Merge pull request #38 from palantir/bugfix/optional-headers

Absent optional headers become the empty string

http-clients/src/main/java/com/palantir/remoting/http/GuavaEmptyOptionalExpander.java

@@ -0,0 +1,37 @@
+/*
+ * Copyright 2016 Palantir Technologies, Inc. All rights reserved.
+ *
+ * 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 com.palantir.remoting.http;
+
+import com.google.common.base.Optional;
+import com.google.common.base.Preconditions;
+import feign.Param.Expander;
+import java.util.Objects;
+
+/**
+ * Expands Optional by using the empty string for {@link Optional#absent()} and the {@link Object#toString()} of
+ * the value otherwise.
+ */
+public final class GuavaEmptyOptionalExpander implements Expander {
+
+    @Override
+    public String expand(Object value) {
+        Preconditions.checkArgument(value instanceof Optional, "Value must be an Optional. Was: %s", value.getClass());
+        Optional<?> optional = (Optional<?>) value;
+        return optional.isPresent() ? Objects.toString(optional.get()) : "";
+    }
+
+}

http-clients/src/main/java/com/palantir/remoting/http/GuavaOptionalExpander.java → http-clients/src/main/java/com/palantir/remoting/http/GuavaNullOptionalExpander.java

@@ -22,9 +22,10 @@
 import java.util.Objects;
 
 /**
- * Expands Optional by using null for Optional.absent and the toString() of the value otherwise.
+ * Expands Optional by using null for {@link Optional#absent()} and the {@link Object#toString()} of the
+ * value otherwise.
  */
-public final class GuavaOptionalExpander implements Expander {
+public final class GuavaNullOptionalExpander implements Expander {
 
     @Override
     public String expand(Object value) {

http-clients/src/main/java/com/palantir/remoting/http/GuavaOptionalAwareContract.java

@@ -16,17 +16,22 @@
 
 package com.palantir.remoting.http;
 
+import com.google.common.base.Function;
 import com.google.common.base.Optional;
+import com.google.common.collect.FluentIterable;
 import feign.Contract;
 import feign.Feign;
 import feign.MethodMetadata;
+import java.lang.annotation.Annotation;
 import java.lang.reflect.Method;
 import java.util.LinkedHashMap;
 import java.util.List;
 import java.util.Map;
+import javax.ws.rs.HeaderParam;
 
 /**
- * Decorates a Contract and uses {@link GuavaOptionalExpander} for any HeaderParam, PathParam or QueryParam parameters.
+ * Decorates a Contract and uses {@link GuavaNullOptionalExpander} for any PathParam or QueryParam parameters
+ * and {@link GuavaEmptyOptionalExpander} for any {@link HeaderParam} parameters.
  */
 public final class GuavaOptionalAwareContract implements Contract {
 
@@ -52,15 +57,27 @@ public List<MethodMetadata> parseAndValidatateMetadata(Class<?> targetType) {
             MethodMetadata md = methodMetadataByConfigKey.get(configKey);
             if (md != null) {
                 Class<?>[] parameterTypes = method.getParameterTypes();
+                Annotation[][] annotations = method.getParameterAnnotations();
                 for (int i = 0; i < parameterTypes.length; i++) {
                     Class<?> cls = parameterTypes[i];
                     if (cls.equals(Optional.class)) {
-                        md.indexToExpanderClass().put(i, GuavaOptionalExpander.class);
+                        if (FluentIterable.of(annotations[i]).transform(EXTRACT_CLASS).contains(HeaderParam.class)) {
+                            md.indexToExpanderClass().put(i, GuavaEmptyOptionalExpander.class);
+                        } else {
+                            md.indexToExpanderClass().put(i, GuavaNullOptionalExpander.class);
+                        }
                     }
                 }
             }
         }
         return mdList;
     }
 
+    private static final Function<Annotation, Class<?>> EXTRACT_CLASS = new Function<Annotation, Class<?>>() {
+        @Override
+        public Class<?> apply(Annotation input) {
+            return input.annotationType();
+        }
+    };
+
 }

http-clients/src/test/java/com/palantir/remoting/http/GuavaOptionalAwareContractTest.java

@@ -114,7 +114,7 @@ public void testStringQuery() throws Exception {
     public void testAbsentHeader() throws Exception {
         proxy.header(Optional.<String>absent(), "str2");
         RecordedRequest takeRequest = server.takeRequest();
-        assertThat(takeRequest.getHeader("opt"), is("{opt}"));
+        assertThat(takeRequest.getHeader("opt"), is(""));
         assertThat(takeRequest.getHeader("req"), is("str2"));
     }