itext PDF 分页 并 解决PdfReader not opened with owner password

package com.xiuye.util;

import java.io.BufferedOutputStream;
import java.io.IOException;

import javax.servlet.http.HttpServletResponse;

import com.itextpdf.text.Document;
import com.itextpdf.text.DocumentException;
import com.itextpdf.text.pdf.PdfCopy;
import com.itextpdf.text.pdf.PdfImportedPage;
import com.itextpdf.text.pdf.PdfReader;
import com.xiuye.logger.Logger;

public class PdfOutputCustomPagesUtil {

private static Logger log = Logger
.getLogger(PdfOutputCustomPagesUtil.class);

/**
* split pdf for my bookstore
*
* @param pdfFilename
* @param startPage
*            not equal 0 since 1
* @param os
*/
public static void partOfPdfOutputPages(String pdfFilename, int startPage,
HttpServletResponse response) {
int expectEndPage = 0;
Document doc = null;
PdfCopy pdfCopy = null;

PdfReader reader = null;
try {
reader = new PdfReader(pdfFilename);

/**
* 解决Exception in thread "main" java.lang.IllegalArgumentException:
* PdfReader not opened with owner password
*
*
*/
java.lang.reflect.Field f = reader.getClass().getDeclaredField(
"encrypted");
f.setAccessible(true);
f.set(reader, false);

int totalPages = reader.getNumberOfPages();
log.info("文档总页数:" + totalPages + "页");
if (totalPages == 0) {
return;
} else if (totalPages > 0 && totalPages < 10) {
expectEndPage = totalPages;
} else if (totalPages >= 10 && totalPages <= 50) {
expectEndPage = totalPages / 10;
} else {
expectEndPage = 50;
}
log.info("需要传送多少页:" + expectEndPage + "页");

doc = new Document(reader.getPageSize(1));
BufferedOutputStream bos = new BufferedOutputStream(
response.getOutputStream());
pdfCopy = new PdfCopy(doc, bos);

doc.open();
pdfCopy.open();
for (int i = startPage; i <= expectEndPage; i++) {

doc.newPage();
PdfImportedPage page = pdfCopy.getImportedPage(reader, i);
pdfCopy.addPage(page);
pdfCopy.flush();

}

} catch (IOException e) {
e.printStackTrace();
} catch (DocumentException e) {
e.printStackTrace();
} catch (IllegalArgumentException e) {
e.printStackTrace();
} catch (IllegalAccessException e) {
e.printStackTrace();
} catch (NoSuchFieldException e) {
e.printStackTrace();
} catch (SecurityException e) {
e.printStackTrace();
} finally {
if (doc != null && doc.isOpen()) {

doc.close();
doc = null;
}
if (pdfCopy != null) {
pdfCopy.close();
pdfCopy = null;
}
if (reader != null) {
reader.close();
reader = null;
}
}

}

}