Chronicle Runtime Compiler
This takes a String, compiles it and loads it returning you a class from what you built. By default it uses the current ClassLoader. It supports nested classes, otherwise builds one class at a time.
On Maven Central
You can include in your project with
<dependency>
<groupId>net.openhft</groupId>
<artifactId>compiler</artifactId>
<version><!-- The latest version (see above) --></version>
</dependency>Simple example
You need a CachedCompiler and access to your JDK’s tools.jar.
// dynamically you can call
String className = "mypackage.MyClass";
String javaCode = "package mypackage;\n" +
"public class MyClass implements Runnable {\n" +
" public void run() {\n" +
" System.out.println(\"Hello World\");\n" +
" }\n" +
"}\n";
Class aClass = CompilerUtils.CACHED_COMPILER.loadFromJava(className, javaCode);
Runnable runner = (Runnable) aClass.newInstance();
runner.run();I suggest making your class implement a KnownInterface of your choice as this will allow you to call/manipulate instances of you generated class.
Another more hacky way is to use this to override a class, provided it hasn’t been loaded already. This means you can redefine an existing class and provide the methods and fields used match, you have compiler redefine a class and code already compiled to use the class will still work.
Using the CachedCompiler.
In this example, you can configure the compiler to write the files to a specific directory when you are in debug mode.
private static final CachedCompiler JCC = CompilerUtils.DEBUGGING ?
new CachedCompiler(new File(parent, "src/test/java"), new File(parent, "target/compiled")) :
CompilerUtils.CACHED_COMPILER;By selecting the src directory to match where your IDE looks for those files, it will allow your debugger to set into the code you have generated at runtime.
Note: you may need to delete these files if you want to regenerate them.