Nirvana Studio Blog Archive cglib 指南 :: 分享知...

cglib，全称是Code Generation Library，它可以用来动态继承Java类或者实现接口，很多知名的开源项目中用到了它，譬如Hibernate，Spring之类用它来实现动态代理。

增强一个已有类

public class MyClass {
 
public void method() {
System.out.println("MyClass.method()");
}
}

import java.lang.reflect.Method;
 
import net.sf.cglib.proxy.Enhancer;
import net.sf.cglib.proxy.MethodProxy;
import net.sf.cglib.proxy.MethodInterceptor;
 
public class Main {
 
public static void main(String[] args) {
 
Enhancer enhancer = new Enhancer();
 
enhancer.setSuperclass(MyClass.class);
enhancer.setCallback( new MethodInterceptorImpl() );
 
 
MyClass my = (MyClass)enhancer.create();
 
my.method();
}
 
private static class MethodInterceptorImpl implements MethodInterceptor {
public Object intercept(Object obj,
Method method,
Object[] args,
MethodProxy proxy) throws Throwable {
 
System.out.println(method);
 
proxy.invokeSuper(obj, args);
 
return null;
}
}
}

执行结果：

public void cglib_test.MyClass.method()
MyClass.method()

使用CallbackFilter

public class MyClass {
 
public void method() {
System.out.println("MyClass.method()");
}
 
public void method2() {
System.out.println("MyClass.method2()");
}
}

import java.lang.reflect.Method;
 
import net.sf.cglib.proxy.Enhancer;
import net.sf.cglib.proxy.MethodProxy;
import net.sf.cglib.proxy.MethodInterceptor;
import net.sf.cglib.proxy.NoOp;
import net.sf.cglib.proxy.Callback;
import net.sf.cglib.proxy.CallbackFilter;
 
 
public class Main {
 
public static void main(String[] args) {
 
Callback[] callbacks =
new Callback[] { new MethodInterceptorImpl(),  NoOp.INSTANCE };
 
Enhancer enhancer = new Enhancer();
 
enhancer.setSuperclass(MyClass.class);
enhancer.setCallbacks( callbacks );
enhancer.setCallbackFilter( new CallbackFilterImpl() );
 
 
MyClass my = (MyClass)enhancer.create();
 
my.method();
my.method2();
}
 
private static class CallbackFilterImpl implements CallbackFilter {
 
public int accept(Method method) {
 
if ( method.getName().equals("method2") ) {
return 1;
 
} else {
return 0;
}
}
}
 
private static class MethodInterceptorImpl implements MethodInterceptor {
public Object intercept(Object obj,
Method method,
Object[] args,
MethodProxy proxy) throws Throwable {
 
System.out.println(method);
 
return proxy.invokeSuper(obj, args);
}
}
}

执行结果：

public void cglib_test.MyClass.method()
MyClass.method()
MyClass.method2()

使用Mixin

public interface MyInterfaceA {
 
public void methodA();
}
 
public interface  MyInterfaceB {
public void methodB();
}
 
public class MyInterfaceAImpl implements MyInterfaceA {
 
public void methodA() {
System.out.println("MyInterfaceAImpl.methodA()");
}
}
 
public class MyInterfaceBImpl implements MyInterfaceB {
 
public void methodB() {
System.out.println("MyInterfaceBImpl.methodB()");
}
}

import net.sf.cglib.proxy.Mixin;
 
public class Main {
 
public static void main(String[] args) {
 
Class[] interfaces =
new Class[] { MyInterfaceA.class, MyInterfaceB.class };
Object[] delegates =
new Object[] { new MyInterfaceAImpl(), new MyInterfaceBImpl() };
Object obj = Mixin.create(interfaces, delegates);
 
 
MyInterfaceA myA = (MyInterfaceA)obj;
myA.methodA();
 
 
MyInterfaceB myB = (MyInterfaceB)obj;
myB.methodB();
}
}

执行结果：

MyInterfaceAImpl.methodA()
MyInterfaceBImpl.methodB()

This entry was posted on 星期二, 六月 6th, 2006 at 3:18 pm and is filed under Java. You can follow any responses to this entry through the RSS 2.0 feed. You can leave a response, or trackback from your own site.