1, create an ExcelExportAction class

import java.io.ByteArrayInputStream;
import java.io.ByteArrayOutputStream;
import java.io.IOException;
import java.io.InputStream;
import org.apache.poi.hssf.usermodel.HSSFCell;
import org.apache.poi.hssf.usermodel.HSSFCellStyle;
import org.apache.poi.hssf.usermodel.HSSFFont;
import org.apache.poi.hssf.usermodel.HSSFRow;
import org.apache.poi.hssf.usermodel.HSSFSheet;
import org.apache.poi.hssf.usermodel.HSSFWorkbook;
import org.apache.poi.hssf.util.HSSFColor;
import com.opensymphony.xwork2.ActionSupport;
public class ExcelExportAction extends ActionSupport{
    private static final long serialVersionUID = 4565154051377016557L;
    // private static final long cen = 2565374152L;
    Private static final String[] header = { "serial number", "employee number", "employee name", "affiliation department", "position", "job date", "remark" };
    private String excelFileName;
    private InputStream excelStream;

    /**
     * export excel
     * 
     * @return
     */
    public String exportExcel() {
	try {
	     // Create excel
	    HSSFWorkbook workbook = new HSSFWorkbook();
	     HSSFSheet sheet = workbook.createSheet("test file 1");
	     // Here is createRow(int), don't remember with sheet.getRow(int). . . .
	    HSSFRow row = sheet.createRow(0);
	    row.setHeightInPoints(25);
	    HSSFCellStyle cellstyle = workbook.createCellStyle();
	    cellstyle.setAlignment(HSSFCellStyle.ALIGN_CENTER);
	    cellstyle.setVerticalAlignment(HSSFCellStyle.VERTICAL_CENTER);
	    cellstyle.setFillForegroundColor(HSSFColor.GREY_25_PERCENT.index);
	    cellstyle.setFillPattern(HSSFCellStyle.SOLID_FOREGROUND);
	    HSSFFont font = workbook.createFont();
	    font.setBoldweight(HSSFFont.BOLDWEIGHT_BOLD);
	    cellstyle.setFont(font);
	    HSSFCell cell;
	    for (int i = 0; i < header.length; i++) {
		cell = row.createCell(i);
		cell.setCellStyle(cellstyle);
		sheet.setColumnWidth(i,25*256);
		cell.setCellValue(header[i]);
	    }
	     // Define 20 rows of data to be inserted into the excel table
	    for (int j = 1; j <= 50; j++) {
		row = sheet.createRow(j);
		row.setHeightInPoints(20);
		HSSFCell cell0 = row.createCell(0);
		cell0.setCellValue(j);

		HSSFCell cell1 = row.createCell(1);
		 cell1.setCellValue("employee number" + j);

		HSSFCell cell2 = row.createCell(2);
		 cell2.setCellValue("employee name" + j);

		HSSFCell cell3 = row.createCell(3);
		 cell3.setCellValue("Soft Research" + j + "Parts");

		HSSFCell cell4 = row.createCell(4);
		 cell4.setCellValue("programmer" + j);

		HSSFCell cell5 = row.createCell(5);
		cell5.setCellValue("2013-05-28");

		HSSFCell cell6 = row.createCell(6);
		cell6.setCellValue("remark");
	    }
	     // save the file in the stream
	    ByteArrayOutputStream bos = new ByteArrayOutputStream();
	    workbook.write(bos);
	    byte[] fileContent = bos.toByteArray();
	    ByteArrayInputStream bis = new ByteArrayInputStream(fileContent);

	    excelStream = bis;
	     excelFileName = "EXCEL file export test.xls";
	    excelFileName = new String(excelFileName.getBytes(),"iso-8859-1");
	} catch (IOException e) {
	    e.printStackTrace();
	}

	return SUCCESS;
    }

    /** getter/setter method **/
    public String getExcelFileName() {
	return excelFileName;
    }

    public void setExcelFileName(String excelFileName) {
	this.excelFileName = excelFileName;
    }

    public InputStream getExcelStream() {
	return excelStream;
    }

    public void setExcelStream(InputStream excelStream) {
	this.excelStream = excelStream;
    }

}

2, struts.xml configuration

<!-- exprot excel file -->
		<action name="exportExcel" class="com.hnyyzw.trm.action.ExcelExportAction"
			method="exportExcel">
			<result name="success" type="stream">
				 <!-- Download file type -->
				<param name="contentType">application/vnd.ms-excel</param>
				 <!-- return stream excelStream variable name in Action -->
				<param name="inputName">excelStream</param>
				 <!-- attachment The parameters of this location are quite special. You can set whether to download a prompt box when downloading, or download it directly. fileName specifies the name of the generated file (suitable for dynamically generating file names, such as when reporting, generally speaking, it is a few months of statistical data) for the action variable -->
				<param name="contentDisposition">attachment;filename=${excelFileName}</param>
				<param name="bufferSize">1024</param>
			</result>
		</action>