pdf转换base64流字符串

public void writePdfToImage(Manifest manifest, HttpServletResponse response) {
if(manifest==null){
System.out.println("用户信息不存在");
return ;
}
byte[] pdfByte=manifest.getPdfDone();
if (pdfByte == null) {
System.out.println("pdfdone is null ");
return ;
}
PDDocument pdDocument=null;
PDFRenderer renderer =null;
PdfReader reader =null;
OutputStream os=null;
try {
pdDocument = PDDocument.load(pdfByte);
renderer=new PDFRenderer(pdDocument);
reader = new PdfReader(pdfByte);
int pageNum = reader.getNumberOfPages();
os=response.getOutputStream();
for (int j = 0; j < pageNum; j++) {
BufferedImage image = renderer.renderImageWithDPI(j, 100);
ImageIO.write(image, "png", os);
os.flush();
os.write(j);
os.close();
}
} catch (Exception e) {
e.printStackTrace();
logger.info(e.getMessage(), e);
}finally{
try{
if(os!=null){
os.close();
}
if(reader!=null){
reader.close();
}
if(pdDocument!=null){
pdDocument.close();
}
}catch (Exception e) {
e.printStackTrace();
}
}
}