Download file

Implemented using Spring MVC, rest service.

Display file on screen or download as attachment.

@Controller
public class FileController
{
private static final Logger log = LoggerFactory.getLogger(FileController.class);

@RequestMapping(value = "/file/{id}", method = RequestMethod.GET)
public void getFileViaAttachment(@PathVariable String id, HttpServletResponse response)
{
log.info("getFile " + id);
try
{

String content = "testing file download";
String fileName = "mojFileIzStringa.txt";
InputStream in = new ByteArrayInputStream(content.getBytes(StandardCharsets.UTF_8));

IOUtils.copy(in, response.getOutputStream());

response.setContentType("application/text");
response.setHeader("Content-Disposition", "attachment; filename=" + fileName);
response.flushBuffer();
}
catch (IOException e)
{
e.printStackTrace();
}
}

@RequestMapping(value = "/many", method = RequestMethod.GET)
public void getManyLinesViaAttachment(HttpServletResponse response)
{
log.info("getManyLines ");
try
{
String[] linesArrays = { "prva linija", "druga linija", "xxx linija" };
List<String> linesList = Arrays.asList(linesArrays);
String fileName = "mojFileSpunoLinija.csv";
IOUtils.writeLines(linesList, null, response.getOutputStream(), StandardCharsets.UTF_8);

response.setContentType("application/text");
response.setHeader("Content-Disposition", "attachment; filename=" + fileName);
response.flushBuffer();
}
catch (IOException e)
{
e.printStackTrace();
}
}

// every line in new row
@RequestMapping(value = "/getFileAsItIs", method = RequestMethod.GET, produces = "text/plain")
@ResponseBody
public String getFileAsItIs()
{
log.info("getFileAsItIs ");
String[] linesArrays = { "prva linija", "druga linija", "xxx linija" };
List<String> linesList = Arrays.asList(linesArrays);
StringBuilder sb = new StringBuilder();

for (String s : linesList)
{
sb.append(s).append(System.lineSeparator());
}

return sb.toString();
}
}

Export to pdf

There is datatable and when user click on particular row it needs to be printed.

data table in xhtml:
 <ice:dataTable value="#{activeBackingBean.selectedEntity.subjectableList}" var="bill" ...

inside column put link component instead outputTex, which will pass bill number:
<ice:commandLink value="#{bill.GUINumber}" actionListener="#{activeBackingBean.billToPdf}" style="color:black;" title="Print bill">
   <f:param name="billNumber" value="#{bill.GUINumber}" />
</ice:commandLink>

In backing beanu there is (actionListener) method:
public void billToPdf(ActionEvent ae)
{
read request parametar and save object in class field for later use, call hidden button
String parameter = FacesContext.getCurrentInstance().getExternalContext().getRequestParameterMap().get("billNumber");
log.debug("billToPdf: " + parameter);
//find appropriate object (bill)
JavascriptContext.addJavascriptCall(FacesContext.getCurrentInstance(), "document.getElementById('PrintForm:PrintButton').click();");
}

hidden button in xhtml:
<ice:form id="PrintForm">
<ice:commandButton id="PrintButton" visible="false" actionListener="#"
onclick="{location.href='#{downloadServlet}?fileCreator=null&amp;fileType=pdf&amp;fileAction=activeBackingBean.billToPdf'}" />
</ice:form>

Click will call servlet which will call appropriate method in bean via reflection (fileAction -our method which needs to be called):
ApplicationContext ctx = WebApplicationContextUtils.getWebApplicationContext(getServletContext());
ctx.getBean("activeBackingBean");
Object result = MethodUtils.invokeMethod(bean, methodName, iS); //iS is InputStream
ServletOutputStream stream = response.getOutputStream();  ...

in backing beanu method that exports to PDF:
public FileObject billToPdf() throws JRException, IOException
{
if (log.isDebugEnabled()) log.debug("monthBillToPdf: " + bill);
return billManager.billToPdf(bill);
}


Second approach:
call servlet with submitted oid. Via refection call bean method, fetch appropriate object and print it.