[英]Java: combine 2000-5000 PDFs into 1 using iText yield OutOfMemorryError
I have eyeballing this code for a long time, trying to reducing the amount of memory the code use and still it generated java.lang.OutOfMemoryError: Java heap space
. 我长时间盯着这段代码,试图减少代码使用的内存量,并且仍然生成
java.lang.OutOfMemoryError: Java heap space
。 As my last resort, I want to ask the community on how can I improve this code to avoid OutOfMemoryError
作为我的最后选择,我想向社区询问如何改进此代码以避免
OutOfMemoryError
I have a driver/manifest file (.txt file) that contain information about the PDFs. 我有一个驱动程序/清单文件(.txt文件),其中包含有关PDF的信息。 I have about 2000-5000 pdf inside a zip file that I need to combine together.
我需要合并在一起的zip文件中包含大约2000-5000 pdf。 Before the combining, for each pdf, I need to add 2-3 more pdf pages to it.
在合并之前,对于每个pdf,我需要再添加2-3个pdf页面。
Manifest
object holds information about a pdf. Manifest
对象包含有关pdf的信息。
try{
blankPdf = new PdfReader(new FileInputStream(config.getBlankPdf()));
mdxBacker = new PdfReader(new FileInputStream(config.getMdxBacker()));
theaBacker = new PdfReader(new FileInputStream(config.getTheaBacker()));
mdxAffidavit = new PdfReader(new FileInputStream(config.getMdxAffidavit()));
theaAffidavit = new PdfReader(new FileInputStream(config.getTheaAffidavit()));
ImmutableList<Manifest> manifestList = //Read manifest file and obtain List<Manifest>
File zipFile = new File(config.getInputDir() + File.separator + zipName);
//Extracting PDF into `process` folder
ZipUtil.extractAll(config.getExtractPdfDir(), zipFile);
outputPdfName = zipName.replace(".zip", ".pdf");
outputZipStream = new FileOutputStream(config.getOutputDir() +
File.separator + outputPdfName);
document = new Document(PageSize.LETTER, 0, 0, 0, 0);
writer = new PdfCopy(document , outputZipStream);
document.open(); //Open the document
//Start combining PDF files together
for(Manifest m : manifestList){
//Obtain full path to the current pdf
String pdfFilePath = config.getExtractPdfDir() + File.separator + m.getPdfName();
//Before combining PDF, add backer and affidavit to individual PDF
PdfReader pdfReader = PdfUtil.addBackerAndAffidavit(config, pdfType, m,
pdfFilePath, blankPdf, mdxBacker, theaBacker, mdxAffidavit,
theaAffidavit);
for(int pageNumber=1; pageNumber<=pdfReader.getNumberOfPages(); pageNumber++){
document.newPage();
PdfImportedPage page = writer.getImportedPage(pdfReader, pageNumber);
writer.addPage(page);
}
}
} catch (DocumentException e) {
} catch (IOException e) {
} finally{
if(document != null) document.close();
try{
if(outputZipStream != null) outputZipStream.close();
if(writer != null) writer.close();
}catch(IOException e){
}
}
Please, rest assure that I have look at this code for a long time, and try rewrite it many times to reduce the amount of memory it using. 请确保我已经看了很长时间此代码,并尝试多次重写它以减少使用的内存量。 After the OutOfMemoryError, there are still lots of pdf files that have not been added 2-3 extra pages, so I think it is inside
addBackerAndAffidavit
, however, I try to close every resources I opened, but it still exception out. 在OutOfMemoryError之后,仍然有很多未添加2-3个额外页面的pdf文件,因此我认为它位于
addBackerAndAffidavit
,但是,我尝试关闭我打开的所有资源,但它仍然例外。 Please help. 请帮忙。
You need to invoke PdfWriter#freeReader()
by end of every loop to free the involved PdfReader
. 您需要在每个循环结束时调用
PdfWriter#freeReader()
以释放涉及的PdfReader
。 The PdfCopy#freeReader()
has this method inherited from PdfWriter
and does the same. PdfCopy#freeReader()
具有从PdfWriter
继承的此方法,并且执行相同的操作。 See also the javadoc : 另请参阅javadoc :
freeReader
freeReader
public void freeReader(PdfReader reader) throws IOException
Description copied from class :
PdfWriter
从类复制的描述 :
PdfWriter
Use this method to writes the reader to the document and free the memory used by it.使用此方法将阅读器写入文档并释放其使用的内存。 The main use is when concatenating multiple documents to keep the memory usage restricted to the current appending document.
主要用途是在串联多个文档时将内存使用量限制在当前附加文档中。
Overrides :
覆盖 :
freeReader
in classPdfWriter
freeReader
类PdfWriter
Parameters :
参数 :
reader
- thePdfReader
to freereader
-在PdfReader
免费Throws :
抛出 :
IOException
- on errorIOException
错误
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