Itextpdf realizes the merging of multiple PDF files into one PDF document

1、 introduce POM

    <dependencies>
        <dependency>
            <groupId>com.itextpdf</groupId>
            <artifactId>itextpdf</artifactId>
            <version>5.5.13.3</version>
        </dependency>
    </dependencies>

2、 Write a tool class

public class PdfUtils {
    
/** *  establish pdf file  * * @param response * @param fileName * @return */
    public static Document createDocument(HttpServletResponse response, String fileName) {
    
        try {
    
            response.reset();
            response.setHeader("Content-Type", "application/pdf-stream");
            response.setHeader("Content-Disposition", "attachment;filename=" + URLEncoder.encode(fileName, "UTF-8"));
            response.setHeader("Pragma", "no-cache");
            response.setHeader("Cache-Control", "no-cache");
        } catch (Exception e) {
    
            e.printStackTrace();
        }

        //  Set size 
        return new Document(PageSize.A4, 50, 50, 80, 50);
    }

    /** *  Merge pdf * * @param response * @param document * @param byteList */
    public static void mergePdf(HttpServletResponse response, Document document, List<byte[]> byteList) {
    
        try {
    
            OutputStream os = response.getOutputStream();
            //  Create with any page pdf Templates 
            document = new Document(new PdfReader(byteList.get(0)).getPageSize(1));

            PdfCopy copy = new PdfCopy(document, os);

            //  Open the document 
            document.open();
            //  Traverse pdf file 
            for (byte[] bytes : byteList) {
    
                //  Read pdf
                PdfReader reader = new PdfReader(bytes);

                //  Get pages 
                int numberOfPages = reader.getNumberOfPages();
                //  Start with the first page 
                for (int i = 1; i <= numberOfPages; i++) {
    
                    //  New document page 
                    document.newPage();
                    //  Copy operation 
                    PdfImportedPage page = copy.getImportedPage(reader, i);
                    copy.addPage(page);
                }
            }
        } catch (Exception e) {
    
            e.printStackTrace();
            throw new RuntimeException("PDF Merger failed ！");
        } finally {
    
            if (document != null) {
    
                document.close();
            }
        }
    }
}

3、 Code implementation

Support upload MultipartFile File or through Local files Path Merge with PDF

@RestController
@RequestMapping("/test")
public class PdfController {
    
/** *  Upload files for merging  * * @param files * @param response */
    @PostMapping("pdfStream")
    public void pdf(@RequestParam("files") MultipartFile[] files, HttpServletResponse response) {
    
        try {
    
            //  Judge whether the document is compliant 、 And convert it into an input stream 
            List<byte[]> byteList = new ArrayList<>();
            for (MultipartFile file : files) {
    
                //  The restricted format can only be pdf
                if (file == null) {
    
                    throw new RuntimeException(" The file cannot be empty ！");
                }
                String originalFilename = file.getOriginalFilename();
                String substring = originalFilename.substring(originalFilename.lastIndexOf(".") + 1);
                if (!substring.equals("pdf")) {
    
                    throw new RuntimeException(" Can only upload pdf Format file ！");
                }

                //  Get input stream 
                //  Get input stream 
                InputStream inputStream = file.getInputStream();
                byte[] bytes = inputStreamToByte(inputStream);
                byteList.add(bytes);
            }

            // 1. Set the output stream name 
            String fileName = " Merge files .pdf";
            Document document = PdfUtils.createDocument(response, fileName);

            // 2. Open merge 
            PdfUtils.mergePdf(response, document, byteList);
        } catch (Exception e) {
    
            e.printStackTrace();
            throw new RuntimeException(e.getMessage());
        }
    }

    /** *  Local file conversion and merging  * * @param response */
    @GetMapping("pdfPath")
    public void pdfPath(HttpServletResponse response) {
    
        try {
    
            //  Load local file 
            List<String> paths = new ArrayList<>();
            paths.add("C:\\Users\\LiGezZ\\Desktop\\1.pdf");
            paths.add("C:\\Users\\LiGezZ\\Desktop\\2.pdf");

            //  Judge whether the document is compliant 、 And convert it into an input stream 
            List<byte[]> byteList = new ArrayList<>();
            for (String path : paths) {
    
                File file = new File(path);
                //  The restricted format can only be pdf
                if (!file.exists()) {
    
                    throw new RuntimeException(" file does not exist ！");
                }
                if (file.length() <= 0) {
    
                    throw new RuntimeException(" The file cannot be empty ！");
                }

                String name = file.getName();
                String substring = name.substring(name.lastIndexOf(".") + 1);
                if (!substring.equals("pdf")) {
    
                    throw new RuntimeException(" Can only upload pdf Format file ！");
                }

                //  Get input stream 
                FileInputStream inputStream = new FileInputStream(file);
                byte[] bytes = inputStreamToByte(inputStream);
                byteList.add(bytes);
            }

            // 1. Set the output stream name 
            String fileName = " Merge files .pdf";
            Document document = PdfUtils.createDocument(response, fileName);

            // 2. Open merge 
            PdfUtils.mergePdf(response, document, byteList);
        } catch (Exception e) {
    
            e.printStackTrace();
            throw new RuntimeException(e.getMessage());
        }
    }

    private byte[] inputStreamToByte(InputStream inputStream) {
    
        try (ByteArrayOutputStream os = new ByteArrayOutputStream()) {
    
            byte[] bytes = new byte[1024];
            int len = 0;
            while ((len = inputStream.read(bytes)) != -1) {
    
                os.write(bytes, 0, len);
            }
            os.flush();
            return os.toByteArray();
        } catch (Exception e) {
    
            throw new RuntimeException("InputStream switch views ！");
        }
    }
}