From 1dce6f140c1e44b19c9f5e5c7c431e5325cb6d98 Mon Sep 17 00:00:00 2001
From: ohl-nemeses <pohl@nemeses.de>
Date: Wed, 11 May 2022 09:36:18 +0200
Subject: [PATCH] 12319 avoid StringIndexOutOfBoundsException on empty
 HttpHeaders (#12327)

---
 .../resources/Java/libraries/resttemplate/ApiClient.mustache   | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/modules/openapi-generator/src/main/resources/Java/libraries/resttemplate/ApiClient.mustache b/modules/openapi-generator/src/main/resources/Java/libraries/resttemplate/ApiClient.mustache
index 56ce0754e82..b5de6ce3a19 100644
--- a/modules/openapi-generator/src/main/resources/Java/libraries/resttemplate/ApiClient.mustache
+++ b/modules/openapi-generator/src/main/resources/Java/libraries/resttemplate/ApiClient.mustache
@@ -832,6 +832,9 @@ public class ApiClient{{#jsr310}} extends JavaTimeFormatter{{/jsr310}} {
         }
 
         private String headersToString(HttpHeaders headers) {
+            if(headers == null || headers.isEmpty()) {
+                return "";
+            }
             StringBuilder builder = new StringBuilder();
             for (Entry<String, List<String>> entry : headers.entrySet()) {
                 builder.append(entry.getKey()).append("=[");