问题
I am trying to return an iText generated PDF from the server side to the client side to enable the user to store it. I am following How to convert iTextPDF Document to Byte Array (AceFunk)
private static ByteArrayOutputStream byteArrayOutputStream = new ByteArrayOutputStream();
public static byte[] main(java.util.List<Transcript> listymAwards, String scoutName, String groupName) {
Document document = new Document(PageSize.A4, 0f, 0f, 0f, 0f);
try {
//PdfWriter.getInstance(document, new FileOutputStream(FILE));
PdfWriter.getInstance(document, byteArrayOutputStream); // Do this BEFORE document.open()
document.open();
addMetaData(document);
addImages(document);
addTitlePage(document, scoutName);
//Add the table of achievements
if (listymAwards == null || listymAwards.isEmpty()) {
//Nothing to do.
//System.out.println("Scout not found.");
}else{
Paragraph preface = new Paragraph();
PdfPTable table = new PdfPTable(3);
table.setWidths(new int[]{1, 3, 1});
table.setHeaderRows(1);
PdfPCell c1 = new PdfPCell(new Phrase("Section"));
c1.setHorizontalAlignment(Element.ALIGN_CENTER);
table.addCell(c1);
c1 = new PdfPCell(new Phrase("Award"));
c1.setHorizontalAlignment(Element.ALIGN_CENTER);
table.addCell(c1);
c1 = new PdfPCell(new Phrase("Date"));
c1.setHorizontalAlignment(Element.ALIGN_CENTER);
table.addCell(c1);
table.setHeaderRows(1);
String storedName = null;
int noRows = 0;
String firstTable = "Yes";
DateFormat df1 = new SimpleDateFormat("yyyy-MM-dd");
DateFormat df2 = new SimpleDateFormat("dd-MM-yyyy");
// We add three empty lines
addEmptyLine(preface, 1);
addEmptyLine(preface, 1);
addEmptyLine(preface, 1);
for (final Transcript scoutNamesDescription : listymAwards) {
if (firstTable.equals("Yes") && noRows > 30){ // Change this to number of rows required
noRows = 0;
firstTable = "No";
document.add(table);
document.newPage();
table.flushContent();
}else{
if (firstTable.equals("No") && noRows > 50){ // Change this to number of rows required
// We add three empty lines if not the first table
document.add(preface);
}
}
noRows++;
if (scoutNamesDescription.getSection().equals(storedName)){
table.addCell(" ");
}else{
storedName = scoutNamesDescription.getSection();
table.addCell(scoutNamesDescription.getSection());
}
table.addCell(scoutNamesDescription.getAwardName());
Date awardedDate = df1.parse(scoutNamesDescription.getAwardedDate());
String awardedString = df2.format(awardedDate);
table.addCell(awardedString);
}
//Print the remaining rows.
// We add three empty lines if not the first table
if (firstTable.equals("No")){
document.add(preface);
}else{
firstTable = "No";
}
document.add(table);
}
//Add signature
addSignaturePage(document, groupName);
document.close();
} catch (Exception e) {
e.printStackTrace();
}
byte[] pdfBytes = byteArrayOutputStream.toByteArray();
return pdfBytes;
}
This is returned to the server side:
byte[] pdfBytes = ScoutTranscript.main(listymAwards, scoutName, groupName);
System.out.println("Point 3");
return pdfBytes;
Which is then returned to the client side:
Window.open("data:application/pdf;base64,"+result,"_parent", "location=no");
Where I get the error message:
This site can’t be reached
The webpage at data:application/pdf;base64,[B@154 might be temporarily down or it may have moved permanently to a new web address.
回答1:
Error #1:
Let's start with a small test that doesn't involve iText in any way. Try this:
byte[] test = "Test".getBytes();
System.out.println("Test " + test);
What is written to the output? In my case, it's:
Test [B@3da3da69
The [ indicates that I am trying to convert an array to a String; the B indicates that the array contains bytes; the @ separates the type from the ID; the characters that follow are the ID in hexadecimal format (a hashcode). See Java: Syntax and meaning behind "[B@1ef9157"? Binary/Address?
If result is of type byte[] and you have this line:
Window.open("data:application/pdf;base64,"+result,"_parent", "location=no");
Then "data:application/pdf;base64,"+result results in something like "data:application/pdf;base64,[B@154". That doesn't make any sense, does it?
Now try this:
byte[] test = "Test".getBytes();
System.out.println("Test " + new String(test));
The output is:
Test Test
You were using a byte[] as if it was a String. This is your first error.
I was going to say something nasty because this is not an error that a Java developer would make. However, I've just read your bio, and I see that you're new at Java and you are (probably) teaching yourself how to code in Java (just like I did 20 years ago), so I censored myself ;-)
Error #2:
You can not solve your problem by replacing your code by:
Window.open("data:application/pdf;base64,"+ new String(result),"_parent", "location=no");
You can't do that because you are making a second error: the bytes in result represent a binary file, and the JavaScript in your browser expects a Base64 encoded file. Base64 encoding is used to convert binary to text, and vice-versa. See What is base 64 encoding used for?
If you want to send the binary PDF file to the browser as a Base64-encoded string, you have to Base64 encode your bytes. This can be done with this class: http://itextsupport.com/apidocs/itext5/latest/com/itextpdf/text/pdf/codec/Base64.html
For instance:
Window.open("data:application/pdf;base64,"+ Base64.encodeBytes(result),"_parent", "location=no");
This should already work for some browsers, but not for all. I have no idea where you are using Window.open(), nor why you want to involve Base64. You may want to elaborate on that. In my opinion, it's a bad idea.
How it should be done:
Typically, you will write a Servlet that runs in an application server. That servlet can be reached from a browser using a URL. You do not need to save the generated file on the server as suggested in the other answer (I down-voted that answer because it is not helpful and totally wrong). Your approach that creates a ByteArrayOutputStream and then gets a byte[] is correct, but you have to serve those bytes to a HttpServletResponse object.
See How can I serve a PDF to a browser without storing a file on the server side? for a full example.
Regarding Window.open()
You can use Window.open() on the client side, to open a web page in a new window. For instance:
window.open("http://www.itextpdf.com");
You can serve a page that has contains this snippet, but in your case, you have to replace http://www.itextpdf.com with the URL that was defined for your servlet.
You may have found your "solution" here: Opening PDF String in new window with javascript
But if you read the comments, you'll notice that this approach is problematic in combination with some browsers.
来源：https://stackoverflow.com/questions/39885410/how-to-return-an-itext-pdf-document-to-the-client-side