Springboot 调用外部接口的三种方式

03 SpringBoot 评论

1. 简介

在Springboot项目中，存在需要访问外部模块接口，或者外部URL链接的需求，下面就介绍三种调用外部接口的方式（不使用dubbo的方式）

2. 使用原始HttpClient请求

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@RequestMapping("/submit/{documentId}")
public String submit(@PathVariable String documentId) throws ParseException {
    //此处将要发送的数据转换为json格式字符串
    Map<String,Object> map =task2Service.getMap(documentId);
    String jsonStr = JSON.toJSONString(map, SerializerFeature.WRITE_MAP_NULL_FEATURES,SerializerFeature.QuoteFieldNames);
    JSONObject jsonObject = JSON.parseObject(jsonStr);
    JSONObject sr = doPost(jsonObject);
    return sr.toString();
}
/**
 * httpclient请求
 */
public static JSONObject doPost(JSONObject date) {
    String assessToken="eyJ0eXAiOiJKV1QiLCJhbGciOiJIUzUxMiJ9.eyJ4ZGFwYXBwaWQiOiIzNDgxMjU4ODk2OTI2OTY1NzYiLCJleHAiOjE2NjEyMjY5MDgsImlhdCI6MTY2MTIxOTcwOCwieGRhcHRlbmFudGlkIjoiMzAwOTgxNjA1MTE0MDUyNjA5IiwieGRhcHVzZXJpZCI6IjEwMDM0NzY2MzU4MzM1OTc5NTIwMCJ9.fZAO4kJSv2rSH0RBiL1zghdko8Npmu_9ufo6Wex_TI2q9gsiLp7XaW7U9Cu7uewEOaX4DTdpbFmMPvLUtcj_sQ";
    CloseableHttpClient client = HttpClients.createDefault();
    // 要调用的接口url
    String url = "http://192.1680.96:9091/xdap-open/open/process/v1/submit";
    HttpPost post = new HttpPost(url);
    JSONObject jsonObject = null;
    try {
        //创建请求体并添加数据
        StringEntity s = new StringEntity(date.toString());
        //此处相当于在header里头添加content-type等参数
        s.setContentType("application/json");
        s.setContentEncoding("UTF-8");
        post.setEntity(s);
        //此处相当于在Authorization里头添加Bear token参数信息
        post.addHeader("Authorization", "Bearer " +assessToken);
        HttpResponse res = client.execute(post);
        String response1 = EntityUtils.toString(res.getEntity());
        if (res.getStatusLine().getStatusCode() == HttpStatus.SC_OK) {
            // 返回json格式：
            String result = EntityUtils.toString(res.getEntity());
            jsonObject = JSONObject.parseObject(result);
        }
    } catch (Exception e) {
        throw new RuntimeException(e);
    }
    return jsonObject;
}

3. 使用RestTemplate方法

在Springboot开发中，RestTemplate同样提供了对外访问的接口API。

3.1. Get请求

提供了getForObject、getForEntity两种方式，其中getForEntity如下三种方法实现:

  1. getForEntity(URI url, Class responseType) 
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    //该方法使用URI对象来替代之前的url和urlVariables参数来指定访问地址和参数绑定。URI是JDK java.net包下的一个类，表示一个统一资源标识符(Uniform Resource Identifier)引用。参考如下：
    RestTemplate restTemplate=new RestTemplate();
            UriComponents
            uriComponents=UriComponentsBuilder.fromUriString("http://USER-SERVICE/user?name={name}")
            .build()
            .expand("dodo")
            .encode();
            URI uri=uriComponents.toUri();
            ResponseEntityresponseEntity=restTemplate.getForEntity(uri,String.class).getBody();
  2. getForEntity(Stringurl,Class responseType,Object…urlVariables) 
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    //该方法提供了三个参数，其中url为请求的地址，responseType为请求响应body的包装类型，urlVariables为url中的参数绑定，该方法的参考调用如下：
    // http://USER-SERVICE/user?name={name)
    RestTemplate restTemplate=new RestTemplate();
    Mapparams=new HashMap<>();
    params.put("name","dada"); //
    ResponseEntityresponseEntity=restTemplate.getForEntity("http://USERSERVICE/user?name={name}",String.class,params);

getForObject，存在以下三种方式重载:

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getForObject(String url,Class responseType,Object...urlVariables)
getForObject(String url,Class responseType,Map urlVariables)
getForObject(URI url,Class responseType)

getForObject方法可以理解为对getForEntity的进一步封装，它通过HttpMessageConverterExactor对Http请求响应体body内容进行对象转化，实现请求直接返回包装好的对象内容。

3.2. Post请求

ost请求提供有postForEntity、postForObject和postForLocation三种方式，其中每种方式都有三种方法，下面介绍postForEntity的使用方法。

postForEntity，存在以下三种方式重载:

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postForEntity(String url,Object request,Class responseType,Object...  uriVariables) 
postForEntity(String url,Object request,Class responseType,Map  uriVariables) 
postForEntity(URI url,Object request，Class responseType)

如下仅演示第二种重载方式: 

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public String submit(String documentId){
    String assessToken="eyJ0eXAiOiJKV1QiLCJhbGciOiJIUzUxMiJ9.eyJ4ZGFwYXBwaWQiOiIzNDgxMjU4ODk2OTI2OTY1NzYiLCJleHAiOjE2NjEyMjY5MDgsImlhdCI6MTY2MTIxOTcwOCwieGRhcHRlbmFudGlkIjoiMzAwOTgxNjA1MTE0MDUyNjA5IiwieGRhcHVzZXJpZCI6IjEwMDM0NzY2MzU4MzM1OTc5NTIwMCJ9.fZAO4kJSv2rSH0RBiL1zghdko8Npmu_9ufo6Wex_TI2q9gsiLp7XaW7U9Cu7uewEOaX4DTdpbFmMPvLUtcj_sQ";
    RestTemplate restTemplate = new RestTemplate();
    //创建请求头
    HttpHeaders httpHeaders = new HttpHeaders();
    //此处相当于在Authorization里头添加Bear token参数信息
    httpHeaders.add(HttpHeaders.AUTHORIZATION, "Bearer " + assessToken);
    //此处相当于在header里头添加content-type等参数
    httpHeaders.add(HttpHeaders.CONTENT_TYPE,"application/json");
    Map<String, Object> map = getMap(documentId);
    String jsonStr = JSON.toJSONString(map);
    //创建请求体并添加数据
    HttpEntity<Map> httpEntity = new HttpEntity<Map>(map, httpHeaders);
    String url = "http://39.103.201.110:30661/xdap-open/open/process/v1/submit";
    ResponseEntity<String> forEntity = restTemplate.postForEntity(url,httpEntity,String.class);//此处三个参数分别是请求地址、请求体以及返回参数类型
    return forEntity.toString();
}

4. 使用Feign进行消费

  1. 在maven项目中添加依赖

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    <dependency>
        <groupId>org.springframework.cloud</groupId>
        <artifactId>spring-cloud-starter-feign</artifactId>
        <version>1.4.2.RELEASE</version>
    </dependency>

  2. 在启动类上加上@EnableFeignClients

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    @SpringBootApplication
    @EnableFeignClients
    public class ChapterApplication {
        public static void main(String[] args) {
            SpringApplication.run(MobilecardApplication.class, args);
        }
    }

    此处编写接口模拟外部接口供feign调用外部接口方式使用

  1. 定义service以及controller

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    @Service
    public interface PrintService {
        public String print(TestDto testDto);
    }
    public class PrintServiceImpl implements PrintService {

        @Override
        public String print(TestDto testDto) {
            return "模拟外部系统的接口功能"+testDto.getId();
        }
    }
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    @Autowired
    PrintService printService;

    @PostMapping("/outSide")
    public String test(@RequestBody TestDto testDto) {
        return printService.print(testDto);
    }

  2. 定义FeignService

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    //此处name需要设置不为空，url需要在.properties中设置
    @Service
    @FeignClient(url = "${outSide.url}", name = "service2")
    public interface FeignService {
        @RequestMapping(value = "/custom/outSide", method = RequestMethod.POST)
        @ResponseBody
        public String getMessage(@Valid @RequestBody TestDto testDto);
    }

  3. 定义调用Controller

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    @Autowired
    FeignService feignService;
    //测试feign调用外部接口入口
    @PostMapping("/test")
    public String test(@RequestBody TestDto testDto) {
        return feignService.getMessage(testDto);
    }

  4. postman测试

4.1. 补充信息

添加Header解决方法

将token等信息放入Feign请求头中，主要通过重写RequestInterceptor的apply方法实现

  1. 定义config

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    @Configuration
    public class FeignConfig implements RequestInterceptor {
        @Override
        public void apply(RequestTemplate requestTemplate) {
            //添加token
            requestTemplate.header("token", "eyJ0eXAiOiJKV1QiLCJhbGciOiJIUzUxMiJ9.eyJ4ZGFwYXBwaWQiOiIzNDgxMjU4ODk2OTI2OTY1NzYiLCJleHAiOjE2NjEyMjY5MDgsImlhdCI6MTY2MTIxOTcwOCwieGRhcHRlbmFudGlkIjoiMzAwOTgxNjA1MTE0MDUyNjA5IiwieGRhcHVzZXJpZCI6IjEwMDM0NzY2MzU4MzM1OTc5NTIwMCJ9.fZAO4kJSv2rSH0RBiL1zghdko8Npmu_9ufo6Wex_TI2q9gsiLp7XaW7U9Cu7uewEOaX4DTdpbFmMPvLUtcj_sQ");
        }
    }

  2. 定义service

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    @Service
    @FeignClient(url = "${outSide.url}",name = "feignServer", configuration = FeignDemoConfig.class)
    public interface TokenDemoClient {
        @RequestMapping(value = "/custom/outSideAddToken", method = RequestMethod.POST)
        @ResponseBody
        public String getMessage(@Valid @RequestBody TestDto testDto);
    }

  3. 定义Controller

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    //测试feign调用外部接口入口，加上token
    @PostMapping("/testToken")
    public String test4(@RequestBody TestDto testDto) {
        return tokenDemoClient.getMessage(testDto);
    }

参考作者：Chelsea的文章：Springboot中调用外部接口的三种方式

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