SpringBoot调用外部接口的几种方式

SpringBoot调用外部接口的几种方式

使用FeignClient调用

FeignClient调用大多用于微服务开发中，各服务之间的接口调用。它以Java接口注解的方式调用HTTP请求，使服务间的调用变得简单

1、在使用方引入依赖

<!--Feign注解 这里openFeign的版本要和自己使用的SpringBoot匹配--><dependency><groupId>org.springframework.cloud</groupId><artifactId>spring-cloud-starter-openfeign</artifactId><!--<version>4.0.1</version>--></dependency>

2、服务接口调用方

2.1、在启动类上加上@EnableFeigncliens注解

importorg.springframework.boot.SpringApplication;importorg.springframework.boot.autoconfigure.SpringBootApplication;importorg.springframework.cloud.openfeign.EnableFeignClients;@SpringBootApplication@EnableFeignClientspublicclassStudyfeignApplication{publicstaticvoidmain(String[] args){SpringApplication.run(StudyfeignApplication.class, args);System.out.println("项目启动成功");}}

2.2、编写Feign接口调用服务controller层

importcom.hysoft.studyfeign.service.SysUserClient;importorg.springframework.beans.factory.annotation.Autowired;importorg.springframework.web.bind.annotation.PostMapping;importorg.springframework.web.bind.annotation.RequestMapping;importorg.springframework.web.bind.annotation.RestController;@RestController@RequestMapping("feign")publicclassSysUserController{@AutowiredprivateSysUserClient sysUserClient;@PostMapping("getUserId")publicvoidgetUserId(String userId){this.sysUserClient.getUserById(userId);}}

2.3、服务接口调用service层

feign的客户端需要使用@FeignClient注解进行表示，这样扫描时才知道这是一个feign客户端。@FeignClient最常用的就两个属性，一个name，用于给客户端定义一个唯一的名称，另一个就是url，用于定义该客户端调用的远程地址。url中的内容，可以写在配置文件application.yml中，便于管理

@Service@FeignClient(name ="feign-service",url ="${master-getuserbyId}")publicinterfaceSysUserClient{@PostMapping("/master/test")StringgetUserById(String id);}

application.yml中的配置如下

server:
  port:8081
master-getuserbyId: http://localhost:8080

3、服务接口提供者

对于接口提供者来说没有特别要求，和正常的接口开发一样

4、说明

需要说明的是，在接口调用方，可以继续拓展service层，书写service实现层，进一步进行拓展    

importorg.springframework.stereotype.Service;@ServicepublicclassSysUserClientImplimplementsSysUserClient{@OverridepublicStringgetUserById(String id){return"";}}

使用RestTemplate调用

RestTemplate中几个常用的方法：getForObject()、getForEntity()、postForObject()、postForEntity()。其中，getForObject() 和 getForEntity() 方法可以用来发送 GET 请求

1、引入依赖

<dependency><groupId>org.springframework.boot</groupId><artifactId>spring-boot-starter-web</artifactId></dependency>

2、RestTemplateConfig配置类

SimpleClientHttpRequestFactory类对应的HTTP库是JDK自带的HttpUrlConnection，当然我们可以根据自身的需求使用其他的HTTP库，例如HttpComponentsAsyncClientHttpRequestFactory

@ConfigurationpublicclassRestTemplateConfig{@BeanpublicRestTemplaterestTemplate(ClientHttpRequestFactory factory){returnnewRestTemplate(factory);}@BeanpublicClientHttpRequestFactorysimpleClientHttpRequestFactory(){SimpleClientHttpRequestFactory factory =newSimpleClientHttpRequestFactory();
        factory.setReadTimeout(5000);//单位为ms
        factory.setConnectTimeout(5000);//单位为msreturn factory;}}

3、接口调用

@RestControllerpublicclassTestRestTemplate{@ResourceprivateRestTemplate restTemplate;@GetMapping(value ="/saveUser")publicvoidsaveUser(String userId){String url ="http://127.0.0.1:8080/master/test";Map map =newHashMap<>();
        map.put("userId","hy001");String results = restTemplate.postForObject(url, map,String.class);}}

使用WebClient调用

Spring3.0引入了RestTemplate，但是在后来的官方源码中介绍，RestTemplate有可能在未来的版本中被弃用，所谓替代RestTemplate，在Spring5中引入了WebClient作为异步的非阻塞、响应式的HTTP客户端。

1、引入依赖

<dependency><groupId>org.springframework.boot</groupId><artifactId>spring-boot-starter-webflux</artifactId></dependency>

2、接口调用示例

publicclassTestWebClient{@TestpublicvoiddoGet(){String userId ="郭郭";String url ="http://127.0.0.1:8080/master/test/getSysUserById?userId={userId}";Mono<String> mono =WebClient//创建WebClient实例.create()//方法调用，WebClient中提供了多种方法.get()//请求url.uri(url, userId)//获取响应结果.retrieve()//将结果转换为指定类型.bodyToMono(String.class);//返回最终结果：block是阻塞的/subscribe()非阻塞式获取响应结果System.out.println("响应结果："+ mono.block());}@TestpublicvoiddoPost(){Map map =newHashMap<>();
        map.put("name","郭郭");String requestBody =JSON.toJSONString(map);String url ="http://127.0.0.1:8080/master/test/saveUser";Mono<String> mono =WebClient//创建WebClient实例.create()//方法调用，WebClient中提供了多种方法.post()//请求url.uri(url)//指定请求的Content-Type为JSON.contentType(MediaType.APPLICATION_JSON)//使用bodyValue方法传递请求体.bodyValue(requestBody)//获取响应结果.retrieve()//将结果转换为指定类型.bodyToMono(String.class);//返回最终结果：block是阻塞的/subscribe()非阻塞式获取响应结果System.out.println("响应结果："+ mono.block());}}

在上述doPost请求中，我们的请求接口入参是一个Map，但是需要转换为JSON格式传递，这是因为WebClient默认是使用JSON序列化的。

使用Apache HttpClient调用

publicclassTestHttpClient{@TestpublicvoiddoGet()throwsIOException{//步骤一：创建httpClient实例CloseableHttpClient httpClient =HttpClients.createDefault();//步骤二：创建HTTP请求HttpGet httpGet =newHttpGet("http://127.0.0.1:8094/masterdata/sysUser/getSysUserById?userId=郭郭");//步骤三：发送请求并获取响应数据CloseableHttpResponse response = httpClient.execute(httpGet);//步骤四：处理响应数据HttpEntity entity = response.getEntity();String result =EntityUtils.toString(entity);//步骤五：关闭httpClient和response
        response.close();
        httpClient.close();}@TestpublicvoiddoPost()throwsIOException{//步骤一：创建httpClient实例CloseableHttpClient httpClient =HttpClients.createDefault();//步骤二：创建HTTP请求HttpPost httpPost =newHttpPost("http://127.0.0.1:8094/masterdata/sysUser/saveUser");//步骤三：设置请求体数据，使用JSON格式Map map =newHashMap<>();
        map.put("name","郭郭");String requestBody =JSON.toJSONString(map);StringEntity stringEntity =newStringEntity(requestBody,"UTF-8");
        stringEntity.setContentType("application/json");
        httpPost.setEntity(stringEntity);//步骤四：发送请求并获取响应数据CloseableHttpResponse response = httpClient.execute(httpPost);//步骤五：处理响应数据HttpEntity entity = response.getEntity();String result =EntityUtils.toString(entity);//步骤五：关闭httpClient和response
        response.close();
        httpClient.close();}}

使用HttpURLConnection调用

publicclassTestHttpURLConnection{@TestpublicvoiddoGet()throwsIOException{String userId ="郭郭";// 参数值
        userId =URLEncoder.encode(userId,"UTF-8");// 对参数值进行URL编码//步骤一：创建URL对象URL url =newURL("http://127.0.0.1:8094/masterdata/sysUser/getSysUserById?userId="+ userId);//步骤二：打开连接HttpURLConnection conn =(HttpURLConnection) url.openConnection();//步骤三：设置请求方式
        conn.setRequestMethod("GET");//步骤四：读取响应内容BufferedReader reader =newBufferedReader(newInputStreamReader(conn.getInputStream()));StringBuilder sb =newStringBuilder();String line;while((line = reader.readLine())!=null){
            sb.append(line);}
        reader.close();System.out.println(sb.toString());}@TestpublicvoiddoPost()throwsIOException{//创建URL对象URL url =newURL("http://127.0.0.1:8094/masterdata/sysUser/saveUser");//打开连接HttpURLConnection conn =(HttpURLConnection) url.openConnection();//设置请求方式
        conn.setRequestMethod("POST");// 设置请求头
        conn.setRequestProperty("Content-Type","application/json");//启用输出流
        conn.setDoOutput(true);//设置请求体数据Map map =newHashMap<>();
        map.put("name","郭郭");String requestBody =JSON.toJSONString(map);//发送请求体数据try(DataOutputStream outputStream =newDataOutputStream(conn.getOutputStream())){
            outputStream.write(requestBody.getBytes(StandardCharsets.UTF_8));}//读取响应内容BufferedReader reader =newBufferedReader(newInputStreamReader(conn.getInputStream()));StringBuilder sb =newStringBuilder();String line;while((line = reader.readLine())!=null){
            sb.append(line);}
        reader.close();System.out.println(sb.toString());}}

使用OkHttp调用

1、引入依赖

<!--okhttp依赖--><dependency><groupId>com.squareup.okhttp3</groupId><artifactId>okhttp</artifactId><version>4.0.0</version></dependency>

2、示例代码

publicclassTestOkHttp{@TestpublicvoiddoGet()throwsIOException{OkHttpClient client =newOkHttpClient();String url ="http://127.0.0.1:8080/master/test/getSysUserById?userId=郭郭";Request request =newRequest.Builder().url(url).build();try(Response response = client.newCall(request).execute()){ResponseBody body = response.body();System.out.println(body.string());}}@TestpublicvoiddoPost()throwsIOException{OkHttpClient client =newOkHttpClient();String url ="http://127.0.0.1:8080/master/test/saveUser";MediaType mediaType =MediaType.get("application/json; charset=utf-8");//requestBody请求入参Map map =newHashMap<>();
        map.put("name","admin");RequestBody requestBody =RequestBody.create(mediaType,JSON.toJSONString(map));Request request =newRequest.Builder().url(url).post(requestBody).build();try(Response response = client.newCall(request).execute()){ResponseBody body = response.body();System.out.println(body.string());}}}

使用AsyncHttpClient调用

1、引入依赖

<dependency><groupId>org.asynchttpclient</groupId><artifactId>async-http-client</artifactId><version>2.12.3</version></dependency>

2、示例代码

publicclassTestAsyncHttpClient{@TestpublicvoiddoGet()throwsIOException{try(AsyncHttpClient client =newDefaultAsyncHttpClient();){BoundRequestBuilder requestBuilder = client.prepareGet("http://127.0.0.1:8080/master/test/getSysUserById?userId=hy001");CompletableFuture<String> future = requestBuilder.execute().toCompletableFuture().thenApply(Response::getResponseBody);//使用join等待响应完成String responseBody = future.join();System.out.println(responseBody);}}@TestpublicvoiddoPost()throwsIOException{try(AsyncHttpClient client =newDefaultAsyncHttpClient();){BoundRequestBuilder requestBuilder = client.preparePost("http://127.0.0.1:8094/8080/master/test/saveUser");//requestBody请求入参Map map =newHashMap<>();
            map.put("name","admin");String requestBody =JSON.toJSONString(map);
            requestBuilder.addHeader("Content-Type","application/json");
            requestBuilder.setBody(requestBody);CompletableFuture<String> future = requestBuilder.execute().toCompletableFuture().thenApply(Response::getResponseBody);//使用join等待响应完成String responseBody = future.join();System.out.println(responseBody);}}}