java - 如何使用 Spring 和 Java 创建动态代理

Question

我有这样的情况: 我有一个聚合所有服务接口(interface)的接口(interface)服务。例如，如果我有两个接口(interface) ILoginService1 和 ILoginService2，服务接口(interface)看起来像这样

Service extends ILoginService1,ILoginService2. 

我需要在给定的上下文中访问此接口(interface)，如下所示:

service.login();

这是我的解决方案(类似于 http://artofsoftwarereuse.com/tag/dynamic-proxy/ ):

我创建了一个注解 ServiceFacade，我把它放在服务接口(interface)上，然后我有 BeanPostProcessor，我在其中为服务接口(interface)创建了 DynamicProxy。 但问题是 Service 接口(interface)没有从 spring 组件扫描中获取，即使我把 @Component 放在上面，但其他组件放在 Spring 容器中也是如此。

到目前为止，我该如何解决我的解决方案，或者我遗漏了什么，或者是否有其他解决方案？ 这是源代码: 应用上下文.xml

<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
       xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
       xmlns:context="http://www.springframework.org/schema/context"
       xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans-3.0.xsd
http://www.springframework.org/schema/context http://www.springframework.org/schema/context/spring-context-3.0.xsd">

    <context:annotation-config/>    
    <context:component-scan base-package="org.finki.auction.ui.application"/>
    <context:component-scan base-package="org.finki.auction.services"/>

</beans>

注释:

@Target(ElementType.TYPE)
@Retention(RetentionPolicy.RUNTIME)
public @interface ServiceFacade{}

动态代理的调用处理程序:

/**
 * 
 */
package org.finki.auction.services;

import java.lang.reflect.InvocationHandler;
import java.lang.reflect.InvocationTargetException;
import java.lang.reflect.Method;
import java.util.HashMap;
import java.util.Map;

import org.springframework.beans.BeansException;
import org.springframework.context.ApplicationContext;
import org.springframework.context.ApplicationContextAware;
import org.springframework.stereotype.Component;
import org.springframework.stereotype.Service;

/**
 * 
 */
@Component("serviceLayer")
public class ServiceLayer implements InvocationHandler, ApplicationContextAware
{

    private static ApplicationContext applicationContext = null;
    private static Map<String, String> serviceMap = new HashMap<>();

    @Override
    public Object invoke(Object proxy, Method method, Object[] args) throws Throwable
    {
        Object result;
        try
        {
            String searchKey = method.getName();
            String beanName = serviceMap.get(searchKey);
            Object methodObject = applicationContext.getBean(beanName);
            result = method.invoke(methodObject, args);
        } catch (InvocationTargetException e)
        {
            throw e.getTargetException();
        } catch (Exception e)
        {
            throw new RuntimeException("unexpected invocation exception: " + e.getMessage());
        }
        return result;
    }

    @Override
    public void setApplicationContext(ApplicationContext applicationContext) throws BeansException
    {
        ServiceLayer.applicationContext = applicationContext;

        Map<String, Object> beans = applicationContext.getBeansWithAnnotation(Service.class);
        for (Map.Entry<String, Object> entryBean : beans.entrySet())
        {
            String beanName = entryBean.getKey();
            Object beanObject = entryBean.getValue();
            Method[] beanMethods = beanObject.getClass().getDeclaredMethods();
            for (Method bMethod : beanMethods)
            {
                serviceMap.put(bMethod.getName(), beanName);
            }
        }
    }

}

BeanPostProcessor 类:

/**
 * 
 */
package org.finki.auction.services.annotation;

import java.lang.reflect.Proxy;
import java.util.Arrays;

import org.finki.auction.services.Service;
import org.finki.auction.services.ServiceLayer;
import org.springframework.beans.BeansException;
import org.springframework.beans.factory.config.BeanPostProcessor;
import org.springframework.context.ApplicationContext;
import org.springframework.context.ApplicationContextAware;
import org.springframework.stereotype.Component;

/**
 * 
 */
@Component("serviceFacadeProcessor")
public class ServiceFacadeProcessor implements BeanPostProcessor, ApplicationContextAware
{

    private static ApplicationContext applicationContext = null;

    @Override
    public Object postProcessBeforeInitialization(Object bean, String beanName) throws BeansException
    {
        return bean;
    }

    @Override
    public Object postProcessAfterInitialization(Object bean, String beanName) throws BeansException
    {
        Class<?> clz = bean.getClass();
        Class<?>[] tmpInterfaces = clz.getInterfaces();
        System.out.println("ServiceFacadeProcessor : " + bean);
        if (tmpInterfaces != null && tmpInterfaces.length == 1
                && tmpInterfaces[0].isAnnotationPresent(ServiceFacade.class))
        {

            System.out.println("Find serviceFacade >>>>");
            Class<?>[] interfaces = Arrays.copyOf(tmpInterfaces, tmpInterfaces.length + 1);

            interfaces[tmpInterfaces.length] = Service.class;
            ClassLoader cl = bean.getClass().getClassLoader();
            ServiceLayer serviceLayerBean = applicationContext.getBean("serviceLayer", ServiceLayer.class);
            Object t = Proxy.newProxyInstance(cl, interfaces, serviceLayerBean);
            System.out.println("Find serviceFacade <<<<");
            return t;
        }

        return bean;

    }

    @Override
    public void setApplicationContext(ApplicationContext applicationContext) throws BeansException
    {
        ServiceFacadeProcessor.applicationContext = applicationContext;
    }

}

所以，我的问题不是配置，我的问题是如何将服务接口(interface)附加到 spring 容器，以便被 BeanPostProcessor 捕获并为其创建动态代理。到目前为止，这是我的解决方案，也许我遗漏了一些东西，但如果有人有更好的方法，现在就让我来吧。 提前致谢

解决方法:

/**
 * 
 */
package org.finki.auction.services.annotation;

import java.lang.reflect.Proxy;
import java.util.Arrays;

import org.finki.auction.services.Service;
import org.finki.auction.services.ServiceLayer;
import org.springframework.beans.BeansException;
import org.springframework.beans.factory.FactoryBean;
import org.springframework.context.ApplicationContext;
import org.springframework.context.ApplicationContextAware;
import org.springframework.stereotype.Component;

/**
 * @author
 * 
 */
@Component
public class ServiceFactoryBean implements FactoryBean<Service>, ApplicationContextAware
{

    private static ApplicationContext applicationContext = null;

    @Override
    public Service getObject() throws Exception
    {

        Class<?>[] tmpInterfaces = Service.class.getInterfaces();
        Class<?>[] interfaces = Arrays.copyOf(tmpInterfaces, tmpInterfaces.length + 1);
        interfaces[tmpInterfaces.length] = Service.class;
        ServiceLayer serviceLayerBean = applicationContext.getBean("serviceLayer", ServiceLayer.class);
        ClassLoader cl = serviceLayerBean.getClass().getClassLoader();
        Object t = Proxy.newProxyInstance(cl, interfaces, serviceLayerBean);
        return (Service) t;
    }

    @Override
    public Class<?> getObjectType()
    {
        return Service.class;
    }

    @Override
    public boolean isSingleton()
    {
        return true;
    }

    @Override
    public void setApplicationContext(ApplicationContext applicationContext) throws BeansException
    {
        ServiceFactoryBean.applicationContext = applicationContext;
    }

}

还需要删除BeanPostProcessor和注解。

Answer 1

我遇到了类似的事情，相信您可以使用 Spring 的 Java 配置功能让您的场景正常工作。

@Configuration
public class ServiceConfiguration {

    // you can wire your service1 and service2 here

    @Bean
    Service service() {
         // create and return dynamic proxy here
    }
}

通过这种方式，您最终会得到一个类型为“Service”且名称为“service”的 bean，它将成为具有调用处理程序等的动态代理。

我确信 Java 配置不会限制您使用上面概述的方法(您将 service1 和 service2 连接到配置中)- 我认为这是实现细节。