我有个要求,我需要从网站上下载一份PDF。PDF需要在代码中生成,我认为这将是freemarker和像iText这样的PDF生成框架的组合。还有更好的办法吗?
然而,我的主要问题是如何允许用户通过Spring控制器下载文件?
我有个要求,我需要从网站上下载一份PDF。PDF需要在代码中生成,我认为这将是freemarker和像iText这样的PDF生成框架的组合。还有更好的办法吗?
然而,我的主要问题是如何允许用户通过Spring控制器下载文件?
当前回答
我能很快想到的是,生成pdf并将其存储在webapp/downloads/< RANDOM-FILENAME>.pdf代码中,并使用HttpServletRequest发送一个转发到这个文件
request.getRequestDispatcher("/downloads/<RANDOM-FILENAME>.pdf").forward(request, response);
或者你可以这样配置你的视图解析器,
<bean id="pdfViewResolver"
class="org.springframework.web.servlet.view.InternalResourceViewResolver">
<property name="viewClass"
value="org.springframework.web.servlet.view.JstlView" />
<property name="order" value=”2″/>
<property name="prefix" value="/downloads/" />
<property name="suffix" value=".pdf" />
</bean>
然后返回
return "RANDOM-FILENAME";
其他回答
@RequestMapping(value = "/files/{file_name}", method = RequestMethod.GET)
public void getFile(
@PathVariable("file_name") String fileName,
HttpServletResponse response) {
try {
// get your file as InputStream
InputStream is = ...;
// copy it to response's OutputStream
org.apache.commons.io.IOUtils.copy(is, response.getOutputStream());
response.flushBuffer();
} catch (IOException ex) {
log.info("Error writing file to output stream. Filename was '{}'", fileName, ex);
throw new RuntimeException("IOError writing file to output stream");
}
}
一般来说,当你有response.getOutputStream()时,你可以在那里写任何东西。您可以将此输出流作为将生成的PDF放置到生成器的位置。另外,如果你知道你要发送什么文件类型,你可以设置
response.setContentType("application/pdf");
如果你:
不想在发送到响应之前将整个文件加载到字节[]中; 希望/需要通过InputStream发送/下载; 想要有Mime类型和文件名发送的完全控制; 让其他@ControllerAdvice为你(或不)拾取异常。
下面的代码是你需要的:
@RequestMapping(value = "/stuff/{stuffId}", method = RequestMethod.GET)
public ResponseEntity<FileSystemResource> downloadStuff(@PathVariable int stuffId)
throws IOException {
String fullPath = stuffService.figureOutFileNameFor(stuffId);
File file = new File(fullPath);
long fileLength = file.length(); // this is ok, but see note below
HttpHeaders respHeaders = new HttpHeaders();
respHeaders.setContentType("application/pdf");
respHeaders.setContentLength(fileLength);
respHeaders.setContentDispositionFormData("attachment", "fileNameIwant.pdf");
return new ResponseEntity<FileSystemResource>(
new FileSystemResource(file), respHeaders, HttpStatus.OK
);
}
More on setContentLength(): First of all, the content-length header is optional per the HTTP 1.1 RFC. Still, if you can provide a value, it is better. To obtain such value, know that File#length() should be good enough in the general case, so it is a safe default choice. In very specific scenarios, though, it can be slow, in which case you should have it stored previously (e.g. in the DB), not calculated on the fly. Slow scenarios include: if the file is very large, specially if it is on a remote system or something more elaborated like that - a database, maybe.
InputStreamResource
如果你的资源不是一个文件,例如你从DB中获取数据,你应该使用InputStreamResource。例子:
InputStreamResource isr = new InputStreamResource(...);
return new ResponseEntity<InputStreamResource>(isr, respHeaders, HttpStatus.OK);
在我的情况下,我需要生成一些文件,所以url也必须生成。
对我来说是这样的:
@RequestMapping(value = "/files/{filename:.+}", method = RequestMethod.GET, produces = "text/csv")
@ResponseBody
public FileSystemResource getFile(@PathVariable String filename) {
String path = dataProvider.getFullPath(filename);
return new FileSystemResource(new File(path));
}
非常重要的是,mime类型在produces中,文件名也是链接的一部分所以你必须使用@PathVariable。
HTML代码是这样的:
<a th:href="@{|/dbreport/files/${file_name}|}">Download</a>
其中${file_name}是由thymleaf在控制器中生成的,即:result_20200225.csv,因此链接的整个url是:example.com/aplication/dbreport/files/result_20200225.csv。
点击链接后,浏览器问我如何处理文件-保存或打开。
下面的解决方案对我很有效
@RequestMapping(value="/download")
public void getLogFile(HttpSession session,HttpServletResponse response) throws Exception {
try {
String fileName="archivo demo.pdf";
String filePathToBeServed = "C:\\software\\Tomcat 7.0\\tmpFiles\\";
File fileToDownload = new File(filePathToBeServed+fileName);
InputStream inputStream = new FileInputStream(fileToDownload);
response.setContentType("application/force-download");
response.setHeader("Content-Disposition", "attachment; filename="+fileName);
IOUtils.copy(inputStream, response.getOutputStream());
response.flushBuffer();
inputStream.close();
} catch (Exception exception){
System.out.println(exception.getMessage());
}
}
我能够通过使用Spring的ResourceHttpMessageConverter中的内置支持来进行流处理。如果可以确定mime类型,这将设置内容长度和内容类型
@RequestMapping(value = "/files/{file_name}", method = RequestMethod.GET)
@ResponseBody
public FileSystemResource getFile(@PathVariable("file_name") String fileName) {
return new FileSystemResource(myService.getFileFor(fileName));
}