使用阿里EasyExcel实现上传下载、导入导出Excel

首先引入pom依赖：

        
		    com.alibaba
		    easyexcel
		    3.1.3
		

1.下载

后端java代码如下：

@WebServlet("/download")
public class DownloadServlet extends HttpServlet {
	/**
	 * 
	 */
	private static final long serialVersionUID = 1L;

	protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
		response.setContentType("application/octet-stream;charset=UTF-8");
        response.setHeader("Content-disposition", "attachment;filename=down.xlsx");

        EasyExcel.write(response.getOutputStream(), DownloadData.class).sheet("模板").doWrite(data());
	}
	
	private List data() {
        List list = new ArrayList<>();
        for (int i = 0; i < 7; i++) {
            DownloadData data = new DownloadData();
            data.setString("字符串" + i);
            data.setDate(new Date());
            data.setDoubleData(0.56+i);
            list.add(data);
        }
        return list;
    }
}


public class DownloadData {
    @ExcelProperty("字符串标题")
    private String string;
    @ExcelProperty("日期标题")
    private Date date;
    @ExcelProperty("数字标题")
    private Double doubleData;
    
	public String getString() {
		return string;
	}
	public void setString(String string) {
		this.string = string;
	}
	public Date getDate() {
		return date;
	}
	public void setDate(Date date) {
		this.date = date;
	}
	public Double getDoubleData() {
		return doubleData;
	}
	public void setDoubleData(Double doubleData) {
		this.doubleData = doubleData;
	}
}

web端访问即可获得名为down.xlsx的Excel文件，文件内容如下：

 2.上传

前端html代码：

	
Hello tomcat1!
	

		用户名:
 
		上传文件:
 
		
	

后端java代码：

@MultipartConfig
@WebServlet("/upload")
public class UploadServlet extends HttpServlet {
	private static final long serialVersionUID = 1L;

	protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
		Part uploadFile = request.getPart("uploadFile");
		InputStream inputStream = uploadFile.getInputStream();
		UploadDAO uploadDAO = new UploadDAO();
		EasyExcel.read(inputStream, DownloadData.class, new UploadDataListener(uploadDAO)).sheet().doRead();
	}
}


/**
 * 存储上传的数据的类
 *
 **/
public class UploadDAO {

    public void save(List list) {
    	for(int i=0;i {
    /**
     * 每隔5条存储数据库，实际使用中可以100条，然后清理list ，方便内存回收
     */
    private static final int BATCH_COUNT = 5;
    private List cachedDataList = new ArrayList<>(BATCH_COUNT);
    private UploadDAO uploadDAO;
    /**
     * DataListener不能被spring管理，每次读取excel都要new,同时使用这个构造方法把spring管理的类传进来
     */
    public UploadDataListener(UploadDAO uploadDAO) {
        this.uploadDAO = uploadDAO;
    }
    /**
     * 每一条数据解析都会来调用这个方法
     */
    @Override
    public void invoke(DownloadData data, AnalysisContext context) {
        cachedDataList.add(data);
        // 达到BATCH_COUNT了，需要去存储一次数据库，防止数据几万条数据在内存，容易OOM
        if (cachedDataList.size() >= BATCH_COUNT) {
            saveData();
            // 存储完成清理 list
            cachedDataList.clear();
        }
    }

    /**
     * 所有数据解析完成了 都会来调用
     *
     * @param context
     */
    @Override
    public void doAfterAllAnalysed(AnalysisContext context) {
        // 这里也要保存数据，确保最后遗留的数据也存储到数据库
        saveData();
    }

    /**
     * 加上存储数据库
     */
    private void saveData() {
        uploadDAO.save(cachedDataList);
    }
}

数据实体沿用下载类DownloadData.java，在前端页面上传之前下载的附件down.xlsx

点击上传后，后台输出如下： 

成功读取到上传的文件内容。 

3.下载文件样式

一般情况下，需要对导出的Excel进行样式微调：

import java.util.Date;

import org.apache.poi.ss.usermodel.IndexedColors;

import com.alibaba.excel.annotation.ExcelIgnore;
import com.alibaba.excel.annotation.ExcelProperty;
import com.alibaba.excel.annotation.write.style.ColumnWidth;
import com.alibaba.excel.annotation.write.style.ContentFontStyle;
import com.alibaba.excel.annotation.write.style.HeadFontStyle;
import com.alibaba.excel.annotation.write.style.HeadStyle;
import com.alibaba.excel.enums.poi.FillPatternTypeEnum;

//设置头背景颜色 org.apache.poi.ss.usermodel.IndexedColors IndexedColors.CORNFLOWER_BLUE.getIndex()
@HeadStyle(fillForegroundColor = 24)
//头字体设置成20
@HeadFontStyle(fontHeightInPoints = 20)
//内容的背景设置成绿色 IndexedColors.GREEN.getIndex()
//@ContentStyle(fillPatternType = FillPatternTypeEnum.SOLID_FOREGROUND, fillForegroundColor = 17)
//内容字体设置成12
@ContentFontStyle(fontHeightInPoints = 12)
@ColumnWidth(25)
public class DownloadData {
    @ExcelProperty("字符串标题")
    private String string;
    /**
     * 忽略这个字段
     */
    @ExcelIgnore
    @ExcelProperty("日期标题")
    private Date date;
    /**
     * 宽度为50
     */
    @ColumnWidth(50)
    @ExcelProperty("数字标题")
    private Double doubleData;
    
	public String getString() {
		return string;
	}
	public void setString(String string) {
		this.string = string;
	}
	public Date getDate() {
		return date;
	}
	public void setDate(Date date) {
		this.date = date;
	}
	public Double getDoubleData() {
		return doubleData;
	}
	public void setDoubleData(Double doubleData) {
		this.doubleData = doubleData;
	}
}

其中ColumnWidth可以设置列宽，根据以上所示，可以调整标题的背景色、字体大小，内容行的背景色、字体大小等，调整后效果如下：

更多样式调整，请参考easyexcel: easyexcel —— JAVA 解析 Excel 工具 Java 解析、生成 Excel 比较有名的框架有 Apache poi、jxl - Gitee.com