jxl excelUtils

package com.ruijie.dinnerorder.web.utils;

import java.io.File;
import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.IOException;
import java.util.List;

import javax.faces.context.FacesContext;
import javax.servlet.ServletContext;
import javax.servlet.ServletOutputStream;
import javax.servlet.http.HttpServletResponse;

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;

public class ExcelUtils {
	private static String sheetName = "data";  
	private HSSFWorkbook wb;  
	private HSSFSheet sheet;  
	private HSSFRow row;  
	private HSSFCell cell;  
	private HSSFFont font;  
	private HSSFCellStyle cellStyle;  
	private FileOutputStream fileOut;  
	public ExcelUtils() { 
		wb = new HSSFWorkbook();  
	} 						

	/**  
	 * @param excelName 
	 * excel名称。 
	 * @param list  
	 * 这个list里面存放的是对象数组。数组元素可以转化为字符串显示的。这个对象数组一般对应数据库里的几列。  
	 * @param firstRowValue 
	 * */  
	public void outputExcel(String excelName, List list, String[] firstRowValue) { 
		try {  
			this.createSheet(firstRowValue);  
			this.setValueToRow(excelName, list);  
		} catch (Exception ex) {  
			System.out.print(ex); 
		}  // System.out.println("文件名是:" + excelName);  downloadFile(excelName);  }  
	}
	
	public void outputExcel(String excelName, List list) {
	    try {
	      this.setValueToRow(excelName, list);
	    } catch (Exception e) {
	      // TODO: handle exception
	    }
	    downloadFile(excelName);
	  }

	/**
	 * 设置excel的没一行的值...
	 * @param excelName
	 * @param list
	 */
	 private void setValueToRow(String excelName, List list) {
		    // 获得JSF上下文环境
		    FacesContext context = FacesContext.getCurrentInstance();
		    // 获得ServletContext对象
		    ServletContext servletContext = (ServletContext) context
		        .getExternalContext().getContext();
		    // 取得文件的绝对路径
		    excelName = servletContext.getRealPath("/UploadFile") + "/" + excelName;
		    System.out.println("生成文件的路径是：" + excelName);
		    Object[] obj;
		    try {
		      for (int i = 0; i < list.size(); i++) {
		        row = sheet.createRow(i + 1);
		        obj = (Object[]) list.get(i);
		        this.createCell(row, obj);
		      }
		      fileOut = new FileOutputStream(excelName);
		      wb.write(fileOut);

		    } catch (Exception ex) {
		      System.out.print("生成报表有误:" + ex);
		    } finally {
		      try {
		        fileOut.flush();
		        fileOut.close();
		      } catch (Exception e) {
		        System.out.println("ExcelUtil.setValueToRow()");
		      }
		    }
		  }

	 	/**
	 	 * 创建表头
	 	 * @param firstRowValue
	 	 */
		  private void createSheet(String[] firstRowValue) {
		    try {
		      sheet = wb.createSheet(ExcelUtils.sheetName);
		      row = sheet.createRow(0);
		      font = wb.createFont();
		      font.setBoldweight(HSSFFont.BOLDWEIGHT_BOLD);
		      cellStyle = wb.createCellStyle();
		      cellStyle.setFont(font);
		      for (int i = 0; i < firstRowValue.length; i++) {
		        cell = row.createCell((short) i);
		        cell.setCellStyle(cellStyle);
//		        cell.setEncoding(HSSFCell.ENCODING_UTF_16);
		        cell.setCellValue(firstRowValue[i]);
		      }
		    } catch (Exception ex) {
		      System.out.print(ex);
		    }
		  }
		  
		  /**
		   * 创建表格的值
		   * @param row
		   * @param obj
		   */
		  private void createCell(HSSFRow row, Object[] obj) {
		    try {
		      for (int i = 0; i < obj.length; i++) {
		        cell = row.createCell((short) i);
//		        cell.setEncoding(HSSFCell.ENCODING_UTF_16);
		        cell.setCellValue(obj[i].toString());
		      }
		    } catch (Exception ex) {
		      System.out.print(ex);
		    }
		  }

		  /**
		   * <p>
		   * 功能说明：根据提供的文件名下载文件,不支持中文文件名
		   * </p>
		   * 此方法由yongtree添加,实现文件生成后的下载
		   * 
		   * @param strfileName
		   *            String
		   * @return void
		   */
		  private static void downloadFile(String strfileName) {
		    try {
		      // 获得JSF上下文环境
		      FacesContext context = FacesContext.getCurrentInstance();
		      // 获得ServletContext对象
		      ServletContext servletContext = (ServletContext) context
		          .getExternalContext().getContext();
		      // 取得文件的绝对路径
		      String excelName = servletContext.getRealPath("/UploadFile") + "/"
		          + strfileName;
		      File exportFile = new File(excelName);
		      
		      HttpServletResponse httpServletResponse = (HttpServletResponse) FacesContext
		          .getCurrentInstance().getExternalContext().getResponse();
		      ServletOutputStream servletOutputStream = httpServletResponse
		          .getOutputStream();
		      httpServletResponse.setHeader("Content-disposition",
		          "attachment; filename=" + strfileName);
		      httpServletResponse.setContentLength((int) exportFile.length());
		      httpServletResponse.setContentType("application/x-download");
		      // httpServletResponse.setContentType("application/vnd.ms-excel");

		      byte[] b = new byte[1024];
		      int i = 0;
		      FileInputStream fis = new java.io.FileInputStream(exportFile);
		      while ((i = fis.read(b)) > 0) {
		        servletOutputStream.write(b, 0, i);
		      }
		    } catch (IOException e) {
		      e.printStackTrace();
		    }
		    FacesContext.getCurrentInstance().responseComplete();
		  }
}