Spring Boot Starter HttpClient

在Spring Boot下整合http client,方便客户端使用.

为何要使用spring-boot-starter-httpclient

http client已经非常简单啦,为何还需要创建一个starter httpclient,其主要的目的如下:

• 让使用更简单,如全局proxy,timeout等
• 结合dropwizard metrics,添加对metrics的管理

如何使用

• 在Spring Boot项目的pom.xml中添加以下依赖:

      <dependency>
             <groupId>org.mvnsearch.spring.boot</groupId>
             <artifactId>spring-boot-starter-httpclient</artifactId>
             <version>1.0.0-SNAPSHOT</version>
      </dependency>
  

• 在Spring Boot的application.properties文件中添加http client的一些相关配置,当然也可以不需要配置如下:

      spring.httpclient.connectTimeout=2000
  

• 接下来在你的代码中直接应用cacheManager，然后就可以啦。

        @Autowired
        private HttpClient httpClient;
        @Autowired
        private Executor executor;
  

spring-boot-start-httpclient提供的服务

• org.apache.http.client.HttpClient: Http Client
• org.apache.http.client.fluent.Executor: Executor

典型的例子:

• http client:

        reporter.start(1, TimeUnit.SECONDS);
        HttpGet httpGet = new HttpGet("https://www.yahoo.com/tech/s/favorite-iphone-feature-apple-added-ios-9-2-183202009.html");
        HttpResponse response = httpClient.execute(httpGet);
        EntityUtils.toString(response.getEntity());
  

• executor:

       String content = executor.execute(Request.Get("https://www.yahoo.com/")).returnContent().asString();
  

httpclient metrics

HttpClient结合了DropWizard的metrics,这样很方便获取http client的metrics信息, 目前可以记录的级别主要是: METHOD_ONLY, HOST_AND_METHOD(default), QUERYLESS_URL_AND_METHOD, 以下是metrics的输出:

      -- Gauges ----------------------------------------------------------------------
      org.apache.http.conn.HttpClientConnectionManager.available-connections
                   value = 1
      org.apache.http.conn.HttpClientConnectionManager.leased-connections
                   value = 0
      org.apache.http.conn.HttpClientConnectionManager.max-connections
                   value = 20
      org.apache.http.conn.HttpClientConnectionManager.pending-connections
                   value = 0
      
      -- Timers ----------------------------------------------------------------------
      org.apache.http.client.HttpClient.www.yahoo.com.get-requests
                   count = 1
               mean rate = 1.74 calls/second
           1-minute rate = 0.00 calls/second
           5-minute rate = 0.00 calls/second
          15-minute rate = 0.00 calls/second
                     min = 117.63 milliseconds
                     max = 117.63 milliseconds
                    mean = 117.63 milliseconds
                  stddev = 0.00 milliseconds
                  median = 117.63 milliseconds
                    75% <= 117.63 milliseconds
                    95% <= 117.63 milliseconds
                    98% <= 117.63 milliseconds
                    99% <= 117.63 milliseconds
                  99.9% <= 117.63 milliseconds

FAQ

• HttpClient线程安全吗? HttpClient implementations are expected to be thread safe. It is recommended that the same instance of this class is reused for multiple request executions.

• 我用Commons HttpClient 3.x挺好的,为何换到http components上? Http Components是 commons-httpclient的替代者,建议使用http components

参考文档

• Http Components: http://hc.apache.org/
• HttpClient 4 Tutorial: http://www.baeldung.com/httpclient-guide