java使用PDFRenderer实现预览PDF功能

 package com.wonders.stpt.attach.action; import java.awt.Image; import java.awt.Rectangle; import java.awt.image.BufferedImage; import java.io.File; import java.io.FileInputStream; import java.io.FilenameFilter; import java.io.FileOutputStream; import java.io.InputStream; import java.io.OutputStream; import java.io.RandomAccessFile; import java.nio.ByteBuffer; import java.nio.channels.FileChannel; import java.util.Arrays; import java.util.Comparator; import javax.imageio.*; import javax.servlet.http.HttpServletRequest; import javax.servlet.http.HttpServletResponse; import org.apache.struts2.convention.annotation.Action; import org.apache.struts2.convention.annotation.Namespace; import org.apache.struts2.convention.annotation.ParentPackage; import org.apache.struts2.convention.annotation.Result; import org.springframework.beans.factory.annotation.Autowired; import org.springframework.beans.factory.annotation.Qualifier; import org.springframework.context.annotation.Scope; import org.springframework.stereotype.Component; import com.sun.image.codec.jpeg.JPEGCodec; import com.sun.image.codec.jpeg.JPEGImageEncoder; import com.sun.pdfview.PDFFile; import com.sun.pdfview.PDFPage; import com.wonders.stpt.attach.model.vo.UploadFile; import com.wonders.stpt.attach.service.FjshService; import com.wonders.stpt.userMsg.action.AbstractParamAction; @SuppressWarnings("serial") @ParentPackage("struts-default") @Namespace(value="/attach") @Component("attachViewerAction") @Scope("prototype") public class AttachViewerAction extends AbstractParamAction{ private FjshService fjshService; private final int maxPage = 30; public FjshService getFjshService() { return fjshService; } @Autowired(required=false) public void setFjshService(@Qualifier("fjshService")FjshService fjshService) { this.fjshService = fjshService; } /** * PDF文档在线以图片格式预览. * */ @Action(value="/pdfPreview",results={@Result(name="pdf",location="/attachPreview/pdfViewer.jsp")}) public String pdfPreview() { //按fileId查找出该文件的路径以及文件名. //该部分代码copy自附件上传组件 HttpServletRequest request = servletRequest; HttpServletResponse response = servletResponse; String fileId = request.getParameter("fileId"); if("".equals(fileId) || null == fileId) { servletRequest.setAttribute("state", "f"); return "pdf"; } UploadFile upFile = this.fjshService.loadFileById(fileId); if(upFile == null) { servletRequest.setAttribute("state", "f"); return "pdf"; } String path = upFile.getPath();   // 文件所在磁盘路径. String fileName = upFile.getFileAllName(); // 真实文件名. String saveFileName = upFile.getSaveFileName(); // 磁盘上的文件名. String version = upFile.getVersion(); if ("old".equals(request.getParameter("ver"))){ if (version != null){ saveFileName = saveFileName.replace(".dat","_v"+version+".dat"); } } //当前应用绝对路径 String appPath = request.getSession().getServletContext().getRealPath (""); String imageSavePath = appPath + "\\preview_images\\"; //按照文件路径读取PDF文档，并将其按页转换为图片 String filePath = path + saveFileName ; if(filePath == null || "".equals(filePath)) { servletRequest.setAttribute("state", "f"); return "pdf"; }else { PDFFile pdfFile = this.getPdfFile(filePath); if(this.pdf2Images(pdfFile,imageSavePath,String.valueOf(upFile.getId()))) { //如果转换成功 return "pdf"; }else { servletRequest.setAttribute("state", "f"); return "pdf"; } } } /** * 图片文件在线预览 * */ @Action(value="/imagePreview",results={@Result(name="image",location="/attachPreview/imageViewer.jsp")}) public String imagePreview() { //按fileId查找出该文件的路径以及文件名. //该部分代码copy自附件上传组件 HttpServletRequest request = servletRequest; HttpServletResponse response = servletResponse; String fileId = request.getParameter("fileId"); if("".equals(fileId) || null == fileId) { servletRequest.setAttribute("state", "f"); return "image"; } UploadFile upFile = this.fjshService.loadFileById(fileId); if(upFile == null) { servletRequest.setAttribute("state", "f"); return "image"; } String path = upFile.getPath();   // 文件所在磁盘路径. String fileName = upFile.getFileAllName(); // 真实文件名. String saveFileName = upFile.getSaveFileName(); // 磁盘上的文件名. String version = upFile.getVersion(); if ("old".equals(request.getParameter("ver"))){ if (version != null){ saveFileName = saveFileName.replace(".dat","_v"+version+".dat"); } } //当前应用绝对路径 String appPath = request.getSession().getServletContext().getRealPath (""); String imageSavePath = appPath + "\\preview_images\\"; //按照文件路径读取文件 String filePath = path + saveFileName ; if(filePath == null || "".equals(filePath)) { servletRequest.setAttribute("state", "f"); return "image"; }else { //如果成功读取文件 String imageName = String.valueOf(upFile.getId()); String extName = upFile.getFileExtName(); if(getImageFile(filePath,imageSavePath,imageName,extName)) { return "image"; }else { servletRequest.setAttribute("state", "f"); return "image"; } } } /** * image文件读取. * @param filePath -- 待读取文件的路径. * @param imageSavePath -- 图片保存路径. * @param imageName -- 图片文件保存后的文件名称（包括后缀）. * @return boolean instance. */ private boolean getImageFile(String filePath,String imageSavePath,String dirName,String extName) { String path = imageSavePath + dirName + "\\"; File file = new File(path); if(!file.exists()){ //判断以文件名命名的文件夹是否存在. file.mkdirs(); } try { InputStream is = new FileInputStream(filePath); String imagePath = path + dirName + "." + extName; FileOutputStream os = new FileOutputStream(imagePath); // 输出到文件流. byte[] buffer = new byte[1024]; int n = 0; while ((n = is.read(buffer, 0, 1024)) > 0) { os.write(buffer, 0, n); } os.close(); is.close(); } catch (Exception ex) { ex.printStackTrace(); return false; } servletRequest.setAttribute("state", "s"); servletRequest.setAttribute("dirName", dirName); servletRequest.setAttribute("imageName", dirName + "." + extName); return true; } /** * PDF文档读取. * @param filePath -- 待读取PDF文件的路径. * @return null 或者 PDFFile instance. */ private PDFFile getPdfFile(String filePath) { try { //load a pdf file from byte buffer. File file = new File(filePath); RandomAccessFile raf = new RandomAccessFile(file, "r"); FileChannel channel = raf.getChannel(); ByteBuffer buf = channel.map(FileChannel.MapMode.READ_ONLY, 0, channel.size()); PDFFile pdfFile = new PDFFile(buf); return pdfFile; } catch (Exception ex) { ex.printStackTrace(); } return null; } /** * PDF文档按页转换为图片. * @param pdfFile -- PDFFile instance * @param imageSavePath -- 图片保存路径. * @param fileName -- 保存图片文件夹名称. */ private boolean pdf2Images(PDFFile pdfFile,String imageSavePath,String fileName) { if(pdfFile == null ) { //待转换文档不存在，返回false. return false; } //将转换后图片存放于path路径下 String path = imageSavePath + fileName + "\\"; File filePath = new File(path); if(!filePath.exists()){ //判断以文件名命名的文件夹是否存在. filePath.mkdirs(); } //取得当前文件夹下的所有jpg格式的文件名. String[] imageNames = filePath.list(new ImageFilter()); if(imageNames.length == 0) { //当前文件夹下没有文件. //将pdf文档按页转为图片. String imagePath = ""; try { //对转换页数进行限制,最多只转换前maxPage页. int pages = pdfFile.getNumPages(); if(pages > maxPage){ pages = maxPage; } for (int i = 1; i <= pages; i++) { // draw the page to an image PDFPage page = pdfFile.getPage(i); // get the width and height for the doc at the default zoom Rectangle rect = new Rectangle(0, 0, (int) page.getBBox().getWidth(), (int) page.getBBox().getHeight()); // generate the image 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, 0, 0, rect.width, rect.height, null); imagePath = path + i + ".jpg-600"; FileOutputStream out = new FileOutputStream(imagePath); // 输出到文件流. JPEGImageEncoder encoder = JPEGCodec.createJPEGEncoder(out); encoder.encode(tag);  // JPEG编码. out.close(); } }catch (Exception ex) { ex.printStackTrace(); return false; } } //取得当前文件夹下的所有jpg格式的文件名. imageNames = filePath.list(new ImageFilter()); //对文件名排序. Arrays.sort(imageNames,new FileNameComparator()); servletRequest.setAttribute("state", "s"); servletRequest.setAttribute("fileName", fileName); servletRequest.setAttribute("imageNames", imageNames); return true; } //图片后缀名过滤类 //图片jpg过滤器类 class ImageFilter implements FilenameFilter { public boolean isImageFile(String fileName){ if(fileName.toLowerCase().endsWith("jpg")) { return true; }else { return false; } } public ImageFilter() {} public boolean accept(File dir,String name){ return isImageFile(name); } } //文件名称比较类 class FileNameComparator implements Comparator { public final int compare(Object first, Object second) { String[] fir = ((String)first).split("\\."); String[] sec = ((String)second).split("\\."); int firstPage = Integer.parseInt(fir[0]); int secondPage = Integer.parseInt(sec[0]); int diff = firstPage - secondPage; if (diff > 0) return 1; if (diff <0) return -1; else return 0; } } }