[GitHub] [arrow] Oooorchid opened a new issue, #13698: [Java][C++] Java VectorSchemaRoot to C++ RecordBatchreader

[GitBox <gi...@apache.org>]

Oooorchid opened a new issue, #13698:
URL: https://github.com/apache/arrow/issues/13698

   I have a Java library that is writing an Arrow Table to a VectorSchemaRoot object in memory.  And I want read the data with C++. But it keeps getting an error, what should I do?
   
   From the docs I only find C++ to Java,  not Java to C++ [docs](https://arrow.apache.org/docs/java/cdata.html)
   
   Here is my example:
   [Java]
   `
   public String rootToString(){
       try(
           BufferAllocator allcator = new RootAllocator();
           FileInputStream fileInputStream = new FileInputStream(filepath);
           ArrowFileReader reader = new ArrowFileReader(fileInputStream.getChannel(), allcator);
           ByteArrayOutputStream out = new ByteArrayOutputStream();
        ){
           System.out.println("Record batches in file : " + reader.getRecordBlocks().size());           // Actually size =  1
           ArrowBlock arrowBlock = reader.getRecordBlocks().get(0);
           VectorSchemaRoot root = reader.getVectorSchemaRoot();
           reader.loadRecordBatch(arrowBlock);
           System.out.println(root.contentToTSVString());
      
           ArrowFileWriter writer = new ArrowFileWriter(root, null, Channels.newChannel(out));
           writer.start();
           writer.writeBatch();
           writer.end();
           writer.close();
   
           return out.toString();
   }
   }
   `
   
   
   [C++]
   `
   ....
   std::String JStringToString(JNIEnv* env, jstring string){
       if(string == nullptr){
           return std::string();
       }
       const char* chars = env->GetStringUTFChars(string, nullptr);
       std::string ret(chars);
       env->ReleaseStringUTFChars(string, chars);
       return ret;
   }
   
   std::string test(std::string name){
       if (status != JNI_ERR){
           jclass cls = env->FindClass("com/xxxxx");
           jmethodID mid = env->GetMethodID(cls, "<init>", "(Ljava/lang/String;)V");
           jstring arg = NewJString(name.c_str());
           jobject obj = env->NewObject(cls, mid, arg);
           mid = env->GetMethodID(cls, "rootToString", "()Ljava/lang/String;");
          
           jstring ret = *(jstring)env->CallObjectMethod(test, mid);
           std::cout << "Java String length is : " << env->GetStringLength(ret) << std::endl;         // length is 2563
           std::string result = JStringToCString(env, ret);
           std::cout << "result length is : " << result.length() << std::endl;    // length is 4609
           return result;
           }
   }
   
   
   int main(){
       std::string test_result = test("/data/...../4stock_5day.arrow");
       std::shared_ptr<arrow::io::BufferReader> bufferReader = std::make_shared<arrow::io::BufferReader>(test_result);
       std::shared_ptr<arrow::ipc::RecordBatchFileReader> reader = arrow::ipc::RecordBatchFileReader::Open(bufferReader.get()).ValueOrDie();
       std::cout << reader -> num_record_batches() << std::endl;
       return 0;
   }
   `
   
   The error is as follow：
   `xxxxxxxxxxx/work/cpp/src/arrow/result.cc:28 : ValueOrDie called on an error : Invalid: File is smaller than indicated metadata size
   /usr/local/conda3/lib/libarrow.so.500(+0x518f0c)[0x7f44fc2d3f0c]
   /usr/local/conda3/lib/libarrow.so.500(_ZN)
   ...
   `
   
   what should I do? Is there any other way ?    Thanks
   
   


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[GitHub] [arrow] Oooorchid closed issue #13698: [Java][C++] Java VectorSchemaRoot to C++ RecordBatchreader

[GitBox <gi...@apache.org>]

Oooorchid closed issue #13698: [Java][C++] Java VectorSchemaRoot to C++ RecordBatchreader
URL: https://github.com/apache/arrow/issues/13698


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[GitHub] [arrow] Oooorchid closed issue #13698: [Java][C++] Java VectorSchemaRoot to C++ RecordBatchreader

[GitBox <gi...@apache.org>]

Oooorchid closed issue #13698: [Java][C++] Java VectorSchemaRoot to C++ RecordBatchreader
URL: https://github.com/apache/arrow/issues/13698


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