需要的库
<!-- 生成pdf-->
<dependency>
<groupId>com.itextpdf</groupId>
<artifactId>itextpdf</artifactId>
<version>5.5.10</version>
</dependency>
<!-- https://mvnrepository.com/artifact/commons-net/commons-net FTPClient -->
<dependency>
<groupId>commons-net</groupId>
<artifactId>commons-net</artifactId>
<version>3.6</version>
</dependency>
代码一，生成本地pdf文件
if (list.size() > 0) {
Document document = new Document();
FTPClient ftp = new FTPClient();
try {
//1、创建一个document对象
//2、创建一个PdfWriter实例
FileData fileData1=list.get(0);
String filenamePdf=fileData1.getCatalogname()+fileData1.getCatalogid()+".pdf";
PdfWriter.getInstance(document, new FileOutputStream(filenamePdf));
//3、打开文档
document.open();
int pagenum = 0;
for (FileData filePage : list) {
//页码
pagenum++;
String folder = filePage.getFolder();
//服务器主机
String host = filePage.getHost();
//服务器端口
int port = Integer.parseInt(filePage.getPort());
//登录用户名
String username = filePage.getUsername();
//登录密码
String pwd = filePage.getPassword();
ftp.setControlEncoding(filePage.getEncoding());
ftp.addProtocolCommandListener(new PrintCommandListener(new PrintWriter(System.out)));
ftp.connect(host, port);
if (!FTPReply.isPositiveCompletion(ftp.getReplyCode())) {
ftp.disconnect();
}
ftp.login(username, pwd);
ftp.setFileType(FTP.BINARY_FILE_TYPE);
ftp.enterLocalPassiveMode();
ftp.changeWorkingDirectory(folder);
final ByteArrayOutputStream bos = new ByteArrayOutputStream();
ftp.retrieveFile(filePage.getFilename(), bos);
Image img = Image.getInstance(bos.toByteArray());
img.setAlignment(Image.ALIGN_CENTER);
// 根据图片大小设置页面，一定要先设置页面，再newPage（），否则无效
document.setPageSize(new Rectangle(img.getWidth(), img.getHeight()));
document.newPage();
document.add(img);
}
} catch (Exception e) {
e.printStackTrace();
} finally {
try {
ftp.logout();
} catch (IOException e) {
e.printStackTrace();
}
try {
ftp.disconnect();
} catch (IOException e) {
e.printStackTrace();
}
if (document.isOpen()) {
document.close();
}
}
}
代码二、生成pdf直接发送到响应中
上方代码加入和替换此两行，请求添加 在游览器可以直接预览，页面调用打印方法
页面参数直接在后端取
response.setContentType("application/pdf;charset=utf-8");
PdfWriter.getInstance(document, response.getOutputStream());
<body>
<iframe style="display: none;" id="printIframe" src="/controllers/viewimagecontroller/printImageByPageIds.do"></iframe>
<script type="text/javascript">
$(function () {
doPrint();
});
//点击打印按钮，触发事件】
function doPrint(){
$("#printIframe")[0].contentWindow.print();
}
</script>
</body>