生成 excel 直接用 httpServletResponse 输出

　　之前写过一篇文章《超详细的java生成excel文件并下载》，该文章虽然够详细，也行得通，但还是有一定的缺陷，该文章可以拆分成两个部分，一是指定位置生成excel文件，二是根据地址下载文件。缺陷的部分是会产生中间文件，而这个中间文件我们并不需要，如果每次下载的时候都会生成一个这样的文件，那久而久之岂不是浪费空间，而且生成文件之后再读取输出这样也耗时间。所以今天就对之前的文章进行优化处理下。

package com.test.demo.controllers;import com.test.demo.domain.entities.Address;
import com.test.demo.services.ExcelService;
import jxl.Workbook;
import jxl.format.Alignment;
import jxl.format.Border;
import jxl.format.BorderLineStyle;
import jxl.format.Colour;
import jxl.format.*;
import jxl.format.VerticalAlignment;
import jxl.write.*;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RestController;
import org.springframework.web.context.request.RequestContextHolder;
import org.springframework.web.context.request.ServletRequestAttributes;import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.File;
import java.io.FileInputStream;
import java.io.InputStream;
import java.io.OutputStream;
import java.text.SimpleDateFormat;
import java.util.List;/*** @author dyh* @create 2018-11-15 下午10:20* @desc excle表格功能编写**/
@RestController
@RequestMapping("/excel")
public class ExcelController {@Autowiredprivate ExcelService excelService;/*** 下载文件** @return*/@RequestMapping({"/download"})public void download() {ServletRequestAttributes requestAttributes = (ServletRequestAttributes) RequestContextHolder.getRequestAttributes();HttpServletResponse response = requestAttributes.getResponse();HttpServletRequest request = requestAttributes.getRequest();// 文件名String filename = "地址列表.xls";OutputStream out = null;try {// 下面几行是为了解决文件名乱码的问题httpServletResponse.setHeader("Content-Disposition", "attachment;filename=" + new String(filename.getBytes(), "iso-8859-1"));httpServletResponse.setContentType("application/vnd.ms-excel;charset=UTF-8");httpServletResponse.setHeader("Pragma", "no-cache");httpServletResponse.setHeader("Cache-Control", "no-cache");httpServletResponse.setDateHeader("Expires", 0);out = httpServletResponse.getOutputStream();// 创建写工作簿对象，这里直接采用流输出，而不会再生成一个文件WritableWorkbook workbook = Workbook.createWorkbook(out);// 工作表WritableSheet sheet = workbook.createSheet("地址列表", 0);// 设置字体;WritableFont font = new WritableFont(WritableFont.ARIAL, 14, WritableFont.BOLD, false, UnderlineStyle.NO_UNDERLINE, Colour.BLACK);WritableCellFormat cellFormat = new WritableCellFormat(font);// 设置背景颜色;
            cellFormat.setBackground(Colour.WHITE);// 设置边框;
            cellFormat.setBorder(Border.ALL, BorderLineStyle.DASH_DOT);// 设置文字居中对齐方式;
            cellFormat.setAlignment(Alignment.CENTRE);// 设置垂直居中;
            cellFormat.setVerticalAlignment(VerticalAlignment.CENTRE);// 分别给1,5,6列设置不同的宽度;sheet.setColumnView(0, 15);sheet.setColumnView(4, 60);sheet.setColumnView(5, 35);// 给sheet电子版中所有的列设置默认的列的宽度;sheet.getSettings().setDefaultColumnWidth(20);// 给sheet电子版中所有的行设置默认的高度，高度的单位是1/20个像素点,但设置这个貌似就不能自动换行了// sheet.getSettings().setDefaultRowHeight(30 * 20);// 设置自动换行;cellFormat.setWrap(true);// 单元格Label label0 = new Label(0, 0, "ID", cellFormat);Label label1 = new Label(1, 0, "省", cellFormat);Label label2 = new Label(2, 0, "市", cellFormat);Label label3 = new Label(3, 0, "区", cellFormat);Label label4 = new Label(4, 0, "详细地址", cellFormat);Label label5 = new Label(5, 0, "创建时间", cellFormat);sheet.addCell(label0);sheet.addCell(label1);sheet.addCell(label2);sheet.addCell(label3);sheet.addCell(label4);sheet.addCell(label5);// 给第二行设置背景、字体颜色、对齐方式等等;WritableFont font2 = new WritableFont(WritableFont.ARIAL, 14, WritableFont.NO_BOLD, false, UnderlineStyle.NO_UNDERLINE, Colour.BLACK);WritableCellFormat cellFormat2 = new WritableCellFormat(font2);// 设置文字居中对齐方式;
            cellFormat2.setAlignment(Alignment.CENTRE);// 设置垂直居中;
            cellFormat2.setVerticalAlignment(VerticalAlignment.CENTRE);cellFormat2.setBackground(Colour.WHITE);cellFormat2.setBorder(Border.ALL, BorderLineStyle.THIN);cellFormat2.setWrap(true);// 记录行数int n = 1;// 查找所有地址List<Address> addressList = excelService.findAll();if (addressList != null && addressList.size() > 0) {// 遍历for (Address a : addressList) {SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");String createTime = sdf.format(a.getCreateTime());Label lt0 = new Label(0, n, a.getId() + "", cellFormat2);Label lt1 = new Label(1, n, a.getProvince(), cellFormat2);Label lt2 = new Label(2, n, a.getCity(), cellFormat2);Label lt3 = new Label(3, n, a.getArea(), cellFormat2);Label lt4 = new Label(4, n, a.getAddress(), cellFormat2);Label lt5 = new Label(5, n, createTime, cellFormat2);sheet.addCell(lt0);sheet.addCell(lt1);sheet.addCell(lt2);sheet.addCell(lt3);sheet.addCell(lt4);sheet.addCell(lt5);n++;}}//开始执行写入操作
            workbook.write();//关闭流
            workbook.close();out.close();} catch (Exception e) {e.printStackTrace();}}
}