怎么在java中使用PDFRenderer实现一个预览PDF功能？很多新手对此不是很清楚，为了帮助大家解决这个难题，下面小编将为大家详细讲解，有这方面需求的人可以来学习下，希望你能有所收获。
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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;
}
}
}看完上述内容是否对您有帮助呢？如果还想对相关知识有进一步的了解或阅读更多相关文章，请关注创新互联行业资讯频道，感谢您对创新互联的支持。