如何将Blob从db转换为列表 <Object> 在java中

Question

All I'm trying to do is to convert my java List to BLOB and vice-versa. I have successfully done the first part where I have converted my List and stored it as BLOB in DB. However, I'm to get the BLOB but unable to convert it back to List. I have tried searching at many places but not able to figure out a way to solve this problem I'm facing. Hope I'll get a solution here.

Converting the List and storing it as BLOB in DB:

List<CustomerDTO> customersList = new ArrayList<CustomerDTO>();
.
.
some code to store the data in to List<CustomerDTO>
.
.

ByteArrayOutputStream baos = new ByteArrayOutputStream();
ObjectOutputStream oos = new ObjectOutputStream(baos);
oos.writeObject(customersList);
byte[] bytes = baos.toByteArray();

// set parameters  
    pstmt.setBinaryStream(1, new ByteArrayInputStream(bytes));
    pstmt.executeUpdate();

Failed attempts of converting BLOB to List:

1)

Blob blob = rs.getBlob("CUSTOMERS_LIST");   
byte[] bdata = blob.getBytes(1, (int) blob.length());
ByteArrayInputStream bais = new ByteArrayInputStream(bdata);
ObjectInputStream ois = new ObjectInputStream(bais);

List<CustomerDTO> list = (ArrayList<CustomerDTO>) ois.readObject();

This attempt has given me empty list

2)

Stream<T> stream = (Stream<T>) rs.getBinaryStream("CUSTOMERS_LIST");
List<CustomerDTO> list = (List<CustomerDTO>) stream.collect(Collectors.toList());

This attempt thrown me error java.lang.ClassCastException: java.io.ByteArrayInputStream cannot be cast to java.util.stream.Stream

3)

IntStream bais = (IntStream) rs.getBinaryStream("CUSTOMERS_LIST");
Stream<Integer> stream = (Stream<Integer>) bais.boxed().collect(Collectors.toList());
List<Integer> ll = (List<Integer>)stream.collect(Collectors.toList());

I'm lost here as I don't get how to convert List<Integer> to List<CustomerDTO>

Looking forward for your help.. TIA!

Answer 1

I have modified your first attempt slightly as follows:

Blob blob = rs.getBlob("CUSTOMERS_LIST");   
byte[] bdata = blob.getBytes(1, (int) blob.length());
ArrayList<Object> arraylist = new ArrayList<>();
for(byte b : bdata) {
    arraylist.add(new Byte(b));
}