Question

Background

Write an XML document to a browser’s response stream and cause the browser to display a “Save As” dialog.

Problem

Consider the following download() method:

  HttpServletResponse response = getResponse();

  BufferedWriter bw = new BufferedWriter( new OutputStreamWriter(
      response.getOutputStream() ) );

  String filename = "domain.xml";
  String mimeType = new MimetypesFileTypeMap().getContentType( filename );

  // Prints "application/octet-stream"
  System.out.println( "mimeType: " + mimeType );

  // response.setContentType( "text/xml;charset=UTF-8" );
  response.setContentType( mimeType );
  response.setHeader( "Content-Disposition", "attachment;filename="
      + filename );

  bw.write( getDomainDocument() );
  bw.flush();
  bw.close();

In Firefox, the XML content is displayed in the browser window. In IE 7, the XML content is not displayed — you have to view the document source. Neither situation is the desired result.

The web page uses the following code for the button:

    <a4j:commandButton action="#{domainContent.download}" value="Create Domain" reRender="error" />

The XML that is generated does not start with <?xml version="1.0"?>, rather the XML content resembles:

<schema xmlns="http://www.jaspersoft.com/2007/SL/XMLSchema" version="1.0">
  <items>
    <item description="EDT Class Code" descriptionId="" label="EDT Class Code" labelId="" resourceId="as_pay_payrolldeduction.edtclass"/>
  </items>
  <resources>
    <jdbcTable datasourceId="JNDI" id="as_pay_payrolldeduction" tableName="as_pay.payrolldeduction">
      <fieldList>
        <field id="payamount" type="java.math.BigDecimal"/>
      </fieldList>
    </jdbcTable>
  </resources>
</schema>

Update #1

Note the following line of code:

response.setHeader( "Content-Disposition", "attachment;filename=" + filename );

Update #2

Using <a4j:commandButton ... /> is the problem; a regular <h:commandButton .../> performs as expected. Using the <h:commandBUtton .../> prevents the <a4j:outputPanel .../> from refreshing any error messages.

Related Seam Message.

Mime Type

The following mime types do not trigger the “Save As” dialog:

• "application/octet-stream"
• "text/xml"
• "text/plain"

Question

What changes will cause the a4j:commandButton to trigger a “Save As” dialog box so that the user is prompted to save the XML file (as domain.xml)?

Thank you.

Answer 1

Problems

The code has the following issues:

• An Ajax call (<a4j:commandButton .../>) does not work with attachments.
• Creating the output content must happen first.
• Displaying the error messages also cannot use Ajax-based a4j tags.

Solution

1. Change <a4j:commandButton .../> to <h:commandButton .../>.
2. Update the source code:
   1. Change bw.write( getDomainDocument() ); to bw.write( document );.
   2. Add String document = getDomainDocument(); to the first line of the try/catch.
3. Change the <a4j:outputPanel.../> (not shown) to <h:messages showDetail="false"/>.

Essentially, remove all the Ajax facilities related to the commandButton. It is still possible to display error messages and leverage the RichFaces UI style.

References

• Using a commandButton in a jsf Page to download a file
• http://www.coderanch.com/t/483892/JSF/java/when-commandButton-commandLink
• http://seamframework.org/135584.lace