fix: [PromptRegistry] Register new File converter in resttemplate

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

@@ -0,0 +1,87 @@
+package com.sap.ai.sdk.prompt.registry;
+
+import java.io.File;
+import java.io.IOException;
+import java.io.InputStream;
+import java.io.OutputStream;
+import java.nio.file.Files;
+import javax.annotation.Nonnull;
+import org.springframework.http.HttpInputMessage;
+import org.springframework.http.HttpOutputMessage;
+import org.springframework.http.MediaType;
+import org.springframework.http.converter.AbstractHttpMessageConverter;
+import org.springframework.http.converter.HttpMessageConverter;
+import org.springframework.http.converter.HttpMessageNotReadableException;
+import org.springframework.http.converter.HttpMessageNotWritableException;
+import org.springframework.util.StreamUtils;
+
+/**
+ * A custom implementation {@link HttpMessageConverter} for Spring's RestTemplate to read and write
+ * {@link java.io.File} objects in {@code application/octet-stream} payloads.
+ *
+ * @see org.springframework.http.converter.AbstractHttpMessageConverter
+ */
+class FileHttpMessageConverter extends AbstractHttpMessageConverter<File> {
+
+  FileHttpMessageConverter() {
+    super(MediaType.APPLICATION_OCTET_STREAM);
+  }
+
+  /**
+   * Indicates whether this converter supports the given class.
+   *
+   * <p>This implementation supports only {@link File}.
+   *
+   * @param clazz the target class to check
+   * @return {@code true} if and only if {@code clazz} is {@link File}
+   */
+  @Override
+  protected boolean supports(@Nonnull final Class clazz) {
+    return File.class == clazz;
+  }
+
+  /**
+   * Reads the {@link HttpInputMessage} body into a new file in system's temporary directory.
+   *
+   * <p>The response body is streamed directly into this file without buffering the entire content
+   * in memory.
+   *
+   * <p>The caller is responsible for deleting the returned file.
+   *
+   * @param clazz the expected target class (always {@link File}
+   * @param inputMessage the HTTP message containing the response body
+   * @return a {@link File} containing the streamed response data
+   * @throws IOException if file creation or streaming fails
+   * @throws HttpMessageNotReadableException if the message cannot be read
+   */
+  @Nonnull
+  @Override
+  protected File readInternal(
+      @Nonnull final Class<? extends File> clazz, @Nonnull final HttpInputMessage inputMessage)
+      throws IOException, HttpMessageNotReadableException {
+    final var tempFile = File.createTempFile("tmp", ".bin");
+    try (OutputStream out = Files.newOutputStream(tempFile.toPath())) {
+      StreamUtils.copy(inputMessage.getBody(), out);
+    }
+    return tempFile;
+  }
+
+  /**
+   * Writes the contents of a {@link File} into the HTTP request body.
+   *
+   * <p>The file is streamed directly into the output message, avoiding unnecessary buffering.
+   *
+   * @param file the file whose contents should be written
+   * @param outputMessage the HTTP message whose body should be written to
+   * @throws IOException if reading the file or writing the body fails
+   * @throws HttpMessageNotWritableException if the message cannot be written
+   */
+  @Override
+  protected void writeInternal(
+      @Nonnull final File file, @Nonnull final HttpOutputMessage outputMessage)
+      throws IOException, HttpMessageNotWritableException {
+    try (InputStream in = Files.newInputStream(file.toPath())) {
+      StreamUtils.copy(in, outputMessage.getBody());
+    }
+  }
+}

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

@@ -65,7 +65,7 @@ private static ApiClient addMixin(@Nonnull final AiCoreService service) {
                             JacksonMixin.ResponseFormat.class)));
 
     rt.setRequestFactory(new BufferingClientHttpRequestFactory(httpRequestFactory));
-
+    rt.getMessageConverters().add(new FileHttpMessageConverter());
     return new ApiClient(rt).setBasePath(destination.asHttp().getUri().toString());
   }
 

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

@@ -0,0 +1,89 @@
+package com.sap.ai.sdk.prompt.registry;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+import java.io.ByteArrayInputStream;
+import java.io.ByteArrayOutputStream;
+import java.io.File;
+import java.io.IOException;
+import java.io.InputStream;
+import java.io.OutputStream;
+import java.nio.file.Files;
+import java.nio.file.Path;
+import javax.annotation.Nonnull;
+import jdk.jfr.Description;
+import org.junit.jupiter.api.Test;
+import org.junit.jupiter.api.io.TempDir;
+import org.springframework.http.HttpHeaders;
+import org.springframework.http.HttpInputMessage;
+import org.springframework.http.HttpOutputMessage;
+
+class FileHttpMessageConverterTest {
+
+  @Test
+  void testSupports() {
+    final var converter = new FileHttpMessageConverter();
+
+    assertThat(converter.supports(File.class)).isTrue();
+    assertThat(converter.supports(String.class)).isFalse();
+  }
+
+  @Test
+  @Description("Test conversion from HttpInputMessage to File")
+  void testReadInternal() throws IOException {
+    final var converter = new FileHttpMessageConverter();
+    final var messageContent = "Hello, World!".getBytes();
+
+    final var inputMessage =
+        new HttpInputMessage() {
+          @Nonnull
+          @Override
+          public InputStream getBody() {
+            return new ByteArrayInputStream(messageContent);
+          }
+
+          @Nonnull
+          @Override
+          public HttpHeaders getHeaders() {
+            return new HttpHeaders();
+          }
+        };
+
+    final var generatedFile = converter.readInternal(File.class, inputMessage);
+    try {
+      assertThat(generatedFile).exists().isFile();
+      assertThat(Files.readAllBytes(generatedFile.toPath())).isEqualTo(messageContent);
+    } finally {
+      Files.deleteIfExists(generatedFile.toPath());
+    }
+  }
+
+  @Test
+  @Description("Test conversion from File to HttpOutputMessage")
+  void testWriteInternal(@TempDir final Path tempDir) throws IOException {
+    final var converter = new FileHttpMessageConverter();
+    final var fileContent = "Hello, World!".getBytes();
+    final var tempFilePath = tempDir.resolve("testFile.txt");
+    Files.write(tempFilePath, fileContent);
+
+    final var outputStream = new ByteArrayOutputStream();
+    final var outputMessage =
+        new HttpOutputMessage() {
+
+          @Nonnull
+          @Override
+          public HttpHeaders getHeaders() {
+            return new HttpHeaders();
+          }
+
+          @Nonnull
+          @Override
+          public OutputStream getBody() {
+            return outputStream;
+          }
+        };
+
+    converter.writeInternal(tempFilePath.toFile(), outputMessage);
+    assertThat(outputStream.toByteArray()).isEqualTo(fileContent);
+  }
+}

sample-code/spring-app/pom.xml

@@ -232,6 +232,11 @@
       <artifactId>assertj-core</artifactId>
       <scope>test</scope>
     </dependency>
+    <dependency>
+      <groupId>com.fasterxml.jackson.dataformat</groupId>
+      <artifactId>jackson-dataformat-yaml</artifactId>
+      <scope>test</scope>
+    </dependency>
   </dependencies>
 
   <build>

sample-code/spring-app/src/test/java/com/sap/ai/sdk/app/controllers/PromptRegistryTest.java

@@ -1,19 +1,27 @@
 package com.sap.ai.sdk.app.controllers;
 
+import static java.nio.charset.StandardCharsets.UTF_8;
 import static org.assertj.core.api.Assertions.assertThat;
 
+import com.fasterxml.jackson.databind.JsonNode;
+import com.fasterxml.jackson.databind.ObjectMapper;
+import com.fasterxml.jackson.dataformat.yaml.YAMLFactory;
 import com.sap.ai.sdk.prompt.registry.model.PromptTemplate;
 import com.sap.ai.sdk.prompt.registry.model.PromptTemplateDeleteResponse;
 import com.sap.ai.sdk.prompt.registry.model.PromptTemplateListResponse;
 import com.sap.ai.sdk.prompt.registry.model.PromptTemplatePostResponse;
 import com.sap.ai.sdk.prompt.registry.model.PromptTemplateSubstitutionResponse;
 import com.sap.ai.sdk.prompt.registry.model.SingleChatTemplate;
 import java.io.IOException;
+import java.nio.file.Files;
 import java.util.List;
 import org.junit.jupiter.api.Test;
+import org.springframework.core.io.ClassPathResource;
 
 public class PromptRegistryTest {
 
+  static final ObjectMapper YAML_MAPPER = new ObjectMapper(new YAMLFactory());
+
   @Test
   void listTemplates() {
     var controller = new PromptRegistryController();
@@ -56,7 +64,13 @@ void importExportTemplate() throws IOException {
     PromptTemplatePostResponse template = controller.importTemplate();
     assertThat(template.getMessage()).contains("successful");
 
-    // export TODO: NOT WORKING
+    // export
+    final var exportedTemplate = controller.exportTemplate();
+
+    final var resource = new ClassPathResource("prompt-template.yaml");
+    final JsonNode expectedYaml = YAML_MAPPER.readTree(resource.getContentAsString(UTF_8));
+    assertThat(YAML_MAPPER.readTree(exportedTemplate)).isEqualTo(expectedYaml);
+    Files.deleteIfExists(exportedTemplate.toPath());
 
     // cleanup
     List<PromptTemplateDeleteResponse> deletedTemplate = controller.deleteTemplate();