Generate and download file with jboss seam - file

Question

I need to add an 'export' function to an existing web app using seam. The purpose is to export search results to a csv file. I have no problem generating a csv, but I do not know how the send the csv back to the user.
I do not want to store the csv on the server because that would be waisted storage space. How could I achieve this in jboss seam?

Answer 1

Use the Document Store Servlet provided by Seam.
Almost copying and pasting from the reference doc, declare the servlet in web.xml like this:
<servlet>
<servlet-name>Document Store Servlet</servlet-name>
<servlet-class>org.jboss.seam.document.DocumentStoreServlet</servlet-class>
</servlet>
<servlet-mapping>
<servlet-name>Document Store Servlet</servlet-name>
<url-pattern>/seam/docstore/*</url-pattern>
</servlet-mapping>
Then create a export.xhtml file with only <s:resource> tag:
<s:resource xmlns="http://www.w3.org/1999/xhtml"
xmlns:s="http://jboss.com/products/seam/taglib"
data="#{myComponent.csvData}"
contentType="application/vnd.ms-excel"
fileName="#{myComponent.csvFileName}"/>
Generate link for downloading the file in your page with <s:download>:
<s:download src="/csv/export.xhtml">
<h:outputText value="Download CSV"/>
<f:param name="param1" value="somevalue"/>
<f:param name="param2" value="someOtherValue"/>
</s:download>
Finally, implement getCsvData() and getCsvFileName() methods in your component:
// could be byte[], File or InputStream
public InputStream getCsvData() {
// generate data to be downloaded
}
public String getCsvFileName() {
return "myfile.csv";
}
Note that <s:download> propagates conversation (unless you set propagation=none). If you propagate the conversation context probably you won't need to pass any parameter. For large data set it may be preferable to not propagate the conversation and pass parameter to select the data in a request scoped component.

Answer 2

There's a couple of ways:
1) Check the Seam docs for info on using Seam-Excel to programmatically generate your file and then write it out using a mime-type set for CSV - this is all detailed in the docs.
However, I could not get this to work in the latest version of Seam, as it requires a response object, which used to be available from the Seam context but now only returns null.
2) Code the CSV file you want as an Excel xhtml template (see the Seam docs and example projects) and simply render this as normal using an tag.
I do this regularly and it works well, bar the restriction that you cannot supply a filename.
HTH.