为我代理的每个方法执行 InvocationHandler 调用方法 class

Question

我实现了一个动态代理，以便在我的方法开始之前执行一些操作。现在我在从代理 class 调用两个方法时遇到问题，这里是代码：

动态代理class:

public class IPageProxy implements InvocationHandler {

    private Class <? extends IPage> screenClazz;

    public IPageProxy(final Class <? extends IPage> screenClazz) {
        this.screenClazz = screenClazz;
    }

    @SuppressWarnings("unchecked")
    public static <T extends IPage> T getInstance(final Class<? extends IPage> type)
            throws InstantiationException, IllegalAccessException {

        List<Class<?>> interfaces = new ArrayList<>();
        interfaces.addAll(Arrays.asList(type.getInterfaces()));

        return (T) Proxy.newProxyInstance(
                type.getClassLoader(),
                findInterfaces(type),
                new IPageProxy(type)
             );

    }


    static Class<?>[] findInterfaces(final Class<? extends IPage> type) {
        Class<?> current = type;

        do {
            final Class<?>[] interfaces = current.getInterfaces();

            if (interfaces.length != 0) {
                return interfaces;
            }
        } while ((current = current.getSuperclass()) != Object.class);

        throw new UnsupportedOperationException("The type does not implement any interface");
    }





    @Override
    public Object invoke(final Object proxy, final Method method, final Object[] args) throws InvocationTargetException,
            IllegalAccessException, IllegalArgumentException, InstantiationException, ParserConfigurationException, XPathExpressionException, NoSuchFieldException, SecurityException {

        // before method executed this code will be done
        System.out.println("*   Dynamic proxy invoke method executed for " +  method.getName());

        // Invoke original method
        return method.invoke(screenClazz.newInstance(), args);
    }
}

主要class：

public static void main(String[] args) {
        try {
            //IEventDesignDialog a = new EventDesignDialog();
            IEventDesignDialog a  = (IEventDesignDialog)getInstance(EventDesignDialog.class);
            a.getEventType().getShow();

        } catch (InstantiationException | IllegalAccessException e) {
            e.printStackTrace();
        }
    }


    @SuppressWarnings("unchecked")
    public static <T extends IPage> T getInstance(final Class<? extends IPage> type) throws InstantiationException, IllegalAccessException {
        return (T) IPageProxy.getInstance(type);
    }

代理 class:

public class EventDesignDialog implements IEventDesignDialog{


        private String show;


        private String dateAndTimeDisplayFormat;
        private String eventType;


        @Entity(visibileName = "Show")
        public IEventDesignDialog getShow() {
            System.out.println("get show method invokde successfully");
            return this;
        }

        @Entity(visibileName = "Date And Time display format")
        public IEventDesignDialog getDateAndTimeDisplayFormat() {
            System.out.println("get date and time display format method invokde successfully");
            return this;
        }

        @Entity(visibileName = "Event Type")
        public IEventDesignDialog getEventType() {
            System.out.println("get event type method invokde successfully");
            return this;
        }



}

实际输出：

***   Dynamic proxy invoke method executed for getEventType
get event type method invokde successfully
get show method invokde successfully**

如图所示，invoke 方法仅在初始化代理后的第一个方法调用时执行，第二个方法直接调用，没有代理功能。

我的目标是每次调用我的集合中出现的方法时执行invoke方法，预期结果应该如下所示。

预期输出：

***   Dynamic proxy invoke method executed for getEventType
get event type method invokde successfully
*   Dynamic proxy invoke method executed for getShow
get show method invokde successfully**

如果需要更多解释，请告诉我。

Answer 1

我已经通过使用 return 代理实例的默认方法创建一个接口解决了这个问题，然后在执行调用的方法功能后 return 编辑它：

更新代码：

public interface IPage {
    default <T extends IPage> T getProxyInstance() {
        try {
            return (T) IPageProxy.getInstance(this.getClass());
        } catch (InstantiationException | IllegalAccessException e) {
            e.printStackTrace();
        }
        return null;
    }
}

我的页面界面：

@Page(path = "MyPath")
public interface IEventDesignDialog extends IPage{
    @Entity(visibileName = "Show")
    public IEventDesignDialog getShow();

    @Entity(visibileName = "Date And Time display format")
    public IEventDesignDialog getDateAndTimeDisplayFormat();

    @Entity(visibileName = "Event Type")
    public IEventDesignDialog getEventType();    
}

我的主页class:

@Page(path = "MyPath")
public class EventDesignDialog implements IEventDesignDialog{
        @Entity(visibileName = "Show")
        public IEventDesignDialog getShow() {
            System.out.println("get show method invokde successfully");
            return getProxyInstance();
        }

        @Entity(visibileName = "Date And Time display format")
        public IEventDesignDialog getDateAndTimeDisplayFormat() {
            System.out.println("get date and time display format method invokde successfully");
            return getProxyInstance();
        }

        @Entity(visibileName = "Event Type")
        public IEventDesignDialog getEventType() {
            System.out.println("get event type method invokde successfully");
            return getProxyInstance();
        }
}

主要class:

public class Main {

    public static void main(String[] args) {
        try {
            IEventDesignDialog a  = ((IEventDesignDialog)getInstance(EventDesignDialog.class)).getEventType().getShow();

            ((IShowDesignDialog)getInstance(ShowDesignDialog.class)).getShowName().getShowType();
        } catch (InstantiationException | IllegalAccessException e) {
            e.printStackTrace();
        }
    }


    @SuppressWarnings("unchecked")
    public static <T extends IPage> T getInstance(final Class<? extends IPage> type) throws InstantiationException, IllegalAccessException {
        return (T) IPageProxy.getInstance(type);
    }

}

IProxy 页面保持不变，没有变化。

Answer 2

发生的事情是，首先您仅代理第一次调用，但随后您在未代理的 class 上调用 getShow()，这就是您得到上述结果的原因。如果您想实现您提到的目标，您需要根据创建的实例创建另一个代理，而不仅仅是 class.

更新：我将提供示例代码，您可以粘贴任何 java 文件并执行它。在你看到 TODO 的地方，你可以根据你想如何提供代理来放置你自己的逻辑。有关重要时刻，请参阅注意事项。为了演示简单，我将所有 classes 放在一个文件中。

import java.lang.reflect.InvocationHandler;
import java.lang.reflect.Method;
import java.lang.reflect.Proxy;
import java.util.Arrays;
import java.util.List;

class Scratch {
    public static void main(String[] args) {
        try {
            IEventDesignDialog a  = proxy(EventDesignDialog.class);
            a.getEventType().getShow();
            a.getDateAndTimeDisplayFormat().getShow();
        } catch (InstantiationException | IllegalAccessException e) {
            e.printStackTrace();
        }
    }


    @SuppressWarnings("unchecked")
    private static <T extends IPage> T proxy(final Class<? extends IPage> type) throws InstantiationException, IllegalAccessException {
        return (T) IPageProxy.proxy(type);
    }
}
interface IPage{}
interface IEventDesignDialog extends IPage{
    IEventDesignDialog getShow();
    IEventDesignDialog getEventType();
    IEventDesignDialog getDateAndTimeDisplayFormat();
}
class EventDesignDialog implements IEventDesignDialog{

    public IEventDesignDialog getShow() {
        System.out.println("get show method invoked successfully");

        //NOTE: this will be treated as same proxy but not this
        return this;
    }

    public IEventDesignDialog getDateAndTimeDisplayFormat() {
        System.out.println("get date and time display format method invoked successfully");

        // NOTE: we supply some iinstance which will be proxied
        return new MyIEventDesignDialog();
    }

    public IEventDesignDialog getEventType() {
        System.out.println("get event type method invoked successfully");

        //NOTE: this will be treated as same proxy but not this
        return this;
    }

}
class IPageProxy implements InvocationHandler {

    private IPage instance;
    private List<Class<?>> interfaces;


    public IPageProxy(IPage instance, List<Class<?>> interfaces) {
        this.instance = instance;
        this.interfaces = interfaces;
    }

    @SuppressWarnings("unchecked")
    public static <T extends IPage> T proxy(final Class<? extends IPage> type)
            throws InstantiationException, IllegalAccessException {

        List<Class<?>> interfaces = Arrays.asList(type.getInterfaces());


        //TODO: get interfaces properly recursively
        return (T) Proxy.newProxyInstance(
                type.getClassLoader(),
                type.getInterfaces(),
                new IPageProxy(type.newInstance(), interfaces)
        );

    }

    @SuppressWarnings("unchecked")
    public static <T extends IPage> T proxy(T object) {

        //TODO: get interfaces properly recursively
        List<Class<?>> interfaces = Arrays.asList(object.getClass().getInterfaces());

        return (T) Proxy.newProxyInstance(
                object.getClass().getClassLoader(),
                object.getClass().getInterfaces(),
                new IPageProxy(object, interfaces)
        );

    }




    @Override
    public Object invoke(final Object proxy, final Method method, final Object[] args) throws Exception {

        // before method executed this code will be done
        System.out.println("*   Dynamic proxy invoke method executed for " +  method.getName());

        // Invoke original method
        Object invoke = method.invoke(instance, args);
        if (invoke == null) {
            return null;
        }

        //If some of the method returns the original object
        //we swap the returned object by our proxy
        if (invoke == instance) {
            return proxy;
        }

        //TODO: check if you want to swap in place
        //other interfaces
        if (interfaces.contains(method.getReturnType())) {
            return IPageProxy.proxy((IPage)invoke);
        }
        return invoke;
    }
}

class MyIEventDesignDialog implements IEventDesignDialog {
    @Override
    public IEventDesignDialog getShow() {
        return null;
    }

    @Override
    public IEventDesignDialog getEventType() {
        return null;
    }

    @Override
    public IEventDesignDialog getDateAndTimeDisplayFormat() {
        return null;
    }
}

输出：

*   Dynamic proxy invoke method executed for getEventType
get event type method invoked successfully
*   Dynamic proxy invoke method executed for getShow
get show method invoked successfully
*   Dynamic proxy invoke method executed for getDateAndTimeDisplayFormat
get date and time display format method invoked successfully
*   Dynamic proxy invoke method executed for getShow

您可以从 Mockito 的工作原理中获得灵感。请查看此页面：https://static.javadoc.io/org.mockito/mockito-core/2.27.0/org/mockito/Mockito.html#spy-T-

我知道这是为了测试，但你仍然可以从中获得灵感。所以你可以在 class 和一个对象上应用 spy() 来监视它。

为我代理的每个方法执行 InvocationHandler 调用方法 class

Execute InvocationHandler invoke method for each method at my proxied class

java

reflection

dynamic-proxy

invocationhandler