Spring的RestTempalte客户端实现

分手后的思念是犯贱 2022-01-23 11:51 193阅读 0赞

RestTemplate 是srping封装的http客户端，它简化了与http服务的通信方式，统一了RESTful的标准。

## 实现方式 ##

<table> 
 <thead> 
  <tr> 
   <th>实现类型</th> 
   <th>连接池</th> 
   <th>超时设置</th> 
  </tr> 
 </thead> 
 <tbody> 
  <tr> 
   <td>默认（HttpURLConnection）</td> 
   <td>N</td> 
   <td>Y</td> 
  </tr> 
  <tr> 
   <td>Apache HttpComponents</td> 
   <td>Y</td> 
   <td>Y</td> 
  </tr> 
  <tr> 
   <td>Netty</td> 
   <td>N</td> 
   <td>Y</td> 
  </tr> 
  <tr> 
   <td>OkHttp</td> 
   <td>Y</td> 
   <td>Y</td> 
  </tr> 
 </tbody> 
</table>

### HttpURLConnection参数 ###

<table> 
 <thead> 
  <tr> 
   <th>设置</th> 
   <th>描述</th> 
  </tr> 
 </thead> 
 <tbody> 
  <tr> 
   <td>conn.setConnectTimeout(1000)</td> 
   <td>设置连接超时时间，单位毫秒。连接超时是指TCP连接握手成功的时间，可以参考<a href="https://blog.csdn.net/sq4521/article/details/90751241" rel="nofollow">http握手和连接</a></td> 
  </tr> 
  <tr> 
   <td>conn.setReadTimeout(1000)</td> 
   <td>设置读取超时时间，单位毫秒。是指从服务器一次读取数据的时间。参考<a href="https://blog.csdn.net/sq4521/article/details/90751241" rel="nofollow">http超时</a></td> 
  </tr> 
  <tr> 
   <td>setUseCaches(boolean)</td> 
   <td>是否使用缓存</td> 
  </tr> 
  <tr> 
   <td>setDoOutput(boolean)</td> 
   <td>是否输入参数</td> 
  </tr> 
  <tr> 
   <td>setDoInput(boolean)</td> 
   <td>是否读取参数</td> 
  </tr> 
 </tbody> 
</table>

> 注意：HttpURLConnection 没有数据连接池的功能，每个请求建立一个连接。

### RestTemplate 实现超时 ###

*  基于HttpURLConnection实现超时

@Bean
      public RestTemplate getRestTemplate(){ 
      
        //default
        SimpleClientHttpRequestFactory requestFactory = new SimpleClientHttpRequestFactory();
        requestFactory.setReadTimeout(15000);//读取超时
        requestFactory.setConnectTimeout(5000);//连接超时
        RestTemplate restTemplate = new RestTemplate(requestFactory);
        return restTemplate;
      }

*  基于Apache 客户端实现超时

@Bean
      public RestTemplate getRestTemplate(){ 
        //apache
        return new RestTemplate(getHttpCommonFactory());
      }
      @Bean
      public ClientHttpRequestFactory getHttpCommonFactory(){ 
        return new HttpComponentsClientHttpRequestFactory(httpClient());
      }
    @Bean
      public HttpClient httpClient() { 
        Registry<ConnectionSocketFactory> registry = RegistryBuilder.<ConnectionSocketFactory>create()
            .register("http", PlainConnectionSocketFactory.getSocketFactory())
            .register("https", SSLConnectionSocketFactory.getSocketFactory())
            .build();
        //连接池设置
        PoolingHttpClientConnectionManager connectionManager = new PoolingHttpClientConnectionManager(registry);
        //#最大连接数
        connectionManager.setMaxTotal(200);
        //#并发数
        connectionManager.setDefaultMaxPerRoute(20);
        //connectionManager.setValidateAfterInactivity(httpPoolProperties.getValidateAfterInactivity());
        RequestConfig requestConfig = RequestConfig.custom()
            .setSocketTimeout(15000) //服务器返回数据(response)的时间，超过抛出read timeout
            .setConnectTimeout(1000) //连接上服务器(握手成功)的时间，超出抛出connect timeout
            //从连接池中获取连接的超时时间，超时间未拿到可用连接，会抛出org.apache.http.conn.ConnectionPoolTimeoutException: Timeout waiting for connection from pool
            .setConnectionRequestTimeout(30000)
            .build();
        return HttpClientBuilder.create()
            .setDefaultRequestConfig(requestConfig)
            .setConnectionManager(connectionManager)
            .build();
      }

*  netty 超时实现

引入netty 依赖：

<dependency>
         <groupId>io.netty</groupId>
         <artifactId>netty-all</artifactId>
         <version>4.1.36.Final</version>
       </dependency>

初始化RestTemplate

@Bean
     public RestTemplate getRestTemplate(){ 
      //netty
       Netty4ClientHttpRequestFactory nettyFactory = new Netty4ClientHttpRequestFactory();
       nettyFactory.setReadTimeout(15000);
       nettyFactory.setConnectTimeout(5000);
       return new RestTemplate((ClientHttpRequestFactory)nettyFactory);
       
     }

> 注意：netty 是一个NIO的实现框架，连接数受到操作系统的限制，在处理客户端超时的时候，注意服务端的处理连接数和并发（非netty服务端设置）。

*  okhttp 客户端超时

引入okhttp3 客户端依赖

<dependency>
          <groupId>com.squareup.okhttp3</groupId>
          <artifactId>okhttp</artifactId>
          <version>3.14.1</version>
        </dependency>

使用okhttp3初始化RestTemplate

@Bean
      public RestTemplate getRestTemplate(){ 
        //okhttp
        OkHttpClient client = new OkHttpClient.Builder()
            .readTimeout(15000,TimeUnit.MILLISECONDS)
            .connectTimeout(Duration.ofMillis(5000))
            .connectionPool(new ConnectionPool())
            .retryOnConnectionFailure(false)
            .build();
        OkHttp3ClientHttpRequestFactory okhttpFactory=new OkHttp3ClientHttpRequestFactory(client);
        return new RestTemplate((ClientHttpRequestFactory)okhttpFactory);
      }

> 这里的连接池是ConnectionPool，maxPool=2147483647。  
> static \{  
> executor = new ThreadPoolExecutor(0, 2147483647, 60L, TimeUnit.SECONDS, new SynchronousQueue(), Util.threadFactory(“OkHttp ConnectionPool”, true));  
> \}