https://stackoverflow.com/questions/15061757
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RussianAn applet (and even a JavaFX applet) can work in this situation if the applet is signed. There are numerous subtle pitfalls with applets, so I would advise prototyping before committing to that technology. Follow the JavaFX deployment guide to see how to deploy a JavaFX based applet.
I had thought that to compile Java, you needed to have the full Java Development Kit installed (which would be tricky to ensure in an applet deployment situation). But it seems that the compile API is included in the javax.tools API included with the standard Java Runtime Environment. So this likely means that you could develop your solution, including client based deployment and compilation of Java code, without requiring the user install the full Java Development Kit.
You may alternately wish to consider a client/server solution where the compilation can be performed on the server. An example of such an approach (with a Java WebStart based solution) is the TopCoder Algorithm Competition Application. Here is a jnlp file (http://apps.topcoder.com/wiki/display/tc/The+Algorithm+Competition+Arena) to run this application. I suggest you register an ID at TopCoder using the application and try out writing and compiling some code using it. The TopCoder implementation uses plain Swing as it was written before JavaFX existed, but you could equally use JavaFX for your implementation if you preferred.
If you additionally need an editor (with syntax aware text styling) for the code you will be compiling, you could use something like this CodeMirror based editor embedded in JavaFX. The CodeMirror based solution wraps the editor in html based WebView control. For JavaFX 8 you will probably be able to make use of the new TextFlow control for a syntax highlighting text editor, but that API is not part of a supported public release yet.
Update
I got this work using the strategy outlined in this answer.
The image is an html page allowing access as an applet or a webstart application to the client code editor. The top area of the image is the code editing area which is based on a WebEngine with an embedded syntax highlighting CodeMirror JavaScript editor that supports Java editing. The bottom area of the image is the output of compiling the code in the editor locally on the client machine and subsequently running it. The output constists of any compilation errors, any program output to sysout, as well as any runtime exceptions printed to syserr. The tricky parts of the solution were:
- Working out how to capture sysout and syserr and redirect them to a JavaFX control.
- Finding the Java compiler.
The default Oracle Java Runtime Environment Provider merely provides a generic interface to a Java Compiler implementation, but it provides no java compiler implementation itself - that implementation is only included in the tools.jar included with the jdk. So when I packaged my applet, I included the tools.jar in the packaging for the applet. I had some difficulty getting the service provider interface to get me an instance of the javac compiler, so in the end, I just instantiated it using the following line:
JavaCompiler compiler = new com.sun.tools.javac.api.JavacTool();
The above is somewhat brittle as sun may change their private com.sun classes at any time - but at least it worked in this instance.
Another thing to be aware of is that if you ship a tools.jar with a javac compiler which is earlier than the runtime environment that you have available for your system, then you might get some warnings such as below:
warning: C:\Program Files\Java\jre8\lib\rt.jar(java/lang/Object.class): major version 52 is newer than 51, the highest major version supported by this compiler.
It is recommended that the compiler be upgraded.
The above warning occurred because I shipped the applet with a java 7 tools.jar and ran the applet with a java 8 runtime (note that the applet worked fine regardless of those warnings).
Update
I put the code for this solution in a github repository (project name conception). The updated solution uses the Eclipse Compiler for Java rather than the Oracle Java Compiler. Mostly because, for the Eclipse Compiler, it is a separate jar (only 1.8meg rather than the 14meg tool jar of the oracle distribution) and the licensing is a bit clearer. Because the Java compiler interface is pluggable, the Oracle compiler can still be used if tools.jar is placed on the classpath.
