Java中将Word生成缩略图

解决思路

1、先将word生成pdf，这个采用openoffice或者jacob

2、然后将pdf生成图片

注：需要安装OpenOffice依赖，并启动soffice服务

依赖引入

需要的jar包是pdfrenderer.jar和jodconverter-2.2.2.jar包，如果使用jacob还得加入jacob.jar

注：Maven上pdfrenderer.jar不能下载，jodconverter.jar只能下载2.2.1版本的，两者均需要手动下载或部署至私服

• JODConverter下载地址：https://sourceforge.net/projects/jodconverter/files/JODConverter/
• PDFRenderer下载地址：https://artifacts.alfresco.com/nexus/content/repositories/public/com/sun/pdfview/pdfrenderer/

<!-- https://mvnrepository.com/artifact/com.artofsolving/jodconverter -->
<dependency>
  <groupId>com.artofsolving</groupId>
  <artifactId>jodconverter</artifactId>
  <version>2.2.2</version>
</dependency>
<!-- https://mvnrepository.com/artifact/com.sun.pdfview/pdfrenderer -->
<dependency>
  <groupId>com.sun.pdfview</groupId>
  <artifactId>pdfrenderer</artifactId>
  <version>0.9.1-patched</version>
</dependency>
<!-- https://mvnrepository.com/artifact/org.openoffice/ridl -->
<dependency>
  <groupId>org.openoffice</groupId>
  <artifactId>ridl</artifactId>
  <version>4.1.2</version>
</dependency>
<!-- https://mvnrepository.com/artifact/org.slf4j/slf4j-api -->
<dependency>
  <groupId>org.slf4j</groupId>
  <artifactId>slf4j-api</artifactId>
  <version>1.7.30</version>
</dependency>
<!-- https://mvnrepository.com/artifact/commons-io/commons-io -->
<dependency>
  <groupId>commons-io</groupId>
  <artifactId>commons-io</artifactId>
  <version>2.8.0</version>
</dependency>

代码实现

具体代码如下：

public static void main(String[] args) throws IOException {
    File officeFile = new File("D:/test.doc");
    File pdfFile = new File("D:/test.pdf");
    officeToPdf(officeFile, pdfFile);
    pdfToJPG("D:/test.pdf", "D:/");
}

private static void officeToPdf(File officeFile, File pdfFile) {
    OpenOfficeConnection connection = new SocketOpenOfficeConnection("127.0.0.1", 8100);
    try {
        connection.connect();
        DocumentConverter converter = new OpenOfficeDocumentConverter(
                connection);
        converter.convert(officeFile, pdfFile);
    } catch (ConnectException e) {
        e.printStackTrace();
    } finally {
        // close the connection
        connection.disconnect();
    }
}

// 将PDF格式的文件转换为JPG格式的文件
private static void pdfToJPG(String pdfPath, String imagePath) throws IOException {
    // load a pdf from a byte buffer
    File file = new File(pdfPath);

    RandomAccessFile raf = new RandomAccessFile(file, "r");
    FileChannel channel = raf.getChannel();
    //这句代码通道建立了map映射,如果要删除file那么得接触映射
    ByteBuffer buf = channel.map(FileChannel.MapMode.READ_ONLY, 0,
            channel.size());
    PDFFile pdffile = new PDFFile(buf);
    int totalPage = pdffile.getNumPages();
    for (int i = 1; i <= totalPage; i++) {
        if (i == 1) {
            // draw the first page to an image
            // 以图片的形式来描绘首页
            PDFPage page = pdffile.getPage(i);
            Rectangle rect = new Rectangle(0, 0, (int) page.getBBox()
                    .getWidth(), (int) page.getBBox().getHeight());

            // generate the image
            // 生成图片
            Image img = page.getImage(rect.width, rect.height, // width & height
                    rect, // clip rect
                    null, // null for the ImageObserver
                    true, // fill background with white
                    true // block until drawing is done
            );
            BufferedImage tag = new BufferedImage(rect.width, rect.height,
                    BufferedImage.TYPE_INT_RGB);
            tag.getGraphics().drawImage(img.getScaledInstance(rect.width, rect.height, Image.SCALE_SMOOTH), 0, 0, rect.width, rect.height,
                    null);

            FileOutputStream out = new FileOutputStream(imagePath + File.separator + pdfPath.substring(pdfPath.lastIndexOf("/") + 1, pdfPath.lastIndexOf("."))
                    + ".jpg"); // 输出到文件流
            JPEGImageEncoder encoder = JPEGCodec.createJPEGEncoder(out);
            encoder.encode(tag); // JPEG编码
            // 关闭输出流
            out.close();
            break;
        }
    }
    buf.clear();
    channel.close();
    raf.close();
    unmap(buf);
    //file.delete();
}

//解除map映射
public static <T> void unmap(final Object buffer) {
    AccessController.doPrivileged(new PrivilegedAction<T>() {
        @Override
        public T run() {
            try {
                Method getCleanerMethod = buffer.getClass().getMethod("cleaner", new Class[0]);
                getCleanerMethod.setAccessible(true);
                Cleaner cleaner = (sun.misc.Cleaner) getCleanerMethod.invoke(buffer, new Object[0]);
                cleaner.clean();
            } catch (Exception e) {
                e.printStackTrace();
            }
            return null;
        }
    });
}

需要注意的是，生成完图片后将pdf删除，但是删除失败，经过大牛的指点加上了unmap就ok了，故写下来分享给大家。