During my studies, I have to make a project connected with programming in Java. I learn Java from a few months and I would like to make something interesting (not an application for bank, library, car renting etc). I'm wondering whether it is possible to create real-time web game/application, where you can type something and your friend on another laptop see this message and can send you response? (using internet/Bluetooth) If yes, what I should look for to find information about this type of applications?
Yes, creating something like this is definitely possible. It really will just depend on exactly how you want to implement this (it sounds like you're still not sure EXACTLY what you want, as your description is vague).
What I mean by that, is what do you want as your medium? Would you like the two users to be on their laptops and communicating through their web browsers? Or would you rather have a standalone application that accomplishes this? If so, what Operating Systems will you support? Will it have a graphical user interface, or will it run on the command line?
Let's assume that you want to develop a standalone Windows application that allows the users to exchange messages. Keep in mind that doing this gracefully would involve users logging into your system with authentication, a fairly sophisticated GUI, and lots of encryption for privacy reasons. That being said, a very basic implementation of this could probably be as follows:
You'd have an app that runs locally on the users machine, and also some sort of database backend that your app communicates with. I'd recommend using a mySQL database hosted by Amazons RDS (Here's a tutorial that got me using Javas JDBC library to work with an Amazon RDS database - https://www.youtube.com/watch?v=2i4t-SL1VsU).
Rather than worry about a GUI, I'd suggest trying to get your prototype working on the command line. Your app could preform the following steps when booting up:
Ask user to input the word send followed by a message to send messages ("SEND %MESSAGE%"), or "RECEIVE" to receive messages.
If "SEND %MESSAGE%" is input, add message to database
if "RECEIVE" is input, query the database for all message entries and output them to the user.
You can see that this would accomplish a very crude version of what you asked for, and the devil is in the details. I'd suggest building something very simple like this, and then adding functionality by tweaking and improving features one at a time.
Related
Read an interesting article about securing XP,http://www.expertreviews.co.uk/software/1304965/when-windows-xp-support-ends-this-is-how-you-secure-your-pc-and-save-all-updates.
With these suggestions is building apps for the marketplace ok with this setup to get by w/o headaches.
Here are my noob thoughts and question:
Just learning to code. Do you think I could run a limited setup to learn languages Java and C# while still being able to use my desktop for deployment of apps? A limited login as described only allows certain actions which I believe is different than a typical guest account. I wonder if my comp could still act as a server to retrieve data requested by users away from my machine. I figure I would need to be logged in as an admin to make some changes but, would hope that tasking processes or jobs could still be done.
I guess my question is, do users of a program you made need access to a local machine for some functions and would that work in limited?
I would like to get something portable and keep my desktop for business to be economical and not run the risk of logging on to an unsecure Wi-Fi with a portable that has business use. Ideally, I'd pony up for newer, better. I'm just learning though.
Do users of a program you made need access to a local machine for some functions and would that work in limited.
No. If you need some sort of server backend for your app a personal computer would be a bad choice for several reasons:
It would need to be available at all times: you can't frequently turn it off or restart.
It would require the same ip address.
It could consume a good amount of you're computer's resources, making it difficult to use for personal use
Instead you should probably be using a dedicated server or a cloud based solution, of which several offer free usage tiers.
I'm curious to know if it's possible to fetch data from other applications to my Java program. I know java is running in a virtual environment, hence JVM and therefore have problems communicating with other applications unless you were to use the Robot class or so forth.
What I would like to do, for starters as educational purposes is to take let's say a music application like Spotify/iTunes, fetch the playlist (text data) and send/display it in a text file. I've tried a few things so far, and the only thing I've come close to is by using the Robot class, opening the application, doing Ctrl+A, pasting it in to a text document and so forth but that's more like a macro. I would like to make a java application that would do this automatically. Is that possible in any sense with Java or are you just better off changing languages? I wish to do it with Java though because it's the language I've studied for the past year and what I'm trying to master. (Sorry for the long explanation.)
It's nothing to do with Java and the JVM. Any language has the same problems and solutions for this sort of situation.
The thing you need to talk to has to provide you a way to talk to it. You need to talk to it using that way.
Methods include pipes, custom network protocols, SOAP and Restful web services, etc.
Just because an application runs in a virtual machine doesn't mean it cannot access external data through an API provided by an external program. For example, iTunes has a COM-based API for accessing playlists, and here is an example of using it from C#. You'll need something which allows accessing COM objects from Java.
(Please note I know nothing about this topic, this is just what I found with a little searching...)
You need to know which data interfaces provides the application you want to connect to.
As an example, maybe the application writes files to disk or stores some info in a database.
Then with Java you can read files, query the database, use an API (web services, REST, etc..) and so on...
I would like to create a native ipad application that displays data fetched from a webserver. The application should be able to fetch tabular data, schedule things on the webserver and receive alerts
I suppose i could do the following
For fetching tabular data, use a single webservice call (will this work? what should be data interchange format? are there limitations to the data payload?)
For receiving alerts, would a persistent connection strategy work be the best way and are there better alternatives that i can tap into natively?
What remoting mechanisms are supported natively?
I have glassfish/spring setup.
Thanks
Having no idea of the data makes it hard to answer.
A successful method applied by many is the web service method, with simple query when the app loads, or is used, and fall back to show data that was loaded last time it had a connection.
If the data is time sensitive, this is more of a dilema.
You could simply note the last refresh time. If your app will be used primarily in the office, this might suffice.
Having a refresh button is a must.
The only reason to think about a persistent connection is if you want some form of server push. That is, do you need the server to inform the device of updates. Use cases for this are things like "chat".
Otherwise a timer asking for updates from the server is the way to go, since it is SO much easier to develop.
Apples toolbox supplies NSUrlConnection
Your iPad app and your web server would have to be very loosely coupled.
Your question is very broad at the moment. While you go, other question will arise.
One pointer though: You must find an exchange protocol that suits your needs (e. g. JSON) and implement this on both sides. The choice depends on your experience and the data you want to exchange.
I am trying to set up a webserver on an old machine of mine. I have installed ubuntu server edition and aim to use it for the following:
I want to run a java program on the server. I want to be able to retrieve data from the program from another computer/phone using an internet connection. I also want to be able to give the program data, and get a response saying whether or not the data has been received correctly.
So for example:
A .jar program runs on my server and holds a variable x
I want to be able to query the value of x from another device (over the internet).
I want to be able to set the value of x remotely from another device, and get a response saying it was successful in altering the value.
What are my options here? I would like to try and keep things simple. It is perhaps worth mentioning that I will be the only one using the system. The server will be used exclusively for dealing with the two requests outline above.
Is it simply the case of creating a java program that listens out for incoming requests and running that on the server?
As you mentioned, you can start with custom ServerSocket wrapper which will decode incoming requests and do as it's bid. Currently, whole frameworks are done to encapsulate common code of this task -- see my 3rd point.
Old-school java solution: use RMI. See RMI tutorial.
New-school java solution: devise some simple text-based protocol with 2 commands:
Read()
Set(newVal)
Then implement that protocol over some new trendy Java framework, like Apache MINA, which is created specifically to facilitate quick development of network apps in Java.
I, personally, started with RMI for such kind of tasks. Since RMI is considered Core Java technology, it's wise to learn it.
Now there is a new requirement. I have got some adhoc work at hand. The requirement is to connect a desktop based Java application to read data from Mainframe generated by some CICS Transaction. [Basically I have to read all the records being appended into a file (same way as we do tail-f filename in linux). This is just for FYI my requirement is something different.]
I inquired, and came to know that my employer cannot provide MQ or CICS Transaction Gateway access to me. He suggested some method of screen scraping. I have already done that using VB.Net application and Quick3270 as well as IBM Communicator Emulators. Both these emulators provide functions which can be used to read whatever is there on the screen.
You can refer to EHILLAPI programming details (Language for Emulator programming) - http://publib.boulder.ibm.com/infocenter/pcomhelp/v5r9/index.jsp?topic=/com.ibm.pcomm.doc/books/html/emulator_programming07.htm if you are interested in learning.
But this method is restricting me to the maximum number of bytes that can come on the screen. With this method there is significant network delay as I have to refresh (basically move from one page to another on CICS) everytime to get data which is spanning across multiple pages.
Can you suggest me some method so that the my employer does not need to ask the client to open any port on his Mainframe or install any software (as this is not possible for my employer).
Can I use the 3270 terminal emulation and retrieve all (or at least more data). This way the requirement of my employer is fulfilled and he does not need to ask anything to his client. (In any case from the emulator we are firing CICS Transactions). We want everything to be done at my employer's end itself without disturbing the client's Mainframe even a single bit.
Please do not suggest MQ as the client does not have it.
If you are still suggesting CICS Transaction Gateway, then please let me know how would I connect to the remote machine (I need technical details).
- What information do I need to ask from the client.
- What software do I need to install on my machine.
- Technical details of using that software.
Regards,
Nitin
I have two suggestions for you to look at. I have done both successfully. Your client setup can decide if either is palatable (the question doesn't mention not doing these things).
You can call your CICS code on the mainframe via a DB2 stored procedure. There is a standard one supplied by IBM called EXECCICS that we used for a project. You supply the standard CICS parameters and comm area. The stored procedure executes the program in the mainframe and returns you the comm area. You use JDBC. This solution is simple and easy the execute.
We have also enabled HTTP access to the CICS program on the mainframe. To my understanding (remember I just called it -- not enabled it) it is a pretty standard configuration. The client code just performs an HTTP POST to a specific end point. The resulting document is the comm area plus other goodies.
These solutions were developed independently for the same project and are both in production. The only reason the HTTP method was added to the mix was because of a data size limit in the stored procedure that HTTP removed.