聊聊feign的RequestInterceptor

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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 {
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 private final String headerValue;
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 /**
 * 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);
 }
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 /**
 * 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));
 }
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 /*
 * 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);
 }
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 @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 {
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 /**
 * The encoding properties.
 */
 private final FeignClientEncodingProperties properties;
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 /**
 * 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;
 }
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 /**
 * 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) {
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 if (!requestTemplate.headers().containsKey(name)) {
 requestTemplate.header(name, values);
 }
 }
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 protected FeignClientEncodingProperties getProperties() {
 return this.properties;
 }
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}

• 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 {
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 /**
 * Creates new instance of {@link FeignAcceptGzipEncodingInterceptor}.
 * @param properties the encoding properties
 */
 protected FeignAcceptGzipEncodingInterceptor(
 FeignClientEncodingProperties properties) {
 super(properties);
 }
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 /**
 * {@inheritDoc}
 */
 @Override
 public void apply(RequestTemplate template) {
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 addHeader(template, HttpEncoding.ACCEPT_ENCODING_HEADER,
 HttpEncoding.GZIP_ENCODING, HttpEncoding.DEFLATE_ENCODING);
 }
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}

• 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 {
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 /**
 * Creates new instance of {@link FeignContentGzipEncodingInterceptor}.
 * @param properties the encoding properties
 */
 protected FeignContentGzipEncodingInterceptor(
 FeignClientEncodingProperties properties) {
 super(properties);
 }
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 /**
 * {@inheritDoc}
 */
 @Override
 public void apply(RequestTemplate template) {
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 if (requiresCompression(template)) {
 addHeader(template, HttpEncoding.CONTENT_ENCODING_HEADER,
 HttpEncoding.GZIP_ENCODING, HttpEncoding.DEFLATE_ENCODING);
 }
 }
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 /**
 * 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) {
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 final Map<String, Collection<String>> headers = template.headers();
 return matchesMimeType(headers.get(HttpEncoding.CONTENT_TYPE))
 && contentLengthExceedThreshold(headers.get(HttpEncoding.CONTENT_LENGTH));
 }
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 /**
 * 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) {
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 try {
 if (contentLength == null || contentLength.size() != 1) {
 return false;
 }
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 final String strLen = contentLength.iterator().next();
 final long length = Long.parseLong(strLen);
 return length > getProperties().getMinRequestSize();
 }
 catch (NumberFormatException ex) {
 return false;
 }
 }
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 /**
 * 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;
 }
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 if (getProperties().getMimeTypes() == null
 || getProperties().getMimeTypes().length == 0) {
 // no specific mime types has been set - matching everything
 return true;
 }
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 for (String mimeType : getProperties().getMimeTypes()) {
 if (contentTypes.contains(mimeType)) {
 return true;
 }
 }
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 return false;
 }
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}

• 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