how to return excel in Struts2 result?

Question

I am trying to return an Excel sheet from my struts2 action class.

I am not sure what result-type should I be using? Has anyone tried to return an excel from struts2 action class?
I would like the user to be presented with open/save/cancel dialog box

Answer 1

Omnipresent covered what you need in struts.xml. I'm adding an example with the Action as well:

InputStream excelStream
String contentDisposition
String documentFormat = "xlsx"

String excel() {

    ServletContext servletContext = ServletActionContext.getServletContext()
    String filePath = servletContext.getRealPath("/WEB-INF/template/excel/mytemplate.${documentFormat}")

    File file = new File(filePath)
    Workbook wb = WorkbookFactory.create(new FileInputStream(file))

    Sheet sheet = wb.getSheetAt(0)

<write to excel file>

    ByteArrayOutputStream baos = new ByteArrayOutputStream()
    wb.write(baos)
    excelStream = new ByteArrayInputStream(baos.toByteArray())
    contentDisposition = "filename=\"myfilename.${documentFormat}\""

    return SUCCESS
}

String getExcelContentType() {
    return documentFormat == "xlsx" ? "application/vnd.openxmlformats-officedocument.spreadsheetml.sheet" : "application/vnd.ms-excel"
}

I'm using the poi model: org.apache.poi.ss.usermodel.

You can replace "xlsx" with "xls" if you want.

struts.xml:

<action name="myaction" class="com.example.MyAction" method="excel">
        <result type="stream">
            <param name="contentType">${excelContentType}</param>
            <param name="inputName">excelStream</param>
            <param name="contentDisposition">contentDisposition</param>
            <param name="bufferSize">1024</param>
        </result>
    </action>

(add semicolons and stuff to translate to valid Java)

Answer 2

You can utilize the Stream Result type

an Example will look like this:

<result name="excel" type="stream">
    <param name="contentType">application/vnd.ms-excel</param>
    <param name="inputName">excelStream</param>
    <param name="contentDisposition">attachment; filename="${fileName}"</param>
    <param name="bufferSize">1024</param>
    <param name="contentLength">${contentLength}</param>
 </result>

excelStream will be a method in your action class, contentLength will be length of the stream, fileName will be a getter which will return back the name of the file.

Answer 3

If you need to dynamically generate an Excel file using POI/HSSF and return in Struts 2,

JSP

<s:url action="DownloadExcel.action" var="downloadUrl">
</s:url>
<s:a href="%{downloadUrl}">Click to Download</s:a>

Action Method

@Action(value = "DownloadExcel")
public void download() throws Exception {
    
    HttpServletRequest request = ServletActionContext.getRequest();
    HttpServletResponse response = ServletActionContext.getResponse();
    
    String filename = "report.xlsx"; // or any other filename strategy
    String mimeType = "application/vnd.openxmlformats-officedocument.spreadsheetml.sheet";
    String characterEncoding = response.getCharacterEncoding();
    if (characterEncoding != null) {
        mimeType += "; charset=" + characterEncoding;
    }
    response.setContentType("application/octet-stream");
    response.setHeader("Content-Disposition", "attachment;filename=" + filename);

    XSSFWorkbook workbook = new XSSFWorkbook();
    XSSFSheet sheet = workbook.getSheetAt(0);
    // Fill out workbook as necessary... (simple example)
    XSSFRow row = sheet.createRow(0);
    XSSFCell cell = row.createCell(0);
    cell.setCellValue("test");
    //...

    ServletOutputStream out = null;
    try {
        out = response.getOutputStream();
        workbook.write(out);
        workbook.close();
    } catch (IOException e) {
        log.error("Failed to write into response - fileName=" + filename + ", mimeType=" + mimeType, e);
    }
    finally {
        if (out != null) {
            out.flush();
            out.close();
        }
    }
}