spring-cloud之openfeign学习笔记

1. 添加依赖

   <dependency>
       <groupId>org.springframework.cloud</groupId>
       <artifactId>spring-cloud-starter-openfeign</artifactId>
   </dependency>
   

2. 启动类添加注释@EnableFeignClients

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

3. 编写feign接口

   @FeignClient(name = "github-client", url = "https://api.github.com", configuration = HelloFeignServiceConfig.class)
   public interface HelloFeignService {
         
         
       @RequestMapping(value = "/search/repositories", method = RequestMethod.GET)
       String searchRepo(@RequestParam("q") String queryStr) ;
   }
   // 注意HelloFeignServiceConfig放在spring扫描包路径外，否则此配置将作为全局feign生效
   @Configuration
   public class HelloFeignServiceConfig {
         
         
      @Bean
      public Logger.Level feignLoggerLevel() {
         
         
         return Logger.Level.FULL;
      }
   }
   

4. 编写业务方法使用feign接口

   @Controller
   public class HelloFeignController {
         
         
       @Autowired
       private HelloFeignService helloFeignService ;
       @GetMapping("/search/github")
       public String searchGithubRepoByStr(@RequestParam("str") String queryStr){
         
         
           return helloFeignService.searchRepo(queryStr);
       }
   }
   

GET 传递对象参数问题（post添加@RequestBody直接传递对象即可）\

1. 方式一: feign接口中接收Map<String,Object> 参数，我们在controller中手动转map

   @RequestMapping(value = "/feignGet/addUser",
       method = RequestMethod.GET,
       produces = MediaType.APPLICATION_JSON_UTF8_VALUE
   )
   ResponseEntity<byte[]> addUser(@RequestParam Map<String, Object> user) ;
   

2. 方式二： 添加@SpringQueryMap注解 （open feign 2.1之后版本可用）

   @RequestMapping(value = "/feignGet/addUser",
               method = RequestMethod.GET,
               produces = MediaType.APPLICATION_JSON_UTF8_VALUE
       )
       ResponseEntity<byte[]> addUser3(@SpringQueryMap User user) ;
   

3. 方式三： 自定义RequestInterceptor （open feign支持支持对象传递的，但是得是Map形式，而且不能为空）

   @Component
   public class FeignGetInterceptor implements RequestInterceptor {
         
         
       @Autowired
       private ObjectMapper objectMapper ;
       @Override
       public void apply(RequestTemplate template) {
         
         
           if ("GET".equalsIgnoreCase(template.method()) && template.requestBody() != null){
         
         
               Request.Body body = template.requestBody();
               if (body.length() ==0){
         
         
                   return;
               }
               try {
         
         
                   JsonNode jsonNode = objectMapper.readTree(body.asBytes());
                   // 这里必须设置为空，否则报错
                   template.body(Request.Body.empty()) ;
                   Map<String, Collection<String>> queries = buildQuery(jsonNode);
                   template.queries(queries) ;
               } catch (IOException e) {
         
         
                   e.printStackTrace();
               }
           }
       }
       // 暂时仅支持平铺得对象属性传递，不支持对象嵌套对象以及数组传递
       private Map<String, Collection<String>> buildQuery(JsonNode jsonNode) {
         
         
           Map<String, Collection<String>> queries = new HashMap<>() ;
           Iterator<Map.Entry<String, JsonNode>> iterator = jsonNode.fields();
           while (iterator.hasNext()){
         
         
               Map.Entry<String, JsonNode> next = iterator.next();
               String name = next.getKey();
               JsonNode value = next.getValue();
               queries.put(name, Collections.singletonList(value.asText())) ;
           }
           return queries ;
       }
   }
   

调用传递token

1. 自定义RequestInterceptor

   @Component
   public class FeignTokenInterceptor implements RequestInterceptor {
         
         
       @Override
       public void apply(RequestTemplate template) {
         
         
           HttpServletRequest request = ((ServletRequestAttributes)
                   RequestContextHolder.getRequestAttributes()).getRequest();
           if (request == null){
         
         
               return;
           }
           // 将token对应值往下传递
           String xtoken = request.getHeader("x-token");
           if (xtoken != null){
         
         
               template.header("x-token", xtoken) ;
           }
       }
   }