Download file

[eraser]

I want to Download a file with GWT.

Which way can i go?

The Client-javascript send params to Server (RPC) and should get a file like csv, xml or xls back. Then the client should show the download-dialog to save the data on the client-PC.

Any hints?

[mike.art1]

RPC will not work. Just have your link point to a url that returns the file. Make sure your servlet/controller does something along the lines of

//if returning an image
response.setContentType("image/jpeg");
OutputStream out = response.getOutputStream();
byte[] image = readImageData(....)
out.write(image);
out.flush();
out.close();

[nlotz]

If you want the browser to show a dialog asking if the response should be saved as a file:

//if returning csv-data
response.setContentType("text/csv");
response.setHeader("Content-Disposition", "attachment; filename=\"example-data.csv\"");
OutputStream out = response.getOutputStream();
byte[] data = readCsvData(....);
out.write(data);
out.flush();
out.close();

This will show a dialog asking the user if he wants to save the response as a file named "example-data.csv".

[J-Pro]

If you want the browser to show a dialog asking if the response should be saved as a file
...
This will show a dialog asking the user if he wants to save the response as a file named "example-data.csv".

Dear nlotz, I've tried this way, but having this exception and can't understand where is the error... can you help me please?

java.lang.RuntimeException: Unable to report failure
	at com.google.gwt.user.server.rpc.AbstractRemoteServiceServlet.doUnexpectedFailure(AbstractRemoteServiceServlet.java:107)
	at com.google.gwt.user.server.rpc.AbstractRemoteServiceServlet.doPost(AbstractRemoteServiceServlet.java:67)
	at javax.servlet.http.HttpServlet.service(HttpServlet.java:637)
	at javax.servlet.http.HttpServlet.service(HttpServlet.java:717)
	at org.mortbay.jetty.servlet.ServletHolder.handle(ServletHolder.java:487)
	at org.mortbay.jetty.servlet.ServletHandler.handle(ServletHandler.java:362)
	at org.mortbay.jetty.security.SecurityHandler.handle(SecurityHandler.java:216)
	at org.mortbay.jetty.servlet.SessionHandler.handle(SessionHandler.java:181)
	at org.mortbay.jetty.handler.ContextHandler.handle(ContextHandler.java:729)
	at org.mortbay.jetty.webapp.WebAppContext.handle(WebAppContext.java:405)
	at org.mortbay.jetty.handler.HandlerWrapper.handle(HandlerWrapper.java:152)
	at org.mortbay.jetty.handler.RequestLogHandler.handle(RequestLogHandler.java:49)
	at org.mortbay.jetty.handler.HandlerWrapper.handle(HandlerWrapper.java:152)
	at org.mortbay.jetty.Server.handle(Server.java:324)
	at org.mortbay.jetty.HttpConnection.handleRequest(HttpConnection.java:505)
	at org.mortbay.jetty.HttpConnection$RequestHandler.content(HttpConnection.java:843)
	at org.mortbay.jetty.HttpParser.parseNext(HttpParser.java:647)
	at org.mortbay.jetty.HttpParser.parseAvailable(HttpParser.java:205)
	at org.mortbay.jetty.HttpConnection.handle(HttpConnection.java:380)
	at org.mortbay.io.nio.SelectChannelEndPoint.run(SelectChannelEndPoint.java:395)
	at org.mortbay.thread.QueuedThreadPool$PoolThread.run(QueuedThreadPool.java:488)
Caused by: java.io.IOException: Closed
	at org.mortbay.jetty.AbstractGenerator$Output.write(AbstractGenerator.java:627)
	at org.mortbay.jetty.AbstractGenerator$Output.write(AbstractGenerator.java:587)
	at com.google.gwt.user.server.rpc.RPCServletUtils.writeResponse(RPCServletUtils.java:277)
	at com.google.gwt.user.server.rpc.RemoteServiceServlet.writeResponse(RemoteServiceServlet.java:315)
	at com.google.gwt.user.server.rpc.RemoteServiceServlet.processPost(RemoteServiceServlet.java:232)
	at com.google.gwt.user.server.rpc.AbstractRemoteServiceServlet.doPost(AbstractRemoteServiceServlet.java:62)
	... 19 more

My code is:

public class MyServiceImpl extends RemoteServiceServlet implements MyService
{
...
  public Boolean giveFileToDownload(List<MyClass> myClassList)
  {
      HttpServletResponse response = this.getThreadLocalResponse();
      
      response.setContentType("text/csv");
      response.setHeader("Content-Disposition", "attachment; filename=\"data.csv\"");
      
      try
      {
          OutputStream out = response.getOutputStream();
          byte[] data = generateCSV(myClassList).getBytes(); // generateCSV() returns String
          out.write(data);               // here is where the exception is thrown
          out.flush();
          out.close();
          return true;
      }
      catch(IOException ioEx)
      {
          ioEx.printStackTrace();            
          return false;
      }
  }
...
}

[J-Pro]

I've changed the line

byte[] data = generateCSV(myClassList).getBytes();

to

byte[] data = "Test text".getBytes();

and got the same exception, BUT printing the stack trace on the client from onFailure(Throwable caught) method by invoking "caught.printStackTrace()" gave me strange thing:

com.google.gwt.user.client.rpc.InvocationException: Test text
	at com.google.gwt.user.client.rpc.impl.RequestCallbackAdapter.onResponseReceived(RequestCallbackAdapter.java:201)
	at com.google.gwt.http.client.Request.fireOnResponseReceived(Request.java:287)
	at com.google.gwt.http.client.RequestBuilder$1.onReadyStateChange(RequestBuilder.java:393)
	at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
	at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)
	at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
	at java.lang.reflect.Method.invoke(Method.java:597)
	at com.google.gwt.dev.shell.MethodAdaptor.invoke(MethodAdaptor.java:103)
	at com.google.gwt.dev.shell.MethodDispatch.invoke(MethodDispatch.java:71)
	at com.google.gwt.dev.shell.OophmSessionHandler.invoke(OophmSessionHandler.java:157)
	at com.google.gwt.dev.shell.BrowserChannel.reactToMessagesWhileWaitingForReturn(BrowserChannel.java:1713)
	at com.google.gwt.dev.shell.BrowserChannelServer.invokeJavascript(BrowserChannelServer.java:165)
	at com.google.gwt.dev.shell.ModuleSpaceOOPHM.doInvoke(ModuleSpaceOOPHM.java:120)
	at com.google.gwt.dev.shell.ModuleSpace.invokeNative(ModuleSpace.java:507)
	at com.google.gwt.dev.shell.ModuleSpace.invokeNativeObject(ModuleSpace.java:264)
	at com.google.gwt.dev.shell.JavaScriptHost.invokeNativeObject(JavaScriptHost.java:91)
	at com.google.gwt.core.client.impl.Impl.apply(Impl.java)
	at com.google.gwt.core.client.impl.Impl.entry0(Impl.java:188)
	at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
	at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)
	at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
	at java.lang.reflect.Method.invoke(Method.java:597)
	at com.google.gwt.dev.shell.MethodAdaptor.invoke(MethodAdaptor.java:103)
	at com.google.gwt.dev.shell.MethodDispatch.invoke(MethodDispatch.java:71)
	at com.google.gwt.dev.shell.OophmSessionHandler.invoke(OophmSessionHandler.java:157)
	at com.google.gwt.dev.shell.BrowserChannel.reactToMessages(BrowserChannel.java:1668)
	at com.google.gwt.dev.shell.BrowserChannelServer.processConnection(BrowserChannelServer.java:401)
	at com.google.gwt.dev.shell.BrowserChannelServer.run(BrowserChannelServer.java:222)
	at java.lang.Thread.run(Thread.java:619)

Can someone explain it please?

[J-Pro]

Sorry, forgot to mention my environment: I'm using smartwgt 2.2 (just downloaded this version and tried it there), GWT SDK 2.0.3 with Eclipse 3.5 SR1 and jdk 1.6.0 u18 from Windows 7 Enterprise x64 and Mozilla Firefox 3.5.9 as browser.

Please, advise me something, maybe I'm just doing something wrong... I work with file download in GWT for the first time.

Thank you in advance.