From 7897690a3be55f8d0ddf3640209bc3e7a2b64cb3 Mon Sep 17 00:00:00 2001
From: Julien Perrochet <julien.perro@gmail.com>
Date: Fri, 19 Apr 2024 00:02:23 +0200
Subject: [PATCH] [fix] ServiceOutputParser fails if class has no fields

---
 .../dev/langchain4j/service/ServiceOutputParser.java   | 10 +++-------
 1 file changed, 3 insertions(+), 7 deletions(-)

diff --git a/langchain4j/src/main/java/dev/langchain4j/service/ServiceOutputParser.java b/langchain4j/src/main/java/dev/langchain4j/service/ServiceOutputParser.java
index 092943f1a..d4fb07cdb 100644
--- a/langchain4j/src/main/java/dev/langchain4j/service/ServiceOutputParser.java
+++ b/langchain4j/src/main/java/dev/langchain4j/service/ServiceOutputParser.java
@@ -119,20 +119,16 @@ public class ServiceOutputParser {
     }
 
     private static String jsonStructure(Class<?> structured, Set<Class<?>> visited) {
-        StringBuilder jsonSchema = new StringBuilder();
-
-        jsonSchema.append("{\n");
+        List<String> descriptions = new ArrayList<>();
         for (Field field : structured.getDeclaredFields()) {
             String name = field.getName();
             if (name.equals("__$hits$__") || java.lang.reflect.Modifier.isStatic(field.getModifiers())) {
                 // Skip coverage instrumentation field.
                 continue;
             }
-            jsonSchema.append(format("\"%s\": (%s),\n", name, descriptionFor(field, visited)));
+            descriptions.add(format("\"%s\": (%s)", name, descriptionFor(field, visited)));
         }
-        jsonSchema.delete(jsonSchema.lastIndexOf(","), jsonSchema.lastIndexOf(",")+1);
-        jsonSchema.append("}");
-        return jsonSchema.toString();
+        return "{\n" + String.join(",\n", descriptions) + "\n}";
     }
 
     private static String descriptionFor(Field field, Set<Class<?>> visited) {