【干货来了】如何使用 MuleSoft 合并多个 PDF

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<dependency>
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    <groupId>org.apache.pdfbox</groupId>
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    <artifactId>pdfbox</artifactId>
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    <version>2.0.1</version>
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</dependency>

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package com.mulesoft.mergePDF;
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import org.apache.pdfbox.io.MemoryUsageSetting;
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import org.apache.pdfbox.multipdf.PDFMergerUtility;
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import java.io.ByteArrayInputStream;
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import java.io.ByteArrayOutputStream;
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import java.io.File;
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import java.io.IOException;
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import java.util.Base64;
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public class MergeMultiplePDF {
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    /*  
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    Merge PDF and store it in a local directory
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    listPdfFileNames= ["src/main/resources/input/PDF1.pdf", "src/main/resources/input/PDF2.pdf"]
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    mergedPdfFileName= "src/main/resources/output/mergedPDF.pdf"    
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    */
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    public static void mergeAndStorePDF(String[] listPdfFileNames, String mergedPdfFileName) throws IOException {
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        /* Create and initialize object of PDFMergerUtility */
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        PDFMergerUtility obj = new PDFMergerUtility();
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        /* Set Destination File in the PDFMergerUtility Object */
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        obj.setDestinationFileName(mergedPdfFileName);
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        /* Iterate through the list of PDF filenames */
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        for (String file : listPdfFileNames) {
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        /* Add Each PDF files in the PDFMergerUtility Object */
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            obj.addSource(new File(file));
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        }
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        /* Now the PDFMergerUtility Object has all the PDFs. Use mergeDocuments method to merge the PDFs */
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        obj.mergeDocuments(null);
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        /* This will store the merged PDF in the destination path passed as argument */
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    }
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    /* 
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    Merge PDFs and return the merged PDF as a byte array 
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    base64PDF= List of base64 encoded PDF strings
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    Eg. ["PDF1 base64 encoded string", "PDF2 base64 encoded string"]
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    */
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    public static byte[] mergePDFs(String[] base64PDF) throws Exception {
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        /* Create and initialize ByteArrayOutputStream to return the merged PDF as a byte array */      
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        try (ByteArrayOutputStream destination = new ByteArrayOutputStream()) {
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          /* Create and initialize object of PDFMergerUtility */
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            PDFMergerUtility obj = new PDFMergerUtility();
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          /* Set Destination Stream as the ByteArrayOutputStream object in the PDFMergerUtility Object */
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            obj.setDestinationStream(destination);
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            /* Iterate through the list of Base64 encoded PDF strings */  
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            for (String pdf : base64PDF) {  
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            /* Initialize ByteArrayInputStream object and store each PDF as bytes */
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                ByteArrayInputStream bais = new ByteArrayInputStream(pdf.getBytes());
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            /* Add each base64 decoded PDF in the PDFMergerUtility Object  */
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                obj.addSource(Base64.getDecoder().wrap(bais));
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            }   
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          /* Now the PDFMergerUtility Object has all the PDFs. Use mergeDocuments method to merge the PDFs */
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            obj.mergeDocuments(MemoryUsageSetting.setupMainMemoryOnly());
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         /* Return the mergedPDF as a byte array using the ByteArrayOutputStream object */
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            return destination.toByteArray();
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        } catch (IOException e) {
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            throw new Exception("Error occurred while merging pdf files", e);
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        }
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    }
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}
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