Java Apache Poi Util

本文主要是java整合apache poi，可以实现下载到本地或者返回输出流的util。

代码还有很大的优化空间，自行优化！！！

STEP1:

导入依赖：

我用的3.15版本

<dependency>
      <groupId>org.apache.poi</groupId>
      <artifactId>poi</artifactId>
      <version>${apache.poi.version}</version>
    </dependency>
    <dependency>
      <groupId>org.apache.poi</groupId>
      <artifactId>poi-ooxml</artifactId>
      <version>${apache.poi.version}</version>
    </dependency>
    <dependency>
      <groupId>org.apache.poi</groupId>
      <artifactId>poi-ooxml-schemas</artifactId>
      <version>${apache.poi.version}</version>
    </dependency>

STEP2:

参数dataList,就是对象的集合，比如User对象，那么传入的就是List<User>,会自动解析生成表头(第一列)；  

Util如下：

package com.dzh.extra.utils;

import org.apache.poi.xssf.usermodel.XSSFRow;
import org.apache.poi.xssf.usermodel.XSSFSheet;
import org.apache.poi.xssf.usermodel.XSSFWorkbook;

import java.io.ByteArrayOutputStream;
import java.io.FileOutputStream;
import java.util.ArrayList;
import java.util.Iterator;
import java.util.List;
import java.util.Map;

public class POIUtil {

    /**
     * 写到本地指定目录
     */
    public static void writeExcelData(List<Map> dataList, String filePath){
//        String filePath = new StringBuffer("E:\\es_less\\").append(index).append("_").append(differentList.size()).append(XLSX).toString();
        try {
            XSSFWorkbook workbook = getWork(dataList);
            FileOutputStream fos = new FileOutputStream(filePath);
            workbook.write(fos);
            System.out.println("写入成功");
            fos.flush();
            fos.close();
        } catch (Exception e) {
            e.printStackTrace();
        }
    }

    /**
     * 输出流
     */
    public static ByteArrayOutputStream getExcelOutStream(List<Map> dataList){
        try {
            XSSFWorkbook workbook = getWork(dataList);
            ByteArrayOutputStream out = new ByteArrayOutputStream();
            workbook.write(out);
            return out;
        } catch (Exception e) {
            e.printStackTrace();
        }
        return null;
    }

    private static XSSFWorkbook getWork(List<Map> dataList) throws Exception{
        if (CollectionUtil.isEmpty(dataList)){
            return null;
        }
        List<String> columns = new ArrayList<>();
        Map mapFirst = dataList.get(0);
        Iterator iterator = mapFirst.entrySet().iterator();
        while(iterator.hasNext()){
            java.util.Map.Entry entry = (java.util.Map.Entry)iterator.next();
            columns.add(String.valueOf(entry.getKey()));
        }
        // 创建文档以及工作簿
        XSSFWorkbook workbook = new XSSFWorkbook();
        XSSFSheet sheet = workbook.createSheet("sheet1");
        // 写入第一行表头(标题)
        XSSFRow row = sheet.createRow(0);
        for (int i = 0; i < columns.size(); i++) {
            row.createCell(i).setCellValue(columns.get(i));
        }
        // 具体数据
        for (int i = 0; i < dataList.size(); i++) {
            XSSFRow row1 = sheet.createRow(i + 1);
            Map map = dataList.get(i);
            // 创建单元格并设值
            for (int j = 0; j < columns.size(); j++) {
                row1.createCell(j).setCellValue(String.valueOf(map.get(columns.get(j))));
            }
        }
        return workbook;
    }
}