From e0ef2928964bcaffbf2301e25f0ebbc19d9797e6 Mon Sep 17 00:00:00 2001
From: Yannick Reifschneider <yannick.reifschneider.extern@dvag.com>
Date: Wed, 10 Jul 2024 11:33:50 +0200
Subject: [PATCH 1/2] Allows adding literal header values to RequestTemplate

This change adds a new method RequestTemplate#headerLiteral which allows adding headers which are not interpreted as Template expressions. This allows adding empty JSON objects to headers in RequestInterceptor implementations.

Fixes #2252, #1987
---
 core/src/main/java/feign/RequestTemplate.java | 30 +++++++++++++++++++
 .../test/java/feign/RequestTemplateTest.java  | 20 +++++++++++++
 2 files changed, 50 insertions(+)

diff --git a/core/src/main/java/feign/RequestTemplate.java b/core/src/main/java/feign/RequestTemplate.java
index 7309cdfa1..8157e3887 100644
--- a/core/src/main/java/feign/RequestTemplate.java
+++ b/core/src/main/java/feign/RequestTemplate.java
@@ -728,6 +728,36 @@ public RequestTemplate header(String name, Iterable<String> values) {
     return appendHeader(name, values);
   }
 
+  /**
+   * @see RequestTemplate#headerLiteral(String, Iterable)
+   */
+  public RequestTemplate headerLiteral(String name, String... values) {
+    if (values == null) {
+      return appendHeader(name, Collections.emptyList(), true);
+    }
+
+    return headerLiteral(name, Arrays.asList(values));
+  }
+
+  /**
+   * Specify a Header, with the specified values. Values are treated as literals. Template
+   * expressions are not resolved.
+   *
+   * @param name of the header.
+   * @param values for this header.
+   * @return a RequestTemplate for chaining.
+   */
+  public RequestTemplate headerLiteral(String name, Iterable<String> values) {
+    if (name == null || name.isEmpty()) {
+      throw new IllegalArgumentException("name is required.");
+    }
+    if (values == null) {
+      values = Collections.emptyList();
+    }
+
+    return appendHeader(name, values, true);
+  }
+
   /**
    * Clear on reader from {@link RequestTemplate}
    *
diff --git a/core/src/test/java/feign/RequestTemplateTest.java b/core/src/test/java/feign/RequestTemplateTest.java
index c8d29a4b2..4c40b6ad0 100644
--- a/core/src/test/java/feign/RequestTemplateTest.java
+++ b/core/src/test/java/feign/RequestTemplateTest.java
@@ -246,6 +246,26 @@ void resolveTemplateWithHeaderEmptyResult() {
     assertThat(template).hasNoHeader("Encoded");
   }
 
+  @Test
+  void templateWithEmptyJsonObjectLiteralHeader() {
+    String emptyJsonObject = "{}";
+    RequestTemplate template =
+        new RequestTemplate().method(HttpMethod.GET).headerLiteral("A-Header", emptyJsonObject);
+
+    template.resolve(new LinkedHashMap<>());
+    assertThat(template).hasHeaders(entry("A-Header", Collections.singletonList(emptyJsonObject)));
+  }
+
+  @Test
+  void templateWithTemplateExpressionLiteralHeader() {
+    String header = "{var}";
+    RequestTemplate template =
+        new RequestTemplate().method(HttpMethod.GET).headerLiteral("A-Header", header);
+
+    template = template.resolve(mapOf("var", "value"));
+    assertThat(template).hasHeaders(entry("A-Header", Collections.singletonList(header)));
+  }
+
   @Test
   void resolveTemplateWithMixedRequestLineParams() {
     RequestTemplate template = new RequestTemplate().method(HttpMethod.GET)//

From faac0804f1c6c36c4e8c46a4bedbce4d8fa107c1 Mon Sep 17 00:00:00 2001
From: Marvin <velo@users.noreply.github.com>
Date: Wed, 10 Jul 2024 08:17:23 -0300
Subject: [PATCH 2/2] Update RequestTemplate.java

---
 core/src/main/java/feign/RequestTemplate.java | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/core/src/main/java/feign/RequestTemplate.java b/core/src/main/java/feign/RequestTemplate.java
index 8157e3887..f5c5022a9 100644
--- a/core/src/main/java/feign/RequestTemplate.java
+++ b/core/src/main/java/feign/RequestTemplate.java
@@ -733,7 +733,7 @@ public RequestTemplate header(String name, Iterable<String> values) {
    */
   public RequestTemplate headerLiteral(String name, String... values) {
     if (values == null) {
-      return appendHeader(name, Collections.emptyList(), true);
+      return headerLiteral(name, Collections.emptyList());
     }
 
     return headerLiteral(name, Arrays.asList(values));