HTTP请求异步编程解决堵塞之痛-Apache HttpClient5.0

Posted 2021-04-01 老吕架构

序言

        相信很多同学用过  Apache HttpClient 组件进行过 http请求，尤其是对第三方系统的http  api  进行调用。在spring cloud 大行其道的今天，微服务之间通过http协议进行调用的场景应用越来越多，今天大黄鸭就 Apache HttpClient5.0的同步、异步、fluent风格、cache插件的使用写个demo，希望可以帮到需要的同学。

一、maven坐标引入

<dependency>
 <groupId>org.apache.httpcomponents.client5</groupId>
 <artifactId>httpclient5</artifactId>
 <version>5.0.3</version>
</dependency>
<dependency>
 <groupId>org.apache.httpcomponents.client5</groupId>
 <artifactId>httpclient5-fluent</artifactId>
 <version>5.0.3</version>
</dependency>
<dependency>
 <groupId>org.apache.httpcomponents.client5</groupId>
 <artifactId>httpclient5-cache</artifactId>
 <version>5.0.3</version>
</dependency>

二、经典的堵塞式编程

/**
* @Description HttpClient用法演示
* @Author lvaolin
* @Date 2021/2/9 4:07 下午
*/
public class HttpClientClassic {
 public static void main(String[] args) throws IOException, ParseException {
 //关于CloseableHttpClient实例的创建HttpClients提供了多种方式，高级用法可以使用定制方法 HttpClients.custom()
 try (CloseableHttpClient httpclient = HttpClients.createDefault()) {
 //创建一个get类型的http请求
 HttpGet httpGet = new HttpGet("http://www.baidu.com/");
 try (CloseableHttpResponse response1 = httpclient.execute(httpGet)) {
 System.out.println(response1.getCode() + " " + response1.getReasonPhrase());
 HttpEntity entity1 = response1.getEntity();
 EntityUtils.consume(entity1);
 }
 //创建一个post类型的http请求
 HttpPost httpPost = new HttpPost("http://www.baidu.com/");
 List<NameValuePair> nvps = new ArrayList<>();
 nvps.add(new BasicNameValuePair("username", "aaa"));
 nvps.add(new BasicNameValuePair("password", "12345"));
 //这是一个form表单类型的数据格式，放入request body中
 httpPost.setEntity(new UrlEncodedFormEntity(nvps,Charsets.UTF_8));
 //如果是json格式，如下处理,统一使用 UTF-8 可以避免 客户端与服务器端编码不一致问题
 //httpPost.setEntity(new StringEntity("{}",Charsets.UTF_8));
 try (CloseableHttpResponse response2 = httpclient.execute(httpPost)) {
 //响应编码 以及 原因， 比如： 502 Bad Gateway
 System.out.println(response2.getCode() + " " + response2.getReasonPhrase());
 HttpEntity entity2 = response2.getEntity();
 //将响应流转为字符串形式，你可以自己根据需要使用EntityUtils工具进行处理，当然也可以自己解析 InputStream 流
 String stringBody = EntityUtils.toString(entity2, Charsets.UTF_8);
 //简单打印下
 System.out.println(stringBody);
 //确保关闭流资源
 EntityUtils.consume(entity2);
 }
 }
 }
}

三、异步编程

/**
* @Description http client 异步编程
* @Author lvaolin
* @Date 2021/2/9 4:40 下午
*/
public class HttpClientAsync {
 public static void main(String[] args) throws IOException, ExecutionException, InterruptedException {
 //CloseableHttpAsyncClient的实例创建同样也有多种方式，高级用法就是用HttpAsyncClients.custom() 定制自己的参数
 try (CloseableHttpAsyncClient httpclient = HttpAsyncClients.createDefault()) {
 //这句话是异步编程api 独有的
 httpclient.start();
 //-----1、 下面是第一种用法--通过获取Future句柄来灵活控制逻辑---
 //执行一个get请求
 SimpleHttpRequest request10 = SimpleHttpRequests.get("http://www.baidu.com/");
 SimpleHttpRequest request11 = SimpleHttpRequests.get("https://yonyou.com/");
 //下面这2步是关键，非堵塞的，返回 future句柄
 Future<SimpleHttpResponse> future10 = httpclient.execute(request10, null);
 Future<SimpleHttpResponse> future11 = httpclient.execute(request11, null);
 //等待响应返回
 SimpleHttpResponse response10 = future10.get();
 System.out.println(response10.getBodyText());
 SimpleHttpResponse response11 = future11.get();
 //-----2、 下面是第二种用法--通过FutureCallback 来实现理想中的异步回调 ---
 //CountDownLatch 是否使用 取决于你的业务需要，
 //你如果想在它回调完成时 再去做一些事情，就可以用 CountDownLatch来控制，否则就可以去掉CountDownLatch的代码
 final CountDownLatch latch1 = new CountDownLatch(1);
 final SimpleHttpRequest request2 = SimpleHttpRequests.get("http://www.baidu.com/");
 httpclient.execute(request2, new FutureCallback<SimpleHttpResponse>() {
 @Override
 public void completed(SimpleHttpResponse response2) {
 latch1.countDown();
 System.out.println(request2.getRequestUri() + "->" + response2.getCode());
 }
 @Override
 public void failed(Exception ex) {
 latch1.countDown();
 System.out.println(request2.getRequestUri() + "->" + ex);
 }
 @Override
 public void cancelled() {
 latch1.countDown();
 System.out.println(request2.getRequestUri() + " cancelled");
 }
 });
 latch1.await();
 }
 }
}

四、fluent风格编程

public class HttpClientFluent {
 public static void main(String[] args) throws IOException {
 //这种风格的编程确实很简洁清晰，给人流畅的感觉------
 Content content = Request.get("http://www.baidu.com/")
 .setHeader("Connection","keep-alive")
 .execute()
 .returnContent();
 System.out.println(content.asString());
 Content content2 = Request.post("http://www.baidu.com/")
 .setHeader("Connection","keep-alive")
 .setHeader("Accept", "application/json")
 .setHeader("Content-Type", "application/json")//设置header信息
 .bodyByteArray("{ }".getBytes(Charsets.UTF_8))//发送json格式的数据
 .execute()
 .returnContent();
 System.out.println(content2.asString());
 }
}

五、脱离了浏览器如何缓存http 静态资源信息

/**
* @Description HttpClientCache插件的用途
* @Author lvaolin
* @Date 2021/2/9 3:36 下午
*/
public class HttpClientCache {
 public static void main(String[] args) throws IOException {
 CacheConfig cacheConfig = CacheConfig.custom()
 .setMaxCacheEntries(1000)
 .setMaxObjectSize(8192)
 .build();
 RequestConfig requestConfig = RequestConfig.custom()
 .setConnectTimeout(3, TimeUnit.SECONDS)
 .setConnectionRequestTimeout(10, TimeUnit.SECONDS)
 .build();
 CloseableHttpClient cachingClient = CachingHttpClients.custom()
 .setCacheConfig(cacheConfig)
 .setDefaultRequestConfig(requestConfig)
 .build();
 HttpCacheContext context = HttpCacheContext.create();
 HttpGet httpget = new HttpGet("http://www.baidu.com/");
 for (int i = 0; i <3 ; i++) {
 CloseableHttpResponse response = cachingClient.execute(httpget, context);
 try {
 CacheResponseStatus responseStatus = context.getCacheResponseStatus();
 switch (responseStatus) {
 case CACHE_HIT:
 System.out.println("A response was generated from the cache with " +
 "no requests sent upstream");
 break;
 case CACHE_MODULE_RESPONSE:
 System.out.println("The response was generated directly by the " +
 "caching module");
 break;
 case CACHE_MISS:
 System.out.println("The response came from an upstream server");
 break;
 case VALIDATED:
 System.out.println("The response was generated from the cache " +
 "after validating the entry with the origin server");
 break;
 }
 } finally {
 response.close();
 }
 }
 cachingClient.close(CloseMode.GRACEFUL);
 }
}

六、总结

         在合适的场景使用异步编程能很好的提高程序的性能，打个比喻就是 你在蒸米饭的同时可以去炒菜，还可以同时去烧水，三件事情并行执行，花费的总时间就是最耗时的那个活，如果是堵塞式串行执行，那么花费总时间就是三件事情的时间之和，有没有运筹学的味道在里面。

        fluent风格编程确实清晰易懂简洁流畅，有兴趣的同学可以学习这种风格。