Take a look at JavaCompiler
The following is based on the example given in the JavaDocs
This will save a File in the testcompile directory (based on the package name requirements) and the compile the File to a Java class...
package inlinecompiler; import java.io.File; import java.io.FileWriter; import java.io.IOException; import java.io.Writer; import java.net.URL; import java.net.URLClassLoader; import java.util.ArrayList; import java.util.Arrays; import java.util.List; import javax.tools.Diagnostic; import javax.tools.DiagnosticCollector; import javax.tools.JavaCompiler; import javax.tools.JavaFileObject; import javax.tools.StandardJavaFileManager; import javax.tools.ToolProvider; public class InlineCompiler { public static void main(String[] args) { StringBuilder sb = new StringBuilder(64); sb.append("package testcompile;\n"); sb.append("public class HelloWorld implements inlinecompiler.InlineCompiler.DoStuff {\n"); sb.append(" public void doStuff() {\n"); sb.append(" System.out.println(\"Hello world\");\n"); sb.append(" }\n"); sb.append("}\n"); File helloWorldJava = new File("testcompile/HelloWorld.java"); if (helloWorldJava.getParentFile().exists() || helloWorldJava.getParentFile().mkdirs()) { try { Writer writer = null; try { writer = new FileWriter(helloWorldJava); writer.write(sb.toString()); writer.flush(); } finally { try { writer.close(); } catch (Exception e) { } } /** Compilation Requirements *********************************************************************************************/ DiagnosticCollector<JavaFileObject> diagnostics = new DiagnosticCollector<JavaFileObject>(); JavaCompiler compiler = ToolProvider.getSystemJavaCompiler(); StandardJavaFileManager fileManager = compiler.getStandardFileManager(diagnostics, null, null); // This sets up the class path that the compiler will use. // I've added the .jar file that contains the DoStuff interface within in it... List<String> optionList = new ArrayList<String>(); optionList.add("-classpath"); optionList.add(System.getProperty("java.class.path") + File.pathSeparator + "dist/InlineCompiler.jar"); Iterable<? extends JavaFileObject> compilationUnit = fileManager.getJavaFileObjectsFromFiles(Arrays.asList(helloWorldJava)); JavaCompiler.CompilationTask task = compiler.getTask( null, fileManager, diagnostics, optionList, null, compilationUnit); /********************************************************************************************* Compilation Requirements **/ if (task.call()) { /** Load and execute *************************************************************************************************/ System.out.println("Yipe"); // Create a new custom class loader, pointing to the directory that contains the compiled // classes, this should point to the top of the package structure! URLClassLoader classLoader = new URLClassLoader(new URL[]{new File("./").toURI().toURL()}); // Load the class from the classloader by name.... Class<?> loadedClass = classLoader.loadClass("testcompile.HelloWorld"); // Create a new instance... Object obj = loadedClass.newInstance(); // Santity check if (obj instanceof DoStuff) { // Cast to the DoStuff interface DoStuff stuffToDo = (DoStuff)obj; // Run it baby stuffToDo.doStuff(); } /************************************************************************************************* Load and execute **/ } else { for (Diagnostic<? extends JavaFileObject> diagnostic : diagnostics.getDiagnostics()) { System.out.format("Error on line %d in %s%n", diagnostic.getLineNumber(), diagnostic.getSource().toUri()); } } fileManager.close(); } catch (IOException | ClassNotFoundException | InstantiationException | IllegalAccessException exp) { exp.printStackTrace(); } } } public static interface DoStuff { public void doStuff(); } }
Now updated to include suppling a classpath for the compiler and loading and execution of the compiled class!
