I am currently trying to use JSP to build some small litle apps and have not got stuck on something, downloading files from a webserver. I just cant seem to work out how I should go about this task.
Are there any JSP developers here who know to go about this and could point me in the right direction?
If the resource is static, just put it in the public webcontent (there where your JSP/HTML/CSS/JS/etc files also are) and include a link to it in your JSP.
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The servletcontainer will worry about setting the right HTTP response headers.
If the resource is dynamic, create a servlet which obtains an InputStream of the content somehow (new FileInputStream, resultSet.getBinaryStream(), etc..etc..) and writes it to the OutputStream of the response along at least the Content-Type and Content-Disposition response headers. Finally just link to that servlet in your JSP.
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You can find a basic example in this article.
The Content-Type header informs the client about the content type of the file so that it knows what application it should use to open it. The Content-Disposition header informs the client what to do with it, displaying it inline or saving as attachment.
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I am new to web programming. My web application can upload files (uploaded by drag and drop method in javascripts ) and i want to retrieve them in servlet using Json . servlet file only needs the contents of the text files to do the calculation.
Can any one suggest how to do this ?
softwares used - netbeans ,tomcat
Thank you.
I'm not quite sure if you mean rendering your files in servlets or actually downloading them from your browser. I'm going to assume you mean rendering them. If so, then what you have to do is set up a URI which is associated with the content you want to render. Let's say this is a simple "hello world" rendering in the browser. what you would do is set up a URI as such:
localhost:3000/helloWorld.html.jsp
What you do on your back end is then wait to receive a http GET request to "/helloWorld.html.jsp" page, and then have your router send over the correct page. Luckily, with tools such as tomcat, the routing from local host is straight forward enough, and as your comments mentioned this is simple enough to do with the ample resources on the web.
Also an important point, you don't need JSON when using servlets (if i understood your problem correctly). If you want to send over data in a JSON format, then all you would do is modify the above steps to listen for "/sendJSON.html.jsp" (this could be an empty jsp), and you send over JSON from your back end in your response.
For my web site, I need to get some data from an URL whose response headers contains Content-Disposition attribute which forces me to download the file. I would like to know how I can read the content of the file without downloading the file to disk and do I/O to read it.
Doing so in either Java or JavaScript would be fine.
Content-Disposition is just advisory. If you use a non-browser client (Java, curl, wget...) and do a GET request, you can just do whatever you want.
(I guess this means your question isn't sufficiently specific)
I have a BIRT report that I've created in GWT and I'd like to save it to the server and then open it back up. I feel like hardcoding the url is the wrong route to go (ie C:/files/foo/foo.html) but I'm not having much luck figuring out another way of doing it. I tried using GWT.getModuleBaseForStaticFiles() but if i use that I get an unsatisfied link error in BIRT. What can I use to save/open a file, what is considered the best practice? Thanks.
edit: bad wording, the BIRT report is generated server-side. I'd like to be able to save it server side and then open it up in a new browser window (using window.open I'd imagine?). Nothing is uploaded from the client side.
If your BIRT report is a static file (Not generated during the runtime of your application) You can create a simple Servlet that read the file and copy the data to the OutputStream of the response. If it's generated at the runtime, the client will request it to the server, the server will generate it and return the URL location of the report. The client can open the report with that URL.
Example:
If your BIRT is located under foo/foo.bar you can map a servlet as /foo/*. After mapping it the user will request the url www.yourselver.com/foo/foo.bar The servlet at the doGet method can read the file and stream the content back to the client.
I'm creating a java web application runing on a Tomcat server.
One of the functions fill in a StringBuffer variable with data.
At the end, I would like to propose the user to download the generated content packaged in a text file. This without having to store the file on the server.
I've been searching for a code snippet but couldn't find anything corresponding ...
I hope I've been clear enough on my problem.
Thanks in advance,
See Making A Download Servlet
Don't forget to add the servlet to your web.xml.
You have to send a content-type along with the response, so that the browser knows what to do with the body of the response.
Normal text has the content-type text/plain, html is text/html. Images are image/gif and so on. For an unknown mime type you normally set "application/octet", which afaik every browser treats as a download. But I recommend to use the propery content type, so the browser might start a matching application to handle the content (e.g. Office for Documents or XML Editor for XML Files ..)
To send a filename along, which the browser suggests for saving, use the following header (example):
Content-Disposition: attachment; filename="downloaded.pdf"
For sending custom headers, use the setHeader() method in the response object.
Is there any way of just getting the content of the browsed file without any upload/file transfer operations? I currently use ICEFaces inputFile component but I do not need the default uploading operation of the file.
Thanks.
That's not possible. The client needs to send (upload) the file content along the request body to the server side whenever you want to have the file content at the server side.
If you'd expect that you can solve this by passing only the file path around and use the usual java.io.File stuff and so on, then you're on the wrong track. Imagine that I am the client and I have a c:/passwords.txt, how would you as being the server at the other end of the network ever get its content by java.io.File?
I don't thnik this is possible. Browsers do not allow any file transfer from the client to the server without user interaction.
Tough, if you do not stick to IceFaces, it may be possible to achieve this by writing an applet, wich is granted the necessary permissions.