fix: Response.protocolVersion may cause NPE (#2351)

* fix: set Response.protocolVersion default value

* refactor: add default protocol version field

* refactor: change to default protocol version value using builder field.

Author: etff

core/src/main/java/feign/Response.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2012-2023 The Feign Authors
+ * Copyright 2012-2024 The Feign Authors
  *
  * 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
@@ -51,13 +51,14 @@ public static Builder builder() {
   }
 
   public static final class Builder {
+    private static final ProtocolVersion DEFAULT_PROTOCOL_VERSION = ProtocolVersion.HTTP_1_1;
     int status;
     String reason;
     Map<String, Collection<String>> headers;
     Body body;
     Request request;
     private RequestTemplate requestTemplate;
-    private ProtocolVersion protocolVersion = ProtocolVersion.HTTP_1_1;
+    private ProtocolVersion protocolVersion = DEFAULT_PROTOCOL_VERSION;
 
     Builder() {}
 
@@ -125,7 +126,7 @@ public Builder request(Request request) {
      * HTTP protocol version
      */
     public Builder protocolVersion(ProtocolVersion protocolVersion) {
-      this.protocolVersion = protocolVersion;
+      this.protocolVersion = (protocolVersion != null) ? protocolVersion : DEFAULT_PROTOCOL_VERSION;
       return this;
     }
 

core/src/test/java/feign/ResponseTest.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2012-2023 The Feign Authors
+ * Copyright 2012-2024 The Feign Authors
  *
  * 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
@@ -110,4 +110,17 @@ void statusCodesOfAnyValueAreAllowed() {
       assertThat(response.status()).isEqualTo(statusCode);
     });
   }
+
+  @Test
+  void protocolVersionDefaultsToHttp1_1() {
+    Response response = Response.builder()
+        .status(200)
+        .request(Request.create(HttpMethod.GET, "/api", Collections.emptyMap(), null, Util.UTF_8))
+        .protocolVersion(null)
+        .body(new byte[0])
+        .build();
+
+    assertThat(response.protocolVersion()).isEqualTo(Request.ProtocolVersion.HTTP_1_1);
+    assertThat(response.toString()).startsWith("HTTP/1.1 200");
+  }
 }