聊聊feign的RequestInterceptor

序

本文主要研究一下feign的RequestInterceptor

RequestInterceptor

feign-core-10.2.3-sources.jar!/feign/RequestInterceptor.java

public interface RequestInterceptor {

  /**
   * Called for every request. Add data using methods on the supplied {@link RequestTemplate}.
   */
  void apply(RequestTemplate template);
}

• RequestInterceptor接口定义了apply方法，其参数为RequestTemplate；它有一个抽象类为BaseRequestInterceptor，还有几个实现类分别为BasicAuthRequestInterceptor、FeignAcceptGzipEncodingInterceptor、FeignContentGzipEncodingInterceptor

BasicAuthRequestInterceptor

feign-core-10.2.3-sources.jar!/feign/auth/BasicAuthRequestInterceptor.java

public class BasicAuthRequestInterceptor implements RequestInterceptor {

  private final String headerValue;

  /**
   * Creates an interceptor that authenticates all requests with the specified username and password
   * encoded using ISO-8859-1.
   *
   * @param username the username to use for authentication
   * @param password the password to use for authentication
   */
  public BasicAuthRequestInterceptor(String username, String password) {
    this(username, password, ISO_8859_1);
  }

  /**
   * Creates an interceptor that authenticates all requests with the specified username and password
   * encoded using the specified charset.
   *
   * @param username the username to use for authentication
   * @param password the password to use for authentication
   * @param charset the charset to use when encoding the credentials
   */
  public BasicAuthRequestInterceptor(String username, String password, Charset charset) {
    checkNotNull(username, "username");
    checkNotNull(password, "password");
    this.headerValue = "Basic " + base64Encode((username + ":" + password).getBytes(charset));
  }

  /*
   * This uses a Sun internal method; if we ever encounter a case where this method is not
   * available, the appropriate response would be to pull the necessary portions of Guava's
   * BaseEncoding class into Util.
   */
  private static String base64Encode(byte[] bytes) {
    return Base64.encode(bytes);
  }

  @Override
  public void apply(RequestTemplate template) {
    template.header("Authorization", headerValue);
  }
}

• BasicAuthRequestInterceptor实现了RequestInterceptor接口，其apply方法往RequestTemplate添加名为Authorization的header

BaseRequestInterceptor

spring-cloud-openfeign-core-2.2.0.M1-sources.jar!/org/springframework/cloud/openfeign/encoding/BaseRequestInterceptor.java

public abstract class BaseRequestInterceptor implements RequestInterceptor {

    /**
     * The encoding properties.
     */
    private final FeignClientEncodingProperties properties;

    /**
     * Creates new instance of {@link BaseRequestInterceptor}.
     * @param properties the encoding properties
     */
    protected BaseRequestInterceptor(FeignClientEncodingProperties properties) {
        Assert.notNull(properties, "Properties can not be null");
        this.properties = properties;
    }

    /**
     * Adds the header if it wasn't yet specified.
     * @param requestTemplate the request
     * @param name the header name
     * @param values the header values
     */
    protected void addHeader(RequestTemplate requestTemplate, String name,
            String... values) {

        if (!requestTemplate.headers().containsKey(name)) {
            requestTemplate.header(name, values);
        }
    }

    protected FeignClientEncodingProperties getProperties() {
        return this.properties;
    }

}

• BaseRequestInterceptor定义了addHeader方法，往requestTemplate添加非重名的header

FeignAcceptGzipEncodingInterceptor

spring-cloud-openfeign-core-2.2.0.M1-sources.jar!/org/springframework/cloud/openfeign/encoding/FeignAcceptGzipEncodingInterceptor.java

public class FeignAcceptGzipEncodingInterceptor extends BaseRequestInterceptor {

    /**
     * Creates new instance of {@link FeignAcceptGzipEncodingInterceptor}.
     * @param properties the encoding properties
     */
    protected FeignAcceptGzipEncodingInterceptor(
            FeignClientEncodingProperties properties) {
        super(properties);
    }

    /**
     * {@inheritDoc}
     */
    @Override
    public void apply(RequestTemplate template) {

        addHeader(template, HttpEncoding.ACCEPT_ENCODING_HEADER,
                HttpEncoding.GZIP_ENCODING, HttpEncoding.DEFLATE_ENCODING);
    }

}

• FeignAcceptGzipEncodingInterceptor继承了BaseRequestInterceptor，它的apply方法往RequestTemplate添加了名为Accept-Encoding，值为gzip,deflate的header

FeignContentGzipEncodingInterceptor

spring-cloud-openfeign-core-2.2.0.M1-sources.jar!/org/springframework/cloud/openfeign/encoding/FeignContentGzipEncodingInterceptor.java

public class FeignContentGzipEncodingInterceptor extends BaseRequestInterceptor {

    /**
     * Creates new instance of {@link FeignContentGzipEncodingInterceptor}.
     * @param properties the encoding properties
     */
    protected FeignContentGzipEncodingInterceptor(
            FeignClientEncodingProperties properties) {
        super(properties);
    }

    /**
     * {@inheritDoc}
     */
    @Override
    public void apply(RequestTemplate template) {

        if (requiresCompression(template)) {
            addHeader(template, HttpEncoding.CONTENT_ENCODING_HEADER,
                    HttpEncoding.GZIP_ENCODING, HttpEncoding.DEFLATE_ENCODING);
        }
    }

    /**
     * Returns whether the request requires GZIP compression.
     * @param template the request template
     * @return true if request requires compression, false otherwise
     */
    private boolean requiresCompression(RequestTemplate template) {

        final Map<String, Collection<String>> headers = template.headers();
        return matchesMimeType(headers.get(HttpEncoding.CONTENT_TYPE))
                && contentLengthExceedThreshold(headers.get(HttpEncoding.CONTENT_LENGTH));
    }

    /**
     * Returns whether the request content length exceed configured minimum size.
     * @param contentLength the content length header value
     * @return true if length is grater than minimum size, false otherwise
     */
    private boolean contentLengthExceedThreshold(Collection<String> contentLength) {

        try {
            if (contentLength == null || contentLength.size() != 1) {
                return false;
            }

            final String strLen = contentLength.iterator().next();
            final long length = Long.parseLong(strLen);
            return length > getProperties().getMinRequestSize();
        }
        catch (NumberFormatException ex) {
            return false;
        }
    }

    /**
     * Returns whether the content mime types matches the configures mime types.
     * @param contentTypes the content types
     * @return true if any specified content type matches the request content types
     */
    private boolean matchesMimeType(Collection<String> contentTypes) {
        if (contentTypes == null || contentTypes.size() == 0) {
            return false;
        }

        if (getProperties().getMimeTypes() == null
                || getProperties().getMimeTypes().length == 0) {
            // no specific mime types has been set - matching everything
            return true;
        }

        for (String mimeType : getProperties().getMimeTypes()) {
            if (contentTypes.contains(mimeType)) {
                return true;
            }
        }

        return false;
    }

}

• FeignContentGzipEncodingInterceptor继承了BaseRequestInterceptor，其apply方法先判断是否需要compression，即mimeType是否符合要求以及content大小是否超出阈值，需要compress的话则添加名为Content-Encoding，值为gzip,deflate的header

小结

• RequestInterceptor接口定义了apply方法，其参数为RequestTemplate；它有一个抽象类为BaseRequestInterceptor，还有几个实现类分别为BasicAuthRequestInterceptor、FeignAcceptGzipEncodingInterceptor、FeignContentGzipEncodingInterceptor
• BasicAuthRequestInterceptor实现了RequestInterceptor接口，其apply方法往RequestTemplate添加名为Authorization的header
• BaseRequestInterceptor定义了addHeader方法，往requestTemplate添加非重名的header；FeignAcceptGzipEncodingInterceptor继承了BaseRequestInterceptor，它的apply方法往RequestTemplate添加了名为Accept-Encoding，值为gzip,deflate的header；FeignContentGzipEncodingInterceptor继承了BaseRequestInterceptor，其apply方法先判断是否需要compression，即mimeType是否符合要求以及content大小是否超出阈值，需要compress的话则添加名为Content-Encoding，值为gzip,deflate的header

doc

• RequestInterceptor