关于spring-cloud:如何阅读-Spring-Cloud-OpenFein-源码

背景

始终以来，应用 Spring Cloud OpenFeign 都是浏览官网文档，尽管也大略晓得其实现原理，但究竟是没有 ” 证据 ” 的。对于 Spring 的源码浏览，自认为是一件非常令人头疼的事件。最近，在学习 Feign 的原生 API，乘此机会，也就浏览一下 Spring Cloud OpenFeign 的源码，并将分享进去，心愿能帮到有须要的人吧。

概述

对于 Spring Cloud OpenFeign 源码的博客有很多，然而，不晓得为什么，照着博客，一边读博客，一边读源码，还一边 debug，总是认为还有很多不分明的中央。究其原因，我认为，博客都是依照源码的流程解说，尽管附上了大段代码，可能还是无奈清晰的了解。不晓得你们是不是，反正我是这样的。

指标

首先，咱们明确一下明天探索的问题：

1. 咱们晓得，当咱们应用 @FeignClient，是应用了 JDK 动静代理，那么是如何实现的，那一步创立的代理类。
2. 当咱们晓得第一个问题后，咱们就根本分明整个流程了，那么，咱们就能够手写一个繁难的入门测试了。

源码

启动流程

• org.springframework.cloud.openfeign.EnableFeignClients
• org.springframework.cloud.openfeign.FeignAutoConfiguration
• org.springframework.cloud.openfeign.FeignClientsRegistrar
• org.springframework.cloud.openfeign.FeignClientsRegistrar#registerBeanDefinitions
• org.springframework.cloud.openfeign.FeignClientsRegistrar#registerFeignClient
• org.springframework.cloud.openfeign.FeignClientFactoryBean#getObject
• org.springframework.cloud.openfeign.Targeter
• feign.Feign.Builder#build
• feign.SynchronousMethodHandler.Factory
• feign.ReflectiveFeign.ParseHandlersByName
• feign.ReflectiveFeign#ReflectiveFeign
• feign.Feign#newInstance
• feign.ReflectiveFeign#newInstance
• feign.InvocationHandlerFactory#create
• feign.InvocationHandlerFactory.Default#create
• feign.ReflectiveFeign.FeignInvocationHandler#FeignInvocationHandler

贴上图吧，看看完整版的

注册流程：

主动配置：

调用流程

• feign.ReflectiveFeign.FeignInvocationHandler#invoke
• feign.InvocationHandlerFactory.MethodHandler#invoke
• feign.SynchronousMethodHandler#invoke

MyRpc

通过下面的流程，咱们手写一个 RPC。

上面给出次要代码。

@Retention(RetentionPolicy.RUNTIME)
@Target(ElementType.TYPE)
@Documented
@Import({MyRpcRegister.class, MyRpcAutoConfig.class})
public @interface EnableMyRpc {}

getObject()

@Data
public class MyRpcFactoryBean implements FactoryBean<Object> {

    private String url;

    private String contextPath;

    private String name;

    private Class<?> type;

    private BeanFactory beanFactory;

    private MyClient myClient;

    @Override
    public Object getObject() {Map<Method, RpcBean> map = new HashMap<>();

        Method[] methods = type.getMethods();

        myClient = beanFactory.getBean(MyClient.class);

        for (Method method : methods) {Annotation[] annotations = method.getAnnotations();
            String httpMethod = "";
            String path = "";
            for (Annotation annotation : annotations) {if (annotation.annotationType() == PostMapping.class) {
                    httpMethod = "POST";
                    path = ((PostMapping) annotation).value()[0];
                    break;
                } else if (annotation.annotationType() == GetMapping.class) {
                    httpMethod = "GET";
                    path = ((GetMapping) annotation).value()[0];
                    break;
                } else if (annotation.annotationType() == RequestMapping.class) {RequestMapping requestMapping = ((RequestMapping) annotation);
                    httpMethod = requestMapping.method()[0].name();
                    path = requestMapping.value()[0];
                    break;
                }
            }
            RpcBean rpcBean = new RpcBean()
                    .setUrl(url + contextPath)
                    .setPath(path)
                    .setHttpMethod(httpMethod)
                    .setMyClient(myClient)
                    ;
            map.put(method, rpcBean);
        }

        ClassLoader loader = type.getClassLoader();

        return Proxy.newProxyInstance(loader, new Class<?>[] {type}, new MyRpcInvocationHandler(map));
    }

    @Override
    public Class<?> getObjectType() {return type;}

}

handler

@Slf4j
public class MyRpcInvocationHandler implements InvocationHandler {

    private final Map<Method, RpcBean> map;

    public MyRpcInvocationHandler(Map<Method, RpcBean> map) {this.map = map;}

    @Override
    public Object invoke(Object proxy, Method method, Object[] args) throws Throwable {log.info("proxy handler");

        return request(method, args);
    }

    public Object request(Method method, Object[] args) {
        String result = "";
        RpcBean rpcBean = map.get(method);
        Parameter[] parameters = method.getParameters();
        Class<?> returnType = method.getReturnType();
        String url = rpcBean.getUrl() + rpcBean.getPath();
        String httpMethod = rpcBean.getHttpMethod();
        String param = getParam(httpMethod, parameters, args);
        log.info("url: [{}], param: [{}]", url, param);
        MyClient myClient = rpcBean.getMyClient();
        if ("POST".equals(httpMethod)) {result = myClient.post(url, param);
        } else if ("GET".equals(httpMethod)) {result = myClient.get(url, param);
        }
        if (StringUtils.hasText(result)) {return JsonUtils.convertObject(result, returnType);
        }
        return "";
    }

    public String getParam(String httpMethod, Parameter[] parameters, Object[] args) {if ("POST".equals(httpMethod)) {return JsonUtils.convertString(args[0]);
        } else if ("GET".equals(httpMethod)) {if (Objects.isNull(parameters) || parameters.length == 0
                    || Objects.isNull(args) || args.length == 0) {return "";}
            String param = "";
            StringBuilder urlBuilder = new StringBuilder(param);
            for (int i = 0; i < parameters.length; i++) {if (Objects.nonNull(args[i])) {urlBuilder.append(String.format("%s=%s&", parameters[i].getName(), args[i]));
                }
            }
            param = urlBuilder.toString();
            param = param.substring(0, param.length() - 1);
            return param;
        }
        return "";
    }
}

残缺代码