java使用PDFRenderer实现预览PDF功能

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这篇文章主要为大家详细介绍了java使用PDFRenderer实现预览PDF功能，具有一定的参考价值，感兴趣的小伙伴们可以参考一下
本文实例为大家分享了java使用pdfrenderer实现预览pdf功能，供大家参考，具体内容如下
需要一个jar pdfrenderer-0.9.0.jar

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;
 }
 }
}

以上就是本文的全部内容，希望对大家的学习有所帮助，也希望大家多多支持CodeAE代码之家。
原文链接：https://blog.csdn.net/z69183787/article/details/12616099