首页
学习
活动
专区
工具
TVP
发布
社区首页 >专栏 >聊聊feign的Contract

聊聊feign的Contract

作者头像
code4it
发布2019-07-23 16:57:27
7180
发布2019-07-23 16:57:27
举报
文章被收录于专栏:码匠的流水账码匠的流水账

本文主要研究一下feign的Contract

Contract

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

public interface Contract {

  /**
   * Called to parse the methods in the class that are linked to HTTP requests.
   *
   * @param targetType {@link feign.Target#type() type} of the Feign interface.
   */
  // TODO: break this and correct spelling at some point
  List<MethodMetadata> parseAndValidatateMetadata(Class<?> targetType);

  //......

}
  • Contract定义了parseAndValidatateMetadata方法,该方法返回List形式的MethodMetadata

Contract.BaseContract

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

  abstract class BaseContract implements Contract {

    @Override
    public List<MethodMetadata> parseAndValidatateMetadata(Class<?> targetType) {
      checkState(targetType.getTypeParameters().length == 0, "Parameterized types unsupported: %s",
          targetType.getSimpleName());
      checkState(targetType.getInterfaces().length <= 1, "Only single inheritance supported: %s",
          targetType.getSimpleName());
      if (targetType.getInterfaces().length == 1) {
        checkState(targetType.getInterfaces()[0].getInterfaces().length == 0,
            "Only single-level inheritance supported: %s",
            targetType.getSimpleName());
      }
      Map<String, MethodMetadata> result = new LinkedHashMap<String, MethodMetadata>();
      for (Method method : targetType.getMethods()) {
        if (method.getDeclaringClass() == Object.class ||
            (method.getModifiers() & Modifier.STATIC) != 0 ||
            Util.isDefault(method)) {
          continue;
        }
        MethodMetadata metadata = parseAndValidateMetadata(targetType, method);
        checkState(!result.containsKey(metadata.configKey()), "Overrides unsupported: %s",
            metadata.configKey());
        result.put(metadata.configKey(), metadata);
      }
      return new ArrayList<>(result.values());
    }

    /**
     * @deprecated use {@link #parseAndValidateMetadata(Class, Method)} instead.
     */
    @Deprecated
    public MethodMetadata parseAndValidatateMetadata(Method method) {
      return parseAndValidateMetadata(method.getDeclaringClass(), method);
    }

    /**
     * Called indirectly by {@link #parseAndValidatateMetadata(Class)}.
     */
    protected MethodMetadata parseAndValidateMetadata(Class<?> targetType, Method method) {
      MethodMetadata data = new MethodMetadata();
      data.returnType(Types.resolve(targetType, targetType, method.getGenericReturnType()));
      data.configKey(Feign.configKey(targetType, method));

      if (targetType.getInterfaces().length == 1) {
        processAnnotationOnClass(data, targetType.getInterfaces()[0]);
      }
      processAnnotationOnClass(data, targetType);


      for (Annotation methodAnnotation : method.getAnnotations()) {
        processAnnotationOnMethod(data, methodAnnotation, method);
      }
      checkState(data.template().method() != null,
          "Method %s not annotated with HTTP method type (ex. GET, POST)",
          method.getName());
      Class<?>[] parameterTypes = method.getParameterTypes();
      Type[] genericParameterTypes = method.getGenericParameterTypes();

      Annotation[][] parameterAnnotations = method.getParameterAnnotations();
      int count = parameterAnnotations.length;
      for (int i = 0; i < count; i++) {
        boolean isHttpAnnotation = false;
        if (parameterAnnotations[i] != null) {
          isHttpAnnotation = processAnnotationsOnParameter(data, parameterAnnotations[i], i);
        }
        if (parameterTypes[i] == URI.class) {
          data.urlIndex(i);
        } else if (!isHttpAnnotation) {
          checkState(data.formParams().isEmpty(),
              "Body parameters cannot be used with form parameters.");
          checkState(data.bodyIndex() == null, "Method has too many Body parameters: %s", method);
          data.bodyIndex(i);
          data.bodyType(Types.resolve(targetType, targetType, genericParameterTypes[i]));
        }
      }

      if (data.headerMapIndex() != null) {
        checkMapString("HeaderMap", parameterTypes[data.headerMapIndex()],
            genericParameterTypes[data.headerMapIndex()]);
      }

      if (data.queryMapIndex() != null) {
        if (Map.class.isAssignableFrom(parameterTypes[data.queryMapIndex()])) {
          checkMapKeys("QueryMap", genericParameterTypes[data.queryMapIndex()]);
        }
      }

      return data;
    }

    private static void checkMapString(String name, Class<?> type, Type genericType) {
      checkState(Map.class.isAssignableFrom(type),
          "%s parameter must be a Map: %s", name, type);
      checkMapKeys(name, genericType);
    }

    private static void checkMapKeys(String name, Type genericType) {
      Class<?> keyClass = null;

      // assume our type parameterized
      if (ParameterizedType.class.isAssignableFrom(genericType.getClass())) {
        Type[] parameterTypes = ((ParameterizedType) genericType).getActualTypeArguments();
        keyClass = (Class<?>) parameterTypes[0];
      } else if (genericType instanceof Class<?>) {
        // raw class, type parameters cannot be inferred directly, but we can scan any extended
        // interfaces looking for any explict types
        Type[] interfaces = ((Class) genericType).getGenericInterfaces();
        if (interfaces != null) {
          for (Type extended : interfaces) {
            if (ParameterizedType.class.isAssignableFrom(extended.getClass())) {
              // use the first extended interface we find.
              Type[] parameterTypes = ((ParameterizedType) extended).getActualTypeArguments();
              keyClass = (Class<?>) parameterTypes[0];
              break;
            }
          }
        }
      }

      if (keyClass != null) {
        checkState(String.class.equals(keyClass),
            "%s key must be a String: %s", name, keyClass.getSimpleName());
      }
    }


    /**
     * Called by parseAndValidateMetadata twice, first on the declaring class, then on the target
     * type (unless they are the same).
     *
     * @param data metadata collected so far relating to the current java method.
     * @param clz the class to process
     */
    protected abstract void processAnnotationOnClass(MethodMetadata data, Class<?> clz);

    /**
     * @param data metadata collected so far relating to the current java method.
     * @param annotation annotations present on the current method annotation.
     * @param method method currently being processed.
     */
    protected abstract void processAnnotationOnMethod(MethodMetadata data,
                                                      Annotation annotation,
                                                      Method method);

    /**
     * @param data metadata collected so far relating to the current java method.
     * @param annotations annotations present on the current parameter annotation.
     * @param paramIndex if you find a name in {@code annotations}, call
     *        {@link #nameParam(MethodMetadata, String, int)} with this as the last parameter.
     * @return true if you called {@link #nameParam(MethodMetadata, String, int)} after finding an
     *         http-relevant annotation.
     */
    protected abstract boolean processAnnotationsOnParameter(MethodMetadata data,
                                                             Annotation[] annotations,
                                                             int paramIndex);

    /**
     * links a parameter name to its index in the method signature.
     */
    protected void nameParam(MethodMetadata data, String name, int i) {
      Collection<String> names =
          data.indexToName().containsKey(i) ? data.indexToName().get(i) : new ArrayList<String>();
      names.add(name);
      data.indexToName().put(i, names);
    }
  }
  • Contract.BaseContract是个抽象类,它processAnnotationOnClass、processAnnotationOnMethod、processAnnotationsOnParameter的抽象方法需要子类去实现;它的parseAndValidatateMetadata方法的实现主要是调用了parseAndValidateMetadata方法,而该方法会调用processAnnotationOnClass、processAnnotationOnMethod、processAnnotationsOnParameter这些方法

Contract.Default

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

  class Default extends BaseContract {

    static final Pattern REQUEST_LINE_PATTERN = Pattern.compile("^([A-Z]+)[ ]*(.*)$");

    @Override
    protected void processAnnotationOnClass(MethodMetadata data, Class<?> targetType) {
      if (targetType.isAnnotationPresent(Headers.class)) {
        String[] headersOnType = targetType.getAnnotation(Headers.class).value();
        checkState(headersOnType.length > 0, "Headers annotation was empty on type %s.",
            targetType.getName());
        Map<String, Collection<String>> headers = toMap(headersOnType);
        headers.putAll(data.template().headers());
        data.template().headers(null); // to clear
        data.template().headers(headers);
      }
    }

    @Override
    protected void processAnnotationOnMethod(MethodMetadata data,
                                             Annotation methodAnnotation,
                                             Method method) {
      Class<? extends Annotation> annotationType = methodAnnotation.annotationType();
      if (annotationType == RequestLine.class) {
        String requestLine = RequestLine.class.cast(methodAnnotation).value();
        checkState(emptyToNull(requestLine) != null,
            "RequestLine annotation was empty on method %s.", method.getName());

        Matcher requestLineMatcher = REQUEST_LINE_PATTERN.matcher(requestLine);
        if (!requestLineMatcher.find()) {
          throw new IllegalStateException(String.format(
              "RequestLine annotation didn't start with an HTTP verb on method %s",
              method.getName()));
        } else {
          data.template().method(HttpMethod.valueOf(requestLineMatcher.group(1)));
          data.template().uri(requestLineMatcher.group(2));
        }
        data.template().decodeSlash(RequestLine.class.cast(methodAnnotation).decodeSlash());
        data.template()
            .collectionFormat(RequestLine.class.cast(methodAnnotation).collectionFormat());

      } else if (annotationType == Body.class) {
        String body = Body.class.cast(methodAnnotation).value();
        checkState(emptyToNull(body) != null, "Body annotation was empty on method %s.",
            method.getName());
        if (body.indexOf('{') == -1) {
          data.template().body(body);
        } else {
          data.template().bodyTemplate(body);
        }
      } else if (annotationType == Headers.class) {
        String[] headersOnMethod = Headers.class.cast(methodAnnotation).value();
        checkState(headersOnMethod.length > 0, "Headers annotation was empty on method %s.",
            method.getName());
        data.template().headers(toMap(headersOnMethod));
      }
    }

    @Override
    protected boolean processAnnotationsOnParameter(MethodMetadata data,
                                                    Annotation[] annotations,
                                                    int paramIndex) {
      boolean isHttpAnnotation = false;
      for (Annotation annotation : annotations) {
        Class<? extends Annotation> annotationType = annotation.annotationType();
        if (annotationType == Param.class) {
          Param paramAnnotation = (Param) annotation;
          String name = paramAnnotation.value();
          checkState(emptyToNull(name) != null, "Param annotation was empty on param %s.",
              paramIndex);
          nameParam(data, name, paramIndex);
          Class<? extends Param.Expander> expander = paramAnnotation.expander();
          if (expander != Param.ToStringExpander.class) {
            data.indexToExpanderClass().put(paramIndex, expander);
          }
          data.indexToEncoded().put(paramIndex, paramAnnotation.encoded());
          isHttpAnnotation = true;
          if (!data.template().hasRequestVariable(name)) {
            data.formParams().add(name);
          }
        } else if (annotationType == QueryMap.class) {
          checkState(data.queryMapIndex() == null,
              "QueryMap annotation was present on multiple parameters.");
          data.queryMapIndex(paramIndex);
          data.queryMapEncoded(QueryMap.class.cast(annotation).encoded());
          isHttpAnnotation = true;
        } else if (annotationType == HeaderMap.class) {
          checkState(data.headerMapIndex() == null,
              "HeaderMap annotation was present on multiple parameters.");
          data.headerMapIndex(paramIndex);
          isHttpAnnotation = true;
        }
      }
      return isHttpAnnotation;
    }

    private static Map<String, Collection<String>> toMap(String[] input) {
      Map<String, Collection<String>> result =
          new LinkedHashMap<String, Collection<String>>(input.length);
      for (String header : input) {
        int colon = header.indexOf(':');
        String name = header.substring(0, colon);
        if (!result.containsKey(name)) {
          result.put(name, new ArrayList<String>(1));
        }
        result.get(name).add(header.substring(colon + 1).trim());
      }
      return result;
    }
  }
  • Contract.Default继承了BaseContract,其processAnnotationOnClass方法处理feign.Headers注解;其processAnnotationOnMethod方法处理feign.RequestLine、feign.Body注解;其processAnnotationsOnParameter方法处理feign.Param、feign.QueryMap、feign.HeaderMap注解

SpringMvcContract

spring-cloud-openfeign-core-2.2.0.M1-sources.jar!/org/springframework/cloud/openfeign/support/SpringMvcContract.java

public class SpringMvcContract extends Contract.BaseContract
implements ResourceLoaderAware {

private static final String ACCEPT = "Accept";

private static final String CONTENT_TYPE = "Content-Type";

private static final TypeDescriptor STRING_TYPE_DESCRIPTOR = TypeDescriptor
.valueOf(String.class);

private static final TypeDescriptor ITERABLE_TYPE_DESCRIPTOR = TypeDescriptor
.valueOf(Iterable.class);

private static final ParameterNameDiscoverer PARAMETER_NAME_DISCOVERER = new DefaultParameterNameDiscoverer();

private final Map<Class<? extends Annotation>, AnnotatedParameterProcessor> annotatedArgumentProcessors;

private final Map<String, Method> processedMethods = new HashMap<>();

private final ConversionService conversionService;

private final ConvertingExpanderFactory convertingExpanderFactory;

private ResourceLoader resourceLoader = new DefaultResourceLoader();

public SpringMvcContract() {
this(Collections.emptyList());
}

public SpringMvcContract(
List<AnnotatedParameterProcessor> annotatedParameterProcessors) {
this(annotatedParameterProcessors, new DefaultConversionService());
}

public SpringMvcContract(
List<AnnotatedParameterProcessor> annotatedParameterProcessors,
ConversionService conversionService) {
Assert.notNull(annotatedParameterProcessors,
"Parameter processors can not be null.");
Assert.notNull(conversionService, "ConversionService can not be null.");

List<AnnotatedParameterProcessor> processors;
if (!annotatedParameterProcessors.isEmpty()) {
processors = new ArrayList<>(annotatedParameterProcessors);
}
else {
processors = getDefaultAnnotatedArgumentsProcessors();
}
this.annotatedArgumentProcessors = toAnnotatedArgumentProcessorMap(processors);
this.conversionService = conversionService;
this.convertingExpanderFactory = new ConvertingExpanderFactory(conversionService);
}

//......

@Override
public void setResourceLoader(ResourceLoader resourceLoader) {
this.resourceLoader = resourceLoader;
}

@Override
public MethodMetadata parseAndValidateMetadata(Class<?> targetType, Method method) {
this.processedMethods.put(Feign.configKey(targetType, method), method);
MethodMetadata md = super.parseAndValidateMetadata(targetType, method);

RequestMapping classAnnotation = findMergedAnnotation(targetType,
RequestMapping.class);
if (classAnnotation != null) {
// produces - use from class annotation only if method has not specified this
if (!md.template().headers().containsKey(ACCEPT)) {
parseProduces(md, method, classAnnotation);
}

// consumes -- use from class annotation only if method has not specified this
if (!md.template().headers().containsKey(CONTENT_TYPE)) {
parseConsumes(md, method, classAnnotation);
}

// headers -- class annotation is inherited to methods, always write these if
// present
parseHeaders(md, method, classAnnotation);
}
return md;
}

@Override
protected void processAnnotationOnClass(MethodMetadata data, Class<?> clz) {
if (clz.getInterfaces().length == 0) {
RequestMapping classAnnotation = findMergedAnnotation(clz,
RequestMapping.class);
if (classAnnotation != null) {
// Prepend path from class annotation if specified
if (classAnnotation.value().length > 0) {
String pathValue = emptyToNull(classAnnotation.value()[0]);
pathValue = resolve(pathValue);
if (!pathValue.startsWith("/")) {
pathValue = "/" + pathValue;
}
data.template().uri(pathValue);
}
}
}
}

@Override
protected void processAnnotationOnMethod(MethodMetadata data,
Annotation methodAnnotation, Method method) {
if (!RequestMapping.class.isInstance(methodAnnotation) && !methodAnnotation
.annotationType().isAnnotationPresent(RequestMapping.class)) {
return;
}

RequestMapping methodMapping = findMergedAnnotation(method, RequestMapping.class);
// HTTP Method
RequestMethod[] methods = methodMapping.method();
if (methods.length == 0) {
methods = new RequestMethod[] { RequestMethod.GET };
}
checkOne(method, methods, "method");
data.template().method(Request.HttpMethod.valueOf(methods[0].name()));

// path
checkAtMostOne(method, methodMapping.value(), "value");
if (methodMapping.value().length > 0) {
String pathValue = emptyToNull(methodMapping.value()[0]);
if (pathValue != null) {
pathValue = resolve(pathValue);
// Append path from @RequestMapping if value is present on method
if (!pathValue.startsWith("/") && !data.template().path().endsWith("/")) {
pathValue = "/" + pathValue;
}
data.template().uri(pathValue, true);
}
}

// produces
parseProduces(data, method, methodMapping);

// consumes
parseConsumes(data, method, methodMapping);

// headers
parseHeaders(data, method, methodMapping);

data.indexToExpander(new LinkedHashMap<Integer, Param.Expander>());
}

@Override
protected boolean processAnnotationsOnParameter(MethodMetadata data,
Annotation[] annotations, int paramIndex) {
boolean isHttpAnnotation = false;

AnnotatedParameterProcessor.AnnotatedParameterContext context = new SimpleAnnotatedParameterContext(
data, paramIndex);
Method method = this.processedMethods.get(data.configKey());
for (Annotation parameterAnnotation : annotations) {
AnnotatedParameterProcessor processor = this.annotatedArgumentProcessors
.get(parameterAnnotation.annotationType());
if (processor != null) {
Annotation processParameterAnnotation;
// synthesize, handling @AliasFor, while falling back to parameter name on
// missing String #value():
processParameterAnnotation = synthesizeWithMethodParameterNameAsFallbackValue(
parameterAnnotation, method, paramIndex);
isHttpAnnotation |= processor.processArgument(context,
processParameterAnnotation, method);
}
}

if (isHttpAnnotation && data.indexToExpander().get(paramIndex) == null) {
TypeDescriptor typeDescriptor = createTypeDescriptor(method, paramIndex);
if (this.conversionService.canConvert(typeDescriptor,
STRING_TYPE_DESCRIPTOR)) {
Param.Expander expander = this.convertingExpanderFactory
.getExpander(typeDescriptor);
if (expander != null) {
data.indexToExpander().put(paramIndex, expander);
}
}
}
return isHttpAnnotation;
}
//......

}
  • SpringMvcContract继承了Contract.BaseContract并实现了ResourceLoaderAware接口;其setResourceLoader存储了resourceLoader
  • 其覆盖了父类的parseAndValidateMetadata方法,它首先调用父类的parseAndValidateMetadata方法,然后对org.springframework.web.bind.annotation.RequestMapping注解进行进一步解析
  • processAnnotationOnClass方法处理了RequestMapping注解;processAnnotationOnMethod方法处理了RequestMapping注解;processAnnotationsOnParameter方法处理了RequestParam、RequestHeader等注解

小结

  • Contract定义了parseAndValidatateMetadata方法,该方法返回List形式的MethodMetadata;它有一个抽象类为Contract.BaseContract,它processAnnotationOnClass、processAnnotationOnMethod、processAnnotationsOnParameter的抽象方法需要子类去实现;它的parseAndValidatateMetadata方法的实现主要是调用了parseAndValidateMetadata方法,而该方法会调用processAnnotationOnClass、processAnnotationOnMethod、processAnnotationsOnParameter这些方法
  • Contract.Default继承了BaseContract,其processAnnotationOnClass方法处理feign.Headers注解;其processAnnotationOnMethod方法处理feign.RequestLine、feign.Body注解;其processAnnotationsOnParameter方法处理feign.Param、feign.QueryMap、feign.HeaderMap注解
  • SpringMvcContract继承了Contract.BaseContract并实现了ResourceLoaderAware接口;其setResourceLoader存储了resourceLoader;其覆盖了父类的parseAndValidateMetadata方法,它首先调用父类的parseAndValidateMetadata方法,然后对org.springframework.web.bind.annotation.RequestMapping注解进行进一步解析;processAnnotationOnClass方法处理了RequestMapping注解;processAnnotationOnMethod方法处理了RequestMapping注解;processAnnotationsOnParameter方法处理了RequestParam、RequestHeader等注解

doc

  • Contract
本文参与 腾讯云自媒体分享计划,分享自微信公众号。
原始发表:2019-07-20,如有侵权请联系 cloudcommunity@tencent.com 删除

本文分享自 码匠的流水账 微信公众号,前往查看

如有侵权,请联系 cloudcommunity@tencent.com 删除。

本文参与 腾讯云自媒体分享计划  ,欢迎热爱写作的你一起参与!

评论
登录后参与评论
0 条评论
热度
最新
推荐阅读
目录
  • Contract
  • Contract.BaseContract
  • Contract.Default
  • SpringMvcContract
  • 小结
  • doc
领券
问题归档专栏文章快讯文章归档关键词归档开发者手册归档开发者手册 Section 归档