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SpringBoot调用外部接口的几种方式

作者：one_smail

SpringBoot应用中,调用外部接口是微服务架构常见需求,本文主要介绍了SpringBoot调用外部接口的几种方式,文中通过示例代码介绍的非常详细,对大家的学习或者工作具有一定的参考学习价值,需要的朋友们下面随着小编来一起学习学习吧

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

import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.cloud.openfeign.EnableFeignClients;

@SpringBootApplication
@EnableFeignClients
public class StudyfeignApplication {

    public static void main(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

import com.hysoft.studyfeign.service.SysUserClient;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.web.bind.annotation.PostMapping;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RestController;

@RestController
@RequestMapping("feign")
public class SysUserController {

    @Autowired
    private SysUserClient sysUserClient;

    @PostMapping("getUserId")
    public void getUserId(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}")
public interface SysUserClient {

    @PostMapping("/master/test")
    String getUserById(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    

import org.springframework.stereotype.Service;

@Service
public class SysUserClientImpl implements SysUserClient{
    @Override
    public String getUserById(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

@Configuration
public class RestTemplateConfig {

    @Bean
    public RestTemplate restTemplate(ClientHttpRequestFactory factory){
        return new RestTemplate(factory);
    }

    @Bean
    public ClientHttpRequestFactory simpleClientHttpRequestFactory(){
        SimpleClientHttpRequestFactory factory = new SimpleClientHttpRequestFactory();
        factory.setReadTimeout(5000);//单位为ms
        factory.setConnectTimeout(5000);//单位为ms
        return factory;
    }
}

3、接口调用

@RestController
public class TestRestTemplate {
    @Resource
    private RestTemplate restTemplate;

    @GetMapping(value = "/saveUser")
    public void saveUser(String userId) {
        String url = "http://127.0.0.1:8080/master/test";
        Map map = new HashMap<>();
        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

public class TestWebClient {
    @Test
    public void doGet() {
        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());
    }
    @Test
    public void doPost() {
        Map map = new HashMap<>();
        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

public class TestHttpClient {
    @Test
    public void doGet() throws IOException {
        //步骤一：创建httpClient实例
        CloseableHttpClient httpClient = HttpClients.createDefault();
        //步骤二：创建HTTP请求
        HttpGet httpGet = new HttpGet("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();
    }
    @Test
    public void doPost() throws IOException {
        //步骤一：创建httpClient实例
        CloseableHttpClient httpClient = HttpClients.createDefault();
        //步骤二：创建HTTP请求
        HttpPost httpPost = new HttpPost("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 = new HashMap<>();
        map.put("name", "郭郭");
        String requestBody = JSON.toJSONString(map);
        StringEntity stringEntity = new StringEntity(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

public class TestHttpURLConnection {

    @Test
    public void doGet() throws IOException {
        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 = new URL("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 = new BufferedReader(new InputStreamReader(conn.getInputStream()));
        StringBuilder sb = new StringBuilder();
        String line;
        while ((line = reader.readLine()) != null) {
            sb.append(line);
        }
        reader.close();
        System.out.println(sb.toString());
    } 
    @Test
    public void doPost() throws IOException {
        //创建URL对象
        URL url = new URL("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 = new HashMap<>();
        map.put("name", "郭郭");
        String requestBody = JSON.toJSONString(map);
        //发送请求体数据
        try (DataOutputStream outputStream = new DataOutputStream(conn.getOutputStream())) {
            outputStream.write(requestBody.getBytes(StandardCharsets.UTF_8));
        }

        //读取响应内容
        BufferedReader reader = new BufferedReader(new InputStreamReader(conn.getInputStream()));
        StringBuilder sb = new StringBuilder();
        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

public class TestOkHttp {

    @Test
    public void doGet() throws IOException {
        OkHttpClient client = new OkHttpClient();
        String url = "http://127.0.0.1:8080/master/test/getSysUserById?userId=郭郭";
        Request request = new Request.Builder().url(url).build();
        try (Response response = client.newCall(request).execute()) {
            ResponseBody body = response.body();
            System.out.println(body.string());
        }
    }

    @Test
    public void doPost() throws IOException{
        OkHttpClient client = new OkHttpClient();
        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 = new HashMap<>();
        map.put("name", "admin");
        RequestBody requestBody = RequestBody.create(mediaType, JSON.toJSONString(map));
        Request request = new Request.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

public class TestAsyncHttpClient {
    @Test
    public void doGet() throws IOException {
        try (AsyncHttpClient client = new DefaultAsyncHttpClient();) {
            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);
        }
    }
    @Test
    public void doPost() throws IOException {
        try (AsyncHttpClient client = new DefaultAsyncHttpClient();) {
            BoundRequestBuilder requestBuilder = client.preparePost("http://127.0.0.1:8094/8080/master/test/saveUser");
            //requestBody请求入参
            Map map = new HashMap<>();
            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);
        }
    }
  }

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