I wan't to create an applet that includes the Java compiler and is able to download and compile .java files from the web (or from a textfield for that matter).
From what I understand, the Java compiler is based on Java, so this should be possible.
However, one thing I wonder is wether the Java compiler is able to store the class file in memory or that it needs explicit disk access.
Also, I want to catch the errors javac produces, but this is natural.
Is there an article on this somewhere maybe? I couldn't find much on the case. What troubles could I walk into?
EDIT: I'm planning on using the applet with OpenCL, so I would have to sign the applet.
EDIT: Similar question here: Hosting the Java compiler in an applet or in Google AppEngine?
Java compiler is always with you. You should use java.lang.Compiler class. But I believe you will have issues with SecurityManager.
If I were you I'd prefer to compile code on server side. It means that I'd develop servlet that is able to get the java source and compile it. The resulted java class should be available over HTTP under path that is configured to be accessible by applet, so your applet will be able to run this class after compilation.
From the documentation on the SSCCE Text Based Compiler:
javax.tools.ToolProvider. The docs for getSystemJavaCompiler() mention that it returns "the compiler provided with this platform or null if no compiler is provided", but do not make clear why it might be null, nor the fact that the compiler will not be available to applets or webstart apps.
Related
It seems to me that the Java Compiler API allows to compile at runtime a class, writing its output (the .class file) to the file system. However, in-memory compilation is not supported. Is this correct ? or is possible to use this API to compile a class in memory (from a String) and instantiating such class afterwards ?
(I know I can compile the class to the file system and load it afterwards with a custom class loader, but I am wondering if I can compile it in memory, without passing by the file system).
Is there another alternative mechanism to do such in memory compilation using the J2SE only?
BeanShell (I library that can do what I want) mentions in its web page that it may be included in the J2SE at "some point in the future", however, the status of its JSR is "Dormant" (whatever does it mean).
Update:
Ideally, I would like to know if this can be done with the J2SE only (or if there are any expected enhancements to J2SE that will allow me to do this in, for example, Java 8). However, tips about how to do that requirying the JDK to be installed are also appreciated (thanks Evgeniy).
It is possible if you have JDK, java complier is in tools.jar which comes with JDK only. See http://docs.oracle.com/javase/7/docs/api/javax/tools/package-summary.html
Java Compiler API .. in-memory compilation is not supported. Is this correct?
No. The STBC uses the JavaCompiler to do exactly that.
..and instantiating such class afterwards?
The STBC does not go as far as trying to load/run the class, but I believe it should be possible. I imagine it might require a custom 'in memory' class loader though.
..the JavaCompiler API can do that independently if the JDK is installed or not?
From the page..
System Requirements
STBC will run on any computer with a version 1.6+ Java Plug-In* JDK (AKA SDK).
* The API that STBC uses is merely a public interface to the compiler in the tools.jar that is distributed only with JDKs (though the 'public JRE' of the JDK also seems to acquire a tools.jar). ..
I am involved in a project that will need to run via web and have access to java's compiler tools and/or javacc api. My team is thinking of using a java applet to make it web based. I'm wondering if there are certain limitations on what an applet can and cannot do in this case. I would assume that since access to the compiler would be done on the server, not the client's machine, that this wouldn't be a problem. Does an applet allow us to separate the two as described?
An 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.
Yeah applets can access them and can be a good choice. But it has very limited/ dull look and feell. Go for JavaFx in this you can define your own StyleSheet so it will give you a very good look and feel and yeah definitely it will separate the two layers too.
JavaFx Oracle Documentation
By using the JRE or some other runtime environment, is it possible to compile Java code on a web server such as Apache or Nginx?
Specifically, I would like to have a web application that would accept user input (Java code), and when the user hits run, it would compile the Java into Java Byte code and display the result, like Eclipse does.
Does this sort of technology even exist?
Does this defy the logic of compiled languages?
Thank you for your time in advance.
Amicably,
James
The server running Apache would also need a JDK. You could easily write the input to a file, compile it, run it, and display the results to the user. This could be done with a CGI script, or a Java EE app or similar, running in Tomcat. A JDK will be required, a JRE will not suffice.
Consider the potential security risk with this, though. Depending on what the program actually does, it could result in problems on your machine or others.
Of course this is possible. But you need a JDK, and some server side scripts (PHP, Ruby, Python, Java ...) which takes the source code as input and calls the Java compiler to compile the code.
What you have to consider are the security implications. Every user could then upload code, which would be executed on the server. So you have to make sure, that the code runs in a sandbox.
There are several websites that do this. One that I've used is at http://www.ideone.com.
You can reproduce this with the JDK and various scripts or you can write your own compiler from scratch. Either way, you need a compiler of some kind to actually compile the code.
I want to create a web based java tutorials kind of project which involves jquery, css, jsp, springs etc .,
so I actually want to practice these technologies resulting a good product. The content of this tutorial can be edited by any user and rated by clients according to the chapter etc.,
I have few such ideas.
One primary idea being have a web based compiler and executor . Similar to w3schools. I know its difficult for a compiler of server side technology on a browser.
My questions are:
Are there any such open source java
compiler/executor services available
which can be used?
Is anyone interested to work on such
project (in case there isnt any)?
EDIT:
I am planning to use Compiler in java and Beanshell. Any better solutions ?
Google App Engine is the one, which one can you help to set up Free online Java Compiler, But for that you need to have an account to proceed.
Few other places you can defnitely Check
http://compilr.com/
If you have Applets,
http://www.innovation.ch/java/java_compile.html
EDIT : As Stephen Suggests, Download JRE and JDE and use it from oracle website
http://www.oracle.com/technetwork/java/javase/downloads/index.html
With http://www.browxy.com you can compile and run java console application and applets
You would need a script on your server that accepts the sourcecode, compiles it and runs it, however I'm pretty sure, you don't want to run arbitrary code.
If you still want to do it, take a look at Google's AppEngine, they do allow users to upload their (compiled) java programs and don't seem to have had any problems with it.
This question is interesting. In fact, Tomcat JSP server is an online compiler for Java Servlet. May help you a little in your case. (Not for traditional Java, though).
Imagine that you gave user an input form for Java codes ( preferably a WYSIWYG editor ), the codes will be written in a temp JSP file, and then your code compile and run the JSP.
But be careful , JSP is too powerful ( as it can touch file system, etc. ). Make sure your security measure is set.
I've used ideone.com before when discussing Java code with someone in a remote location. It is a web based IDE that handles Java as well as a lot of other languages, and is very useful.
If you are trying to do it yourself, you should be aware java6 and above have compilation built into the language in the javax.tools package.
You may want to check out Fixoncloud compiler. It's a web-based collaborative online compiler. Anyone can make changes to the code and you can also track history of your code. The compiler supports C, C++ and Java.
Depending on the permissions set to the code, the owner can also make his code completely private and permit only specific users to view/modify the code.
Here's the link to the compiler:
http://www.fixoncloud.com/Home/compiler/index.php?id=254
Hello All
I am writing some software that will allow users to create their own Java classes for a specific use in my software package. Obviously, my software will need to be able to invoke a Java compiler to compile the user-generated classes for use in my program. However, I do not want to require users to download and install the entire JDK just so they can have access to the javac Java compiler. I understand that in Jave 6 there is a new Java Compiler API but even then, users with just the JRE and not the JDK will get a null object when they try to instantiate the Java compiler tool.
So, what is the best way to enable my program to compile Java classes while requiring the end user to just have the JRE installed on their machines? If this is not possible, what is the minimal set of libraries/jar files I would need to install on the user machine?
I suppose another possibility might be to use JWS (javaws) to launch the app over the web. In this case, is it possible for my software to not require the JDK (mainly tools.jar I think)? Would I somehow have to bundle tools.jar with my software?
You can use standalone Java compiler from Eclipse. It doesn't need JDK installed, and it's single JAR file you can use in your project. This is the compiler that is used inside Eclipse itself, but it can be integrated into other programs too. You can find current latest stable version at http://download.eclipse.org/eclipse/downloads/drops/R-3.6.2-201102101200/index.php, look for Look for JDT Core Batch Compiler. Documentation is available at http://help.eclipse.org/helios/index.jsp?topic=/org.eclipse.jdt.doc.isv/guide/jdt_api_compile.htm
You can also use Janino, which can compile also smaller units than full Java classes: blocks, expressions. It's not full compiler though, it does not support all features of Java language that your users use (generics, annotations, enums, ...)
To use the java compiler, you need to include tools.jar into your application (e.g. it has to be reachable by the classloader who wants to load the compiler - most easily by the System class loader).
Maybe http://asm.ow2.org/ this will be usefull? To generate bytecode on fly?
It sounds like a better solution would be to use some scripting language that can run within the JVM without having to be compiled.
Possible the Java Scripting API would be of use to you. I'm sure there are other options as well.