core/src/main/java/org/sakaiproject/nakamura/lite/storage/spi/types/Types.java
public static InputStream storeMapToStream(String key, Map<String, Object> m, String type)
            throws IOException {
        ByteArrayOutputStream baos = new ByteArrayOutputStream();
        DataOutputStream dos = new DataOutputStream(baos);
        dos.writeUTF(key);
        writeMapToStream(m, dos);
        // add the type in
        dos.writeUTF(type);
        dos.flush();
        baos.flush();
        byte[] b = baos.toByteArray();
        baos.close();
        dos.close();
        return new ByteArrayInputStream(b);
    }
public static InputStream storeMapToStream(String key, Map<String, Object> m, String type)
            throws IOException {
        ByteArrayOutputStream baos = new ByteArrayOutputStream();
        DataOutputStream dos = new DataOutputStream(baos);
        dos.writeUTF(key);
        writeMapToStream(m, dos);
        // add the type in
        dos.writeUTF(type);
        dos.flush();
        baos.flush();
        byte[] b = baos.toByteArray();
        baos.close();
        dos.close();
        return new ByteArrayInputStream(b);
    }
the data isnt there. See the last writeUTF for an example.