GUI sending data to C program

Question

Hi
I am pretty comfortable making a Swing GUI...but i was told today by my mentor that he wants the data ( that user puts in Text fields and etc) to be sent to a c program. so JAVA GUI is just there for the user...all the back ground work is done by a C program....is this doable? and how? lets say i extract a String from a JtextField. How do i go about sending that string to the C program.

Answer 1

alright bharat_java!
this is how i would do it.
create the front end swing gui with the text fields and create the c program so that it takes a parameter(s), which it takes as a pointer in the main function brackets. The c program would be a stand alone program not exeuted by the user but by the java swing gui.
On the gui create a jbutton with an actionlistener added to it.
When the user clickes the button in the actionlistener it would get the text from the texfield and create a string which contains the directory path of the c program exe and add the string at the end.
if the c program is in the same directory as the java class file then i would assume (if someone would like to correct me) just add the c program name exe and the string parameter at the end or statically add a final string of the path of the exe from c:
windows example
c:\myprograms\prog.exe param1 param2 param3
you have can as many parameters for your c program in string form provided that your c program takes the strings in order and knows which is which.
to execute the c program i think you would need to execute an external process using java. The class to use is "Runtime.exec". it creates a process and returns a "Process" class from which you can get various info about the process. i don't know how to use the class exactly but do a google search and you will find something.
i would assume you would need to do som form of process management in your java program like check if the process has crashed and report it and ensure that the java program is running even if the process has crashed. if the process crashes then your java program will be waiting for the process to finish. it can crash your computer if you're not careful!
a little info about creating and managing a process :
in linux c programming you would 'fork()' a process and 'exec()' it with a program or command and it would run it and you would have to wait in your program until the process finished using wait or execute it as a background process so you could execute more commands while it the process is running in the background. every process has a PID process ID which uniquely identifies each process. using the PID you can find a process or wait for a process using the PID.
i hope i haven't gone over the top and that there's enough for you to understand how to do it.
mani