I was wondering if it's possible to send commands from a website to a java program being ran on a computer.
Basically what I'm doing is creating a robot, but I want control over it when I'm away from my computer. So what I was thinking, was that if I could send it commands (Like 'Stop' or 'Start') from a website, I could use my smartphone to control it.
If you know a way that might work or another method that's similar please let me know, thanks!
What I've done in the past is built the Java robot into a Java EE webapp, then deployed the webapp on Tomcat. Tomcat is a Java-based web server. It's a web server, but there's also no reason you can't run arbitrary code inside it, like a robot.
Another alternative is to embed a web server into the robot, and have the robot serve up pages itself. An example of an embedded HTTP server is JETTY.
Using the above two approaches, the web pages and Robot can communicate with each other directly through Java code. It's a single process and a single JVM running both.
A third alternative is to connect the Java robot process with the web server process via sockets or another form of IPC. This could be tricky, but decouples nicely.
one starting point is:
RPC the wikipedia article will guide you through other options and names that can help you. If it is really that basic. Socket Programming is the right way.
I was wondering if it's possible to send commands from a website to a
java program being ran on a computer.
This equivalent to asking if 2 programs can communicate via network.
The answer is yes. It is obvious, right? I mean how do you connect to your website in the first place? Eh?
Related
I am sure this sounds silly, but for a beginner like me, this is cooking my brain up and I am not able to proceed in my quest without clearing this.
Lets say I am building a simple java command line calculator application that takes 2 numbers and an operator as input and returns the operation's result back to the user. Now, I want to build GUI on top of it (similar to like an online calculator). For this, I decided to build a web application so that I can open the application on my browser and use it seamlessly. It leads to the following questions in my head
Will I have to build a web server in java to allow communications between the front end/GUI and the back end? There is no communication with any other networks, its strictly local; yet I am having to create a web server to make this work and that is confusing me. Or do I need one because I decided to build a web application meant to be opened in a web browser? Or is the reason something else entirely?
If I instead decided to build a windows/android/mac/ios application, would I still to bake a web server for communicating? Or can I use something like swings (I know its really primitive) to do this which essentially would allow the GUI to directly communicate with the business logic?
I know front-end languages like javascript allow me to code the entirety of the calculator in itself, and as a result eliminate the need of a web server. However, what if I was building relatively complex application with a backend database, like spotify? (within the same constraint that the application doesn't need to communicate with other applications and all data is stored locally) Would this solution still work?
In brief, I am failing to understand the purpose of building an entire client-server infrastructure even though the entire thing is local and offline(if that makes sense?). Or is my very basic understanding of client-server flawed?
If you want to use a web browser as the tool to interface with your Java app, then you need a web server. The browser is simply an app that tries to make a network connection with another app, and passes some text as defined by the HTTP protocol.
You would have a choice of three scenarios for this:
Write an app that accepts network connections, processes HTTP, and sends back a response.
Write a Java app that uses the very basic web server built into Java 18 and later. Note that this web server is not intended to be a feature-rich or commercial-grade server.
Write a Jakarta Servlet class that runs on top of a Servlet container with a web server. For your needs, either Apache Tomcat or Eclipse Jetty would work well as both the Servlet container and the web server.
For your scenario, the middle option using Java JEP 408 seems most appropriate and easiest.
You said:
There is no communication with any other networks, its strictly local; yet I am having to create a web server to make this work and that is confusing me.
A Border Collie dog herds sheep. That is its most basic basic core mission. Those sheep can be herded across the hills of a mountain range or they can be herded locally within your own farm.
A web browser makes network connections. That is its most basic core mission. Those network connections can be made over the actual network or they can be made locally within a single computer ( a “localhost”).
You said:
Or do I need one because I decided to build a web application meant to be opened in a web browser?
Yes a web application accessed by a web browser needs a web server, by definition.
You said:
If I instead decided to build a windows/android/mac/ios application, would I still to bake a web server for communicating?
Or can I use something like swings (I know its really primitive)
There is nothing “primitive” about Swing. It is a fully-developed feature-rich GUI framework. Swing comes built in with every JDK. And Swing will be supported for many years to come.
However, the design and features of Swing may or may not suit your tastes. And Swing is now in maintenance-mode.
An alternative is JavaFX, now actively developed as the OpenJFX libraries.
To use JavaFX, you must either add the OpenJFX libraries to your project or else deploy to a JDK that comes bundled with the OpenJFX libraries (ZuluFX, LibericaFX, etc.).
to do this which essentially would allow the GUI to directly communicate with the business logic?
Yes the GUI and and your calculator business logic would all be plain Java classes, all peers, all running together within the same JVM.
You said:
I know front-end languages like javascript allow me to code the entirety of the calculator in itself, and as a result eliminate the need of a web server.
Yes. You could cook up JavaScript code to implement your little calculator. This JavaScript could be placed within the text of a file with the HTML of a web page. That web page file could be opened locally by the web browser. Your HTML and JavaScript would render. No web server is needed in this scenario.
But this scenario eliminates Java, and you said you want to (a) write your calculator in Java, and () use a web browser. So we go back to the three options listed above.
You said:
However, what if I was building relatively complex application with a backend database, like spotify? (within the same constraint that the application doesn't need to communicate with other applications and all data is stored locally) Would this solution still work?
Yes you could deploy a database server on your local machine. Then you could find and use a JavaScript binding tool to talk to that database.
But then you would not be using Java and all its goodness. For that scenario I would choose to write a JavaFX app with an embedded Java-based database engine such as H2. This would result in a single all-in-one double-clickable-app solution.
But that would be my choice based on my own preferences and skill set. Other people might choose other solutions.
the purpose of building an entire client-server infrastructure even though the entire thing is local and offline
👉 The “offline” part may be distracting you.
Conventional computers with modern operating systems such as macOS, BSD, Linux, Windows, etc. are always “online” in that they all maintain a networking stack. That network stack can be used locally by processes within the one computer to communicate with each other. Whether you happen to have an Ethernet cable plugged in, or WiFi turned on, makes little difference to the computer. The networking stack in the OS is still available and active regardless of outside network access.
So client-server architecture works just as well within a single computer as it does between computers. (Actually, it’s works faster locally, as hopping on and off the network is terribly slow.)
Why choose client-server architecture for a local app? Either:
You are skilled in, and prefer, the tools for a client-server architecture.
You want to eventually move from local-only to being networked.
If neither of those two is true, then the JavaFX with H2 solution I mentioned is likely a better fit for a Java programmer.
By the way, let me put in a plug for Vaadin Flow, a GUI framework for building web apps in pure Java.
It's not completely necessary to bake web server to host your application even with embedded tomcat application you can host your application. However, main purpose of webserver usage is for setting up your reverse proxy so that your application behind that won't be exposed and your webserver will be acting as endpoint to outside requests.
In case for hosting application in local webserver is not at all required webserver will come handy when your application hosted in production environment.
I designed my java spring application to run a couple of python programs on same server and communicate with them. I run them with ProcessBuilder and communicate via InputStream/OutputStream.
Now I want to achieve that when I restart or shut down my java application, python apps didnt close. I can't get Process object by PID. With ProcessHandler object I can't get input/output streams. It seems that i should use some other mechanism of IPC. So the questions are:
How can I run external applications from java so they wouldn't close when java app restarts?
How can I achieve communication between java and python applications without having Process object?
Thanks in advance, sorry for poor language :)
I give some suggestion on our project experience:
In single server, use docker-compose to run/stop app no matter using java or python. In multi-server，they will be deployed in Istio.
use Restful protocol to communicate between them.
We have some code that must access low level windows XP os calls which do some simple manufacturing machine controls. These are not real time functions- just setup/config type operations.
All the rest of our system is cloud hosted, and is written in ruby on rails. I want to minimize the amount of windows code we have to write, and keep as much of the code running as a browser app. I also want to as much as possibly deploy the code from the rails server, with as little config or specialized setup of the PC's as possible.
I am looking for recommendations to somehow interface browser based html/javascript code to those low level calls, that minimizes the work we have to outside our normal rails framework, and is also fairly simple to set up / learn / etc.
What I would like is to keep everything as a normal web application, that some how can make a call out to some PC code.
These bits of PC code are intended to run on a very limited number of installations on PCs that we have full control of security etc in factory floors.
One way perhaps is to make a small java applet (which can be written in Ruby), but I don't know if you can then communicate between the java applet and javascript?
Another way is to do something with silverlight that just provides a basic interface, again I don't know if silver light allows any kind of communication from the HTML/javascript to the silverlight code.
Another way perhaps is to do something as a firefox plugin not sure at all if this would work...
Another way (I think) is create a .net app that contains a browser control. Then the .net app might be able to load the browser window from our rails server, etc.
What would be really nice, would be if there was some way to simply add a new javascript functions that would handle this low level stuff...
Look forward to your input!
As I interpret your requirements and please correct me if I am wrong, you're looking for a way to modify configuration on a number of factory floor PCs running Windows XP--that manage various manufacturing processes--from a web browser running on an administrator's computer.
If this is correct, you'd need to run a web server on each controller to process HTTP requests, and of course there are lots of options you can choose from, but I'm not sure this is the best path.
If I needed to solve this problem, I'd create a Windows "service" that would monitor a configuration file for changes and reconfigure the controller when they occurred.
Using this approach, you could use SCP or SFTP to copy the config file up to the controller(s) and let them reconfigure themselves. This would be more secure and far more lightweight than a web server.
For information on writing windows services in Ruby, see Running a Ruby Program as a Windows Service?
I work on a standalone Java application that is a command-and-control system for an assortment of hardware. The C&C software basically runs from a command line, and controls the system hardware which is spread out all over the place. It does not require a GUI to meet the business requirements. I have written a small swing GUI just so I can see what the overall status is of the system, but again, that is not essential.
Going forward, we would like to have a Administrative web GUI with system status and something that would give a user some level of control over the hardware. We were thinking that GWT might be a viable solution. Our GWT app would have to have some sort of IPC with the C&C software. I don't know how viable that is, I don't know that we want the C&C software bundled as a web app that has to run under application server.
I just don't have much experience with this. I was thinking that the GWT client would interact through RPC with the GWT server, and the GWT server would have some sort of RPC (RMI???) with the C&C.
Another option you have is to run a Java Applet that can interact with both GWT (using JSNI) and with the OS. A simple example would be to open a common file in the user's home folder and read/write to that file (with the C&C app doing the same as well).
You can embed embedded tomcat or Jetty into your application and let it run a simple servlet/JSP - based or GWT-based web UI. In fact, when you debug/run your GWT application from Eclipse, it starts in an embedded Tomcat instance.
I found a solution by using Spring. We have modified much of our Command and Control app to use Spring IoC, and then we used other Spring libraries to extend its functionality. To interact with GWT, we exposed services and used httpInvokers to make calls from the GWT server code.
Of course, this meant we needed to use Spring with our GWT application too in order to make the http calls from the GWT server code. But all is working.
you dont have direct control on the client system with JavaScript (which GWT is based on). in your use-case that wouldn't even make sense, why using an external server for a website controlling a local program?
If you reverse this (the app server is running on the same system as the C&C software, and the web client is available from everywhere) than that would be possible, but that wouldn't have much to do with GWT. On the server you can write normal java code. GWT just would be used for the web GUI and the RPC-calls to the server.
The call to the C&C software from the app server could be realised with the following line (windows example):
Runtime.getRuntime().exec("C:\\PathTo\\Program.exe")
This function return a instance of class Process which provides an Input- and OutputStream to simulate user input and to read and process the programs output.
Please note that you lose platform independence with this method, because the parameter for exec() looks different for every OS.
EDIT
After re-reading your question, it would even make more sense to integrate the C&C software into the server code directly, as the comment on your question suggests. you need a application server to use GWT-RPC, not a webserver, but thats hairsplitting.
Informations on how GWT-RPC generally works can be found here: (tutorial), (detailed description)
I really don't know what I'm doing, and have been trying to learn about it, but I figured I would ask for help; I have a java server (essentially the one here: http://www.akira.ruc.dk/~keld/teaching/OOP_f02/Book/chap09/BroadcastEchoServer.java, just playing around with stuff so I can learn about it), and I want to be able to run it on the internet , so with the client applet I wrote that you can embed in a browser, say, you can connect to it from different computers. I really have no idea how to go about it. I downloaded some things (Tomcat, Glassfish), signed up for google app engine, and something I think is similar specifically for Java, but I'm not really sure what I am doing. I am thinking I get j2ee or something? I use a mac and xcode, if that's useful at all.
Thanks in advance
Oh, the client applet is like the one from a java socket tutorial here:
java.sun.com/docs/books/tutorial/networking/sockets/readingWriting.html
If your server is already working locally, what you need to do is to put it in a hosting service.
That way it can be accessible by everyone else.
That server, is an stand alone application ( that is, it doesn't need tomcat or glassfish, and certainly won't run on Google App Engine )
The only thing you need to do, is have it install it in a machine which is accessible from the internet. How to host an application is out of the scope of this site though.