如何通过HTTP优雅调用第三方-Feign

目录

Java常用HTTP客户端

  1. Java原生HttpURLConnection

  2. Apache HttpClient

  3. OkHttp

  4. Spring RestTemplate

示例

public interface Client {
    /**
     * 
     * @param body
     * @return
     */
    Response post(Object body) throws Exception;
}

public class ApacheHttpClient implements Client {

    private static final String DEFAULT_CONTENT_TYPE_VALUE = "application/json";

    private static final String DEFAULT_CHARSET_NAME = "UTF-8";

    private String url;

    private final HttpClient client;

    private JsonSerializer jsonSerializer;

    /**
     * 
     * @param url
     */
    public ApacheHttpClient(String url) {
        this(url, HttpClientBuilder.create().build());
    }

    /**
     * 
     * @param url
     * @param client
     */
    public ApacheHttpClient(String url, HttpClient client) {
        this(url, client, new JacksonJsonSerializer());

    }

    /**
     * 
     * @param url
     * @param client
     * @param jsonSerializer
     */
    public ApacheHttpClient(String url, HttpClient client, JsonSerializer jsonSerializer) {
        if (StringUtils.isBlank(url)) {
            throw new IllegalArgumentException("Url can't be null!");
        }
        if (Objects.isNull(client)) {
            throw new IllegalArgumentException("client can't be null!");
        }
        if (Objects.isNull(jsonSerializer)) {
            throw new IllegalArgumentException("jsonSerializer can't be null!");
        }
        this.url = url;
        this.client = client;
        this.jsonSerializer = jsonSerializer;
    }

    @Override
    public Response post(Object body) throws Exception {
        if (Objects.isNull(body)) {
            return Response.NULL_BODY_RESPONSE;
        }
        if (body instanceof Collection && ((Collection<?>) body).size() <= 0) {
            return Response.EMPTY_BODY_RESPONSE;
        }
        HttpPost post = new HttpPost(url);
        String jsonString = jsonSerializer.serialize(body);
        StringEntity entity = new StringEntity(jsonString, DEFAULT_CHARSET_NAME);
        entity.setContentType(DEFAULT_CONTENT_TYPE_VALUE);
        post.setEntity(entity);
        HttpResponse httpResponse = client.execute(post);
        HttpEntity httpEntity = httpResponse.getEntity();
        String result = EntityUtils.toString(httpEntity, "UTF-8");
        Response response = new Response(httpResponse.getStatusLine().getStatusCode(),
                httpResponse.getStatusLine().getReasonPhrase(), result);
        httpResponse.getEntity().getContent().close();
        return response;
    }

}

存在问题

  • 面向方法
  • 耦合HTTP客户端
  • 手动处理请求响应
  • 无法通用，重复编码

面向接口实现HTTP调用

HTTP请求和响应的组成

  • 请求：请求行、请求头、请求体

  • 响应：响应行、响应头、响应体

从访问百度主页开始

声明接口

package com.zby.service;

public interface BaiduClient {

    @RequestLine(url = "http://www.baidu.com", method = "GET")
    String index();

}

声明注解

package com.zby.annotation;

@Inherited
@Documented
@Retention(RetentionPolicy.RUNTIME)
@Target(ElementType.METHOD)
public @interface RequestLine {

    String method();

    String url();

}

  • 如果我能通过注入BaiduClient接口的方式调用第三方，并且新增第三方时，只需要新增类似接口，与面向过程的方式相比，是否更优雅？

  • 要实现注入BaiduClient接口，那么必须解析RequestLine注解，并且生成BaiduClient对象

HOW？

  • 代理模式
  • 模版方法模式
  • 工厂模式

声明工厂类

package com.zby.proxy;

/**
 * @author zby
 * @title HTTP代理工厂
 * @date 2020年6月16日
 * @description
 */
public interface HttpProxyFactory {
    /**
     * 获取HTTP代理对象
     * 
     * @param clazz
     * @return
     */
    <T> T getProxy(Class<T> clazz);

}

抽象工厂，处理注解

package com.zby.proxy;

import java.lang.reflect.Method;
import java.util.HashMap;
import java.util.Map;
import java.util.concurrent.ConcurrentHashMap;

import com.zby.annotation.RequestLine;

/**
 * @author zby
 * @title 抽象代理工厂
 * @date 2020年6月16日
 * @description
 */
public abstract class AbstractHttpProxyFactory implements HttpProxyFactory {

    private Map<Class<?>, Map<Method, RequestLine>> classMethodCacheMap = new ConcurrentHashMap<>();

    @Override
    public <T> T getProxy(Class<T> clazz) {
        if (!clazz.isInterface()) {
            throw new IllegalArgumentException();
        }
        Map<Method, RequestLine> methodCacheMap = classMethodCacheMap.get(clazz);
        if (methodCacheMap == null) {
            methodCacheMap = new HashMap<>();
            Method[] methods = clazz.getDeclaredMethods();
            for (Method method : methods) {
                RequestLine requestLine = method.getDeclaredAnnotation(RequestLine.class);
                if (requestLine == null) {
                    throw new IllegalArgumentException(method.getName());
                }
                methodCacheMap.put(method, requestLine);
            }
            classMethodCacheMap.putIfAbsent(clazz, methodCacheMap);
        }
        return createProxy(clazz, methodCacheMap);
    }

    /**
     * 创建代理对象
     * 
     * @param clazz
     * @param methodCacheMap
     * @return
     */
    protected abstract <T> T createProxy(Class<T> clazz, Map<Method, RequestLine> methodCacheMap);


}

基于代理和HttpURLConnection实现

package com.zby.proxy;

import java.io.BufferedReader;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.lang.reflect.InvocationHandler;
import java.lang.reflect.Method;
import java.lang.reflect.Proxy;
import java.net.HttpURLConnection;
import java.net.URL;
import java.net.URLConnection;
import java.util.Map;

import com.zby.annotation.RequestLine;

/**
 * @author zby
 * @title HttpURLConnectionProxyFactory
 * @date 2020年6月16日
 * @description
 */
public class HttpURLConnectionProxyFactory extends AbstractHttpProxyFactory {

    @Override
    @SuppressWarnings("unchecked")
    protected <T> T createProxy(Class<T> clazz, Map<Method, RequestLine> methodCacheMap) {
        return (T) Proxy.newProxyInstance(clazz.getClassLoader(), new Class[] {clazz}, new InvocationHandler() {

            @Override
            public Object invoke(Object proxy, Method method, Object[] args) throws Throwable {
                RequestLine requestLine = methodCacheMap.get(method);
                if (requestLine == null) {
                    throw new IllegalArgumentException();
                }
                URL url = new URL(requestLine.url());
                URLConnection rulConnection = url.openConnection();
                HttpURLConnection httpUrlConnection = (HttpURLConnection) rulConnection;
                httpUrlConnection.setRequestMethod(requestLine.method());
                httpUrlConnection.connect();
                InputStream inputStream = httpUrlConnection.getInputStream();
                BufferedReader bufferedReader = new BufferedReader(new InputStreamReader(inputStream));
                StringBuilder stringBuilder = new StringBuilder();
                String newLine = null;
                while ((newLine = bufferedReader.readLine()) != null) {
                    stringBuilder.append(newLine);

                }
                return stringBuilder.toString();
            }
        });
    }
}

拉出来溜溜

package com.zby;

import com.zby.proxy.HttpProxyFactory;
import com.zby.proxy.HttpURLConnectionProxyFactory;
import com.zby.service.BaiduClient;

/**
 * @author zby
 * @title HttpProxyDemo
 * @date 2020年6月16日
 * @description
 */
public class HttpProxyDemo {

    public static void main(String[] args) {
        HttpProxyFactory httpProxyFactory = new HttpURLConnectionProxyFactory();
        BaiduClient baiduClient = httpProxyFactory.getProxy(BaiduClient.class);
        System.out.println(baiduClient.index());
    }

}


<!DOCTYPE html><!--STATUS OK--><html> <head><meta http-equiv=content-type content=text/html;charset=utf-8><meta http-equiv=X-UA-Compatible content=IE=Edge><meta content=always name=referrer><link rel=stylesheet type=text/css href=http://s1.bdstatic.com/r/www/cache/bdorz/baidu.min.css><title>百度一下，你就知道</title></head> <body link=#0000cc> <div id=wrapper> <div id=head> <div class=head_wrapper> <div class=s_form> <div class=s_form_wrapper> <div id=lg> <img hidefocus=true src=//www.baidu.com/img/bd_logo1.png width=270 height=129> </div> <form id=form name=f action=//www.baidu.com/s class=fm> <input type=hidden name=bdorz_come value=1> <input type=hidden name=ie value=utf-8> <input type=hidden name=f value=8> <input type=hidden name=rsv_bp value=1> <input type=hidden name=rsv_idx value=1> <input type=hidden name=tn value=baidu><span class="bg s_ipt_wr"><input id=kw name=wd class=s_ipt value maxlength=255 autocomplete=off autofocus></span><span class="bg s_btn_wr"><input type=submit id=su value=百度一下 class="bg s_btn"></span> </form> </div> </div> <div id=u1> <a href=http://news.baidu.com name=tj_trnews class=mnav>新闻</a> <a href=http://www.hao123.com name=tj_trhao123 class=mnav>hao123</a> <a href=http://map.baidu.com name=tj_trmap class=mnav>地图</a> <a href=http://v.baidu.com name=tj_trvideo class=mnav>视频</a> <a href=http://tieba.baidu.com name=tj_trtieba class=mnav>贴吧</a> <noscript> <a href=http://www.baidu.com/bdorz/login.gif?login&amp;tpl=mn&amp;u=http%3A%2F%2Fwww.baidu.com%2f%3fbdorz_come%3d1 name=tj_login class=lb>登录</a> </noscript> <script>document.write('<a href="http://www.baidu.com/bdorz/login.gif?login&tpl=mn&u='+ encodeURIComponent(window.location.href+ (window.location.search === "" ? "?" : "&")+ "bdorz_come=1")+ '" name="tj_login" class="lb">登录</a>');</script> <a href=//www.baidu.com/more/ name=tj_briicon class=bri style="display: block;">更多产品</a> </div> </div> </div> <div id=ftCon> <div id=ftConw> <p id=lh> <a href=http://home.baidu.com>关于百度</a> <a href=http://ir.baidu.com>About Baidu</a> </p> <p id=cp>&copy;2017&nbsp;Baidu&nbsp;<a href=http://www.baidu.com/duty/>使用百度前必读</a>&nbsp; <a href=http://jianyi.baidu.com/ class=cp-feedback>意见反馈</a>&nbsp;京ICP证030173号&nbsp; <img src=//www.baidu.com/img/gs.gif> </p> </div> </div> </div> </body> </html>

面向接口的好处

  • 新增第三方不再是增加方法，而是增加接口
  • 面向接口编程而不是面向方法编程
  • 无需每次自己处理请求响应
  • 随时更换具体实现HttpURLConnectionProxyFactory而不影响原有代码

不要重复造轮子？

  • NO！是不要重复造低级轮子。
  • 如果你的轮子比别人好，那么还是可以尝试一下干掉别人的轮子。
  • 比如SpringMVC干掉了Strust，Mybatis干掉了Hibernate

优化

  • 架构设计
  • 插件式设计
  • 客户端抽象
  • 编解码抽象
  • 注解支持
  • 重试支持
  • 第三方适配
  • Spring整合
  • SpringMVC注解支持
  • 负载均衡支持
  • 等等等等

轮子篇-Feign

  • Feign github地址

  • Feign makes writing java http clients easier

  • 简单来说，就是一个基于接口的HTTP代理生成器

先睹为快

		<dependency>
			<groupId>io.github.openfeign</groupId>
			<artifactId>feign-core</artifactId>
			<version>10.2.0</version>
		</dependency>

package com.zby.feign;

import feign.Feign;
import feign.Logger;
import feign.Logger.ErrorLogger;
import feign.RequestLine;

public class FeignMain {

    public static void main(String[] args) {
        Baidu baidu = Feign.builder()
                .logger(new ErrorLogger())
                .logLevel(Logger.Level.FULL)
                .target(Baidu.class, "http://www.baidu.com");
        System.out.println(baidu.index());
    }

}


interface Baidu {

    @RequestLine(value = "GET /")
    String index();

}


[Baidu#index] ---> GET http://www.baidu.com/ HTTP/1.1
[Baidu#index] ---> END HTTP (0-byte body)
[Baidu#index] <--- HTTP/1.1 200 OK (168ms)
[Baidu#index] content-length: 2381
[Baidu#index] content-type: text/html
[Baidu#index] date: Tue, 16 Jun 2020 06:50:21 GMT
[Baidu#index] server: bfe
[Baidu#index] 
[Baidu#index] 【省略内容。。。。。。】

[Baidu#index] <--- END HTTP (2381-byte body)
【省略内容。。。。。。】

插件式设计

  • 默认使用HttpURLConnection作为HTTP客户端，如果需要修改为HttpClient需要干啥？
		<dependency>
			<groupId>io.github.openfeign</groupId>
			<artifactId>feign-httpclient</artifactId>
			<version>10.2.0</version>
		</dependency>

package com.zby.feign;

import feign.Feign;
import feign.Logger;
import feign.Logger.ErrorLogger;
import feign.RequestLine;
import feign.httpclient.ApacheHttpClient;

public class FeignMain {

    public static void main(String[] args) {
        Baidu baidu = Feign.builder()
                .logger(new ErrorLogger())
                .logLevel(Logger.Level.FULL)
                .client(new ApacheHttpClient())
                .target(Baidu.class, "http://www.baidu.com");
        System.out.println(baidu.index());
    }

}


interface Baidu {

    @RequestLine(value = "GET /")
    String index();

}
  • So Easy

其他组件

  • feign.Feign.Builder
    private final List<RequestInterceptor> requestInterceptors =
        new ArrayList<RequestInterceptor>();
    private Logger.Level logLevel = Logger.Level.NONE;
    private Contract contract = new Contract.Default();
    private Client client = new Client.Default(null, null);
    private Retryer retryer = new Retryer.Default();
    private Logger logger = new NoOpLogger();
    private Encoder encoder = new Encoder.Default();
    private Decoder decoder = new Decoder.Default();
    private QueryMapEncoder queryMapEncoder = new QueryMapEncoder.Default();
    private ErrorDecoder errorDecoder = new ErrorDecoder.Default();
    private Options options = new Options();
    private InvocationHandlerFactory invocationHandlerFactory =
        new InvocationHandlerFactory.Default();
    private boolean decode404;
    private boolean closeAfterDecode = true;
    private ExceptionPropagationPolicy propagationPolicy = NONE;

注解解析：契约

实战篇-对接GIO

一、定义接口

/**
 * 获取事件分析数据，文档地址：
 * https://docs.growingio.com/docs/developer-manual/api-reference/statistics-api/definition/getevent
 * 
 * @author zby
 * @Date 2020年4月20日
 *
 */
public interface EventAnalysisClient {
    /**
     * 获取事件分析数据
     * 
     * @param projectUid 项目ID
     * @param chartId 图表ID
     * @param eventAnalysisRequest 参数
     * @return
     */
    @RequestLine("GET /v2/projects/{project_uid}/charts/{chart_id}.json")
    EventAnalysisResponse getEvent(@Param("project_uid") String projectUid, @Param("chart_id") String chartId,
            @QueryMap EventAnalysisRequest eventAnalysisRequest);

}

二、Feign抽象配置

/**
 * GIOFeign抽象配置
 * 
 * @author zby
 * @Date 2020年4月21日
 *
 */
public class AbstractGIOFeignConfiguration {
    /**
     * GIO官网地址
     */
    @Value("${gio.url}")
    private String gioUrl;
    /**
     * 认证信息
     */
    @Value("${gio.authorization}")
    private String authorization;

    /**
     * 创建Feign代理对象
     * 
     * @param clazz
     * @return
     */
    protected <T> T newInstance(Class<T> clazz) {
        return feign().newInstance(new Target.HardCodedTarget<T>(clazz, gioUrl));
    }

    /**
     * 公用的Feign对象
     * 
     * @return
     */
    @SuppressWarnings("deprecation")
    private Feign feign() {
        return Feign.builder()
                .logger(new Slf4jLogger())
                .logLevel(Level.BASIC)
                .encoder(new JacksonEncoder())
                .decoder(new JacksonDecoder())
                .requestInterceptor(new AuthorizationInterceptor())
                // 处理null
                .queryMapEncoder(new QueryMapEncoder.Default() {
                    @Override
                    public Map<String, Object> encode(Object object) throws EncodeException {
                        if (object == null) {
                            return new HashMap<String, Object>();
                        }
                        return super.encode(object);
                    }
                })
                .build();
    }

    /**
     * GIO认证信息拦截器
     * 
     * @author zby
     * @Date 2020年4月20日
     *
     */
    class AuthorizationInterceptor implements RequestInterceptor {
        @Override
        public void apply(RequestTemplate template) {
            template.header("Authorization", authorization);
        }
    }

}

三、注入IOC容器

/**
 * GIO的feig客户端配置类
 * 
 * @author zby
 * @Date 2020年4月21日
 *
 */
@Configuration
public class GIOFeignConfiguration extends AbstractGIOFeignConfiguration {

    /**
     * 创建事件分析Feign客户端，代优化：定义注解FeignClient直接扫描创建实例放到spring容器
     * 
     * @return
     */
    @Bean
    public EventAnalysisClient eventAnalysisClient() {
        return newInstance(EventAnalysisClient.class);
    }

}

四、使用

/**
 * 事件分析GIO客户端实现
 * 
 * @author zby
 * @Date 2020年4月21日
 *
 */
@Service
public class EventAnalysisGIOClientImpl implements EventAnalysisGIOClient {

    private static final Logger LOGGER = LoggerFactory.getLogger(EventAnalysisGIOClientImpl.class);

    @Autowired
    private EventAnalysisClient eventAnalysisClient;

    @Override
    public List<NewsListEventAnalysisDto> getNewsListData(EventAnalysisRequest eventAnalysisRequest) {
        List<NewsListEventAnalysisDto> list;
        try {
            LOGGER.info("获取GIO新闻列表数据参数：eventAnalysisRequest={}", eventAnalysisRequest);
            EventAnalysisResponse eventAnalysisResponse = eventAnalysisClient.getEvent(GIOConstant.PROJECT_UID,
                    EventAnalysisConstant.CHART_ID_NEWS_LIST, eventAnalysisRequest);
            LOGGER.info("获取GIO新闻列表数据结果：{}", eventAnalysisResponse);
            list = EventAnalysisUtil.parse(eventAnalysisResponse,
                    new AbstractGIOFieldObjectFactory<NewsListEventAnalysisDto>() {});
        } catch (Exception e) {
            LOGGER.error(String.format("获取GIO新闻列表数据出错,请求参数：%s", eventAnalysisRequest), e);
            return null;
        }
        return list;
    }
}

赠送篇-结果封装

  • GIO数据结果通用格式
  • 基于注解、反射、工厂模式、反省、BeanWrapper等封装通用数据格式为业务对象
/**
 * 事件分析响应实体
 * 
 * @author zby
 * @Date 2020年4月20日
 *
 */
@Data
public class EventAnalysisResponse {
    /**
     * Chart Uid
     */
	private String id;
    /**
     * Chart Name
     */
	private String name;
    /**
     * 同参数
     */
	private Long startTime;
    /**
     * 同参数
     */
	private Long endTime;
    /**
     * 同参数
     */
	private Long interval;
    /**
     * 表格头元数据
     */
	private Meta[] meta;
    /**
     * 表格数据
     */
	private String[][] data;

    /**
     * 元数据，标题列
     * 
     * @author zby
     * @Date 2020年4月21日
     *
     */
	@Data
    @NoArgsConstructor
    @AllArgsConstructor
    public static class Meta {
        /**
         * 名称
         */
		private String name;
        /**
         * 方面
         */
		private boolean dimension;
        /**
         * 统计数据
         */
        private boolean metric;
	}
}

Q&A

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原文地址：https://www.cnblogs.com/zby9527/p/13141381.html