fix: fix some bugs and add docs

Author: loupipalien

docs/en/transforms/embedding.md

@@ -105,6 +105,57 @@ vectorization_fields {
 }
 ```
 
+**Multi-field Mixing Multimodal Vectorization:**
+```hocon
+vectorization_fields {
+    # Multi-field text
+    multi_field_text_vector = [product_name, description]
+    
+    # Multi-field image
+    multi_field_image_vector = [
+      {
+        field = product_image_url
+        modality = jpeg
+        format = url
+      },
+      {
+        field = thumbnail_image
+        modality = png
+        format = url
+      }
+    ]
+
+    # Multi-field video
+    multi_field_video_vector = [
+      {
+        field = product_video_url
+        modality = mp4
+        format = url
+      },
+      {
+        field = promotional_video
+        modality = mov
+        format = url
+      }
+    ]
+
+    # Multi-field mix multimodal
+    multi_field_mix_vector = [
+      product_name,
+      {
+        field = product_image_url
+        modality = jpeg
+        format = url
+      },
+      {
+        field = product_video_url
+        modality = mp4
+        format = url
+      }
+    ]
+}
+```
+
 **Field Specification Formats:**
 
 **Supported Modality Types:**

docs/zh/transforms/embedding.md

@@ -98,6 +98,57 @@ vectorization_fields {
 }
 ```
 
+**多字段混合多模态向量化：**
+```hocon
+vectorization_fields {
+    # 多字段文本
+    multi_field_text_vector = [product_name, description]
+
+    # 多字段图片
+    multi_field_image_vector = [
+      {
+        field = product_image_url
+        modality = jpeg
+        format = url
+      },
+      {
+        field = thumbnail_image
+        modality = png
+        format = url
+      }
+    ]
+
+    # 多字段视频
+    multi_field_video_vector = [
+      {
+        field = product_video_url
+        modality = mp4
+        format = url
+      },
+      {
+        field = promotional_video
+        modality = mov
+        format = url
+      }
+    ]
+
+    # 多字段混合多模态
+    multi_field_mix_vector = [
+      product_name,
+      {
+        field = product_image_url
+        modality = jpeg
+        format = url
+      },
+      {
+        field = product_video_url
+        modality = mp4
+        format = url
+      }
+    ]
+}
+```
+
 **字段规范格式：**
 
 **支持的模态类型：**

seatunnel-transforms-v2/src/main/java/org/apache/seatunnel/transform/nlpmodel/embedding/EmbeddingTransform.java

@@ -51,7 +51,7 @@
 import java.net.URISyntaxException;
 import java.nio.ByteBuffer;
 import java.util.ArrayList;
-import java.util.HashMap;
+import java.util.LinkedHashMap;
 import java.util.List;
 import java.util.Map;
 import java.util.Set;
@@ -204,7 +204,7 @@ private void initOutputFields(SeaTunnelRowType inputRowType, ReadonlyConfig conf
         }
 
         List<String> fieldNames = new ArrayList<>();
-        Map<VectorFieldSpec, List<Integer>> fieldSpecMap = new HashMap<>();
+        Map<VectorFieldSpec, List<Integer>> fieldSpecMap = new LinkedHashMap<>();
         for (Map.Entry<String, Object> fieldConfig : fieldsConfig.entrySet()) {
             VectorFieldSpec vectorFieldSpec = new VectorFieldSpec(fieldConfig);
             log.info("Vector field spec: {}", vectorFieldSpec);

seatunnel-transforms-v2/src/main/java/org/apache/seatunnel/transform/nlpmodel/embedding/SrcField.java

@@ -43,6 +43,10 @@ public String toBase64() {
         if (fieldValue == null) {
             throw new IllegalArgumentException("Binary data cannot be null or empty");
         }
-        return Base64.getEncoder().encodeToString(fieldValue.toString().getBytes());
+        if (fieldValue instanceof byte[]) {
+            return Base64.getEncoder().encodeToString((byte[]) fieldValue);
+        } else {
+            return Base64.getEncoder().encodeToString(fieldValue.toString().getBytes());
+        }
     }
 }

seatunnel-transforms-v2/src/test/java/org/apache/seatunnel/transform/embedding/DoubaoMultimodalModelTest.java

@@ -32,6 +32,7 @@
 
 import java.io.IOException;
 import java.util.Arrays;
+import java.util.Base64;
 import java.util.Collections;
 import java.util.HashMap;
 import java.util.List;
@@ -218,6 +219,12 @@ void testMultimodalBodyWithBinaryImage() {
         ObjectNode inputNode = (ObjectNode) result.get("input").get(0);
         Assertions.assertEquals("image_url", inputNode.get("type").asText());
         Assertions.assertTrue(inputNode.has("image_url"));
+        Assertions.assertTrue(
+                inputNode
+                        .get("image_url")
+                        .get("url")
+                        .asText()
+                        .endsWith(Base64.getEncoder().encodeToString(mockImageData)));
     }
 
     /**