fix: [PromptRegistry] oneOf deserialization for proper support of both template types

core-services/prompt-registry/pom.xml

@@ -38,11 +38,11 @@
   </scm>
   <properties>
     <project.rootdir>${project.basedir}/../../</project.rootdir>
-    <coverage.complexity>84%</coverage.complexity>
-    <coverage.line>90%</coverage.line>
-    <coverage.instruction>92%</coverage.instruction>
+    <coverage.complexity>92%</coverage.complexity>
+    <coverage.line>94%</coverage.line>
+    <coverage.instruction>95%</coverage.instruction>
     <coverage.branch>100%</coverage.branch>
-    <coverage.method>80%</coverage.method>
+    <coverage.method>85%</coverage.method>
     <coverage.class>100%</coverage.class>
   </properties>
 
@@ -85,6 +85,10 @@
       <groupId>com.fasterxml.jackson.core</groupId>
       <artifactId>jackson-databind</artifactId>
     </dependency>
+    <dependency>
+      <groupId>com.fasterxml.jackson.core</groupId>
+      <artifactId>jackson-core</artifactId>
+    </dependency>
     <dependency>
       <groupId>com.google.guava</groupId>
       <artifactId>guava</artifactId>

core-services/prompt-registry/src/main/java/com/sap/ai/sdk/prompt/registry/PromptClient.java

@@ -4,10 +4,17 @@
 
 import com.fasterxml.jackson.annotation.JsonSubTypes;
 import com.fasterxml.jackson.annotation.JsonTypeInfo;
+import com.fasterxml.jackson.core.JsonParser;
+import com.fasterxml.jackson.databind.DeserializationContext;
+import com.fasterxml.jackson.databind.JsonDeserializer;
+import com.fasterxml.jackson.databind.JsonMappingException;
+import com.fasterxml.jackson.databind.JsonNode;
 import com.fasterxml.jackson.databind.annotation.JsonDeserialize;
 import com.google.common.collect.Iterables;
 import com.sap.ai.sdk.core.AiCoreService;
 import com.sap.ai.sdk.prompt.registry.client.PromptTemplatesApi;
+import com.sap.ai.sdk.prompt.registry.model.MultiChatContent;
+import com.sap.ai.sdk.prompt.registry.model.MultiChatTemplate;
 import com.sap.ai.sdk.prompt.registry.model.PromptTemplate;
 import com.sap.ai.sdk.prompt.registry.model.PromptTemplateSpecResponseFormat;
 import com.sap.ai.sdk.prompt.registry.model.ResponseFormatJsonObject;
@@ -16,6 +23,8 @@
 import com.sap.ai.sdk.prompt.registry.model.SingleChatTemplate;
 import com.sap.cloud.sdk.cloudplatform.connectivity.ApacheHttpClient5Accessor;
 import com.sap.cloud.sdk.services.openapi.apiclient.ApiClient;
+import java.io.IOException;
+import java.util.ArrayList;
 import javax.annotation.Nonnull;
 import lombok.AccessLevel;
 import lombok.NoArgsConstructor;
@@ -75,7 +84,7 @@ private static ApiClient addMixin(@Nonnull final AiCoreService service) {
   @NoArgsConstructor(access = AccessLevel.PRIVATE)
   private static class JacksonMixin {
     @JsonTypeInfo(use = JsonTypeInfo.Id.NONE)
-    @JsonDeserialize(as = SingleChatTemplate.class)
+    @JsonDeserialize(using = PromptTemplateDeserializer.class)
     interface TemplateMixIn {}
 
     @JsonTypeInfo(
@@ -90,4 +99,40 @@ interface TemplateMixIn {}
     })
     interface ResponseFormat {}
   }
+
+  private static class PromptTemplateDeserializer extends JsonDeserializer<PromptTemplate> {
+
+    @Override
+    public PromptTemplate deserialize(
+        @Nonnull final JsonParser jsonParser,
+        @Nonnull final DeserializationContext deserializationContext)
+        throws IOException {
+
+      final JsonNode root = jsonParser.readValueAsTree();
+      final JsonNode roleNode = root.path("role");
+      final String role = roleNode.asText();
+      final JsonNode content = root.path("content");
+
+      if (!roleNode.isTextual()) {
+        throw JsonMappingException.from(
+            jsonParser, "PromptTemplate requires textual 'role' property.");
+      }
+
+      if (content.isTextual()) {
+        return SingleChatTemplate.create().role(role).content(content.asText());
+      }
+      if (content.isArray()) {
+        final var contentList = new ArrayList<MultiChatContent>();
+        for (final JsonNode item : content) {
+          contentList.add(jsonParser.getCodec().treeToValue(item, MultiChatContent.class));
+        }
+        return MultiChatTemplate.create().role(role).content(contentList);
+      }
+
+      throw JsonMappingException.from(
+          jsonParser,
+          "PromptTemplate content must be either a string or an array, but found: "
+              + content.getNodeType());
+    }
+  }
 }

core-services/prompt-registry/src/main/java/com/sap/ai/sdk/prompt/registry/spring/SpringAiConverter.java

@@ -1,9 +1,13 @@
 package com.sap.ai.sdk.prompt.registry.spring;
 
+import com.sap.ai.sdk.prompt.registry.model.ImageContent;
+import com.sap.ai.sdk.prompt.registry.model.MultiChatTemplate;
 import com.sap.ai.sdk.prompt.registry.model.PromptTemplate;
 import com.sap.ai.sdk.prompt.registry.model.PromptTemplateSubstitutionResponse;
 import com.sap.ai.sdk.prompt.registry.model.SingleChatTemplate;
+import com.sap.ai.sdk.prompt.registry.model.TextContent;
 import java.util.List;
+import java.util.stream.Collectors;
 import javax.annotation.Nonnull;
 import lombok.val;
 import org.springframework.ai.chat.messages.AssistantMessage;
@@ -34,17 +38,44 @@ public static List<Message> promptTemplateToMessages(
     // TRANSFORM TEMPLATE TO SPRING AI MESSAGES
     return res.stream()
         .map(
-            (PromptTemplate t) -> {
-              final SingleChatTemplate message = (SingleChatTemplate) t;
-              return (Message)
-                  switch (message.getRole()) {
-                    case "system" -> new SystemMessage(message.getContent());
-                    case "user" -> new UserMessage(message.getContent());
-                    case "assistant" -> new AssistantMessage(message.getContent());
-                    default ->
-                        throw new IllegalArgumentException("Unknown role: " + message.getRole());
-                  };
+            (PromptTemplate template) -> {
+              if (template instanceof SingleChatTemplate message) {
+                return fromRole(message.getRole(), message.getContent());
+              }
+              if (template instanceof MultiChatTemplate message) {
+                return fromRole(message.getRole(), getMultiTemplateTextContent(message));
+              }
+              throw new IllegalArgumentException(
+                  "Unsupported PromptTemplate type: " + template.getClass().getName());
             })
         .toList();
   }
+
+  @Nonnull
+  private static String getMultiTemplateTextContent(@Nonnull final MultiChatTemplate message) {
+    return message.getContent().stream()
+        .map(
+            item -> {
+              if (item instanceof TextContent textContent) {
+                return textContent.getText();
+              }
+              if (item instanceof ImageContent) {
+                throw new UnsupportedOperationException(
+                    "MultiChatTemplate with image content is not supported by SpringAiConverter yet.");
+              }
+              throw new UnsupportedOperationException(
+                  "Unsupported MultiChatContent type: " + item.getClass().getName());
+            })
+        .collect(Collectors.joining("\n"));
+  }
+
+  @Nonnull
+  private static Message fromRole(@Nonnull final String role, @Nonnull final String content) {
+    return switch (role) {
+      case "system" -> new SystemMessage(content);
+      case "user" -> new UserMessage(content);
+      case "assistant" -> new AssistantMessage(content);
+      default -> throw new IllegalArgumentException("Unknown role: " + role);
+    };
+  }
 }

core-services/prompt-registry/src/test/java/com/sap/ai/sdk/prompt/registry/PromptRegistryClientTest.java

@@ -2,15 +2,21 @@
 
 import static com.github.tomakehurst.wiremock.core.WireMockConfiguration.wireMockConfig;
 import static org.assertj.core.api.Assertions.assertThat;
+import static org.assertj.core.api.Assertions.assertThatThrownBy;
 
 import com.github.tomakehurst.wiremock.junit5.WireMockExtension;
 import com.sap.ai.sdk.core.AiCoreService;
+import com.sap.ai.sdk.prompt.registry.model.MultiChatTemplate;
 import com.sap.ai.sdk.prompt.registry.model.PromptTemplateGetResponse;
+import com.sap.ai.sdk.prompt.registry.model.PromptTemplateSubstitutionRequest;
 import com.sap.ai.sdk.prompt.registry.model.ResponseFormatJsonObject;
 import com.sap.ai.sdk.prompt.registry.model.ResponseFormatJsonSchema;
 import com.sap.ai.sdk.prompt.registry.model.ResponseFormatText;
+import com.sap.ai.sdk.prompt.registry.model.SingleChatTemplate;
+import com.sap.ai.sdk.prompt.registry.model.TextContent;
 import com.sap.cloud.sdk.cloudplatform.connectivity.DefaultHttpDestination;
 import com.sap.cloud.sdk.cloudplatform.connectivity.HttpDestination;
+import java.util.Map;
 import java.util.UUID;
 import org.junit.jupiter.api.BeforeEach;
 import org.junit.jupiter.api.Test;
@@ -95,4 +101,66 @@ void testGetTemplateWithResponseFormatJsonSchema() {
     assertThat(format.getJsonSchema().isStrict()).isFalse();
     assertThat(format.getJsonSchema().getSchema()).isNotNull();
   }
+
+  @Test
+  void testGetTemplateWithMultiChatTemplate() {
+    final var uuid = UUID.fromString("8f79fec4-ae07-4c35-96e3-df7f4a3f1df5");
+    final var response = client.getPromptTemplateByUuid(uuid);
+
+    assertThat(response.getSpec()).isNotNull();
+    assertThat(response.getSpec().getTemplate()).hasSize(2);
+    assertThat(response.getSpec().getTemplate().get(0)).isInstanceOf(SingleChatTemplate.class);
+    assertThat(response.getSpec().getTemplate().get(1)).isInstanceOf(MultiChatTemplate.class);
+
+    final var multiTemplate = (MultiChatTemplate) response.getSpec().getTemplate().get(1);
+    assertThat(multiTemplate.getRole()).isEqualTo("user");
+    assertThat(multiTemplate.getContent()).hasSize(2);
+    assertThat(multiTemplate.getContent().get(0)).isInstanceOf(TextContent.class);
+    assertThat(((TextContent) multiTemplate.getContent().get(0)).getText())
+        .isEqualTo("First content line");
+    assertThat(((TextContent) multiTemplate.getContent().get(1)).getText())
+        .isEqualTo("Second content line");
+  }
+
+  @Test
+  void testGetTemplateWithInvalidRoleType() {
+    final var uuid = UUID.fromString("45cb1358-0bf1-4f43-870b-00f14d0f9f16");
+
+    assertThatThrownBy(() -> client.getPromptTemplateByUuid(uuid))
+        .hasStackTraceContaining("PromptTemplate requires textual 'role' property.");
+  }
+
+  @Test
+  void testGetTemplateWithInvalidContentType() {
+    final var uuid = UUID.fromString("55cb1358-0bf1-4f43-870b-00f14d0f9f16");
+
+    assertThatThrownBy(() -> client.getPromptTemplateByUuid(uuid))
+        .hasStackTraceContaining(
+            "PromptTemplate content must be either a string or an array, but found: BOOLEAN");
+  }
+
+  @Test
+  void testParsePromptTemplateHotPath() {
+    final var request =
+        PromptTemplateSubstitutionRequest.create()
+            .inputParams(Map.of("inputExample", "I love football"));
+
+    final var response =
+        client.parsePromptTemplateByNameVersion(
+            "categorization", "0.0.1", "hotpath-serde", "default", null, false, request);
+
+    assertThat(response.getParsedPrompt()).hasSize(2);
+    assertThat(response.getParsedPrompt().get(0)).isInstanceOf(SingleChatTemplate.class);
+    assertThat(response.getParsedPrompt().get(1)).isInstanceOf(SingleChatTemplate.class);
+
+    final var systemTemplate = (SingleChatTemplate) response.getParsedPrompt().get(0);
+    assertThat(systemTemplate.getRole()).isEqualTo("system");
+    assertThat(systemTemplate.getContent())
+        .isEqualTo(
+            "You classify input text into the two following categories: Finance, Tech, Sports");
+
+    final var userTemplate = (SingleChatTemplate) response.getParsedPrompt().get(1);
+    assertThat(userTemplate.getRole()).isEqualTo("user");
+    assertThat(userTemplate.getContent()).isEqualTo("I love football");
+  }
 }

core-services/prompt-registry/src/test/java/com/sap/ai/sdk/prompt/registry/PromptTemplateSerdeUnitTest.java

@@ -0,0 +1 @@
+

core-services/prompt-registry/src/test/java/com/sap/ai/sdk/prompt/registry/spring/SpringAiConverterTest.java

@@ -7,7 +7,11 @@
 import com.github.tomakehurst.wiremock.junit5.WireMockExtension;
 import com.sap.ai.sdk.core.AiCoreService;
 import com.sap.ai.sdk.prompt.registry.PromptClient;
+import com.sap.ai.sdk.prompt.registry.model.MultiChatContent;
+import com.sap.ai.sdk.prompt.registry.model.MultiChatTemplate;
+import com.sap.ai.sdk.prompt.registry.model.PromptTemplate;
 import com.sap.ai.sdk.prompt.registry.model.PromptTemplateSubstitutionRequest;
+import com.sap.ai.sdk.prompt.registry.model.PromptTemplateSubstitutionResponse;
 import com.sap.cloud.sdk.cloudplatform.connectivity.DefaultHttpDestination;
 import com.sap.cloud.sdk.cloudplatform.connectivity.HttpDestination;
 import java.util.List;
@@ -68,4 +72,65 @@ void testInvalidRoleThrowsException() {
         .isInstanceOf(IllegalArgumentException.class)
         .hasMessageContaining("Unknown role: error");
   }
+
+  @Test
+  void testMultiChatTemplateTextContentToSpringAi() {
+    var client = new PromptClient(SERVICE);
+    val promptResponse =
+        client.parsePromptTemplateByNameVersion(
+            "categorization",
+            "0.0.1",
+            "multi-text",
+            "default",
+            null,
+            false,
+            PromptTemplateSubstitutionRequest.create()
+                .inputParams(Map.of("inputExample", "I love football")));
+
+    List<Message> messages = SpringAiConverter.promptTemplateToMessages(promptResponse);
+    assertThat(messages)
+        .isEqualTo(List.of(new UserMessage("First content line\nSecond content line")));
+  }
+
+  @Test
+  void testMultiChatTemplateImageContentThrowsException() {
+    var client = new PromptClient(SERVICE);
+    val promptResponse =
+        client.parsePromptTemplateByNameVersion(
+            "categorization",
+            "0.0.1",
+            "multi-image",
+            "default",
+            null,
+            false,
+            PromptTemplateSubstitutionRequest.create()
+                .inputParams(Map.of("inputExample", "I love football")));
+
+    assertThatThrownBy(() -> SpringAiConverter.promptTemplateToMessages(promptResponse))
+        .isInstanceOf(UnsupportedOperationException.class)
+        .hasMessageContaining("image content is not supported");
+  }
+
+  @Test
+  void testUnsupportedPromptTemplateTypeThrowsException() {
+    final PromptTemplate unsupportedTemplate = new PromptTemplate() {};
+    final var promptResponse =
+        PromptTemplateSubstitutionResponse.create().parsedPrompt(List.of(unsupportedTemplate));
+
+    assertThatThrownBy(() -> SpringAiConverter.promptTemplateToMessages(promptResponse))
+        .isInstanceOf(IllegalArgumentException.class)
+        .hasMessageContaining("Unsupported PromptTemplate type");
+  }
+
+  @Test
+  void testUnsupportedMultiChatContentTypeThrowsException() {
+    final MultiChatContent unsupportedContent = new MultiChatContent() {};
+    final var message = MultiChatTemplate.create().role("user").content(unsupportedContent);
+    final var promptResponse =
+        PromptTemplateSubstitutionResponse.create().parsedPrompt(List.of(message));
+
+    assertThatThrownBy(() -> SpringAiConverter.promptTemplateToMessages(promptResponse))
+        .isInstanceOf(UnsupportedOperationException.class)
+        .hasMessageContaining("Unsupported MultiChatContent type");
+  }
 }

core-services/prompt-registry/src/test/resources/mappings/templateWithInvalidContentType.json

@@ -0,0 +1,30 @@
+{
+  "request": {
+    "method": "GET",
+    "url": "/v2/lm/promptTemplates/55cb1358-0bf1-4f43-870b-00f14d0f9f16"
+  },
+  "response": {
+    "status": 200,
+    "headers": {
+      "Content-Type": "application/json"
+    },
+    "jsonBody": {
+      "id": "55cb1358-0bf1-4f43-870b-00f14d0f9f16",
+      "name": "invalid-content",
+      "version": "0.0.1",
+      "scenario": "test-retrival",
+      "creationTimestamp": "2025-12-02T16:06:05.400000",
+      "managedBy": "imperative",
+      "isVersionHead": true,
+      "spec": {
+        "template": [
+          {
+            "role": "user",
+            "content": true
+          }
+        ],
+        "tools": []
+      }
+    }
+  }
+}