ASM 進行動態生成class
import org.objectweb.asm.ClassWriter;
import org.objectweb.asm.MethodVisitor;
import org.objectweb.asm.Opcodes;
public class HelloWorld extends ClassLoader implements Opcodes{
public static void main(String[] args) {
ClassWriter cw = new ClassWriter(0);
cw.visit(V1_1, ACC_PUBLIC, "Example", null, "java/lang/Object", null);
MethodVisitor mw = cw.visitMethod(ACC_PUBLIC, "<init>", "()V", null, null);
mw.visitVarInsn(ALOAD, 0);
mw.visitMethodInsn(INVOKESPECIAL, "java/lang/Object", "<init>", "()V");
mw.visitInsn(RETURN);
mw.visitMaxs(1, 1);
mw.visitEnd();
mw = cw.visitMethod(ACC_PUBLIC+ACC_STATIC, "main", "([Ljava/lang/String;)V", null, null);
mw.visitFieldInsn(GETSTATIC, "java/lang/System", "out", "Ljava/io/PrintStream;");
mw.visitLdcInsn("Hello World!");
mw.visitMethodInsn(INVOKEVIRTUAL, "java/io/PrintStream", "println", "(Ljava/lang/String;)V");
mw.visitInsn(RETURN);
mw.visitMaxs(2, 2);
mw.visitEnd();
byte[] code = cw.toByteArray();
FileOutputStream fos;
try {
fos = new FileOutputStream("Example.class");
fos.write(code);
fos.close();
HelloWorld loader = new HelloWorld();
Class exampleClass = loader
.defineClass("Example", code, 0, code.length);
exampleClass.getMethods()[0].invoke(null, new Object[] { null });
} catch (FileNotFoundException e) {
// TODO Auto-generated catch block
e.printStackTrace();
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
} catch (IllegalArgumentException e) {
// TODO Auto-generated catch block
e.printStackTrace();
} catch (SecurityException e) {
// TODO Auto-generated catch block
e.printStackTrace();
} catch (IllegalAccessException e) {
// TODO Auto-generated catch block
e.printStackTrace();
} catch (InvocationTargetException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
}
?
cglib 動態生成class 并進行攔截
?
public class MyClass {
public void print() {
System.out.println("I'm in MyClass.print!");
}
}
import net.sf.cglib.proxy.Callback;
import net.sf.cglib.proxy.Enhancer;
import net.sf.cglib.proxy.MethodInterceptor;
import net.sf.cglib.proxy.MethodProxy;
public class Main {
public static void main(String[] args) {
Enhancer enhancer = new Enhancer();
enhancer.setSuperclass(MyClass.class);
enhancer.setCallback((Callback) new MethodInterceptorImpl());
MyClass my = (MyClass) enhancer.create();
my.print();
}
private static class MethodInterceptorImpl implements MethodInterceptor {
public Object intercept(Object obj, Method method, Object[] args,
MethodProxy proxy) throws Throwable {
// log something
System.out.println(method + " intercepted!");
proxy.invokeSuper(obj, args);
return null;
}
}
}
?
已有 1 人發表留言，猛擊->>這里<<-參與討論
ITeye推薦