怎么在java中使用PDFRenderer实现一个预览PDF功能

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。

具体内容如下

需要一个jar PDFRenderer-0.9.0.jar

packagecom.wonders.stpt.attach.action;

importjava.awt.Image;
importjava.awt.Rectangle;
importjava.awt.image.BufferedImage;
importjava.io.File;
importjava.io.FileInputStream;
importjava.io.FilenameFilter;
importjava.io.FileOutputStream;
importjava.io.InputStream;
importjava.io.OutputStream;
importjava.io.RandomAccessFile;
importjava.nio.ByteBuffer;
importjava.nio.channels.FileChannel;
importjava.util.Arrays;
importjava.util.Comparator;
importjavax.imageio.*;

importjavax.servlet.http.HttpServletRequest;
importjavax.servlet.http.HttpServletResponse;

importorg.apache.struts2.convention.annotation.Action;
importorg.apache.struts2.convention.annotation.Namespace;
importorg.apache.struts2.convention.annotation.ParentPackage;
importorg.apache.struts2.convention.annotation.Result;
importorg.springframework.beans.factory.annotation.Autowired;
importorg.springframework.beans.factory.annotation.Qualifier;
importorg.springframework.context.annotation.Scope;
importorg.springframework.stereotype.Component;

importcom.sun.image.codec.jpeg.JPEGCodec;

importcom.sun.image.codec.jpeg.JPEGImageEncoder;
importcom.sun.pdfview.PDFFile;
importcom.sun.pdfview.PDFPage;
importcom.wonders.stpt.attach.model.vo.UploadFile;
importcom.wonders.stpt.attach.service.FjshService;
importcom.wonders.stpt.userMsg.action.AbstractParamAction;



@SuppressWarnings("serial")
@ParentPackage("struts-default")
@Namespace(value="/attach")
@Component("attachViewerAction")
@Scope("prototype")
publicclassAttachViewerActionextendsAbstractParamAction{

privateFjshServicefjshService;
privatefinalintmaxPage=30;

publicFjshServicegetFjshService(){
returnfjshService;
}

@Autowired(required=false)
publicvoidsetFjshService(@Qualifier("fjshService")FjshServicefjshService){
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")})
publicStringpdfPreview(){
//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

HttpServletRequestrequest=servletRequest;
HttpServletResponseresponse=servletResponse;
StringfileId=request.getParameter("fileId");
if("".equals(fileId)||null==fileId){
servletRequest.setAttribute("state","f");
return"pdf";
}

UploadFileupFile=this.fjshService.loadFileById(fileId);
if(upFile==null){
servletRequest.setAttribute("state","f");
return"pdf";
}
Stringpath=upFile.getPath();//文件所在磁盘路径.
StringfileName=upFile.getFileAllName();//真实文件名.
StringsaveFileName=upFile.getSaveFileName();//磁盘上的文件名.
Stringversion=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
StringappPath=request.getSession().getServletContext().getRealPath("");
StringimageSavePath=appPath+"\\preview_images\\";

//按照文件路径读取PDF文档，并将其按页转换为图片

StringfilePath=path+saveFileName;
if(filePath==null||"".equals(filePath)){
servletRequest.setAttribute("state","f");
return"pdf";
}else{
PDFFilepdfFile=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")})
publicStringimagePreview(){
//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

HttpServletRequestrequest=servletRequest;
HttpServletResponseresponse=servletResponse;
StringfileId=request.getParameter("fileId");
if("".equals(fileId)||null==fileId){
servletRequest.setAttribute("state","f");
return"image";
}

UploadFileupFile=this.fjshService.loadFileById(fileId);
if(upFile==null){
servletRequest.setAttribute("state","f");
return"image";
}
Stringpath=upFile.getPath();//文件所在磁盘路径.
StringfileName=upFile.getFileAllName();//真实文件名.
StringsaveFileName=upFile.getSaveFileName();//磁盘上的文件名.
Stringversion=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
StringappPath=request.getSession().getServletContext().getRealPath("");
StringimageSavePath=appPath+"\\preview_images\\";

//按照文件路径读取文件
StringfilePath=path+saveFileName;
if(filePath==null||"".equals(filePath)){
servletRequest.setAttribute("state","f");
return"image";
}else{
//如果成功读取文件
StringimageName=String.valueOf(upFile.getId());
StringextName=upFile.getFileExtName();
if(getImageFile(filePath,imageSavePath,imageName,extName)){
return"image";
}else{
servletRequest.setAttribute("state","f");
return"image";
}
}
}

/**
*image文件读取.
*@paramfilePath--待读取文件的路径.
*@paramimageSavePath--图片保存路径.
*@paramimageName--图片文件保存后的文件名称（包括后缀）.
*@returnbooleaninstance.
*/
privatebooleangetImageFile(StringfilePath,StringimageSavePath,StringdirName,StringextName){
Stringpath=imageSavePath+dirName+"\\";
Filefile=newFile(path);
if(!file.exists()){//判断以文件名命名的文件夹是否存在.
file.mkdirs();
}

try{
InputStreamis=newFileInputStream(filePath);
StringimagePath=path+dirName+"."+extName;
FileOutputStreamos=newFileOutputStream(imagePath);//输出到文件流.
byte[]buffer=newbyte[1024];
intn=0;
while((n=is.read(buffer,0,1024))>0){
os.write(buffer,0,n);
}
os.close();
is.close();
}catch(Exceptionex){
ex.printStackTrace();
returnfalse;
}

servletRequest.setAttribute("state","s");
servletRequest.setAttribute("dirName",dirName);
servletRequest.setAttribute("imageName",dirName+"."+extName);
returntrue;
}

/**
*PDF文档读取.
*@paramfilePath--待读取PDF文件的路径.
*@returnnull或者PDFFileinstance.
*/
privatePDFFilegetPdfFile(StringfilePath){
try{
//loadapdffilefrombytebuffer.
Filefile=newFile(filePath);
RandomAccessFileraf=newRandomAccessFile(file,"r");
FileChannelchannel=raf.getChannel();
ByteBufferbuf=channel.map(FileChannel.MapMode.READ_ONLY,0,
channel.size());
PDFFilepdfFile=newPDFFile(buf);

returnpdfFile;
}catch(Exceptionex){
ex.printStackTrace();
}
returnnull;
}

/**
*PDF文档按页转换为图片.
*@parampdfFile--PDFFileinstance
*@paramimageSavePath--图片保存路径.
*@paramfileName--保存图片文件夹名称.
*/
privatebooleanpdf2Images(PDFFilepdfFile,StringimageSavePath,StringfileName){
if(pdfFile==null){//待转换文档不存在，返回false.
returnfalse;
}

//将转换后图片存放于path路径下

Stringpath=imageSavePath+fileName+"\\";
FilefilePath=newFile(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(newImageFilter());
if(imageNames.length==0){//当前文件夹下没有文件.
//将pdf文档按页转为图片.
StringimagePath="";
try{
//对转换页数进行限制,最多只转换前maxPage页.
intpages=pdfFile.getNumPages();
if(pages>maxPage){
pages=maxPage;
}

for(inti=1;i<=pages;i++){
//drawthepagetoanimage
PDFPagepage=pdfFile.getPage(i);
//getthewidthandheightforthedocatthedefaultzoom
Rectanglerect=newRectangle(0,
0,
(int)page.getBBox().getWidth(),
(int)page.getBBox().getHeight());
//generatetheimage
Imageimg=page.getImage(rect.width,rect.height,//width&height
rect,//cliprect
null,//nullfortheImageObserver
true,//fillbackgroundwithwhite
true//blockuntildrawingisdone
);

BufferedImagetag=newBufferedImage(rect.width,
rect.height,
BufferedImage.TYPE_INT_RGB);

tag.getGraphics().drawImage(img,
0,
0,
rect.width,
rect.height,
null);


imagePath=path+i+".jpg";
FileOutputStreamout=newFileOutputStream(imagePath);//输出到文件流.
JPEGImageEncoderencoder=JPEGCodec.createJPEGEncoder(out);
encoder.encode(tag);//JPEG编码.
out.close();
}
}catch(Exceptionex){
ex.printStackTrace();
returnfalse;
}
}

//取得当前文件夹下的所有jpg格式的文件名.
imageNames=filePath.list(newImageFilter());
//对文件名排序.
Arrays.sort(imageNames,newFileNameComparator());

servletRequest.setAttribute("state","s");
servletRequest.setAttribute("fileName",fileName);
servletRequest.setAttribute("imageNames",imageNames);

returntrue;
}

//图片后缀名过滤类

//图片jpg过滤器类
classImageFilterimplementsFilenameFilter{
publicbooleanisImageFile(StringfileName){
if(fileName.toLowerCase().endsWith("jpg")){
returntrue;
}else{
returnfalse;
}
}

publicImageFilter(){}

publicbooleanaccept(Filedir,Stringname){
returnisImageFile(name);
}
}

//文件名称比较类

classFileNameComparatorimplementsComparator{
publicfinalintcompare(Objectfirst,Objectsecond){
String[]fir=((String)first).split("\\.");
String[]sec=((String)second).split("\\.");

intfirstPage=Integer.parseInt(fir[0]);
intsecondPage=Integer.parseInt(sec[0]);
intdiff=firstPage-secondPage;
if(diff>0)
return1;
if(diff<0)
return-1;
else
return0;
}
}
}

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