以下是您的代码的工作版本:
import java.io.ByteArrayOutputStream;
import java.io.File;
import java.io.FileWriter;
import java.net.MalformedURLException;
import java.net.URL;
import java.net.URLClassLoader;
public class MyClassGenerator {
static final String generatedClassName = "TestHello_" + System.currentTimeMillis();
static final String javaFileName = generatedClassName + ".java";
static URLClassLoader classLoader;
public static void main(final String args[])
throws MalformedURLException {
generateClass();
loadExecutableInterface();
if (compileClass()) {
System.out.println("Running " + generatedClassName + ":\n\n");
final Executable ex = createExecutable();
ex.execute();
}
else {
System.out.println(javaFileName + " is bad.");
}
}
public static void loadExecutableInterface()
throws MalformedURLException {
final File file = new File("."); // <-- the directory where the generated java class is defined
try {
classLoader = URLClassLoader.newInstance(new URL[] { file.toURI().toURL() }, Executable.class.getClassLoader());
try {
classLoader.loadClass("Executable");
}
catch (final ClassNotFoundException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
catch (final MalformedURLException e) {
e.printStackTrace();
}
System.out.println(file.toURI().toURL());
}
public static void generateClass() {
try {
final FileWriter aWriter = new FileWriter(javaFileName, true);
aWriter.write("public class " + generatedClassName + " implements Executable {");
aWriter.write("\n");
aWriter.write("\n");
aWriter.write(" public void execute() {");
aWriter.write(" System.out.println(\"Hello World!\");");
aWriter.write(" }");
aWriter.write("\n");
aWriter.write("}");
aWriter.flush();
aWriter.close();
}
catch (final Exception e) {
e.printStackTrace();
}
}
public static boolean compileClass() {
final String[] source = { "-classpath", "target/classes", javaFileName };
final ByteArrayOutputStream baos = new ByteArrayOutputStream();
new sun.tools.javac.Main(baos, source[0]).compile(source);
System.out.print(baos.toString());
return (baos.toString().indexOf("error") == -1);
}
public static Executable createExecutable() {
Executable instance = null;
try {
final Class<?> genClass = Class.forName(generatedClassName, true, classLoader);
instance = (Executable) genClass.newInstance();
}
catch (final Exception e) {
e.printStackTrace();
}
return instance;
}
}
这个
主要变化
:classloader和编译部分出错。