Polish support for sending Statements with Attachments

xapi-client/src/main/java/dev/learning/xapi/client/AttachmentHttpMessageWriter.java

@@ -0,0 +1,66 @@
+/*
+ * Copyright 2016-2023 Berry Cloud Ltd. All rights reserved.
+ */
+
+package dev.learning.xapi.client;
+
+import dev.learning.xapi.model.Attachment;
+import java.util.List;
+import java.util.Map;
+import org.reactivestreams.Publisher;
+import org.springframework.core.ResolvableType;
+import org.springframework.core.io.buffer.DataBuffer;
+import org.springframework.core.io.buffer.DataBufferFactory;
+import org.springframework.core.io.buffer.DataBufferUtils;
+import org.springframework.http.MediaType;
+import org.springframework.http.ReactiveHttpOutputMessage;
+import org.springframework.http.codec.HttpMessageWriter;
+import org.springframework.http.codec.multipart.MultipartWriterSupport;
+import org.springframework.lang.Nullable;
+import reactor.core.publisher.Mono;
+
+/**
+ * {@link HttpMessageWriter} for writing {@link Attachment} data into multipart/mixed requests.
+ *
+ * @author István Rátkai (Selindek)
+ */
+public class AttachmentHttpMessageWriter extends MultipartWriterSupport
+    implements HttpMessageWriter<Attachment> {
+
+  public AttachmentHttpMessageWriter() {
+    super(List.of(MediaType.MULTIPART_MIXED));
+  }
+
+  @Override
+  public boolean canWrite(ResolvableType elementType, @Nullable MediaType mediaType) {
+    return Attachment.class.isAssignableFrom(elementType.toClass());
+  }
+
+  @Override
+  public Mono<Void> write(Publisher<? extends Attachment> parts, ResolvableType elementType,
+      @Nullable MediaType mediaType, ReactiveHttpOutputMessage outputMessage,
+      Map<String, Object> hints) {
+
+    return Mono.from(parts).flatMap(part -> {
+      // set attachment part headers
+      outputMessage.getHeaders().setContentType(MediaType.valueOf(part.getContentType()));
+      outputMessage.getHeaders().set("Content-Transfer-Encoding", "binary");
+      outputMessage.getHeaders().set("X-Experience-API-Hash", part.getSha2());
+
+      // write attachment content
+      return outputMessage.writeWith(encodePart(part, outputMessage.bufferFactory()));
+    }).doOnDiscard(DataBuffer.class, DataBufferUtils::release);
+
+  }
+
+  private Mono<DataBuffer> encodePart(Attachment part, DataBufferFactory bufferFactory) {
+
+    return Mono.fromCallable(() -> {
+      final var buffer = bufferFactory.allocateBuffer(part.getContent().length);
+      buffer.write(part.getContent());
+      return buffer;
+    });
+
+  }
+
+}