SpringCloud：服务调用——自定义Feign方式实现

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一，SpringCloud 服务调用

Spring Cloud提供了两种方式进行服务调用，分别为RestTemplate方式和声明式Feign方式，两种代用方式在 SpringCloud：注册中心——Eureka中已经进行了演示；本篇文章参考Feign方式，整合RestTemplate实现自定义的声明式Feign调用

二，步骤解析

1，搭建简易声明式Feign客户端调动环境，并初步调通

2，重写@EnableFeignClients -> @EnableRestFeign，引用注册类为下面自定义注册类

3，重写@FeignClient -> @RestClient

4，重写注册类 -> RestFeignRegisters，通过JDK动态代理获取被@RestClient注解接口的代理对象，并通过BeanDeifinition注册到Spring Bean容器

5，重写JDK动态代理需要的InvocationHandler方法 -> MyInvocationHandler，拼接访问URL后，通过RestTemplate进行调用

三，调用流程

1，启动服务时：

@EnableRestFeign -> RestFeignRegisters ：注册被@RestClient注解的接口代理对象到SpringBean容器中

2，服务调用时：

* 通过调用的接口路径@RequestMapping及参数@RequestParam拼接服务访问路径 http://{serviceName}/{uri}?{param}

* 拼接成功后，通过RestTemplate直接进行服务调用

四，服务端代码

* 接口 -> com-gupao-springcloud-selffeign-server-api

package com.gupao.self.controller;import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RequestParam;/*** @author pj_zhang* @create 2019-01-24 0:38**/
public interface ISelfFeignController {@RequestMapping("/getMessage")String getMessage(@RequestParam("message") String message);
}

* 实现类 -> com-guapo-springcloud-selffeign-server

package com.gupao.self.controller;import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RequestParam;
import org.springframework.web.bind.annotation.RestController;/*** @author pj_zhang* @create 2019-01-24 0:30**/
@RestController
public class SelfFeignController implements ISelfFeignController {@Override@RequestMapping("/getMessage")public String getMessage(@RequestParam("message") String message) {return "SelfFeignController.getMessage : " + message;}}

五，代码实现

1，搭建简易声明式Feign客户端调动环境，并初步调通

* 项目架构，具体方式参考博文SpringCloud：注册中心——Eureka

* 客户端自定义Feign结构

2，重写@EnableFeignClients -> @EnableRestFeign

package com.gupao.self.feign.annotation;import com.gupao.self.feign.register.RestFeignRegisters;
import org.springframework.context.annotation.Import;import java.lang.annotation.*;/*** @author pj_zhang* @create 2019-01-23 23:01**/
@Retention(RetentionPolicy.RUNTIME)
@Target({ElementType.TYPE})
@Documented
@Import({RestFeignRegisters.class})
public @interface EnableRestFeign {/*** 指定RestClient端口* @return*/Class<?>[] clients() default {};}

3，重写@FeignClient -> @RestClient

package com.gupao.self.feign.annotation;import java.lang.annotation.*;/*** @author pj_zhang* @create 2019-01-23 23:08**/
@Target({ElementType.TYPE})
@Retention(RetentionPolicy.RUNTIME)
@Documented
public @interface RestClient {String name() default "";
}

4，重写注册类 -> RestFeignRegisters，通过JDK动态代理获取被@RestClient注解接口的代理对象，并通过BeanDeifinition注册到Spring Bean容器

package com.gupao.self.feign.register;import com.gupao.self.feign.annotation.EnableRestFeign;
import com.gupao.self.feign.annotation.RestClient;
import com.gupao.self.feign.handler.MyInvocationHandler;
import org.springframework.beans.BeansException;
import org.springframework.beans.factory.BeanFactory;
import org.springframework.beans.factory.BeanFactoryAware;
import org.springframework.beans.factory.FactoryBean;
import org.springframework.beans.factory.config.BeanDefinition;
import org.springframework.beans.factory.config.SingletonBeanRegistry;
import org.springframework.beans.factory.support.BeanDefinitionBuilder;
import org.springframework.beans.factory.support.BeanDefinitionRegistry;
import org.springframework.context.annotation.ImportBeanDefinitionRegistrar;
import org.springframework.core.annotation.AnnotationUtils;
import org.springframework.core.type.AnnotationMetadata;import java.lang.reflect.Proxy;
import java.util.Map;
import java.util.stream.Stream;/*** @author pj_zhang* @create 2019-01-23 23:01**/
public class RestFeignRegisters implements ImportBeanDefinitionRegistrar, BeanFactoryAware {private BeanFactory beanFactory;@Overridepublic void registerBeanDefinitions(AnnotationMetadata annotationMetadata,BeanDefinitionRegistry registry) {// 获取@EnableRestFeign模块引用的需要注册的Class类Map<String, Object> attributes =annotationMetadata.getAnnotationAttributes(EnableRestFeign.class.getName());Class<?>[] classes = (Class<?>[]) attributes.get("clients");// 筛选所有被Feign客户端注解的类, @RestFeignStream.of(classes)// 过滤接口.filter(Class::isInterface)// 仅选择标注了@RestClient注解的接口.filter(interfaceClass ->AnnotationUtils.findAnnotation(interfaceClass, RestClient.class) != null)// 过滤requestMapping方法.forEach(restClientClass -> {// 通过@RestClient源数据获取应用名称RestClient restClient =AnnotationUtils.findAnnotation(restClientClass, RestClient.class);String serverName = restClient.name();// @RestClient注解类进行动态代理Object proxy = Proxy.newProxyInstance(registry.getClass().getClassLoader(),new Class[]{restClientClass},new MyInvocationHandler(serverName, beanFactory));// 将@RestClient接口代理实现proxy注册为BeanString beanName = "RestClient." + serverName;// 通过SingletonBeanRegistry注册bean
//                    if (registry instanceof SingletonBeanRegistry) {
//                        SingletonBeanRegistry singletonBeanRegistry = (SingletonBeanRegistry) registry;
//                        singletonBeanRegistry.registerSingleton(serverName, proxy);
//                    }// 通过BeanDefinition注册BeanBeanDefinitionBuilder beanDefinitionBuilder =BeanDefinitionBuilder.genericBeanDefinition(RestClientClassFactoryBean.class);beanDefinitionBuilder.addConstructorArgValue(restClientClass);beanDefinitionBuilder.addConstructorArgValue(proxy);BeanDefinition beanDefinition = beanDefinitionBuilder.getRawBeanDefinition();registry.registerBeanDefinition(beanName, beanDefinition);});}/*** 自定义FactoryBean类,* 通过BeanDefinition方式注册类到Spring Bean容器中*/private static class RestClientClassFactoryBean implements FactoryBean {private final Class<?> restClient;private final Object proxy;private RestClientClassFactoryBean(Class<?> restClient, Object proxy) {this.restClient = restClient;this.proxy = proxy;}@Overridepublic Object getObject() throws Exception {return proxy;}@Overridepublic Class<?> getObjectType() {return restClient;}}/*** 通过集成BeanFactoryWare获取Spring Bean容器* 在通过RestTemplate进行方法调用时, 获取RestTemplate* @param beanFactory* @throws BeansException*/@Overridepublic void setBeanFactory(BeanFactory beanFactory) throws BeansException {this.beanFactory = beanFactory;}
}

5，重写JDK动态代理需要的InvocationHandler方法 -> MyInvocationHandler，拼接访问URL后，通过RestTemplate进行调用

package com.gupao.self.feign.handler;import org.springframework.beans.factory.BeanFactory;
import org.springframework.core.annotation.AnnotationUtils;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RequestParam;
import org.springframework.web.client.RestTemplate;import java.lang.annotation.Annotation;
import java.lang.reflect.InvocationHandler;
import java.lang.reflect.Method;/*** @author pj_zhang* @create 2019-01-23 23:26**/
public class MyInvocationHandler implements InvocationHandler {// ServiceNameprivate final String serviceName;private final BeanFactory beanFactory;public MyInvocationHandler(String serviceName, BeanFactory beanFactory) {this.serviceName = serviceName;this.beanFactory = beanFactory;}@Overridepublic Object invoke(Object proxy, Method method, Object[] args) throws Throwable {// 通过RestTemplate进行调用, 进行拼接访问路径, 访问路径参数如下// http://servierName/uri?param// 此处需要获取三个参数, 分别为// serviceName 从register获取// url 从方法注解获取RequestMapping requestMapping = AnnotationUtils.getAnnotation(method, RequestMapping.class);String[] uri = requestMapping.value();// param// 获取方法参数数量int count = method.getParameterCount();// 获取方法参数类型集合Class<?>[] parameterTypes = method.getParameterTypes();StringBuilder sb = new StringBuilder();for (int i = 0; i < count; i ++) {// 获取方法第i个参数注解Annotation[] annotations = method.getParameterAnnotations()[i];// 遍历注解, 获取参数名称String paramName = null;for (Annotation annotation : annotations) {if (annotation instanceof RequestParam) {paramName = ((RequestParam) annotation).value();break;}}String paramValue = String.valueOf(args[i]);// 拼接参数sb.append("&").append(paramName).append("=").append(paramValue);}// 拼接完整URL// http://servierName/uri?paramStringBuilder acturalUrl = new StringBuilder();acturalUrl.append("http://").append(serviceName).append("/").append(uri[0]).append("?").append(sb.toString());// 从BeanFactory容器中获取RestTemplate, 进行执行RestTemplate restTemplate = beanFactory.getBean("restTemplate", RestTemplate.class);return restTemplate.getForObject(acturalUrl.toString(), String.class);}
}

6，feign接口 -> 注意@FeignClient注解替换为@RestFeign

package com.gupao.self.feign;import com.gupao.self.controller.ISelfFeignController;
import com.gupao.self.feign.annotation.RestClient;
import org.springframework.cloud.openfeign.FeignClient;/*** @author pj_zhang* @create 2019-01-24 0:42**/
@RestClient(name = "server-feign")
public interface ISelfFeign extends ISelfFeignController {
}

7，启动类 -> 注意@EnableFeignClients替换为@EnableRestFeign

package com.gupao;import com.gupao.self.feign.ISelfFeign;
import com.gupao.self.feign.annotation.EnableRestFeign;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.cloud.client.loadbalancer.LoadBalanced;
import org.springframework.cloud.netflix.eureka.EnableEurekaClient;
import org.springframework.cloud.openfeign.EnableFeignClients;
import org.springframework.context.annotation.Bean;
import org.springframework.web.client.RestTemplate;/*** @author pj_zhang* @create 2019-01-24 0:34**/
@SpringBootApplication
//@EnableFeignClients
@EnableRestFeign(clients = ISelfFeign.class)
@EnableEurekaClient
public class SelfFeignClientApp {public static void main(String[] args) {SpringApplication.run(SelfFeignClientApp.class, args);}@LoadBalanced@Beanpublic RestTemplate restTemplate() {return new RestTemplate();}}

8，调用结果