import jdk.internal.org.objectweb.asm.ClassWriter;
import jdk.internal.org.objectweb.asm.MethodVisitor;
import jdk.internal.org.objectweb.asm.Opcodes;
import java.lang.reflect.InvocationHandler;
import java.lang.reflect.Method;
import java.lang.reflect.Proxy;
public class DynamicProxyExample {
public static void main(String[] args) {
HelloService helloService = new HelloServiceImpl();
HelloService helloProxy = createProxy(helloService);
helloProxy.sayHello();
}
public static HelloService createProxy(final HelloService helloService) {
ClassWriter cw = new ClassWriter(ClassWriter.COMPUTE_FRAMES);
cw.visit(Opcodes.V1_8, Opcodes.ACC_PUBLIC, "ProxyClass", null, "java/lang/Object", new String[]{"HelloService"});
MethodVisitor mv = cw.visitMethod(Opcodes.ACC_PUBLIC, "<init>", "()V", null, null);
mv.visitCode();
mv.visitVarInsn(Opcodes.ALOAD, 0);
mv.visitMethodInsn(Opcodes.INVOKESPECIAL, "java/lang/Object", "<init>", "()V", false);
mv.visitInsn(Opcodes.RETURN);
mv.visitMaxs(1, 1);
mv.visitEnd();
mv = cw.visitMethod(Opcodes.ACC_PUBLIC, "sayHello", "()V", null, null);
mv.visitCode();
mv.visitFieldInsn(Opcodes.GETSTATIC, "java/lang/System", "out", "Ljava/io/PrintStream;");
mv.visitLdcInsn("Before method execution");
mv.visitMethodInsn(Opcodes.INVOKEVIRTUAL, "java/io/PrintStream", "println", "(Ljava/lang/String;)V", false);
mv.visitVarInsn(Opcodes.ALOAD, 1);
mv.visitMethodInsn(Opcodes.INVOKEINTERFACE, "HelloService", "sayHello", "()V", true);
mv.visitFieldInsn(Opcodes.GETSTATIC, "java/lang/System", "out", "Ljava/io/PrintStream;");
mv.visitLdcInsn("After method execution");
mv.visitMethodInsn(Opcodes.INVOKEVIRTUAL, "java/io/PrintStream", "println", "(Ljava/lang/String;)V", false);
mv.visitInsn(Opcodes.RETURN);
mv.visitMaxs(2, 2);
mv.visitEnd();
cw.visitEnd();
Class<?> proxyClass = Proxy.defineClass0(ProxyClassLoader.class.getClassLoader(), new String[]{"ProxyClass"}, cw.toByteArray());
try {
return (HelloService) proxyClass.newInstance();
e.printStackTrace();
}
return null;
}
}
interface HelloService {
void sayHello();
}
class HelloServiceImpl implements HelloService {
@Override
public void sayHello() {
System.out.println("Hello World!");
}
}
class ProxyClassLoader extends ClassLoader {
}
import jdk.internal.org.objectweb.asm.ClassWriter;
import jdk.internal.org.objectweb.asm.MethodVisitor;
import jdk.internal.org.objectweb.asm.Opcodes;
import java.lang.reflect.InvocationHandler;
import java.lang.reflect.Method;
import java.lang.reflect.Proxy;
public class AOPExample {
public static void main(String[] args) {
HelloService helloService = new HelloServiceImpl();
HelloService helloProxy = createProxy(helloService);
helloProxy.sayHello();
}
public static HelloService createProxy(final HelloService helloService) {
ClassWriter cw = new ClassWriter(ClassWriter.COMPUTE_FRAMES);
cw.visit(Opcodes.V1_8, Opcodes.ACC_PUBLIC, "ProxyClass", null, "java/lang/Object", new String[]{"HelloService"});
MethodVisitor mv = cw.visitMethod(Opcodes.ACC_PUBLIC, "<init>", "()V", null, null);
mv.visitCode();
mv.visitVarInsn(Opcodes.ALOAD, 0);
mv.visitMethodInsn(Opcodes.INVOKESPECIAL, "java/lang/Object", "<init>", "()V", false);
mv.visitInsn(Opcodes.RETURN);
mv.visitMaxs(1, 1);
mv.visitEnd();
mv = cw.visitMethod(Opcodes.ACC_PUBLIC, "sayHello", "()V", null, null);
mv.visitCode();
mv.visitMethodInsn(Opcodes.INVOKESTATIC, "AOPExample", "before", "()V", false);
mv.visitVarInsn(Opcodes.ALOAD, 1);
mv.visitMethodInsn(Opcodes.INVOKEINTERFACE, "HelloService", "sayHello", "()V", true);
mv.visitMethodInsn(Opcodes.INVOKESTATIC, "AOPExample", "after", "()V", false);
mv.visitInsn(Opcodes.RETURN);
mv.visitMaxs(2, 2);
mv.visitEnd();
cw.visitEnd();
Class<?> proxyClass = Proxy.defineClass0(ProxyClassLoader.class.getClassLoader(), new String[]{"ProxyClass"}, cw.toByteArray());
try {
return (HelloService) proxyClass.newInstance();
e.printStackTrace();
}
return null;
}
public static void before() {
System.out.println("Before method execution");
}
public static void after() {
System.out.println("After method execution");
}
}
interface HelloService {
void sayHello();
}
class HelloServiceImpl implements HelloService {
@Override
public void sayHello() {
System.out.println("Hello World!");
}
}
class ProxyClassLoader extends ClassLoader {
}
