How to create Download Button

[tgallage]

Is there any way to create a "Download" button in smartgwt ? Our application generates a dynamic File/OutputStream in server side. When the user clicks on a particular Button or Link that files needs to be downloaded through browser.

[Isomorphic]

If a GET request is sufficient, just redirect the page to the target URL (the equivalent of window.location.replace()).

If you instead want to do a normal server-side operation that results in a file download, you can do it as a DMI and just use the HttpServletResponse to send back the file, just call RPCManager.doCustomResponse() to signal to the server that you're doing this.

[tgallage]

RPCManager can not be used because we use JSON as the server side communication mechanism. Moreover, the downloadable file size is usually bigger than 4kB . How could you overcome these issues with the above solutions ?

[Isomorphic]

Neither concern is relevant.. Perhaps take a closer look at the suggestions already given.

[zdary]

If a GET request is sufficient, just redirect the page to the target URL (the equivalent of window.location.replace()).

If you instead want to do a normal server-side operation that results in a file download, you can do it as a DMI and just use the HttpServletResponse to send back the file, just call RPCManager.doCustomResponse() to signal to the server that you're doing this.

Hi, I tries to do it as you suggested via a DMI method.

    public void download(HttpServletRequest request, HttpServletResponse response) throws Exception {
    	RPCManager manager = new RPCManager(request, response);
    	manager.doCustomResponse();
    	response.setContentType("text/plain");
    	response.setHeader("Content-Disposition", "attachment; filename=\"example-data.any\"");
    	OutputStream out = response.getOutputStream();
    	byte[] utf8Bytes = "content of the file".getBytes("UTF8");
    	out.write(utf8Bytes);
    	out.flush();
    	out.close();
    }

However, I end up with an exception. What do I do wrong?

=== 2011-07-21 19:05:58,499 [l0-8] DEBUG RPCManager - Content type for RPC transaction: text/plain; charset=UTF-8
=== 2011-07-21 19:05:58,500 [l0-8] ERROR IDACall4Spring - IDACall - Error executing operation: download
java.io.IOException: Error - getWriter() called on request that has already returned an OutputStream - enable debug logging on com.isomorphic.servlet.ProxyHttpServletResponse to see a stack trace of the previous caller.
	at com.isomorphic.servlet.ProxyHttpServletResponse.getWriter(ProxyHttpServletResponse.java:174)
	at com.isomorphic.servlet.RequestContext.out(RequestContext.java:368)
	at com.isomorphic.rpc.RPCManager.completeResponse(RPCManager.java:973)
	at com.isomorphic.rpc.RPCManager.send(RPCManager.java:582)
	at com.isomorphic.servlet.IDACall.processRPCTransaction(IDACall.java:156)
	at com.isomorphic.servlet.IDACall.processRequest(IDACall.java:121)
	at com.isomorphic.servlet.IDACall.doPost(IDACall.java:73)
	at javax.servlet.http.HttpServlet.service(HttpServlet.java:637)
	at com.isomorphic.servlet.BaseServlet.service(BaseServlet.java:152)
	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$CachedChain.doFilter(ServletHandler.java:1097)
	at com.isomorphic.servlet.CompressionFilter.doFilter(CompressionFilter.java:259)

thanks,
Zdary

[Isomorphic]

Don't create a new RPCManager. If you declare an argument of type RPCManager, the current (already created) RPCManager will be passed to you.

[zdary]

thank, it works.

My code looks like this

DMI file

public void download(RPCManager manager, HttpServletResponse response) throws Exception {
    	manager.doCustomResponse();
    	response.setContentType("text/csv");
    	response.setHeader("Content-Disposition", "attachment; filename=\"example-data.any\"");
    	OutputStream out = response.getOutputStream();
    	byte[] utf8Bytes = "content of the file".getBytes("UTF8");
    	out.write(utf8Bytes);
    	out.flush();
    	out.close();
    }

*.ds.xml

	<operationBindings> 
		<operationBinding operationType="downloadFile">
			<serverObject className="cz.bcom.FilesDMI" methodName="download" />
		</operationBinding>
	</operationBindings>

and GUI

DataSource filesDS = DataSource.get("filesDS");
downloadButton.addClickHandler(new ClickHandler() {  
  public void onClick(ClickEvent event) {
    filesDS.downloadFile(fileGrid.getSelectedRecord());
  }  
});