalled. Have a pre installer to validate the platform, your app is being installed.
Never allow, external sources to access the app content. Secure your critical content, in a encrypted container.
may be the below link, provides some more insight!
http://www1.good.com/good-dynamics-platform/
Basically, this is the same question as "how do I know anything is safe". Consumer appliances get recalled periodically, but we trust that they aren't deliberately designed to catch fire. If you aren't sure you trust it, you run it only when/where you can keep an eye on it and/or isolate it so it can't damage more than itself, or you throw it out.
If people don't trust the source of their code, they have two choices: Don't run it, or run it in a highly isolated environment.
The latter is a large part of what the Java Applet and Java security environment is about, but of course that does require that you trust whoever wrote the browser and/or set up the security environment to have done that successfully, and you have to trust that those don't have bugs that can be exploited.
If you're talking about products... There have been various practices published from time to time regarding how code should be written, and tested, for robustness. These days those may include "white hat" security attacks along with full code inspection and so on. If you can show that you're following these practices, it may reassure some folks who otherwise wouldn't trust you... but doing them with full rigor can be expensive, so part of this is knowing what your customers expect and/or will tolerate.
In the end, the real answer is that you need to start by writing trustworthy code, then know what the customer's concerns are and make sure you can meet their requirements either by delivering perfect code and/or by delivering above-average service and/or by being... no, I'm not going to take a cheap shot at that company this time.
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We have a project hand over from on shore team to our team (off shore) not long ago. However we were having difficulties for the hand-over process.
We couldn't think of any questions to ask during their design walk-through, because we were overwhelmed by the sheer amount of information. We wanted to ask, but we didn't know what to ask. Since they got no question from us, the management think that the hand-over process was been done successfully.
We had tried to go through all the documentation from our company wiki page before attending the handover presentation, but there are too many documents, we don't even know where to start with.
I wonder, are there any rules or best practices that we can follow, to ensure a successful project hand-over, either from us, or to us.
Thanks.
In terms of reading the documentation, personally I'd go for this order:
Get a short overview of the basic function of the application - what is it meant to achieve. The business case is probably the best document which will already exist.
Then the functional specification. At this point you're not trying to understand any sort of how or technology, just what the app is meant to do. If it's massive, ask them what they key business processes are and focus on those.
Then the high level technical overview. This should include an architecture diagram, required platforms, versions, config and so on. List any questions you have.
Then skim any other useful looking technical documents - certainly a FAQ if there is one, test scripts can be good too as they outline detailed "how to" type scenarios. Maybe it's just me but I find reading technical documents before I've seen the system a waste - it's too academic and they're normally shockingly written. It's certainly an area I'd limit the time I spent on if I didn't feel I was getting a reasonable return for the time I was spending.
If there are several of you arrage structured reviews between you and discuss the documents you've read, making sure you've got what you need to out of it. If the system is big then each take an area and present to the others on it - give yourselves a reason to learn as much as possible and knowing you're going to be quizzed is a good motivator. Make a list of questions where you don't understand something. Having structured reviews between you will focus your minds and make it more of an interactive task, rather than just trawling through page after page of tedious document.
Once you get face to face with them:
Start with a full system demo. Ask questions as they come up, don't let them fob you off with unclear answers - if they can't answer something have it written down and task them with getting the answer.
Now get the code checked out and running on your machines. Do this on at least two machines - one they lead, one you lead. Document the whole process - this is the most important step. If you can't get the code running you're screwed.
Go through the build process. Ensure that you can build the app (including any automated build and unit tests they may have). Note that all unit tests should pass - if they don't or if they say "oh, that one always fails" then they need to fix that before final acceptance.
Go through the install process. Do this at least twice, one they lead, once you lead. Make sure that it's documented.
Now come up with a set of common business functions carried out with the application. Use this to walk the code with them. The code base will be too big to cover the whole thing but make sure you cover a representative sample.
If there is a database or an API do a similar exercise. Come up with some standard data you might need to extract or some basic tasks you might need to carry out using the API and spend some time working through these with them.
Ask them if there's anything they think you should know.
Make sure that any questions you've written down anywhere else are answered.
You may consider it worth going through the bug list (open and closed) - start with the high priority ones and talk through anything particularly worrying looking. Even if they've fixed it it may point at a bit of code which is troublesome.
And finally if the opportunity exists - if there are any outstanding bugs or changes, see if you can pair program a couple.
Do not finally accept the app unless you are 100% sure you can:
Get the code to compile
Get the code to build (including the database)
Get the application installed
Do not accept handover is complete until they have:
Documented anything you picked up on that wasn't covered to your satisfaction
Answered ALL of your questions - a question they won't answer after being asked repeatedly screams of something they're hiding
And grab their e-mail addresses and phone numbers. Even if it's only informal they'll probably be willing to help out if the shit really hits the fan...
Good luck.
My basic process for receiving a handover would be:
Get a general overview of the app, document it
Get a list of all future work that the client expects
... all known issues
... any implementation specifics
As much up-to-date documentation they have
If possible, have them write some tests for critical components of the system (or at least get them thoroughly documented)
If there is too much documentation (possible) just confirm that it is all up to date, and make sure you find out from them where to start, if it is not clear.
Ask as many question as possible; anything that comes to mind, because you may not have the chance again.
Most handovers, perhaps all of them, will cause a lot of information to be lost. The only effective way to perform a handover that I have seen is to do it gradually. One way to do it is to allow a few key people from phase One to stay on the project well into Phase Two.
The extreme solution is to get rid of all handovers, and start using an Agile mindset.
As a start, define the exit criteria for the handover. This should be discussed, negotiated and agreed with both parties and make sure higher management knows this. Then write up a checklist of all things needed to achieve the exit criteria and chase it.
Check out "Software Requirements" and Software Requirement Patterns for ideas on questions to ask when gathering information about a project. I think that just as they would work for new development, they would also help you to come to terms with an existing project.
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Code can be perfect, and also perfectly useless at the same time. Getting requirements right is as important as making sure that requirements are implemented correctly.
How do you verify that users' requirements are addressed in the code you're working on?
You show it to the users as early and as often as possible.
Chances are that what they've asked for isn't actually what they want - and the best way of discovering that is to show them what you've got, even before it's finished.
EDIT: And yes, this is also an approach to answering questions on StackOverflow :)
You write tests that assert that the behavior the user requires exists. And, as was mentioned in another answer, you get feedback from the users early and often.
even if you talk with the user, and get everything right, the user might have gotten it wrong. They won't know until they use the software that they didn't want what they asked for. the surest way is to do some sore of prototype that allows the user to "try it out" before you write the code. you could try something like paper prototyping
If possible, get your users to write your acceptance tests. This will help them think through what it means for the application to work correctly. Break the development down into small increments that build on each other. Expose these to the customer early (and often), getting them to use it, as others have said, but also have them run their acceptance tests. These should also be developed in tandem with the code under test. Passing the test won't mean that you have completely fulfilled the requirements (the tests themselves may be lacking), but it will give you and the customer some confidence that you are on the right track.
This is just one example of where heavy customer interaction pays off when developing code. The way to get the most assurance that you are developing the right code is having the customer participating in the development effort.
How do you verify that users' requirements are addressed in the code you're working on?
For a question put in this form the answer is "You can't".
The best way is to work with users from the very first days, show them prototypes and incorporate their feedback continuously.
Even so, at the end of the road, there will likely be nothing resembling what was originally discussed and agreed on.
Ask them what they want you to build before you build it.
Write that down and show them the list of requirements you have written down.
Get them to sign off on the functional design.
Build a mock up and confirm that it does what they want it to.
Show them the features as it is being implemented to confirm that they are correct.
Show them the application when it's finished and allow them to go through acceptance testing.
They still wont be happy but you will have done everything you can.
Any features that are not in the document they signed off can be considdered change requests which you can charge them extra. Get them to sign off everything you show them, to limit your liability
by using development method that often controls alignement between the implementation and the requirements.
For me, the best way is to involve a "expert customer" to validate and test in a interative way as often as possible the implementation ....
If you don't, you risk to have, as you said, a very beautiful soft perfectly useless....
you can try personas; a cohort of example users that use the system.
quantify their needs, wants, and make up scenarios of what is important to them; and what they need to get done with the software.
most importantly- make sure that the users (the persona's) goals are met.
here's a post I wrote that explains it in more detail.
You write unit tests that expect an answer that supports the requirements. If the requirement is to sum a set of numbers, you write
testSumInvoice()
{
// create invoice of 3 lines of $1, $2, $3 respectively
Invoice myInvoice = new Invoice().addLine(1).addLine(2).addLine(3);
assertTrue(myInvoice.getSum(), 6);
}
If the unit test failed, either your code is wrong or possible was changed due to some other requirement. Now you know that there is a conflict between the two cases that needs to be resolved. It could be as simple as updating the test code or as complex as going back to the customer with a newly discovered edge case that isn't covered by the requirements.
The beauty of writing unit tests is it forces you to understand what the program should do such that if you have trouble writing the unit test, you should revisit your requirements.
I don't really agree that code can be perfect...but that's outside of the real question. You need to find out from the users prior to any design or coding is done what they want - ask them 'what does success look like', 'what do you expect when the system is complete', 'how do you expect to use it'...and video tape the response, mindmap it, or wireframe it and than give review it with them to ensure you captured the most important aspects. You can than use those items to verify the iterative deliveries...expect the users to change their mind/needs over time and once they have 'it in their hand' (IKIWISI - I Know It When I See It)...and record any change requests in the same fashion.
AlbertoPL is right: "Most of the time even the users don't know what they want!"
And if they know, they have a solution in mind and specify aspects of that solution instead of just telling the problem.
And if they tell you a problem, they may have other problems without being aware that these are related by having a common cause or a common solution.
Thus, before you implement mockups and prototypes, go and watch the use of what the customer already has or what the staff is still doing by hand.
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When you are deciding on what methodology or process to use for your project, should you take into account the human factors? If there is any resistance to things, do you go with the flow or force people to change?
For example, say you want to push for pair programming but the team members resist to working in that mode (or show dislikes), what would you do? Make them get used to it, try to convince them to do it or go with the flow and let them do what they like?
The human factor is the most important one.
If you consider nothing else, consider the culture and proclivities of the group.
People who want a process to fail will succeed. It's far easier to alter process than to alter people.
First try to reason, you may be wrong:
If you have resistance to certain things, you can usually give your points for why you think it's good, and hear their points for why they think it is bad, and come to some common grounds.
You should never force people into doing something against their will, but instead try to convince them based on your logical reasoning. Many times you will see reasons from them that changes your point of view.
If your developer is too afraid to voice their opinion, then you should make them feel comfortable with giving their opinion. If they are still reluctant, then you should consider new developers.
Foot in the door principle:
If you want to try some new concept that neither you nor they have experience in, say pair programming, then you can ask them to try it for 1-2 weeks and then you can sit together again after this trial period and assess the effectiveness. I think most people will find it perfectly reasonable to try something new if they have no experience in it, if it is for the purpose of finding out the method's effectiveness, and if it is only for a trial period.
If after this trial period, the thing you were testing was successful, then your developer will be more open to the idea.
Don't change them, find someone who fits:
If you are 100% for some way of doing things, and your developer is 100% against it, and he won't try it and has no logical reason why, instead of trying to change him you're better off finding a developer that will fit into your way of doing things.
If they are 100% against what you want to change, you have to make a decision. Is the developer themselves more important to you, or is the process that you want to change more important.
If you force someone into something they don't want to do, they will find a way to make your method fail.
Yes. Your development process needs to be humane. That said, there are better and worse development practices and you should strive to use the better practices. The best methodologies understand both human strengths and weaknesses and have practices that promote the former and compensate for the latter.
For example, most agile processes put a high value on trusting developers to do the right thing -- to work hard and value quality. They allow developers to have significant input into the process and into the product. This takes advantage of the human quality of rising to expectations. On the other hand, humans have trouble managing too much complexity at one time, so agile practices insist on breaking things down into manageable chunks.
On the other hand, we know that people don't like to do things that don't directly add value to their work. Agile practices, recognizing the value of things like unit testing, insist on this however and require the developer to conform to it despite the initial reluctance. Using TDD compensates for this somewhat by giving real value to developing tests -- you do them first and let them guide the design. It's a bit of the carrot and stick approach to get developers over the initial reluctance to the point where they can experience the value of the method and buy into it on their own.
Adapting the Process
The key to developing a good process with your people lies in adapting the process to the amount of ceremony that you need or want. We use the RUP where I work and one of the central goals of the RUP is to tailor the amount of ceremony in your process to fit your project and the personnel.
For instance, small projects require far less ceremony and tool support. As well, people new to a process need time to adapt. It's best not to flood them with information and let them adapt at their own pace.
Show Me the Money!
To get people to buy into a new process is to let them make a mistake (or present an example form the past) and then show them how the process could have helped prevent the mistake. Try and draw a direct line to show how the process will help them improve the way they work.
For instance: if people are resistant to automating builds and running tests automatically then the next time they release a fix for something that broke a piece of code that was already working use that opportunity to illustrate that an automated test would have caught the error before it got released, saving everyone time and money.
Automation
To ensure people can adapt to a process is to remove as much human intervention from them as you can. Automate builds, tests, reporting as much as possible using information that is automatically captured.
How this helps support process is by removing the "nag" factor. Many people resist new process because they figure it means more work for them to do or extra work that produces little result in the end. By automating existing tasks and gathering data from them you get a lot of benefit without increasing any individual developers workload.
A classic example is continuous integration. Continuous Integration tools like CruiseControl, TeamCity or Hudson can work with version control repositories to extract latest versions of source code, build that code, execute and archive test results and package stuff for deployment. This requires no extra effort on the part of the developer but you get a lot of extra "process" in return. You now know how good your source code is, you can distribute it easily and you can catch bugs earlier.
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What do you do when you join a team that says they use Scrum, but only use it as a time-management tool and not the whole process?
How can I reinstate back testing and documentation?
I was thinking to start off with adding user stories specifically for testing and documenting.
Perhaps someone else has more experience with this then I do about this as I am sure its not that uncommon.
The key to scrum is that a task be identifiable as "done" before it can be classed as done. How does you company assess whether something is done without reviewing documentation and tests?
Perhaps they have an unusual, but valid, way of doing it. Or perhaps they have missed the point of "done tasks". I'd suggest you start by asking them how they measure down and whether it could be improved. Then suggest documentation and testing as the way of improving the process.
Note that neither testing nor documentation are in fact part of Scrum. Scrum is a pure project management approach - the required engineering practices, like the ones you mention, are supposed to "emerge" during the project. And most specifically, they are supposed to be identified during the heartbeat retrospectives that you do at the end of every sprint. Are you doing those? Can you bring up your concerns there - and are they actually the biggest concerns the team has?
Is the issue that they don't have any documentation and tests, or that they aren't implementing the entire Scrum methodology? Those are 2 very different problems in my mind.
I would much prefer an organization that has taken the time and effort to find and fit a development process that matches their development style as opposed to mandating down from on high the one true process. So I would not be concerned at all if they were using a process that they called Scrum but that didn't meet all the "official" guidelines. Try to determine why the process is the way it is. Chances are that if they have taken the time to tailor it, the team will be receptive to your ideas, especially if you have taken the time to determine why things are the way they are. If you simply approach it as "this isn't Scrum and so isn't right", you will probably not make much headway, but by being pragmatic about the benefits you can likely make some substantial improvements.
Alternatively, if they aren't doing testing and don't have any documentation I would consider that a fairly bad sign. And by documentation I am taking the minimalist view here - a list of features, bug tracking, etc. - I would be very concerned by the absence of these items, less concerned by the absence of items higher up the abstraction list. In the absence of support from management, I would suggest you lead by example. Take it on yourself to setup a simple bug tracking system (there are several - in a pinch, simple text lists in a central location work as well). Don't declare your features complete until someone else has tested it. This can be as simple as walking over to another developer and asking them to try it in front of you. If someone claims a feature is complete, take a few minutes to familiarize yourself with it. If you find a bug, politely mention it to the responsible developer. Slowly build an environment where the team can see the benefits of running tests and tracking features and bugs.
Most teams operate in this manner simply because of a mistaken belief that they don't have time to "do it right", or that they will get to it later. Often this will occur when a simple proof-of-concept done by a developer or two as a side-project turns into a full-on development effort. By showing that it can actually save time and effort, and reducing the initial costs to the rest of the team, you will often find that it becomes ingrained as part of the process without ever actually being officially endorsed or accepted.
If you have management support it will make it much easier, but always be careful to make sure that the team is receptive to the changes. This may mean it takes longer than you want, but so be it, without the team's support any mandated process will fail at the first sign of pressure, which is when you need the process the most.
*Disclaimer - On my last project I spearheaded the movement to tailor the SCRUM process to fit our environment. The "official" process was simply untenable for our client, but it was still an invaluable guide in tailoring our process.
"adding user stories specifically for testing and documenting"
While meta-user stories might make sense in some circles, it rarely works out well. Software folks rarely cope well with meta-user stories, they either don't get the idea that they can change their own processes by writing a story, or -- more typically -- they engineer the meta-user story to death.
When you're interviewing users, it feels like they're making the user story up. Certainly, you're making it up as you listen to them and try to capture it.
When an IT organization tries to make up its own user stories about how IT should work, the process falls apart. Until the organization has done the thing (testing, for example) a bunch of times manually, they're not really qualified to write user stories. Then, after they've done it, they don't need software development processes, they'll just automate the important bits a little at a time.
I think change has to come from a less formal direction. Actually balking at calling something "done" that hasn't been tested is a good starting point.
IT doesn't do things unless forced. So, meet the users and find out why they're not requiring testing. Coach them to require testing. Tell them the consequences and the words to use.
A lot can go wrong in an organization to lead to poor processes. It's important to know what's wrong, and create a demand for change. The best possible thing is to have your boss complaining that you're not fixing it, rather than you suggesting that perhaps it would be good to fix it.
[It doesn't feel right when your boss demands you fix the process, but it's about the only way change will happen.]