OpenAI: use supportedCapabilities(RESPONSE_FORMAT_JSON_SCHEMA) instead of responseFormat("json_schema") to enable structured outputs with JSON schema

Author: dliubarskyi

langchain4j-open-ai-spring-boot-starter/src/main/java/dev/langchain4j/openai/spring/AutoConfig.java

@@ -67,6 +67,7 @@ OpenAiChatModel openAiChatModel(
                 .frequencyPenalty(chatModelProperties.frequencyPenalty())
                 .logitBias(chatModelProperties.logitBias())
                 .responseFormat(chatModelProperties.responseFormat())
+                .supportedCapabilities(chatModelProperties.supportedCapabilities())
                 .strictJsonSchema(chatModelProperties.strictJsonSchema())
                 .seed(chatModelProperties.seed())
                 .user(chatModelProperties.user())

langchain4j-open-ai-spring-boot-starter/src/main/java/dev/langchain4j/openai/spring/ChatModelProperties.java

@@ -1,8 +1,11 @@
 package dev.langchain4j.openai.spring;
 
+import dev.langchain4j.model.chat.Capability;
+
 import java.time.Duration;
 import java.util.List;
 import java.util.Map;
+import java.util.Set;
 
 record ChatModelProperties(
         String baseUrl,
@@ -19,6 +22,7 @@ record ChatModelProperties(
         Double frequencyPenalty,
         Map<String, Integer> logitBias,
         String responseFormat,
+        Set<Capability> supportedCapabilities,
         Boolean strictJsonSchema,
         Integer seed,
         String user,

langchain4j-spring-boot-starter/src/test/java/dev/langchain4j/service/spring/mode/automatic/withStructuredOutput/AiServiceWithStructuredOutput.java

@@ -0,0 +1,9 @@
+package dev.langchain4j.service.spring.mode.automatic.withStructuredOutput;
+
+import dev.langchain4j.service.spring.AiService;
+
+@AiService
+interface AiServiceWithStructuredOutput {
+
+    Person extractPersonFrom(String text);
+}

langchain4j-spring-boot-starter/src/test/java/dev/langchain4j/service/spring/mode/automatic/withStructuredOutput/AiServiceWithStructuredOutputApplication.java

@@ -0,0 +1,12 @@
+package dev.langchain4j.service.spring.mode.automatic.withStructuredOutput;
+
+import org.springframework.boot.SpringApplication;
+import org.springframework.boot.autoconfigure.SpringBootApplication;
+
+@SpringBootApplication
+class AiServiceWithStructuredOutputApplication {
+
+    public static void main(String[] args) {
+        SpringApplication.run(AiServiceWithStructuredOutputApplication.class, args);
+    }
+}

langchain4j-spring-boot-starter/src/test/java/dev/langchain4j/service/spring/mode/automatic/withStructuredOutput/AiServiceWithStructuredOutputIT.java

@@ -0,0 +1,39 @@
+package dev.langchain4j.service.spring.mode.automatic.withStructuredOutput;
+
+import dev.langchain4j.service.spring.AiServicesAutoConfig;
+import org.junit.jupiter.api.Test;
+import org.springframework.boot.autoconfigure.AutoConfigurations;
+import org.springframework.boot.test.context.runner.ApplicationContextRunner;
+
+import static dev.langchain4j.service.spring.mode.ApiKeys.OPENAI_API_KEY;
+import static org.assertj.core.api.Assertions.assertThat;
+
+class AiServiceWithStructuredOutputIT {
+
+    ApplicationContextRunner contextRunner = new ApplicationContextRunner()
+            .withConfiguration(AutoConfigurations.of(AiServicesAutoConfig.class));
+
+    @Test
+    void should_create_AI_service_with_structured_output() {
+        contextRunner
+                .withPropertyValues(
+                        "langchain4j.open-ai.chat-model.api-key=" + OPENAI_API_KEY,
+                        "langchain4j.open-ai.chat-model.model-name=gpt-4o-mini",
+                        "langchain4j.open-ai.chat-model.supported-capabilities=[RESPONSE_FORMAT_JSON_SCHEMA]",
+                        "langchain4j.open-ai.chat-model.strict-schema=true",
+                        "langchain4j.open-ai.chat-model.temperature=0.0"
+                )
+                .withUserConfiguration(AiServiceWithStructuredOutputApplication.class)
+                .run(context -> {
+
+                    // given
+                    AiServiceWithStructuredOutput aiService = context.getBean(AiServiceWithStructuredOutput.class);
+
+                    // when
+                    Person person = aiService.extractPersonFrom("Klaus is 42 years old");
+
+                    // then
+                    assertThat(person).isEqualTo(new Person("Klaus", 42));
+                });
+    }
+}

langchain4j-spring-boot-starter/src/test/java/dev/langchain4j/service/spring/mode/automatic/withStructuredOutput/Person.java

@@ -0,0 +1,4 @@
+package dev.langchain4j.service.spring.mode.automatic.withStructuredOutput;
+
+public record Person(String name, int age) {
+}