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.