Generating, compiling and using Java code at run time?

Question

I have a scenario where I have to generate Java code when my application is running.

Can compile and run than code from my application( as a separate application).

Is it possible to compile and then use it from the same application. Cant think of any possibility

karmakaze · Accepted Answer · 2011-05-18 23:26:59Z

11

Check out Create dynamic applications with javax.tools. Second time I've referenced this today--I swear I don't work for them.

edited May 18, 2011 at 23:26

answered May 18, 2011 at 23:10

karmakaze

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2 Comments

Anderson Green Over a year ago

The link in this answer is broken now.

karmakaze Over a year ago

That's too bad, maybe this other Q/A will be useful.

iruediger · Accepted Answer · 2011-05-18 23:03:43Z

5

You can use an instance of JavaCompiler:

JavaCompiler compiler = ToolProvider.getSystemJavaCompiler();

Follow the link for the an example on how to use it.

answered May 18, 2011 at 23:03

iruediger

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3 Comments

Thorbjørn Ravn Andersen Over a year ago

Note that you will need a JDK for this to work. The JRE install does not include a compiler.

iruediger Over a year ago

Good point Thorbjørn. If he chooses this alternative, the minimum requirement for his application will be JDK 6.

karmakaze Over a year ago

JRE 7 appears to have put javax.tools.ToolProvider right in the rt.jar. Although I haven't tested this out, I do see in jdk1.7.0_05/jre/lib/rt.jar: javax/tools/JavaCompiler.class and javax/tools/ToolProvider.class

ratchet freak · Accepted Answer · 2011-05-18 22:58:58Z

1

using the ProcessBuilder or Runtime.exec() you can run any commandline app from your java code

this includes the javac compiler and java as a separate process

answered May 18, 2011 at 22:58

ratchet freak

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3 Comments

Kevin Meredith Over a year ago

When running MyCompilingUtility.java, which callsRuntime#exec() with a parameter of javac MyFile.java where MyFile.java was created via PrintWriter by MyCompilingUtility.java, I don't see a class file generated for MyFile.java. Why's that?

ratchet freak Over a year ago

check the error output of javac, javac expects the working directory to be the root package of the class it is compiling

Kevin Meredith Over a year ago

Thanks, @ratchet freak. Posting Sotirios Delimanolis's comment to elaborate on your helpful suggestion - stackoverflow.com/questions/21580975/…

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