Let's talk about how to use Feign to construct a POST request with multiple parameters. Assume that the Service Provider's Controller is written as follows:
@RestController
public class UserController {
  @PostMapping("/post")
  public User post(@RequestBody User user) {
    ...
  }
}

How do we use Feign to request for it? The answer is very simple, example:
@FeignClient(name = "microservice-provider-user")
public interface UserFeignClient {
  @RequestMapping(value = "/post", method = RequestMethod.POST)
  public User post(@RequestBody User user);
}

feign:
  httpclient:
    enabled: true

            <!--httpClient-->
            <dependency>
                <groupId>org.apache.httpcomponents</groupId>
                <artifactId>httpclient</artifactId>
                <version>4.5.3</version>
            </dependency>

            <dependency>
                <groupId>com.netflix.feign</groupId>
                <artifactId>feign-httpclient</artifactId>
                <version>8.17.0</version>
            </dependency>

@RequestMapping(value = "/user/list",method = RequestMethod.GET,consumes = "application/json")
    List<User> users(@RequestBody QueryBean queryBean);

@RequestMapping(value = "/user/list",method = RequestMethod.POST,consumes = "application/json")
    List<User> users(@RequestBody QueryBean queryBean){
                      func();
}

public class YryzRequestInterceptor implements RequestInterceptor {
    @Autowired
    private ObjectMapper objectMapper;

    @Override
    public void apply(RequestTemplate template) {
        // feign 不支持 GET 方法传 POJO, json body转query
        if (template.method().equals("GET") && template.body() != null) {
            try {
                JsonNode jsonNode = objectMapper.readTree(template.body());
                template.body(null);

                Map<String, Collection<String>> queries = new HashMap<>();
                buildQuery(jsonNode, "", queries);
                template.queries(queries);
            } catch (IOException e) {
                e.printStackTrace();
            }
        }
    }

    private void buildQuery(JsonNode jsonNode, String path, Map<String, Collection<String>> queries) {
        if (!jsonNode.isContainerNode()) {   // 叶子节点
            if (jsonNode.isNull()) {
                return;
            }
            Collection<String> values = queries.get(path);
            if (null == values) {
                values = new ArrayList<>();
                queries.put(path, values);
            }
            values.add(jsonNode.asText());
            return;
        }
        if (jsonNode.isArray()) {   // 数组节点
            Iterator<JsonNode> it = jsonNode.elements();
            while (it.hasNext()) {
                buildQuery(it.next(), path, queries);
            }
        } else {
            Iterator<Map.Entry<String, JsonNode>> it = jsonNode.fields();
            while (it.hasNext()) {
                Map.Entry<String, JsonNode> entry = it.next();
                if (StringUtils.hasText(path)) {
                    buildQuery(entry.getValue(), path + "." + entry.getKey(), queries);
                } else {  // 根节点
                    buildQuery(entry.getValue(), entry.getKey(), queries);
                }
            }
        }
    }
}

<parent>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-starter-parent</artifactId>
    <version>2.1.2.RELEASE</version>
    <relativePath/> <!-- lookup parent from repository -->
</parent>

<dependencyManagement>
    <dependency>
        <groupId>org.springframework.cloud</groupId>
        <artifactId>spring-cloud-dependencies</artifactId>
        <version>Greenwich.RC2</version>
        <type>pom</type>
        <scope>import</scope>
    </dependency>

   <!--feign相关-->
    <dependency>
        <groupId>io.github.openfeign</groupId>
        <artifactId>feign-httpclient</artifactId>
        <version>10.1.0</version>
    </dependency>
    <dependency>
        <groupId>io.github.openfeign</groupId>
        <artifactId>feign-core</artifactId>
        <version>10.1.0</version>
    </dependency>
    <dependency>
        <groupId>org.apache.httpcomponents</groupId>
        <artifactId>httpclient</artifactId>
        <version>4.5.6</version>
    </dependency>
</dependencyManagement>

@Configurable
public class FeignBasicAuthRequestInterceptor implements RequestInterceptor {
    @Autowired
    private ObjectMapper objectMapper;

    public FeignBasicAuthRequestInterceptor() {}

    @Override
    public void apply(RequestTemplate template) {
        ///**get-pojo贯穿*/
        if (template.method().equals("GET") && template.requestBody().asBytes() != null) {
            try {
                JsonNode jsonNode = objectMapper.readTree(template.requestBody().asBytes());
                //template.body(null);
                Map<String, Collection<String>> queries = new HashMap<>();
                //feign 不支持 GET 方法传 POJO, json body转query
                buildQuery(jsonNode, "", queries);
                template.queries(queries);
            } catch (IOException e) {
                e.printStackTrace();
            }
        }
    }

    //处理 get-pojo贯穿
    private void buildQuery(JsonNode jsonNode, String path, Map<String, Collection<String>> queries) {
        if (!jsonNode.isContainerNode()) { //叶子节点
            if (jsonNode.isNull()) {
                return;
            }
            Collection<String> values = queries.get(path);
            if (null == values) {
                values = new ArrayList<>();
                queries.put(path, values);
            }
            values.add(jsonNode.asText());
            return;
        }
        if (jsonNode.isArray()) { //数组节点
            Iterator<JsonNode> it = jsonNode.elements();
            while (it.hasNext()) {
                buildQuery(it.next(), path, queries);
            }
        } else {
            Iterator<Map.Entry<String, JsonNode>> it = jsonNode.fields();
            while (it.hasNext()) {
                Map.Entry<String, JsonNode> entry = it.next();
                if (StringUtils.hasText(path)) {
                    buildQuery(entry.getValue(), path + "." + entry.getKey(), queries);
                } else { //根节点
                    buildQuery(entry.getValue(), entry.getKey(), queries);
                }
            }
        }
    }
}

@PostMapping("/app")
Response<Integer> appInsert(@RequestBody AppDTO dto);

@DeleteMapping("/app/{appId}")
Response<Integer> appDelete(@PathVariable("appId") String appId);

@PutMapping("/app")
Response<Integer> appUpdate(@RequestBody AppDTO dto);

@GetMapping("/app/{appId}")
Response<AppDTO> appGet(@PathVariable("appId") String appId);

@GetMapping("/app")
Response<List<AppDTO>> appList(AppQTO qto);

@GetMapping("/app/listcount")
Response<List<AppDTO>> appListCount(AppQTO qto);

@PostMapping
public Response<Integer> insert(@RequestBody AppDTO dto) {
    System.out.println("#######insert:"+ JsonUtil.toJson(dto));
    return new Response<>(appService.insert(dto));
}

@DeleteMapping("/{appId}")
public Response<Integer> delete(@PathVariable("appId") String appId) {
    return new Response<>(appService.deleteByIds(appId));
}

@PutMapping
public Response<Integer> update(@RequestBody AppDTO dto) {
    System.out.println("#######update:"+ JsonUtil.toJson(dto));
    return new Response<>(appService.update(dto));
}

@GetMapping("/{appId}")
public Response<AppDTO> get(@PathVariable("appId") String appId) {
    return new Response<>(appService.getObject(appId));
}

@GetMapping
public Response<List<AppDTO>> list(AppQTO qto) {
    System.out.println("#######list:"+ JsonUtil.toJson(qto));
    return new Response<>(appService.listObjects(qto));
}

@GetMapping("/listcount")
public Response<List<AppDTO>> listCount(AppQTO qto) {
    System.out.println("#######listCount:"+ JsonUtil.toJson(qto));
    return appService.list(qto);
}

        byte[] emptyBody = Request.Body.empty().asBytes();
        if (template.method().equals("GET") && !Arrays.equals(template.body(), emptyBody)) {
        //....
             template.body(Request.Body.empty());
        }