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<h1 class="page__title" itemprop="headline">使用ServiceComb客户端轻松调用ServiceCenter
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2 分钟 阅读
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<h2 id="1-问题背景">1. 问题/背景</h2>
<p>在微服务架构中，服务注册中心是必不可少的组件，提供服务注册与管理的能力。目前使用ServiceComb服用中心的java微服务开发者，不仅需要写微服务业务代码，还要写客户端代码去调用ServiceCenter的openAPI。开发者首先需要熟悉ServiceCenter的openAPI文档，然后代码实现http客户端用于发起请求和接收响应，并绑定ServiceCenter配置参数，最后代码实现对服务中心API的调用，才能使用上ServiceCenter。为了简单化开发者使用ServiceCenter，ServiceCenter客户端实现了上述步骤。开发者只需要添加客户端jar包调用API就能轻松使用ServiceCenter，不需要过多关注openAPI文档、不需要写http客户端层代码。使用ServiceComb客户端，开发者可以轻松调用ServiceCenter，更专注于写微服务业务代码。<br />
了解更多ServiceComb-Service-Center：<a href="https://docs.servicecomb.io/service-center/zh_CN/index.html">https://docs.servicecomb.io/service-center/zh_CN/index.html</a><br />
了解更多ServiceCenter客户端：<a href="https://github.com/apache/servicecomb-java-chassis/tree/master/clients/service-center-client">https://github.com/apache/servicecomb-java-chassis/tree/master/clients/service-center-client</a><br />
<img src="/assets/images/client/sc-client.jpg" alt="service-center-client-design" /></p>
<h2 id="2-客户端原理及关键代码解读">2. 客户端原理及关键代码解读</h2>
<p>2.1 基于httpClient设计ServiceCenter客户端</p>
<ul>
<li>
<p>客户端发起请求和接收响应。客户端选择httpclient作为底层组件，用于实际发起请求和接收响应，并对请求和响应类进行了封装。代码中get方法对应发起GET请求，调用doRequest方法首先添加服务注册中心信息到封装过的httpRequest请求头部，再基于httpclient组件发起实际的http请求，最后将请求响应结果转化为封装过的httpResponse对象返回。</p>
<div class="language-java highlighter-rouge"><div class="highlight"><pre class="highlight"><code><span class="c1">//make GET request</span>
<span class="nd">@Override</span>
<span class="kd">public</span> <span class="nc">HttpResponse</span> <span class="nf">get</span><span class="o">(</span><span class="nc">HttpRequest</span> <span class="n">request</span><span class="o">)</span> <span class="kd">throws</span> <span class="nc">IOException</span> <span class="o">{</span>
<span class="n">request</span><span class="o">.</span><span class="na">setMethod</span><span class="o">(</span><span class="nc">HttpRequest</span><span class="o">.</span><span class="na">GET</span><span class="o">);</span>
<span class="k">return</span> <span class="nf">doRequest</span><span class="o">(</span><span class="n">request</span><span class="o">);</span>
<span class="o">}</span>
<span class="o">......</span>
<span class="c1">//make http request with httpClient component</span>
<span class="kd">public</span> <span class="nc">HttpResponse</span> <span class="nf">doRequest</span><span class="o">(</span><span class="nc">HttpRequest</span> <span class="n">httpRequest</span><span class="o">)</span> <span class="kd">throws</span> <span class="nc">IOException</span> <span class="o">{</span>
<span class="c1">//add cse-serviceregistry-client header to identify client</span>
<span class="n">httpRequest</span><span class="o">.</span><span class="na">addHeader</span><span class="o">(</span><span class="no">HEADER_CONTENT_TYPE</span><span class="o">,</span> <span class="s">"application/json"</span><span class="o">);</span>
<span class="n">httpRequest</span><span class="o">.</span><span class="na">addHeader</span><span class="o">(</span><span class="no">HEADER_USER_AGENT</span><span class="o">,</span> <span class="s">"cse-serviceregistry-client/1.0.0"</span><span class="o">);</span>
<span class="k">if</span> <span class="o">(</span><span class="n">globalHeaders</span> <span class="o">!=</span> <span class="kc">null</span><span class="o">)</span> <span class="o">{</span>
<span class="n">globalHeaders</span><span class="o">.</span><span class="na">forEach</span><span class="o">(</span><span class="nl">httpRequest:</span><span class="o">:</span><span class="n">addHeader</span><span class="o">);</span>
<span class="o">}</span>
<span class="c1">//make http request</span>
<span class="n">org</span><span class="o">.</span><span class="na">apache</span><span class="o">.</span><span class="na">http</span><span class="o">.</span><span class="na">HttpResponse</span> <span class="n">response</span> <span class="o">=</span> <span class="n">httpClient</span><span class="o">.</span><span class="na">execute</span><span class="o">(</span><span class="n">httpRequest</span><span class="o">.</span><span class="na">getRealRequest</span><span class="o">());</span>
<span class="kt">int</span> <span class="n">statusCode</span> <span class="o">=</span> <span class="n">response</span><span class="o">.</span><span class="na">getStatusLine</span><span class="o">().</span><span class="na">getStatusCode</span><span class="o">();</span>
<span class="nc">String</span> <span class="n">messgae</span> <span class="o">=</span> <span class="n">response</span><span class="o">.</span><span class="na">getStatusLine</span><span class="o">().</span><span class="na">getReasonPhrase</span><span class="o">();</span>
<span class="nc">String</span> <span class="n">context</span> <span class="o">=</span> <span class="nc">EntityUtils</span><span class="o">.</span><span class="na">toString</span><span class="o">(</span><span class="n">response</span><span class="o">.</span><span class="na">getEntity</span><span class="o">(),</span> <span class="s">"UTF-8"</span><span class="o">);</span>
<span class="k">return</span> <span class="k">new</span> <span class="nf">HttpResponse</span><span class="o">(</span><span class="n">statusCode</span><span class="o">,</span> <span class="n">messgae</span><span class="o">,</span> <span class="n">context</span><span class="o">);</span>
<span class="o">}</span>
</code></pre></div> </div>
</li>
<li>
<p>客户端支持定制化服务中心配置参数。代码中看到，客户端支持开发者定制服务中心IP，端口，项目名称，租户名称，导入TLSConfig和新增请求头，并通过客户端的Builder方法注入配置。TLSConfig为客户端TLS认证配置类，给客户端导入TLS证书配置，即可开启客户端双向认证模式。</p>
<div class="language-java highlighter-rouge"><div class="highlight"><pre class="highlight"><code> <span class="cm">/**
* Customized host, port, projectName, tenantName, TLSConf, headers and any one parameter can be null.
*/</span>
<span class="kd">public</span> <span class="nf">ServiceCenterClient</span><span class="o">(</span><span class="nc">String</span> <span class="n">host</span><span class="o">,</span> <span class="kt">int</span> <span class="n">port</span><span class="o">,</span> <span class="nc">String</span> <span class="n">projectName</span><span class="o">,</span> <span class="nc">String</span> <span class="n">tenantName</span><span class="o">,</span> <span class="nc">TLSConfig</span> <span class="n">tlsConfig</span><span class="o">,</span>
<span class="nc">Map</span><span class="o">&lt;</span><span class="nc">String</span><span class="o">,</span> <span class="nc">String</span><span class="o">&gt;</span> <span class="n">extraGlobalHeaders</span><span class="o">)</span> <span class="o">{</span>
<span class="nc">HttpTransport</span> <span class="n">httpTransport</span> <span class="o">=</span> <span class="nc">HttpTransportFactory</span><span class="o">.</span><span class="na">getDefaultHttpTransport</span><span class="o">();</span>
<span class="k">if</span> <span class="o">(</span><span class="n">tlsConfig</span> <span class="o">!=</span> <span class="kc">null</span><span class="o">)</span> <span class="o">{</span>
<span class="n">httpTransport</span> <span class="o">=</span> <span class="k">new</span> <span class="nc">TLSHttpsTransport</span><span class="o">(</span><span class="n">tlsConfig</span><span class="o">);</span>
<span class="o">}</span>
<span class="n">httpTransport</span><span class="o">.</span><span class="na">addHeaders</span><span class="o">(</span><span class="n">extraGlobalHeaders</span><span class="o">);</span>
<span class="c1">//set configuration parameters</span>
<span class="k">this</span><span class="o">.</span><span class="na">httpClient</span> <span class="o">=</span> <span class="k">new</span> <span class="nc">ServiceCenterRawClient</span><span class="o">.</span><span class="na">Builder</span><span class="o">()</span>
<span class="o">.</span><span class="na">setHost</span><span class="o">(</span><span class="n">host</span><span class="o">)</span>
<span class="o">.</span><span class="na">setPort</span><span class="o">(</span><span class="n">port</span><span class="o">)</span>
<span class="o">.</span><span class="na">setProjectName</span><span class="o">(</span><span class="n">projectName</span><span class="o">)</span>
<span class="o">.</span><span class="na">setTenantName</span><span class="o">(</span><span class="n">tenantName</span><span class="o">)</span>
<span class="o">.</span><span class="na">setHttpTransport</span><span class="o">(</span><span class="n">httpTransport</span><span class="o">).</span><span class="na">build</span><span class="o">();</span>
<span class="o">}</span>
</code></pre></div> </div>
</li>
</ul>
<p>2.2 ServiceCenter客户端核心API</p>
<ul>
<li>服务注册与发现，注册服务和实例到服务注册中心，根据服务ID发现服务实例。registerMicroserviceInstance方法用于注册服务实例，发起httpPOST请求访问服务实例注册URL，并将实例注入到请求body中，返回服务ID字符串; getMicroserviceInstanceList方法用于发现服务的所有实例，根据服务ID，发起httpGET请求访问服务发现URL，返回MicroserviceInstancesResponse对象。
<div class="language-java highlighter-rouge"><div class="highlight"><pre class="highlight"><code> <span class="c1">//service register</span>
<span class="kd">public</span> <span class="nc">String</span> <span class="nf">registerMicroserviceInstance</span><span class="o">(</span><span class="nc">MicroserviceInstance</span> <span class="n">instance</span><span class="o">,</span> <span class="nc">String</span> <span class="n">serviceId</span><span class="o">)</span> <span class="o">{</span>
<span class="k">try</span> <span class="o">{</span>
<span class="nc">ObjectMapper</span> <span class="n">mapper</span> <span class="o">=</span> <span class="k">new</span> <span class="nc">ObjectMapper</span><span class="o">();</span>
<span class="n">mapper</span><span class="o">.</span><span class="na">configure</span><span class="o">(</span><span class="nc">SerializationFeature</span><span class="o">.</span><span class="na">WRAP_ROOT_VALUE</span><span class="o">,</span> <span class="kc">true</span><span class="o">);</span>
<span class="nc">HttpResponse</span> <span class="n">response</span> <span class="o">=</span> <span class="n">httpClient</span><span class="o">.</span><span class="na">postHttpRequest</span><span class="o">(</span><span class="s">"/registry/microservices/"</span> <span class="o">+</span> <span class="n">serviceId</span> <span class="o">+</span> <span class="s">"/instances"</span><span class="o">,</span> <span class="kc">null</span><span class="o">,</span>
<span class="n">mapper</span><span class="o">.</span><span class="na">writeValueAsString</span><span class="o">(</span><span class="n">instance</span><span class="o">));</span>
<span class="k">if</span> <span class="o">(</span><span class="n">response</span><span class="o">.</span><span class="na">getStatusCode</span><span class="o">()</span> <span class="o">==</span> <span class="nc">HttpStatus</span><span class="o">.</span><span class="na">SC_OK</span><span class="o">)</span> <span class="o">{</span>
<span class="k">return</span> <span class="n">response</span><span class="o">.</span><span class="na">getContent</span><span class="o">();</span>
<span class="o">}</span> <span class="k">else</span> <span class="o">{</span>
<span class="k">throw</span> <span class="k">new</span> <span class="nf">OperationException</span><span class="o">(</span>
<span class="s">"register service instance fails, statusCode = "</span> <span class="o">+</span> <span class="n">response</span><span class="o">.</span><span class="na">getStatusCode</span><span class="o">()</span> <span class="o">+</span> <span class="s">"; message = "</span> <span class="o">+</span> <span class="n">response</span>
<span class="o">.</span><span class="na">getMessage</span><span class="o">()</span>
<span class="o">+</span> <span class="s">"; content = "</span> <span class="o">+</span> <span class="n">response</span><span class="o">.</span><span class="na">getContent</span><span class="o">());</span>
<span class="o">}</span>
<span class="o">}</span> <span class="k">catch</span> <span class="o">(</span><span class="nc">IOException</span> <span class="n">e</span><span class="o">)</span> <span class="o">{</span>
<span class="k">throw</span> <span class="k">new</span> <span class="nf">OperationException</span><span class="o">(</span>
<span class="s">"register service instance fails"</span><span class="o">,</span> <span class="n">e</span><span class="o">);</span>
<span class="o">}</span>
<span class="o">}</span>
<span class="c1">//service discovery</span>
<span class="kd">public</span> <span class="nc">MicroserviceInstancesResponse</span> <span class="nf">getMicroserviceInstanceList</span><span class="o">(</span><span class="nc">String</span> <span class="n">serviceId</span><span class="o">)</span> <span class="o">{</span>
<span class="k">try</span> <span class="o">{</span>
<span class="nc">HttpResponse</span> <span class="n">response</span> <span class="o">=</span> <span class="n">httpClient</span>
<span class="o">.</span><span class="na">getHttpRequest</span><span class="o">(</span><span class="s">"/registry/microservices/"</span> <span class="o">+</span> <span class="n">serviceId</span> <span class="o">+</span> <span class="s">"/instances"</span><span class="o">,</span> <span class="kc">null</span><span class="o">,</span> <span class="kc">null</span><span class="o">);</span>
<span class="k">if</span> <span class="o">(</span><span class="n">response</span><span class="o">.</span><span class="na">getStatusCode</span><span class="o">()</span> <span class="o">==</span> <span class="nc">HttpStatus</span><span class="o">.</span><span class="na">SC_OK</span><span class="o">)</span> <span class="o">{</span>
<span class="nc">ObjectMapper</span> <span class="n">mapper</span> <span class="o">=</span> <span class="k">new</span> <span class="nc">ObjectMapper</span><span class="o">();</span>
<span class="k">return</span> <span class="n">mapper</span><span class="o">.</span><span class="na">readValue</span><span class="o">(</span><span class="n">response</span><span class="o">.</span><span class="na">getContent</span><span class="o">(),</span> <span class="nc">MicroserviceInstancesResponse</span><span class="o">.</span><span class="na">class</span><span class="o">);</span>
<span class="o">}</span> <span class="k">else</span> <span class="o">{</span>
<span class="k">throw</span> <span class="k">new</span> <span class="nf">OperationException</span><span class="o">(</span>
<span class="s">"get service instances list fails, statusCode = "</span> <span class="o">+</span> <span class="n">response</span><span class="o">.</span><span class="na">getStatusCode</span><span class="o">()</span> <span class="o">+</span> <span class="s">"; message = "</span> <span class="o">+</span> <span class="n">response</span>
<span class="o">.</span><span class="na">getMessage</span><span class="o">()</span>
<span class="o">+</span> <span class="s">"; content = "</span> <span class="o">+</span> <span class="n">response</span><span class="o">.</span><span class="na">getContent</span><span class="o">());</span>
<span class="o">}</span>
<span class="o">}</span> <span class="k">catch</span> <span class="o">(</span><span class="nc">IOException</span> <span class="n">e</span><span class="o">)</span> <span class="o">{</span>
<span class="k">throw</span> <span class="k">new</span> <span class="nf">OperationException</span><span class="o">(</span>
<span class="s">"get service instances list fails"</span><span class="o">,</span> <span class="n">e</span><span class="o">);</span>
<span class="o">}</span>
<span class="o">}</span>
</code></pre></div> </div>
</li>
<li>心跳，服务实例发送心跳告知服务中心。代码中发起httpPUT请求中访问心跳URL，并导入HeartbeatsRequest （包含服务ID和实例ID）到请求body中，响应状态码为200表示心跳成功。
<div class="language-java highlighter-rouge"><div class="highlight"><pre class="highlight"><code> <span class="c1">//heartBeats</span>
<span class="kd">public</span> <span class="kt">void</span> <span class="nf">sendHeartBeats</span><span class="o">(</span><span class="nc">HeartbeatsRequest</span> <span class="n">heartbeatsRequest</span><span class="o">)</span> <span class="o">{</span>
<span class="k">try</span> <span class="o">{</span>
<span class="nc">ObjectMapper</span> <span class="n">mapper</span> <span class="o">=</span> <span class="k">new</span> <span class="nc">ObjectMapper</span><span class="o">();</span>
<span class="nc">HttpResponse</span> <span class="n">response</span> <span class="o">=</span> <span class="n">httpClient</span>
<span class="o">.</span><span class="na">putHttpRequest</span><span class="o">(</span><span class="s">"/registry/heartbeats"</span><span class="o">,</span> <span class="kc">null</span><span class="o">,</span> <span class="n">mapper</span><span class="o">.</span><span class="na">writeValueAsString</span><span class="o">(</span><span class="n">heartbeatsRequest</span><span class="o">));</span>
<span class="k">if</span> <span class="o">(</span><span class="n">response</span><span class="o">.</span><span class="na">getStatusCode</span><span class="o">()</span> <span class="o">==</span> <span class="nc">HttpStatus</span><span class="o">.</span><span class="na">SC_OK</span><span class="o">)</span> <span class="o">{</span>
<span class="no">LOGGER</span><span class="o">.</span><span class="na">info</span><span class="o">(</span><span class="s">"HEARTBEATS SUCCESS"</span><span class="o">);</span>
<span class="o">}</span> <span class="k">else</span> <span class="o">{</span>
<span class="k">throw</span> <span class="k">new</span> <span class="nf">OperationException</span><span class="o">(</span>
<span class="s">"heartbeats fails, statusCode = "</span> <span class="o">+</span> <span class="n">response</span><span class="o">.</span><span class="na">getStatusCode</span><span class="o">()</span> <span class="o">+</span> <span class="s">"; message = "</span> <span class="o">+</span> <span class="n">response</span><span class="o">.</span><span class="na">getMessage</span><span class="o">()</span>
<span class="o">+</span> <span class="s">"; content = "</span> <span class="o">+</span> <span class="n">response</span><span class="o">.</span><span class="na">getContent</span><span class="o">());</span>
<span class="o">}</span>
<span class="o">}</span> <span class="k">catch</span> <span class="o">(</span><span class="nc">IOException</span> <span class="n">e</span><span class="o">)</span> <span class="o">{</span>
<span class="k">throw</span> <span class="k">new</span> <span class="nf">OperationException</span><span class="o">(</span>
<span class="s">"heartbeats fails "</span><span class="o">,</span> <span class="n">e</span><span class="o">);</span>
<span class="o">}</span>
<span class="o">}</span>
</code></pre></div> </div>
</li>
</ul>
<p>2.3 更多客户端API介绍，参考客户端说明文档 <a href="https://github.com/apache/servicecomb-java-chassis/tree/master/clients/service-center-client">https://github.com/apache/servicecomb-java-chassis/tree/master/clients/service-center-client</a></p>
<h2 id="3-servicecenter客户端实践">3. ServiceCenter客户端实践</h2>
<p>3.1 实践准备</p>
<ul>
<li>启动ServiceComb服务中心：<a href="http://servicecomb.apache.org/cn/docs/service-center/install/">http://servicecomb.apache.org/cn/docs/service-center/install/</a></li>
<li>下载演示代码：<a href="https://github.com/zaneChou1/spring-boot-servicecenter">https://github.com/zaneChou1/spring-boot-servicecenter</a></li>
</ul>
<p>3.2 provider端启动服务，通过客户端注册到ServiceCenter<br />
运行provider模块，启动helloServer服务，并调用客户端API创建客户端对象、创建helloServer服务和实例对象、注册服务和实例到servicecomb 服务中心，并保持30s一次心跳，代码实现如下。</p>
<div class="language-java highlighter-rouge"><div class="highlight"><pre class="highlight"><code> <span class="kd">public</span> <span class="kd">static</span> <span class="kt">void</span> <span class="nf">registerMicroservice</span><span class="o">(){</span>
<span class="c1">//new ServiceCenterClient object</span>
<span class="nc">ServiceCenterClient</span> <span class="n">sc</span> <span class="o">=</span> <span class="k">new</span> <span class="nc">ServiceCenterClient</span><span class="o">();</span>
<span class="c1">//new Microservice object and setting properties and serviceName is necessary</span>
<span class="nc">Microservice</span> <span class="n">microservice</span> <span class="o">=</span> <span class="k">new</span> <span class="nc">Microservice</span><span class="o">();</span>
<span class="n">microservice</span><span class="o">.</span><span class="na">setServiceId</span><span class="o">(</span><span class="s">"1111"</span><span class="o">);</span>
<span class="n">microservice</span><span class="o">.</span><span class="na">setServiceName</span><span class="o">(</span><span class="s">"HelloServer"</span><span class="o">);</span>
<span class="c1">//register microservice to service-center</span>
<span class="n">sc</span><span class="o">.</span><span class="na">registerMicroservice</span><span class="o">(</span><span class="n">microservice</span><span class="o">);</span>
<span class="c1">//new MicroserviceInstance object and bind server IP and port</span>
<span class="nc">MicroserviceInstance</span> <span class="n">instance</span> <span class="o">=</span> <span class="k">new</span> <span class="nc">MicroserviceInstance</span><span class="o">();</span>
<span class="nc">List</span><span class="o">&lt;</span><span class="nc">String</span><span class="o">&gt;</span> <span class="n">endPoints</span> <span class="o">=</span> <span class="k">new</span> <span class="nc">ArrayList</span><span class="o">&lt;</span><span class="nc">String</span><span class="o">&gt;();</span>
<span class="n">endPoints</span><span class="o">.</span><span class="na">add</span><span class="o">(</span><span class="s">"rest://127.0.0.1:8080/"</span><span class="o">);</span>
<span class="n">instance</span><span class="o">.</span><span class="na">setEndpoints</span><span class="o">(</span><span class="n">endPoints</span><span class="o">);</span>
<span class="c1">//setting instance hostName, instanceId and hostName is necessary</span>
<span class="n">instance</span><span class="o">.</span><span class="na">setHostName</span><span class="o">(</span><span class="s">"test"</span><span class="o">);</span>
<span class="n">instance</span><span class="o">.</span><span class="na">setInstanceId</span><span class="o">(</span><span class="s">"2222"</span><span class="o">);</span>
<span class="c1">//register microservice instance to service-center</span>
<span class="n">sc</span><span class="o">.</span><span class="na">registerMicroserviceInstance</span><span class="o">(</span><span class="n">instance</span><span class="o">,</span><span class="n">microservice</span><span class="o">.</span><span class="na">getServiceId</span><span class="o">());</span>
<span class="c1">//send a heartbeat every 30s</span>
<span class="nc">HeartbeatsRequest</span> <span class="n">heartbeatsRequest</span> <span class="o">=</span> <span class="k">new</span> <span class="nc">HeartbeatsRequest</span><span class="o">(</span><span class="s">"1111"</span><span class="o">,</span><span class="s">"2222"</span><span class="o">);</span>
<span class="k">while</span><span class="o">(</span><span class="kc">true</span><span class="o">){</span>
<span class="n">sc</span><span class="o">.</span><span class="na">sendHeartBeats</span><span class="o">(</span><span class="n">heartbeatsRequest</span><span class="o">);</span>
<span class="k">try</span> <span class="o">{</span>
<span class="nc">Thread</span><span class="o">.</span><span class="na">sleep</span><span class="o">(</span><span class="mi">30000</span><span class="o">);</span>
<span class="o">}</span> <span class="k">catch</span> <span class="o">(</span><span class="nc">InterruptedException</span> <span class="n">e</span><span class="o">)</span> <span class="o">{</span>
<span class="n">e</span><span class="o">.</span><span class="na">printStackTrace</span><span class="o">();</span>
<span class="o">}</span>
<span class="o">}</span>
<span class="o">}</span>
</code></pre></div></div>
<p>查看service-center的UI显示如下，helloServer服务注册到服务中心成功，且有一个服务实例test。 <br />
<img src="/assets/images/client/sc-sample-UI.png" alt="" /><br />
访问provider服务监听的8080端口，返回“Hello Spring-Boot-ServiceCenter !”。<br />
<img src="/assets/images/client/sc-sample-provider.png" alt="" /></p>
<p>3.3 consumer端通过客户端发现服务实例，发起服务调用<br />
运行consumer模块，启动consumer服务，调用客户端API新建客户端对象、发现helloServer服务实例、获取服务监听的IP和端口，最后调用provider端helloServer服务返回结果。</p>
<div class="language-java highlighter-rouge"><div class="highlight"><pre class="highlight"><code><span class="c1">//find service instance</span>
<span class="nc">ServiceCenterClient</span> <span class="n">sc</span> <span class="o">=</span> <span class="k">new</span> <span class="nc">ServiceCenterClient</span><span class="o">();</span>
<span class="nc">MicroserviceInstancesResponse</span> <span class="n">instances</span> <span class="o">=</span> <span class="n">sc</span><span class="o">.</span><span class="na">getMicroserviceInstanceList</span><span class="o">(</span><span class="s">"1111"</span><span class="o">);</span>
<span class="c1">//get IP and port that service is listening on</span>
<span class="no">URI</span> <span class="n">endpointURIBuilder</span> <span class="o">=</span> <span class="k">new</span> <span class="nc">URIBuilder</span><span class="o">(</span><span class="n">instances</span><span class="o">.</span><span class="na">getInstances</span><span class="o">().</span><span class="na">get</span><span class="o">(</span><span class="mi">0</span><span class="o">).</span><span class="na">getEndpoints</span><span class="o">().</span><span class="na">get</span><span class="o">(</span><span class="mi">0</span><span class="o">)).</span><span class="na">build</span><span class="o">();</span>
<span class="kt">int</span> <span class="n">port</span> <span class="o">=</span> <span class="n">endpointURIBuilder</span><span class="o">.</span><span class="na">getPort</span><span class="o">();</span>
<span class="nc">String</span> <span class="n">host</span> <span class="o">=</span> <span class="n">endpointURIBuilder</span><span class="o">.</span><span class="na">getHost</span><span class="o">();</span>
<span class="c1">//call service</span>
<span class="nc">RestTemplate</span> <span class="n">restTemplate</span> <span class="o">=</span> <span class="k">new</span> <span class="nc">RestTemplate</span><span class="o">();</span>
<span class="nc">ResponseEntity</span><span class="o">&lt;</span><span class="nc">String</span><span class="o">&gt;</span> <span class="n">result</span> <span class="o">=</span> <span class="n">restTemplate</span><span class="o">.</span><span class="na">getForEntity</span><span class="o">(</span><span class="s">"http://"</span><span class="o">+</span><span class="n">host</span><span class="o">+</span><span class="s">":"</span><span class="o">+</span><span class="n">port</span><span class="o">,</span><span class="nc">String</span><span class="o">.</span><span class="na">class</span><span class="o">);</span>
<span class="k">return</span> <span class="n">result</span><span class="o">.</span><span class="na">getBody</span><span class="o">();</span>
</code></pre></div></div>
<p>访问consumer端监听的8081端口，返回helloServer的响应结果“Hello Spring-Boot-ServiceCenter !”，consumer端通过ServiceComb服务注册中心调用provider端服务成功。 <br />
<img src="/assets/images/client/sc-sample-consumer.png" alt="" /></p>
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