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Feign contract for JAX-RS 2 Annotation
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/*
 * Copyright 2013 Netflix, Inc.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package feign.jaxrs;

import java.lang.annotation.Annotation;
import java.lang.reflect.Method;
import java.util.ArrayList;
import java.util.Collection;

import javax.ws.rs.Consumes;
import javax.ws.rs.FormParam;
import javax.ws.rs.HeaderParam;
import javax.ws.rs.HttpMethod;
import javax.ws.rs.Path;
import javax.ws.rs.PathParam;
import javax.ws.rs.Produces;
import javax.ws.rs.QueryParam;

import feign.Contract;
import feign.MethodMetadata;

import static feign.Util.checkState;
import static feign.Util.emptyToNull;

/**
 * Please refer to the Feign
 * JAX-RS README.
 */
public final class JAXRSContract extends Contract.BaseContract {

  static final String ACCEPT = "Accept";
  static final String CONTENT_TYPE = "Content-Type";

  // Protected so unittest can call us
  // XXX: Should parseAndValidateMetadata(Class, Method) be public instead? The old deprecated parseAndValidateMetadata(Method) was public..
  @Override
  protected MethodMetadata parseAndValidateMetadata(Class targetType, Method method) {
    return super.parseAndValidateMetadata(targetType, method);
  }

  @Override
  protected void processAnnotationOnClass(MethodMetadata data, Class clz) {
    Path path = clz.getAnnotation(Path.class);
    if (path != null) {
      String pathValue = emptyToNull(path.value());
      checkState(pathValue != null, "Path.value() was empty on type %s", clz.getName());
      if (!pathValue.startsWith("/")) {
        pathValue = "/" + pathValue;
      }
      if (pathValue.endsWith("/")) {
          // Strip off any trailing slashes, since the template has already had slashes appropriately added
          pathValue = pathValue.substring(0, pathValue.length() - 1);
      }
      data.template().insert(0, pathValue);
    }
    Consumes consumes = clz.getAnnotation(Consumes.class);
    if (consumes != null) {
      handleConsumesAnnotation(data, consumes, clz.getName());
    }
    Produces produces = clz.getAnnotation(Produces.class);
    if (produces != null) {
      handleProducesAnnotation(data, produces, clz.getName());
    }
  }

  @Override
  protected void processAnnotationOnMethod(MethodMetadata data, Annotation methodAnnotation,
                                           Method method) {
    Class annotationType = methodAnnotation.annotationType();
    HttpMethod http = annotationType.getAnnotation(HttpMethod.class);
    if (http != null) {
      checkState(data.template().method() == null,
                 "Method %s contains multiple HTTP methods. Found: %s and %s", method.getName(),
                 data.template().method(), http.value());
      data.template().method(http.value());
    } else if (annotationType == Path.class) {
      String pathValue = emptyToNull(Path.class.cast(methodAnnotation).value());
      checkState(pathValue != null, "Path.value() was empty on method %s", method.getName());
      String methodAnnotationValue = Path.class.cast(methodAnnotation).value();
      if (!methodAnnotationValue.startsWith("/") && !data.template().url().endsWith("/")) {
        methodAnnotationValue = "/" + methodAnnotationValue;
      }
      // jax-rs allows whitespace around the param name, as well as an optional regex. The contract should
      // strip these out appropriately.
      methodAnnotationValue = methodAnnotationValue.replaceAll("\\{\\s*(.+?)\\s*(:.+?)?\\}", "\\{$1\\}");
      data.template().append(methodAnnotationValue);
    } else if (annotationType == Produces.class) {
      handleProducesAnnotation(data, (Produces) methodAnnotation, "method " + method.getName());
    } else if (annotationType == Consumes.class) {
      handleConsumesAnnotation(data, (Consumes) methodAnnotation, "method " + method.getName());
    }
  }

  private void handleProducesAnnotation(MethodMetadata data, Produces produces, String name) {
    String[] serverProduces = produces.value();
    String clientAccepts = serverProduces.length == 0 ? null : emptyToNull(serverProduces[0]);
    checkState(clientAccepts != null, "Produces.value() was empty on %s", name);
    data.template().header(ACCEPT, (String) null); // remove any previous produces
    data.template().header(ACCEPT, clientAccepts);
  }

  private void handleConsumesAnnotation(MethodMetadata data, Consumes consumes, String name) {
    String[] serverConsumes = consumes.value();
    String clientProduces = serverConsumes.length == 0 ? null : emptyToNull(serverConsumes[0]);
    checkState(clientProduces != null, "Consumes.value() was empty on %s", name);
    data.template().header(CONTENT_TYPE, (String) null); // remove any previous consumes
    data.template().header(CONTENT_TYPE, clientProduces);
  }

  @Override
  protected boolean processAnnotationsOnParameter(MethodMetadata data, Annotation[] annotations,
                                                  int paramIndex) {
    boolean isHttpParam = false;
    for (Annotation parameterAnnotation : annotations) {
      Class annotationType = parameterAnnotation.annotationType();
      if (annotationType == PathParam.class) {
        String name = PathParam.class.cast(parameterAnnotation).value();
        checkState(emptyToNull(name) != null, "PathParam.value() was empty on parameter %s",
                   paramIndex);
        nameParam(data, name, paramIndex);
        isHttpParam = true;
      } else if (annotationType == QueryParam.class) {
        String name = QueryParam.class.cast(parameterAnnotation).value();
        checkState(emptyToNull(name) != null, "QueryParam.value() was empty on parameter %s",
                   paramIndex);
        Collection query = addTemplatedParam(data.template().queries().get(name), name);
        data.template().query(name, query);
        nameParam(data, name, paramIndex);
        isHttpParam = true;
      } else if (annotationType == HeaderParam.class) {
        String name = HeaderParam.class.cast(parameterAnnotation).value();
        checkState(emptyToNull(name) != null, "HeaderParam.value() was empty on parameter %s",
                   paramIndex);
        Collection header = addTemplatedParam(data.template().headers().get(name), name);
        data.template().header(name, header);
        nameParam(data, name, paramIndex);
        isHttpParam = true;
      } else if (annotationType == FormParam.class) {
        String name = FormParam.class.cast(parameterAnnotation).value();
        checkState(emptyToNull(name) != null, "FormParam.value() was empty on parameter %s",
                   paramIndex);
        data.formParams().add(name);
        nameParam(data, name, paramIndex);
        isHttpParam = true;
      }
    }
    return isHttpParam;
  }

  // Not using override as the super-type's method is deprecated and will be removed.
  protected Collection addTemplatedParam(Collection possiblyNull, String name) {
    if (possiblyNull == null) {
      possiblyNull = new ArrayList();
    }
    possiblyNull.add(String.format("{%s}", name));
    return possiblyNull;
  }
}