使用Feign設置請求頭

REST
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04:06 AM · Dec 01 ,2025

1. 概述

有時，在使用 Feign 時，我們需要在 HTTP 調用中設置請求頭。Feign 允許我們僅使用聲明式語法構建 HTTP 客户端。

在本簡短教程中，我們將學習如何使用註解配置請求頭。我們還將通過使用攔截器包含常見的請求頭。

2. 示例

在本文教程中，我們將使用一個示例書店應用程序，它暴露了 REST API 端點。

我們可以輕鬆地克隆項目並在本地運行它:

$ mvn install spring-boot:run

讓我們深入研究客户端實現。

3. Using the Header Annotation

Let’s think of a scenario where specific API calls should always contain a static header. In this situation, we might configure that request header as part of the client. A typical example is to include a Content-Type header.

Using the @Header annotation, we can easily configure a static request header. We can define this header value either statically or dynamically.

3.1. Setting Static Header Value

Let’s configure two static headers, i.e., Accept-Language and Content-Type, into the BookClient:

@Headers("Accept-Language: en-US")
public interface BookClient {
    
    @RequestLine("GET /{isbn}")
    BookResource findByIsbn(@Param("isbn") String isbn);

    @RequestLine("POST")
    @Headers("Content-Type: application/json")
    void create(Book book);
}

In the above code, the header Accept-Language is included in all APIs since it is applied to the BookClient. However, the create method has an additional Content-Type header.

Next, let’s see how to create the BookClient using Feign’s Builder method and passing the HEADERS log level:

Feign.builder()
  .encoder(new GsonEncoder())
  .decoder(new GsonDecoder())
  .logger(new Slf4jLogger(type))
  .logLevel(Logger.Level.HEADERS)
  .target(BookClient.class, "http://localhost:8081/api/books");

Now, let’s test the create method:

String isbn = UUID.randomUUID().toString();
Book book = new Book(isbn, "Me", "It's me!", null, null);
        
bookClient.create(book);

book = bookClient.findByIsbn(isbn).getBook();

Then, let’s verify the headers in the output logger:

18:01:15.039 [main] DEBUG c.b.f.c.h.staticheader.BookClient - [BookClient#create] Accept-Language: en-US
18:01:15.039 [main] DEBUG c.b.f.c.h.staticheader.BookClient - [BookClient#create] Content-Type: application/json
18:01:15.096 [main] DEBUG c.b.f.c.h.staticheader.BookClient - [BookClient#findByIsbn] Accept-Language: en-US

We should note that if the header name is the same in both the client interface and the API method, they will not override each other. Instead, the request will include all such values.

3.2. Setting Dynamic Header Value

Using the @Header annotation, we can also set a dynamic header value. For this, we need to express the value as a placeholder.

Let’s include the x-requester-id header into the BookClient with a placeholder of requester:

@Headers("x-requester-id: {requester}")
public interface BookClient {
   
    @RequestLine("GET /{isbn}")
    BookResource findByIsbn(@Param("requester") String requester, @Param("isbn") String isbn);
}

Here we made the x-requester-id a variable that’s passed into each method. We used the @Param annotation to match the name of the variable. It’s expanded at runtime to satisfy the header specified by the @Headers annotation. It’s expanded at runtime to satisfy the header specified by the @Headers annotation. It’s expanded at runtime to satisfy the header specified by the @Headers annotation. It’s expanded at runtime to satisfy the header specified by the @Headers annotation. It’s expanded at runtime to satisfy the header specified by the @Headers annotation. It’s expanded at runtime to satisfy the header specified by the @Headers annotation. It’s expanded at runtime to satisfy the header specified by the @Headers annotation. It’s expanded at runtime to satisfy the header specified by the @Headers annotation. It’s expanded at runtime to satisfy the header specified by the @Headers annotation. It’s expanded at runtime to satisfy the header specified by the @Headers annotation. 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4. 使用 HeaderMaps 註解

設想一個場景，其中 header 鍵和值都是動態的。在這種情況下，可能鍵的範圍事先未知。此外，不同方法調用在同一客户端上的 header 可能會有所不同。典型的例子是設置某些 metadata header。

使用 Map 參數，並使用 @HeaderMap 設置動態 header：

@RequestLine("POST")
void create(@HeaderMap Map<String, Object> headers, Book book);

現在，讓我們嘗試使用 header map 測試 create 方法：

Map<String,Object> headerMap = new HashMap<>();
    	
headerMap.put("metadata-key1", "metadata-value1");
headerMap.put("metadata-key2", "metadata-value2");
    	
bookClient.create(headerMap, book);

然後，讓我們驗證輸出日誌中的 header：

18:05:03.202 [main] DEBUG c.b.f.c.h.dynamicheader.BookClient - [BookClient#create] metadata-key1: metadata-value1
18:05:03.202 [main] DEBUG c.b.f.c.h.dynamicheader.BookClient - [BookClient#create] metadata-key2: metadata-value2

5. 請求攔截器

攔截器可以對每個請求或響應執行各種隱式任務，例如日誌記錄或身份驗證。

Feign 提供 RequestInterceptor 接口。通過它，我們可以添加請求頭。

當已知頭信息應該包含在每個調用中時，添加請求攔截器是有意義的。這種模式消除了調用代碼實現非功能性要求（如身份驗證或跟蹤）的依賴性。

讓我們通過實現 AuthorisationService 來嘗試一下，該服務將用於生成授權令牌：

public class ApiAuthorisationService implements AuthorisationService {

    @Override
    public String getAuthToken() {
        return "Bearer " + UUID.randomUUID();
    }
}

現在，讓我們實現自定義請求攔截器：

public class AuthRequestInterceptor implements RequestInterceptor {
	
    private AuthorisationService authTokenService;
   
    public AuthRequestInterceptor(AuthorisationService authTokenService) {
        this.authTokenService = authTokenService;
    }

    @Override
    public void apply(RequestTemplate template) {
        template.header("Authorisation", authTokenService.getAuthToken());
    }
}

請注意，請求攔截器可以讀取、刪除或修改任何請求模板的組成部分。

現在，讓我們使用 builder 方法將 AuthInterceptor 添加到 BookClient 中：

Feign.builder()
  .requestInterceptor(new AuthInterceptor(new ApiAuthorisationService()))
  .encoder(new GsonEncoder())
  .decoder(new GsonDecoder())
  .logger(new Slf4jLogger(type))
  .logLevel(Logger.Level.HEADERS)
  .target(BookClient.class, "http://localhost:8081/api/books");

然後，讓我們使用 Authorisation 頭測試 BookClient API：

bookClient.findByIsbn("0151072558").getBook();

現在，讓我們驗證輸出日誌記錄器中的頭信息：

18:06:06.135 [main] DEBUG c.b.f.c.h.staticheader.BookClient - [BookClient#findByIsbn] Authorisation: Bearer 629e0af7-513d-4385-a5ef-cb9b341cedb5

多個請求攔截器也可以應用於Feign 客户端。雖然沒有關於它們應用順序的保證。

6. 結論

在本文中，我們討論了 Feign 客户端如何支持設置請求頭。我們使用 @Headers、@HeaderMaps 註解和請求攔截器來實現這一功能。

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