本文主要介绍Java中,使用URLConnection下载网页上图片文档,通过itext 将多个pdf合成到单个pdf文件中。

1、引用Maven的pom.xml中引用配置

<dependency>
<groupId>com.itextpdf</groupId>
<artifactId>itextpdf</artifactId>
<version>5.5.9</version>
</dependency>
<dependency>
<groupId>com.google.guava</groupId>
<artifactId>guava</artifactId>
<version>28.2-jre</version>
</dependency>

2、使用URLConnection下载多个图片到本地

import java.io.ByteArrayOutputStream;
import java.io.DataInputStream;
import java.io.File;
import java.io.FileOutputStream;
import java.io.IOException;
import java.net.MalformedURLException;
import java.net.URL;
import java.net.URLConnection;
public class Utils {
public static String getParam(String url, String name) {
    String params = url.substring(url.indexOf("?") + 1, url.length());
    Map<String, String> split = Splitter.on("&").withKeyValueSeparator("=").split(params);
    return split.get(name);
}
    /**
    * @Description: 下载多个图片
    * @param   picurls 多个图片地址    path 图片下载存放目录  fileNames 多个文件名称 ,不传fileNames=null则取url中参数值,此时ParamName必须传
    * @return void
    * @throws
    */
    public static void downloadPicture(String[] picurls,String path,String[] fileNames,String ParamName) throws IOException {
        try {
            //多个图片下载地址  
            for(int i=0;i<picurls.length;i++) {
                //根据图片地址构建URL
                URL url= new URL(picurls[i]);
                URLConnection conn = url.openConnection();
                conn.setReadTimeout(10000);
                conn.setConnectTimeout(10000);
                conn.connect();
                DataInputStream dataInputStream = new DataInputStream(conn.getInputStream());
                //创建目录和图片
                File pathFile=new File(path);
                File file =null;
                if(fileNames!=null){
                  file=new File(path+File.separator+fileNames[i]);
                } else {
                  file=new File(path+File.separator+ getParam(picurls[i],ParamName));
               }
                if(!pathFile.exists()) {
                    pathFile.mkdirs();
                    file.createNewFile();
                }
                if(!file.exists()) {
                    file.createNewFile();
                }
                //通过流复制图片
                FileOutputStream fileOutputStream = new FileOutputStream(file);
                ByteArrayOutputStream output = new ByteArrayOutputStream();
                byte[] buffer = new byte[1024];
                int length;
                while ((length = dataInputStream.read(buffer)) > 0) {
                    output.write(buffer, 0, length);
                }
                fileOutputStream.write(output.toByteArray());
                dataInputStream.close();
                fileOutputStream.close();
            }
        } catch (MalformedURLException e) {
            e.printStackTrace();
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
}

3、使用IText合成多个图片到单个pdf

1) 使用IText将多个图片转成多个pdf文件

	public static void imageToPDF(String path,String imagePath) 
	{
		File file = new File(path);
		Document document = new Document();
        try {
			PdfWriter.getInstance(document, new FileOutputStream(file));
		} catch (FileNotFoundException e1) {
			// TODO Auto-generated catch block
			e1.printStackTrace();
		} catch (DocumentException e1) {
			// TODO Auto-generated catch block
			e1.printStackTrace();
		}
        document.open();
            document.newPage();
            Image image = null;
			try {
				try {
					image = Image.getInstance(imagePath);
				} catch (BadElementException e) {
					// TODO Auto-generated catch block
					e.printStackTrace();
				}
			} catch (MalformedURLException e) {
				// TODO Auto-generated catch block
				e.printStackTrace();
			} catch (IOException e) {
				// TODO Auto-generated catch block
				e.printStackTrace();
			}
            image.setAbsolutePosition(0, 0);
            image.setBorderWidth(0);
            image.scaleAbsolute(PageSize.A4);
            try {
				document.add(image);
			} catch (DocumentException e) {
				// TODO Auto-generated catch block
				e.printStackTrace();
			}
        document.close();
	}

2) 使用IText将多个pdf合成到一个pdf文件

import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.util.ArrayList;
import java.util.Iterator;
import java.util.List;
import com.lowagie.text.Document;
import com.lowagie.text.pdf.BaseFont;
import com.lowagie.text.pdf.PdfContentByte;
import com.lowagie.text.pdf.PdfImportedPage;
import com.lowagie.text.pdf.PdfReader;
import com.lowagie.text.pdf.PdfWriter;
public class MergePDF {
    public static void main(String[] args) {
        try {
            List<InputStream> pdfs = new ArrayList<InputStream>();
            pdfs.add(new FileInputStream("c:\\1.pdf"));
            pdfs.add(new FileInputStream("c:\\2.pdf"));
            OutputStream output = new FileOutputStream("c:\\merge.pdf");
            MergePDF.concatPDFs(pdfs, output, true);
        } catch (Exception e) {
            e.printStackTrace();
        }
    }
    public static void concatPDFs(List<InputStream> streamOfPDFFiles,
            OutputStream outputStream, boolean paginate) {
        Document document = new Document();
        try {
            List<InputStream> pdfs = streamOfPDFFiles;
            List<PdfReader> readers = new ArrayList<PdfReader>();
            int totalPages = 0;
            Iterator<InputStream> iteratorPDFs = pdfs.iterator();
            // Create Readers for the pdfs.
            while (iteratorPDFs.hasNext()) {
                InputStream pdf = iteratorPDFs.next();
                PdfReader pdfReader = new PdfReader(pdf);
                readers.add(pdfReader);
                totalPages += pdfReader.getNumberOfPages();
            }
            // Create a writer for the outputstream
            PdfWriter writer = PdfWriter.getInstance(document, outputStream);
            document.open();
            BaseFont bf = BaseFont.createFont(BaseFont.HELVETICA,
                    BaseFont.CP1252, BaseFont.NOT_EMBEDDED);
            PdfContentByte cb = writer.getDirectContent(); // Holds the PDF
            // data
            PdfImportedPage page;
            int currentPageNumber = 0;
            int pageOfCurrentReaderPDF = 0;
            Iterator<PdfReader> iteratorPDFReader = readers.iterator();
            // Loop through the PDF files and add to the output.
            while (iteratorPDFReader.hasNext()) {
                PdfReader pdfReader = iteratorPDFReader.next();
                // Create a new page in the target for each source page.
                while (pageOfCurrentReaderPDF < pdfReader.getNumberOfPages()) {
                    document.newPage();
                    pageOfCurrentReaderPDF++;
                    currentPageNumber++;
                    page = writer.getImportedPage(pdfReader,
                            pageOfCurrentReaderPDF);
                    cb.addTemplate(page, 0, 0);
                    // Code for pagination.
                    if (paginate) {
                        cb.beginText();
                        cb.setFontAndSize(bf, 9);
                        cb.showTextAligned(PdfContentByte.ALIGN_CENTER, ""
                                + currentPageNumber + " of " + totalPages, 520,
                                5, 0);
                        cb.endText();
                    }
                }
                pageOfCurrentReaderPDF = 0;
            }
            outputStream.flush();
            document.close();
            outputStream.close();
        } catch (Exception e) {
            e.printStackTrace();
        } finally {
            if (document.isOpen())
                document.close();
            try {
                if (outputStream != null)
                    outputStream.close();
            } catch (IOException ioe) {
                ioe.printStackTrace();
            }
        }
    }
}

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