I use a servlet to get images that saved out of my project. Code in my servlet is:
String file = request.getParameter("file");
BufferedInputStream in = new BufferedInputStream(new FileInputStream(directory + file));
// Get image contents.
byte[] bytes = new byte[in.available()];
in.read(bytes);
in.close();
// Write image contents to response.
response.getOutputStream().write(bytes);
The HTML image tags are like this:
<img src="/images/?file=example.jpg" />
Everything is good. But now I would like to have image filename in URI instead of as request parameter like so:
<img src="/images/example.jpg" />
How can I achieve it?
Map the servlet on a prefix URL pattern /images/* instead of an apparently exact URL pattern /images. Then, you can specify URLs exactly like that and obtain the filename as URI path information by HttpServletRequest#getPathInfo().
Kickoff example:
#WebServlet("/images/*")
public class ImageServlet extends HttpServlet {
protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
String filename = request.getPathInfo().substring(1);
File file = new File(directory, filename);
response.setHeader("Content-Type", getServletContext().getMimeType(file.getName()));
response.setHeader("Content-Length", String.valueOf(file.length()));
Files.copy(file.toPath(), response.getOutputStream());
}
}
Unrelated to the concrete problem: InputStream#available() as in your initial code doesn't do what you apparently thought it does. It doesn't return the entire length of the content. It just returns the length of the first block which the code can read without blocking the disk file system I/O. I.e. it returns the length of content currently in I/O buffer. This does not necessarily represent the entire content length! For sure not on larger images. If you're on Java 7, just use Files#copy() if the sole purpose is to achieve the job with least possible amount of code as shown above.
Related
I am trying to display an image in a Thymeleaf template that is coming from a MySql Database.
Most of it is working but I have a problem with the controller code :
#GetMapping(value = "/image/{someId}", produces = {MediaType.IMAGE_JPEG_VALUE, MediaType.IMAGE_PNG_VALUE})
public ResponseEntity<byte[]> getPicture(#PathVariable("someId") long someId) throws IOException {
byte[] imageContent = //Getting the blob element from the Repo through a service
final HttpHeaders headers = new HttpHeaders();
headers.setContentType(MediaType.IMAGE_JPEG);
headers.set("Content-Disposition", "attachment; filename=fileName.jpg");
headers.setContentLength(imageContent.length);
return new ResponseEntity<byte[]>(imageContent, headers, HttpStatus.OK);
}
My code is similar to solutions that ware suggested here (see this answer or this one) but my template won't display the image as its content is most probably not valid. If I reach the endpoint directly from the browser, a "filename.jpg" image will download (makes sense following the code above) but that only contains the original name of the image if I open it with a text editor. It's not an image.
There's surely something that I am missing in the configuration of the ResponseEntity. Do you perhaps have some documentation I could read about the process because I don't understand fully what is going on.
I have a Springboot REST application that downloads files from a given directory.
The downloads can be any file file and have any format, and I want to use the original filename as the filename of the downloaded file.
I used the code below to set the filename in the header, and add the header to the response:
#RestController
#RequestMapping("/downloads")
public class DownloadCsontroller {
...
#GetMapping
public void downloadSingleFile(#RequestParam("file") String filename, HttpServletResponse response) throws IOException {
String filepath = m_attachmentPathLocation + File.separator + filename;
File file = new File(filepath);
String contentType = getContentType(file);
response.setStatus(HttpServletResponse.SC_OK);
response.setContentType(contentType);
response.setHeader("Content-Disposition:", "attachment;filename=\"" + file.getName() + "\"");
...
}
...
}
Tested using both "Content-Disposition" and "Content-Disposition:" in setHeader().
Almost everything works (file types), except for PDF, ZIP, RAR, EXE, etc.
Any files (types) not on the list can be downloaded with the desired filenames.
But when any of the file download (PDF, ZIP, RAR, EXE, etc)... it seems it continuously loads like forever... and I cannot even see any request sent in POSTMAN, inspector, firebug, etc.
If I comment out:
//response.setHeader("Content-Disposition:", "attachment;filename=\"" + file.getName() + "\"");
It would work, but the filename would be set to the name of the request mapping. which in this case is "downloads".
I have seen lots of samples that uses "Content-Disposition" header to change the attachment filename... but it seems it fails on these file types.
I have no configurations yet, and it is kinda weird since in most samples I searched... this should be running or working.
TIA
Please add #GetMapping(produces = MediaType.APPLICATION_OCTET_STREAM_VALUE)
and instead of returning direct file try to return stream.
Also make a note that "Content-Disposition:" header will not work if the requesting app IP & Port number is different from server app IP & Port number.
Things would work If you can alter the code a bit, by setting all header values using org.springframework.http.HttpHeaders class.
Now looking at your code, i suspect you trying to expose an API that allows to download a multipart File.
I would suggest you not to use HttpServletResponse Class to set the Content- Dispositionheader but use HttpHeaders class. Below is the reformatted code
#RestController
public class DownloadCsontroller {
#GetMapping(value="/downloads")
public ResponseEntity<Object> downloadSingleFile(#RequestParam("file")
String filename) throws IOException {
String filepath = m_attachmentPathLocation + File.separator + filename;
File file = new File(filepath);
String contentType = getContentType(file);
/* response.setStatus(HttpServletResponse.SC_OK);
response.setContentType(contentType);
response.setHeader("Content-Disposition:", "attachment;filename=\""
+ file.getName() + "\"");
*/
// Here is the below Code you need to reform for Content-
//Disposition and the remaining header values too.
HttpHeaders headers= new HttpHeaders();
headers.add("Content-Disposition", "attachment; filename
=whatever.pdf");
headers.add("Content-Type",contentType);
// you shall add the body too in the ResponseEntity Return object
return new ResponseEntity<Object>(headers, HttpStatus.OK);
}
}
I have a servlet that returns an image as InputStreamResource. There are approx 50 static images that are to be returned based on some get query parameters.
For not having to look up each of those images every time it is requested (which is very often), I'd like to cache those images responses.
#RestController
public class MyRestController {
//code is just example; may be any number of parameters
#RequestMapping("/{code}")
#Cachable("code.cache")
public ResponseEntity<InputStreamResource> getCodeLogo(#PathVariable("code") String code) {
FileSystemResource file = new FileSystemResource("d:/images/" + code + ".jpg");
return ResponseEntity.ok()
.contentType("image/jpg")
.lastModified(file.lastModified())
.contentLength(file.contentLength())
.body(new InputStreamResource(file.getInputStream()));
}
}
When using the #Cacheable annotation (no matter if directly on the RestMapping method or refactored to an external service), I_'m getting the following exception:
cause: java.lang.IllegalStateException: InputStream has already been read - do not use InputStreamResource if a stream needs to be read multiple times - error: InputStream has already been read - do not use InputStreamResource if a stream needs to be read multiple times
org.springframework.core.io.InputStreamResource.getInputStream(InputStreamResource.java:96)
org.springframework.http.converter.ResourceHttpMessageConverter.writeInternal(ResourceHttpMessageConverter.java:100)
org.springframework.http.converter.ResourceHttpMessageConverter.writeInternal(ResourceHttpMessageConverter.java:47)
org.springframework.http.converter.AbstractHttpMessageConverter.write(AbstractHttpMessageConverter.java:195)
org.springframework.web.servlet.mvc.method.annotation.AbstractMessageConverterMethodProcessor.writeWithMessageConverters(AbstractMessageConverterMethodProcessor.java:238)
org.springframework.web.servlet.mvc.method.annotation.HttpEntityMethodProcessor.handleReturnValue(HttpEntityMethodProcessor.java:183)
org.springframework.web.method.support.HandlerMethodReturnValueHandlerComposite.handleReturnValue(HandlerMethodReturnValueHandlerComposite.java:81)
org.springframework.web.servlet.mvc.method.annotation.ServletInvocableHandlerMethod.invokeAndHandle(ServletInvocableHandlerMethod.java:126)
org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.invokeHandlerMethod(RequestMappingHandlerAdapter.java:832)
org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.handleInternal(RequestMappingHandlerAdapter.java:743)
Question: how can I then cache the ResponseEntity of type InputStreamResource at all?
Cache manager will add to cache ResponseEntity with InputStreamResource inside of it. First time it will be ok. But when cached ResponseEntity will try to read InputStreamResouce second time you'll get exception, because it is unable to read stream more than one time.
Solution: don't cache InputStreamResouce itself, but cache the content of stream.
#RestController
public class MyRestController {
#RequestMapping("/{code}")
#Cachable("code.cache")
public ResponseEntity<byte[]> getCodeLogo(#PathVariable("code") String code) {
FileSystemResource file = new FileSystemResource("d:/images/" + code + ".jpg");
byte [] content = new byte[(int)file.contentLength()];
IOUtils.read(file.getInputStream(), content);
return ResponseEntity.ok()
.contentType(MediaType.IMAGE_JPEG)
.lastModified(file.lastModified())
.contentLength(file.contentLength())
.body(content);
}
}
I've used IOUtils.read() from org.apache.commons.io, to copy bytes from stream to array, but you can do it by any preferred way.
You can't cache Streams. Once they are read, they are gone.
The error message is pretty clear about that:
InputStream has already been read -
do not use InputStreamResource if a stream needs to be read multiple times
By your code and comments, it seems to me that you have a big images folder with JPG logos (which might be added, deleted or modified), and you want to have a daily cache of the one's you're being asked for, so you don't have to constantly reload them from disk.
If that's the case, your best option is to read the File's content to a ByteArray and cache/return that instead.
I have this controller methods that depending on the parameters introduced by the user downloads a certain PDF file and shows a view with its different pages converted to PNG.
So the way I approached it works like this:
First I map a method to receive the post data sent by the user, then generate the URL of the actual PDF converter and pass it to the model:
#RequestMapping(method = RequestMethod.POST)
public String formPost(Model model, HttpServletRequest request) {
//Gather parameters and generate PDF url
Long idPdf = Long.parseLong(request.getParam("idPdf"));
//feed the jsp the url of the to-be-generated image
model.addAttribute("image", "getImage?idPdf=" + idPdf);
}
Then in getImageMethod I download the PDF and then generate a PNG out of it:
#RequestMapping("/getImage")
public HttpEntity<byte[]> getPdfToImage(#RequestParam Long idPdf) {
String url = "myPDFrepository?idPDF=" + idPdf;
URL urlUrl = new URL(url);
URLConnection urlConnection;
urlConnection = urlUrl.openConnection();
InputStream is = urlConnection.getInputStream();
return PDFtoPNGConverter.convert(is);
}
My JSP just has an img tag that refers to this url:
<img src="${image}" />
So far this work perfectly. But now I need to allow the possibility of viewing multi page PDFs, converted as PNGS, each of them in a different page. So I would add a page parameter, then feed my model with the image url including that page parameter, and in my getImage method I would convert only that page.
But the way it is implemented, I would be downloading the PDF again for each page, plus an additional time for the view, so it can find out whether this specific PDF has more pages and then show the "prev" and "next" buttons.
What would be a good way to preserve the same file during these requests, so I download it just once? I thought about using temp files but then managing its deletion might be a problem. So maybe storing the PDF in the session would be a good solution? I don't even know if this is good practice or not.
I am using Spring MVC by the way.
I think the simplest way would be using spring cache abstraction. Look at tutorial and will need to change your code a little: move logic that load pdf to separate class.
it will looks like:
interface PDFRepository {
byte[] getImage(long id);
}
#Repository
public class PDFRepositoryImpl implements PDFRepository {
#Cacheable
public byte[] getImage(long id) {
String url = "myPDFrepository?idPDF=" + idPdf;
URL urlUrl = new URL(url);
URLConnection urlConnection;
urlConnection = urlUrl.openConnection();
InputStream is = urlConnection.getInputStream();
return PDFtoPNGConverter.convert(is);
}
}
You will get pluggable cache implementation support and good cache expiration management.
I want to capture the current page and send it to an application that converts it to pdf.
This is what I am using:
FacesContext facesContext=FacesContext.getCurrentInstance();
HttpServletResponse response = (HttpServletResponse)
facesContext.getExternalContext().getResponse();
HttpServletRequest request = (HttpServletRequest) facesContext.getExternalContext().getRequest();
// RequestPrinter.debugString();
response.reset();
// download a pdf file
response.setContentType("application/pdf");
response.setHeader("Content-Disposition","attachment;filename="+new Date().toString()+".pdf");
prince.setVerbose(true);
prince.setLog(logFile);
try{
//getPath() to the page the user is currently on
URL pagePath=new URL(this.getPath());
URLConnection urlConnection = pagePath.openConnection();
urlConnection.setDoOutput(true);
int length = urlConnection.getContentLength();
//Lets use inputStream
BufferedInputStream bis=new BufferedInputStream(urlConnection.getInputStream());
response.setContentLength(length);
//this.getPageUsingJSoup().data().getBytes();
//call prince and pass params for inputstream outputStream
prince.convert(bis,response.getOutputStream());
urlConnection.getInputStream().close();
}catch(MalformedURLException mu){
mu.printStackTrace();
}
catch(IOException ioe){
ioe.printStackTrace();
}
facesContext.responseComplete();
Since the website requires authentication, the pdf generated is the loging error page.
Is there a way to capture the page's content that uses the current user's session?
Thank you in advance.
Just request the page in the same HTTP session as the current request. If your webapp supports URL rewriting (as by default), then just append session ID as jsessionid path fragment:
String sessionId = ((HttpSession) externalContext.getSession()).getId();
InputStream input = new URL("http://localhost:8080/context/page.jsf;jsessionid=" + sessionId).openStream();
// ...
Or if your webapp doesn't accept URL rewriting, but accepts cookies only, then set it as a request cookie the usual way:
URLConnection connection = new URL("http://localhost:8080/context/page.jsf").openConnection();
connection.setRequestProperty("Cookie", "JSESSIONID=" + sessionId);
InputStream input = connection.getInputStream();
// ...
Note that I removed setDoOutput() since you don't seem to be interested in performing a POST request.
I do not know how to capture the page's content using the current user's session, but I can suggest another way to do it - you could move the pdf conversion logic inside a Selenium test-case and use the test-case to navigate and login to the page requiring authentication. After the automated tc has logged in, you could call your pdf conversion logic...?
Yes of course there is. You are sending this content, so you have it. You should store the Content Object. If you dont have it, inspect your byte streams. The content should be there ;)
There of couple of websites which allow you to convert the entire page to pdf and save it as .pdf file. Try out the site http://pdfcrowd.com/ Hope this helps you.