13

JDK Proxy 类只接受工厂方法 newProxyInstance() 中的接口。

是否有可用的解决方法或替代实现？如果我必须将方法提取到接口以使它们能够与代理一起使用，则用例是有限的。我想包装它们以在运行时应用基于注释的操作。

public static <T> T getProxy(T obj) {
   InvocationHandler ih = new InjectProxy( obj );
   ClassLoader classLoader = InjectProxy.class.getClassLoader();
   return (T) Proxy.newProxyInstance( classLoader, obj.getClass().getInterfaces(), ih );
                                                    ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^  
}
4

3 回答 3

16

您可以像这样使用 cglib：

import java.lang.reflect.Array;
import java.lang.reflect.Method;
import java.lang.reflect.Modifier;

import net.sf.cglib.proxy.Enhancer;
import net.sf.cglib.proxy.MethodInterceptor;
import net.sf.cglib.proxy.MethodProxy;


public class AbstractFactory {

    @SuppressWarnings("unchecked")
    public static <A> A createDefaultImplementation(Class<A> abstractClass) {
        Enhancer enhancer = new Enhancer();
        enhancer.setSuperclass(abstractClass);
        enhancer.setCallback(new MethodInterceptor() {
            public Object intercept(Object proxy, Method method, Object[] args, MethodProxy methodProxy) throws Throwable {
                if (!Modifier.isAbstract(method.getModifiers())) {
                    return methodProxy.invokeSuper(proxy, args);
                } else {
                    Class type = method.getReturnType();
                    if (type.isPrimitive() && !void.class.equals(type)) {
                        return Array.get(Array.newInstance(type, 1), 0);
                    } else {
                        return null;
                    }
                }
            }
        });
        return (A) enhancer.create();
    }

    @SuppressWarnings("unchecked")
    public static <A> A createDefaultImplementation(String className) throws ClassNotFoundException{
        return (A) createDefaultImplementation(Class.forName(className));
    }
}

This for example lets you build abstract classes with a default implementation method. But you can change the enhancer to what ever you want.

于 2010-12-15T12:45:21.803 回答
5

有没有可用的解决方法..？

是的。有。从现有类中提取接口。

更新

如果某些特定的类需要它，可以像这样写 smt

//interface that already exists
public interface IDomain {
    String foo();
}
//your class
public class Domain implements IDomain{
    public String foo(){
        return "domain foo";
    }
//method that doesn't placed in IDomain
    public String bar(){
        return "domain bar";   
    }
}
//So you need create new interface with bar()
//it can extend IDomain 
public interface ExtendedIDomain extends IDomain {
    public String bar();
}
//than your wrapper factory will be like this
public class Proxifier {
    public static  ExtendedIDomain getProxy(Domain obj) {
       InvocationHandler ih = new InjectProxy( obj );
       ClassLoader classLoader = InjectProxy.class.getClassLoader();
       return (ExtendedIDomain) Proxy.newProxyInstance( classLoader, new Class[]{ExtendedIDomain.class}, ih );
    }

    static class InjectProxy implements InvocationHandler {
        private final Domain domain;
        private InjectProxy(Domain domain){
            this.domain = domain;
        }

        public String invoke(Object proxy, Method method, Object[] args) throws Throwable{
            for(Method m : domain.getClass().getMethods()){
                //TODO: check signature(name, args etc) or implement some logic with annotations
                if(m.getName().equals(method.getName())){
                    return "wrapped " + m.invoke(domain, args);
                }
            }
            throw new IllegalArgumentException();
        }
    }
}
//test
    public static void main(String[] args) {
        ExtendedIDomain d = Proxifier.getProxy(new Domain());
        System.out.println(d.foo());
        System.out.println(d.bar());
    }

如果你需要一些“通用”的东西，你应该像@Peter Lawrey 所说的那样使用 AOP。

于 2010-12-10T16:50:38.277 回答
2

或替代实现

您可以使用cglib。

关于 cglib 替代品的类似帖子：Cglib有替代品吗？

于 2010-12-13T12:53:23.403 回答