Added support to add literals directly to the header

core/src/main/java/feign/RequestTemplate.java

@@ -705,6 +705,13 @@ public RequestTemplate header(String name, String... values) {
     return header(name, Arrays.asList(values));
   }
 
+  /**
+   * @see RequestTemplate#headerLiteral(String, Iterable)
+   */
+  public RequestTemplate headerLiteral(String name, String... values) {
+    return headerLiteral(name, Arrays.asList(values));
+  }
+
   /**
    * Specify a Header, with the specified values. Values can be literals or template expressions.
    *
@@ -713,16 +720,25 @@ public RequestTemplate header(String name, String... values) {
    * @return a RequestTemplate for chaining.
    */
   public RequestTemplate header(String name, Iterable<String> values) {
-    if (name == null || name.isEmpty()) {
-      throw new IllegalArgumentException("name is required.");
-    }
-    if (values == null) {
-      values = Collections.emptyList();
-    }
+    values = validateHeaderValues(name, values);
 
     return appendHeader(name, values);
   }
 
+  /**
+   * Specify a Header, with the specified values. Values will be evaluated as literal.
+   *
+   * @param name of the header.
+   * @param values for this header.
+   * @return a RequestTemplate for chaining.
+   */
+  public RequestTemplate headerLiteral(String name, Iterable<String> values) {
+    values = validateHeaderValues(name, values);
+
+    return appendHeader(name, values, true);
+  }
+
+
   /**
    * Clear on reader from {@link RequestTemplate}
    *
@@ -787,6 +803,21 @@ private RequestTemplate appendHeader(String name, Iterable<String> values, boole
     return this;
   }
 
+  /**
+   * Validates that both the name and values are valid
+   * 
+   * @param name of the header.
+   * @param values for this header.
+   * @return an Iterable of strings
+   */
+  private Iterable<String> validateHeaderValues(String name, Iterable<String> values) {
+    if (name == null || name.isEmpty()) {
+      throw new IllegalArgumentException("name is required.");
+    }
+
+    return values == null ? Collections.emptyList() : values;
+  }
+
   /**
    * Headers for this Request.
    *
@@ -802,6 +833,21 @@ public RequestTemplate headers(Map<String, Collection<String>> headers) {
     return this;
   }
 
+  /**
+   * Header Literals for this Request.
+   *
+   * @param headers to use.
+   * @return a RequestTemplate for chaining.
+   */
+  public RequestTemplate headerLiterals(Map<String, Collection<String>> headers) {
+    if (headers != null && !headers.isEmpty()) {
+      headers.forEach(this::headerLiteral);
+    } else {
+      this.headers.clear();
+    }
+    return this;
+  }
+
   /**
    * Returns an copy of the Headers for this request.
    *

core/src/test/java/feign/RequestTemplateTest.java

@@ -15,7 +15,6 @@
 
 import static feign.assertj.FeignAssertions.assertThat;
 import static java.util.Arrays.asList;
-import static org.assertj.core.api.Assertions.assertThat;
 import static org.assertj.core.data.MapEntry.entry;
 import static org.junit.Assert.assertEquals;
 import static org.junit.Assert.assertNotNull;
@@ -243,6 +242,18 @@ public void resolveTemplateWithHeaderWithNestedJson() {
         .hasHeaders(entry("A-Header", Collections.singletonList(json)));
   }
 
+  @Test
+  public void shouldNotResolveTemplateWithHeaderWithJsonLiteral() {
+    String json = "{ \"foo\": \"bar\", \"hello\": \"world\"}";
+    RequestTemplate template = new RequestTemplate().method(HttpMethod.GET)
+        .headerLiteral("A-Header", "{aHeader}");
+
+    template = template.resolve(mapOf("aHeader", json));
+
+    assertThat(template)
+        .hasHeaders(entry("A-Header", Collections.singletonList("{aHeader}")));
+  }
+
   /**
    * This ensures we don't mess up vnd types
    */