Adapting this the following code takes a class and function name, a string of Java code, compiles the code and runs the function.
public class Compile {
static void compileAndRun(final String className, final String methodName, final String code) {
JavaCompiler compiler = ToolProvider.getSystemJavaCompiler();
DiagnosticCollector<JavaFileObject> diagnostics = new DiagnosticCollector<>();
JavaFileObject file = new JavaSourceFromString(className, code);
Iterable<? extends JavaFileObject> compilationUnits = Arrays.asList(file);
JavaCompiler.CompilationTask task = compiler.getTask(null, null, diagnostics, null, null, compilationUnits);
boolean success = task.call();
for (Diagnostic diagnostic : diagnostics.getDiagnostics()) {
System.out.println(diagnostic.getCode());
System.out.println(diagnostic.getKind());
System.out.println(diagnostic.getPosition());
System.out.println(diagnostic.getStartPosition());
System.out.println(diagnostic.getEndPosition());
System.out.println(diagnostic.getSource());
System.out.println(diagnostic.getMessage(null));
}
System.out.println("Success: " + success);
if (success) {
try {
URLClassLoader classLoader = URLClassLoader.newInstance(new URL[] { new File("").toURI().toURL() });
Class.forName("HelloWorld", true, classLoader).getDeclaredMethod(methodName, new Class[] { String[].class }).invoke(null, new Object[] { null });
} catch (ClassNotFoundException e) {
System.err.println("Class not found: " + e);
} catch (NoSuchMethodException e) {
System.err.println("No such method: " + e);
} catch (IllegalAccessException e) {
System.err.println("Illegal access: " + e);
} catch (InvocationTargetException e) {
System.err.println("Invocation target: " + e);
} catch (MalformedURLException e) {
e.printStackTrace();
}
}
}
}
class JavaSourceFromString extends SimpleJavaFileObject {
final String code;
JavaSourceFromString(String name, String code) {
super(URI.create("string:///" + name.replace('.','/') + Kind.SOURCE.extension),Kind.SOURCE);
this.code = code;
}
@Override
public CharSequence getCharContent(boolean ignoreEncodingErrors) {
return code;
}
}
You might call this using:
StringWriter writer = new StringWriter();
PrintWriter out = new PrintWriter(writer);
out.println("public class HelloWorld {");
out.println(" public static void main(String args[]) {");
out.println(" System.out.println(\"Hello World !\");");
out.println(" }");
out.println("}");
out.close();
Compile.compileAndRun("HelloWorld", "main", writer.toString());
Is it possible from inside the compiled program to call external functions and variables? e.g.
class SomeClass {
int x = 123;
void myFunc() {
StringWriter writer = new StringWriter();
PrintWriter out = new PrintWriter(writer);
out.println("public class HelloWorld {");
out.println(" public static void main(String args[]) {");
out.println(" y = foo(x);");
out.println(" }");
out.println("}");
out.close();
Compile.compileAndRun("HelloWorld", "main", writer.toString());
}
void foo(int x) {
}
}
or maybe with the foo
and x
in another class? Obviously I tried this, but it fails to compile. Is there a way to achieve this?