技術標籤：java

這段時間接到報表匯出pdf功能的測試，要求相容ie5，所以前端無法相容，就由後端來處理。在開發過程中查找了大量的資料，最終確認用html2pdf工具來進行轉換，開發很順利，但是測試過程中發現當報表列數過多的時顯示不全，後來想到將列數過多的報表先使用html2image工具將其轉為圖片後在插入導pdf中，來實現pdf的匯出，但是現在有個問題就是轉圖片後的清晰度不是很理想。如果大家有更好的方法請指導一下。

需要匯入中文字型：

相關jar的引入

	 <dependency>
        <groupId>com.itextpdf</groupId>
 

        <artifactId>itextpdf</artifactId>
        <version>5.5.11</version>
      </dependency>
      <dependency>
        <groupId>com.itextpdf</groupId>
        <artifactId>itext-asian</artifactId>
        <version>5.2.0</version>
      <
 
/dependency>
      <dependency>
        <groupId>gui.ava</groupId>
        <artifactId>html2image</artifactId>
        <version>0.9</version>
      </dependency>
      <dependency>
        <groupId>com.itextpdf</groupId>
        <artifactId>
 
html2pdf</artifactId>
        <version>2.1.0</version>
      </dependency>

直接上程式碼：列數少的報表直接轉pdf

 public static void exportToPdf(String name, String htmlText,
                                   HttpServletRequest request, HttpServletResponse response) {
        try {

            // 設定檔名稱
            name = name + "_" + DateUtils.getNow("yyyyMMddHHmmss");

            // 設定檔名字編碼集
            String fileName =  URLEncoder.encode(name,"UTF8") + ".pdf";
            ConverterProperties props = new ConverterProperties();
            FontProvider fp = new FontProvider();
            fp.addStandardPdfFonts();
            String resources = ReportHelper.class.getResource("/font").getPath();
            fp.addDirectory(resources);
            props.setFontProvider(fp);
            OutputStream os = response.getOutputStream();
            List<IElement> elements = HtmlConverter.convertToElements(htmlText, props);
            PdfDocument pdf = new PdfDocument(new PdfWriter(os));
            Document document = new Document(pdf, PageSize.A4, true);
            for (IElement element : elements) {
                    document.add((IBlockElement) element);
            }

            // 響應資料
            response.setContentType("application/pdf; charset=utf-8");
            response.setHeader("Content-Disposition", String.format("attachment; filename=%s", fileName));
            response.setHeader("Set-Cookie", "fileDownload=true; path=/");
            document.close();
            os.flush();
            os.close();
        } catch (IOException e) {
            throw new Exception("PDF匯出失敗", e.getMessage());
        }
    }

報表列數過多先將其轉為圖片進行縮小後插入pdf：

public static void exportToPdfImage(String name, String htmlText,
                                        HttpServletRequest request, HttpServletResponse response) {
        String fileName = "";
        try {
            // 設定檔名稱
            name = name + "_" + DateUtils.getNow("yyyyMMddHHmmss");
            // 設定檔名字編碼集
            fileName = URLEncoder.encode(name, "UTF8") + ".pdf";
            OutputStream os = response.getOutputStream();
            Document document = new Document(PageSize.A4);
            // html轉成圖片
            HtmlImageGenerator imageGenerator = new HtmlImageGenerator();
            imageGenerator.loadHtml(htmlText);
            imageGenerator.getBufferedImage();
            imageGenerator.saveAsImage(fileName + ".png");
            // 響應資料
            response.setContentType("application/pdf; charset=utf-8");
            response.setHeader("Content-Disposition", String.format("attachment; filename=%s", fileName));
            response.setHeader("Set-Cookie", "fileDownload=true; path=/");
            PdfWriter.getInstance(document, os);
            document.open();
            Image image = Image.getInstance(fileName + ".png");
            float imageHeight = image.getScaledHeight();
            float imageWidth = image.getScaledWidth();
            int i = 0;
            while (imageHeight > 800 || imageWidth > 500) {
                image.scalePercent(100 - i);
                i++;
                imageHeight = image.getScaledHeight();
                imageWidth = image.getScaledWidth();
            }
            image.setAlignment(Image.MIDDLE);
            document.add(image);
            document.close();
            os.flush();
            os.close();
        } catch (Exception e) {
            throw new Exception("PDF匯出失敗", e.getMessage());
        } finally {
            // 獲取檔案進行刪除
            File file = new File(fileName + ".png");
            boolean isok = file.exists();
            if (isok) {
                file.delete();
            }
        }
    }