java.io.IOException : The document has no pages

Question

我正在尝试创建一个名为“Hello World”的 PDF 并收到错误java.io.IOException:文档没有页面。

这是我的 servlet 的代码:

package org.ritesh;

import java.io.ByteArrayOutputStream;
import java.io.IOException;

import javax.servlet.ServletOutputStream;
import javax.servlet.http.*;

import com.lowagie.text.Document;
import com.lowagie.text.DocumentException;
import com.lowagie.text.Paragraph;
import com.lowagie.text.pdf.PdfWriter;

@SuppressWarnings("serial")
public class PdfmakeServlet extends HttpServlet {
    public void doGet(HttpServletRequest req, HttpServletResponse resp)
            throws IOException {
        resp.setContentType("application/pdf");


        Document document =new Document();
            ByteArrayOutputStream baos = new ByteArrayOutputStream();
            try {
                PdfWriter.getInstance(document, baos);
            } catch (DocumentException e) {
                // TODO Auto-generated catch block
                e.printStackTrace();
            }
            document.open();

                try {
                    document.add(new Paragraph("Hello WOrld "));
                } catch (DocumentException e) {
                    // TODO Auto-generated catch block
                    e.printStackTrace();
                }



            resp.setContentLength(baos.size());

            // write ByteArrayOutputStream to ServletOutputStream
            ServletOutputStream out = resp.getOutputStream();
            baos.writeTo(out);

            out.flush();
            out.close();
            document.close();
    }
}

这是一个 GAE 应用程序，所以我添加了一个兼容的 iText 库，但收到此错误

java.io.IOException: The document has no pages.
    at com.lowagie.text.pdf.PdfPages.writePageTree(Unknown Source)
    at com.lowagie.text.pdf.PdfWriter.close(Unknown Source)
    at com.lowagie.text.pdf.PdfDocument.close(Unknown Source)
    at com.lowagie.text.Document.close(Unknown Source)
    at org.ritesh.PdfmakeServlet.doGet(PdfmakeServlet.java:48)
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:617)
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:717)
    at org.mortbay.jetty.servlet.ServletHolder.handle(ServletHolder.java:511)
    at org.mortbay.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1166)
    at com.google.appengine.tools.development.HeaderVerificationFilter.doFilter(HeaderVerificationFilter.java:35)
    at org.mortbay.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1157)
    at com.google.appengine.api.blobstore.dev.ServeBlobFilter.doFilter(ServeBlobFilter.java:60)
    at org.mortbay.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1157)
    at com.google.apphosting.utils.servlet.TransactionCleanupFilter.doFilter(TransactionCleanupFilter.java:43)
    at org.mortbay.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1157)
    at com.google.appengine.tools.development.StaticFileFilter.doFilter(StaticFileFilter.java:122)
    at org.mortbay.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1157)
    at com.google.appengine.tools.development.BackendServersFilter.doFilter(BackendServersFilter.java:97)
    at org.mortbay.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1157)
    at org.mortbay.jetty.servlet.ServletHandler.handle(ServletHandler.java:388)
    at org.mortbay.jetty.security.SecurityHandler.handle(SecurityHandler.java:216)
    at org.mortbay.jetty.servlet.SessionHandler.handle(SessionHandler.java:182)
    at org.mortbay.jetty.handler.ContextHandler.handle(ContextHandler.java:765)
    at org.mortbay.jetty.webapp.WebAppContext.handle(WebAppContext.java:418)
    at com.google.appengine.tools.development.DevAppEngineWebAppContext.handle(DevAppEngineWebAppContext.java:78)
    at org.mortbay.jetty.handler.HandlerWrapper.handle(HandlerWrapper.java:152)
    at com.google.appengine.tools.development.JettyContainerService$ApiProxyHandler.handle(JettyContainerService.java:369)
    at org.mortbay.jetty.handler.HandlerWrapper.handle(HandlerWrapper.java:152)
    at org.mortbay.jetty.Server.handle(Server.java:326)
    at org.mortbay.jetty.HttpConnection.handleRequest(HttpConnection.java:542)
    at org.mortbay.jetty.HttpConnection$RequestHandler.headerComplete(HttpConnection.java:923)
    at org.mortbay.jetty.HttpParser.parseNext(HttpParser.java:547)
    at org.mortbay.jetty.HttpParser.parseAvailable(HttpParser.java:212)
    at org.mortbay.jetty.HttpConnection.handle(HttpConnection.java:404)
    at org.mortbay.io.nio.SelectChannelEndPoint.run(SelectChannelEndPoint.java:409)
    at org.mortbay.thread.QueuedThreadPool$PoolThread.run(QueuedThreadPool.java:582)

我是 iText 新手，有人可以帮助我如何消除此错误吗？

Answer 1

我建议仅在文档关闭后才将ByeArrayOutputStream分配给servlet OutputStream。在 document.close() 指令之前，ByteArrayOutputStream 的大小为 0。