基于HTTP协议实现简单RPC框架的方法详解

public interface UserService {
    String doSomething();
}
@Service
public class UserServiceImpl implements UserService {
    @Override
    public String doSomething() {
        System.out.println("doSomething......");
    }
}
@Controller
public class UserController {
    @Autowired
    private UserService userService;
    public void test(){
        String response = userService.doSomething();
    }
}

public interface UserService { //假设这是服务端暴露出来的接口
    String doSomething();
}
@Controller
public class UserController {
    @Autowired
    private UserService userService;//对于客户端来说，此时没有实现类，无法直接使用
    public void test(){
        String response = userService.doSomething();
    }
}

@Retention(RetentionPolicy.RUNTIME)
@Target(ElementType.TYPE)
@Import({ServiceBeanDefinitionRegistry.class}) //注意看这个地方比较重要
public @interface RPC {
    String value() default ""; //扫描的路径
}
//简单用法
@SpringBootApplication
@RPC("com.yeyeye.client.service") //扫描对应包下的所有接口，service包下就一个上面示例中的 UserService 接口
public class RpcClientApplication {
    public static void main(String[] args) {
        SpringApplication.run(RpcClientApplication.class, args);
    }
}

public class ServiceBeanDefinitionRegistry implements ImportBeanDefinitionRegistrar {
    @Override
    public void registerBeanDefinitions(AnnotationMetadata importingClassMetadata, BeanDefinitionRegistry registry) {
        //获取RPC注解里的路径
        Map<String, Object> attributes = importingClassMetadata.getAnnotationAttributes(RPC.class.getName());
        if (MapUtil.isEmpty(attributes)) {
            return;
        }
        String basePackages = (String) attributes.get("value");
        if (basePackages == null) {
            return;
        }
        //扫描路径
        RpcScanner rpcScanner = new RpcScanner(registry);
        rpcScanner.addIncludeFilter((metadataReader, metadataReaderFactory) -> true);
        rpcScanner.scan(basePackages);
    }
}

public class RpcScanner extends ClassPathBeanDefinitionScanner {
    public RpcScanner(BeanDefinitionRegistry registry) {
        super(registry);
    }
    @Override
    protected boolean isCandidateComponent(AnnotatedBeanDefinition beanDefinition) {
        //是不是一个接口，是的话就添加为候选组件
        return beanDefinition.getMetadata().isInterface();
    }
    @Override
    protected Set<BeanDefinitionHolder> doScan(String... basePackages) {
        //这里就是具体利用spring帮我们扫描
        Set<BeanDefinitionHolder> beanDefinitionHolders = super.doScan(basePackages);
        //对扫描出来的结果进行处理
        for (BeanDefinitionHolder beanDefinitionHolder : beanDefinitionHolders) {
            //这里获取的beanDefinition都是接口，并没有实现类
            BeanDefinition beanDefinition = beanDefinitionHolder.getBeanDefinition();
            //注册一个我们自己的beanDefinition，这个beanDefinition是一个bean工厂，工厂用于生成接口的代理类
            beanDefinition.setBeanClassName(ServiceBeanFactory.class.getName());
            //这里就是工厂bean构造方法需要的参数
            beanDefinition.getConstructorArgumentValues()
            .addGenericArgumentValue(beanDefinition.getBeanClassName());
        }
        return beanDefinitionHolders;
    }
}

public class ServiceBeanFactory<T> implements FactoryBean<T> {
    private Class<T> interFaceClazz;
    public ServiceBeanFactory(Class<T> interFaceClazz) {
        this.interFaceClazz = interFaceClazz;
    }
    @Override
    public T getObject() throws Exception {
        return (T) Proxy.newProxyInstance(
                interFaceClazz.getClassLoader(),
                new Class[]{interFaceClazz},
                new ServiceInvocationHandler());
    }
    @Override
    public Class<?> getObjectType() {
        return interFaceClazz;
    }
}
public class ServiceInvocationHandler implements InvocationHandler {
    /**
     * 这里就直接进行远程RPC调用了
     */
    @Override
    public Object invoke(Object proxy, Method method, Object[] args) {
        //指定URL
        String url = "http://localhost:8888/" + method.getName();
        //发送get请求并接收响应数据
        return HttpUtil.createGet(url).execute().body();
    }
}