web项目导出excel表格

• 原博地址:https://blog.csdn.net/yuan487639/article/details/76212170
  
• 该功能涉及到两个知识点，一是制作excel相关插件的使用，二是导出文件，spring-mvc该如何配置
• 先说excel插件的使用，这次使用的是org.apache.poi包，版本是3.9，下面粘完整能运行的代码
• maven依赖

<dependency>
    <groupId>org.apache.poi</groupId>
    <artifactId>poi</artifactId>
    <version>3.9</version>
</dependency>

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• 插件的实体类，也可以理解为参数，这里采用了build设计模式，好处是初始化了一些默认值，使用的时候代码写的方便。针对表格导出，我觉得三个参数足够了，标题、表头以及数据，所以，这三个参数构造方法我设计的必传，其它使用默认参数

package com.util;

import java.util.List;

public class ExcelParam {
    String name;
    int width;
    String font;
    String[] headers;
    /**
     * 导出数据的样式
     * 1:String left;
     * 2:String center
     * 3:String right
     * 4 int  right
     * 5:float ###,###.## right
     * 6:number: #.00% 百分比 right
     */
    int[] ds_format;
    /**
     * 每列表格的宽度,默认为256 * 14
     */
    int[] widths;
    List<String[]> data;

    private ExcelParam() {

    }
    //使用Builder模式，设置默认参数和必填参数
    public static class Builder {
        String name;
        int width = 256 * 14;
        String font = "微软雅黑";
        String[] headers;
        int[] ds_format;
        int[] widths;
        List<String[]> data;

        public Builder(String name) {
            this.name = name;
        }

        public Builder font(String font) {
            this.font = font;
            return this;
        }

        public Builder width(int width) {
            this.width = width;
            return this;
        }

        public Builder headers(String[] headers) {
            this.headers = headers;
            return this;
        }

        public Builder ds_format(int[] ds_format) {
            this.ds_format = ds_format;
            return this;
        }

        public Builder widths(int[] widths) {
            this.widths = widths;
            return this;
        }

        public Builder data(List<String[]> data) {
            this.data = data;
            return this;
        }

        public ExcelParam build() {
            ExcelParam excelParam = new ExcelParam();
            excelParam.name = this.name;
            excelParam.data = this.data;
            excelParam.widths = this.widths;
            excelParam.ds_format = this.ds_format;
            excelParam.headers = this.headers;
            excelParam.font = this.font;
            excelParam.width = this.width;
            return excelParam;
        }
    }
}

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• 插件本身

package com.ucredit.util;

import org.apache.poi.hssf.usermodel.*;

import javax.servlet.http.HttpServletResponse;
import java.io.IOException;
import java.io.OutputStream;
import java.net.URLEncoder;

public class ExcelUtil {
    private ExcelUtil() {
    }

    public static void export(ExcelParam excelParam, HttpServletResponse response) throws IOException {
        if (excelParam.widths == null) {
            excelParam.widths = new int[excelParam.headers.length];
            for (int i = 0; i < excelParam.headers.length; i++) {
                excelParam.widths[i] = excelParam.width;
            }
        }
        if (excelParam.ds_format == null) {
            excelParam.ds_format = new int[excelParam.headers.length];
            for (int i = 0; i < excelParam.headers.length; i++) {
                excelParam.ds_format[i] = 1;
            }
        }
        //创建一个工作薄
        HSSFWorkbook wb = new HSSFWorkbook();
        //创建一个sheet
        HSSFSheet sheet = wb.createSheet("excel");
        int rowCount = 0;
        if (excelParam.headers != null) {
            HSSFRow row = sheet.createRow(rowCount);
            //表头样式
            HSSFCellStyle style = wb.createCellStyle();
            HSSFFont font = wb.createFont();
            font.setBoldweight(HSSFFont.BOLDWEIGHT_BOLD);
            font.setFontHeightInPoints((short) 11);
            style.setFont(font);
            style.setAlignment(HSSFCellStyle.ALIGN_CENTER);

            for (int i = 0; i < excelParam.headers.length; i++) {
                sheet.setColumnWidth(i, excelParam.widths[i]);
                HSSFCell cell = row.createCell(i);
                cell.setCellValue(excelParam.headers[i]);
                cell.setCellStyle(style);
            }
            rowCount++;
        }
        HSSFCellStyle style = wb.createCellStyle();
        style.setAlignment(HSSFCellStyle.ALIGN_CENTER);
        //表格主体  解析list
        for (int i = 0; i < excelParam.data.size(); i++) {  //行数
            HSSFRow row = sheet.createRow(rowCount);
            for (int j = 0; j < excelParam.headers.length; j++) {  //列数
                HSSFCell cell = row.createCell(j);
                cell.setCellValue(excelParam.data.get(i)[j]);
                cell.setCellStyle(style);
            }
            rowCount++;
        }
        //设置文件名
        String fileName = excelParam.name + ".xls";
        response.setContentType("application/vnd.ms-excel");
        response.setHeader("Content-disposition", "attachment;filename=" + URLEncoder.encode(fileName, "UTF-8"));
        response.setHeader("Pragma", "No-cache");
        OutputStream outputStream = response.getOutputStream();
        wb.write(outputStream);
        outputStream.flush();
        outputStream.close();
    }
}

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• 其实从这个方法就能看出，文件最后导出，实际上是往response中的outputStream中写入文件，之后的工作是由浏览器来完成的
• controller层写法

    @RequestMapping(value = "download")
    public void download(@RequestParam String username,
                         @RequestParam String operation_module,
                         @RequestParam String operation_type,
                         @RequestParam String start_time,
                         @RequestParam String end_time,
                         HttpServletResponse response) throws Exception {
        List<OperationLogEntity> list = operationLogDao.get(username, operation_module, operation_type, start_time, end_time);
        String[] heads = {"序号", "账号", "姓名", "操作类型", "操作模块", "处理员工号码", "处理结果", "登录IP", "时间", "所在城市"};
        List<String[]> data = new LinkedList<>();
        for (int i = 0; i < list.size(); i++) {
            OperationLogEntity entity = list.get(i);
            String[] temp = new String[10];
            temp[0] = String.valueOf(i + 1);
            temp[1] = entity.getUsername();
            temp[2] = entity.getName();
            temp[3] = entity.getOperation_type();
            temp[4] = entity.getOperation_module();
            temp[5] = entity.getProcess_number();
            temp[6] = entity.getProcess_result();
            temp[7] = entity.getIp();
            temp[8] = DateUtils.getDateBeforeOrAfterStrCN(entity.getOperation_time(), 0);
            temp[9] = entity.getCity();
            data.add(temp);
        }
        ExcelParam param = new ExcelParam.Builder("操作日志").headers(heads).data(data).build();
        ExcelUtil.export(param, response);
    }

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• 实际使用

//这样写很简洁
ExcelParam param = new ExcelParam.Builder("操作日志").headers(heads).data(data).build();