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";
   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;
 }
 }
}