Hi Martin,
sorry for the long delay. However, you should use the user's list for
questions.
Martin Renner wrote:
> Hi,
>
> I have to export lots of objects from a database into a XML file. These
> objects contain large BLOBs, so I started to implement a "BlobConverter".
> As the BLOBs are very large, I cannot use the following approach:
>
> public void marshal(Object source, HierarchicalStreamWriter writer,
> MarshallingContext context) {
> Blob blob = (Blob) source;
> context.convertAnother(blob.getBytes(1, (int) blob.length()));
>
> This would read the whole BLOB into a byte array and delegate to
> EncodedByteArrayConverter, which in turn would write a base64 encoded
> string. This creates two arrays in the heap (the byte array and the char
> array with the base64 encoded data), which are way too large to fit into
> the available heap space.
>
> So I am looking for a solution which would allow to stream the binary data
> into a streaming base64 encoder and to stream that into the output stream.
> However, I could not find any method in HierarchicalStreamWriter which
> would allow to stream character data. There is just "void setValue(String
> text)", which requires the whole data to be in the heap.
>
> Is it possible to stream character data to the output stream?
XStream has no direct support writing or reading an element's text with
streams (XSTR-532). However, although outside of the XStream specification,
it should be possible to call setValue multiple times for stream-based XML
drivers. Therefore you could use a Base64 stream (e.g. from Apache commons-
codec) to write chunks into a buffer and write that one with setValue before
continuing with the next chunk.
- Jörg
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