四，EasyExcel使用

1、EasyExcel介绍

1.1 官网介绍

传统操作Excel大多都是利用Apach POI进行操作的，但是POI框架并不完善，使用过程非常繁琐且有较多的缺陷：

• 动态操作Excel非常繁琐,对于新手来说，很难在短时间内上手;

• 读写时需要占用较大的内存，当数据量大时容易发生内存溢出问题（OOM）;

基于上述原因，阿里开源出一款易于上手，且比较节省内存的Excel框架：EasyExcel

注意：easyExcel底层也是使用POI实现的；

官网地址：EasyExcel（文档已经迁移） · 语雀

?依赖资源：

<!--引入easyexcel-->
<dependency>
    <groupId>com.alibaba</groupId>
    <artifactId>easyexcel</artifactId>
    <version>3.0.4</version>
</dependency>

注意：目前版本与JDK8较为契合，高版本的JDK可能会出现兼容性问题;

1.2 Excel相关结构说明

2、EasyExcel导出数据快速入门

2.1 构建测试实体类

package com.itheima.stock.pojo;

import lombok.AllArgsConstructor;
import lombok.Builder;
import lombok.Data;
import lombok.NoArgsConstructor;

import java.io.Serializable;
import java.util.Date;

/**
 * @author by itheima
 * @Date 2021/12/19
 * @Description
 */
@Data
@NoArgsConstructor
@AllArgsConstructor
@Builder
public class User implements Serializable {
    private String userName;
    private Integer age;
    private String address;
    private Date birthday;
}

?

2.2 数据导出到excel

package com.itheima.stock;

import com.alibaba.excel.EasyExcel;
import com.itheima.stock.pojo.User;
import org.junit.jupiter.api.Test;

import java.util.ArrayList;
import java.util.Date;
import java.util.List;

/**
 * @author by itheima
 * @Date 2021/12/31
 * @Description
 */
public class TestEasyExcel {

    public List<User> init(){
        //组装数据
        ArrayList<User> users = new ArrayList<>();
        for (int i = 0; i < 10; i++) {
            User user = new User();
            user.setAddress("上海"+i);
            user.setUserName("张三"+i);
            user.setBirthday(new Date());
            user.setAge(10+i);
            users.add(user);
        }
        return users;
    }
    /**
     * 直接导出后，表头名称默认是实体类中的属性名称
     */
    @Test
    public void test02(){
        List<User> users = init();
        //不做任何注解处理时，表头名称与实体类属性名称一致
        EasyExcel.write("C:\\Users\\46035\\Desktop\\ex\\用户.xls",User.class).sheet("用户信息").doWrite(users);
    }
}

2.3 自定义表头

修改User实体类,设置表头数据和排序规则：

package com.itheima.stock.pojo;

import com.alibaba.excel.annotation.ExcelProperty;
import lombok.AllArgsConstructor;
import lombok.Builder;
import lombok.Data;
import lombok.NoArgsConstructor;
import java.io.Serializable;
import java.util.Date;

/**
 * @author by itheima
 * @Date 2021/12/19
 * @Description
 */
@Data
@NoArgsConstructor
@AllArgsConstructor
@Builder
/**
  * 通过注解自定义表头名称 注解添加排序规则，值越大 越靠近右边
*/
public class User implements Serializable {
    @ExcelProperty(value = {"用户名"},index = 1)
    private String userName;
    @ExcelProperty(value = {"年龄"},index = 2)
    private Integer age;
    @ExcelProperty(value = {"地址"} ,index = 4)
    private String address;
    @ExcelProperty(value = {"生日"},index = 3)
    private Date birthday;
}

?

3、EasyExcel导出数据高级设置

3.1 自定义日期格式

package com.itheima.stock.pojo;

import com.alibaba.excel.annotation.ExcelProperty;
import com.alibaba.excel.annotation.format.DateTimeFormat;
import lombok.AllArgsConstructor;
import lombok.Builder;
import lombok.Data;
import lombok.NoArgsConstructor;

import java.io.Serializable;
import java.util.Date;

/**
 * @author by itheima
 * @Date 2021/12/19
 * @Description
 */
@Data
@NoArgsConstructor
@AllArgsConstructor
@Builder
public class User implements Serializable {
    @ExcelProperty(value = {"用户名"},index = 1)
    private String userName;
    @ExcelProperty(value = {"年龄"},index = 2)
    private Integer age;
    @ExcelProperty(value = {"地址"} ,index = 4)
    private String address;
    @ExcelProperty(value = {"生日"},index = 3)
    //注意：日期格式注解由alibaba.excel提供
    @DateTimeFormat("yyyy/MM/dd HH:mm")
    private Date birthday;
}

?

3.2 合并表头

添加合并表头信息：

package com.itheima.stock.pojo;

import com.alibaba.excel.annotation.ExcelIgnore;
import com.alibaba.excel.annotation.ExcelProperty;
import com.alibaba.excel.annotation.format.DateTimeFormat;
import lombok.AllArgsConstructor;
import lombok.Builder;
import lombok.Data;
import lombok.NoArgsConstructor;

import java.io.Serializable;
import java.util.Date;

/**
 * @author by itheima
 * @Date 2021/12/19
 * @Description
 */
@Data
@NoArgsConstructor
@AllArgsConstructor
@Builder
public class User implements Serializable {
    @ExcelProperty(value = {"用户基本信息","用户名"},index = 1)
    private String userName;
    @ExcelProperty(value = {"用户基本信息","年龄"},index = 2)
    private Integer age;
    @ExcelProperty(value = {"用户基本信息","地址"} ,index = 4)
    private String address;
    @ExcelProperty(value = {"用户基本信息","生日"},index = 3)
    //注意：日期格式注解由alibaba.excel提供
    @DateTimeFormat("yyyy/MM/dd HH:mm")
    private Date birthday;
}

?效果：

3.3 忽略指定表头信息

/**
 * @author by itheima
 * @Date 2021/12/19
 * @Description
 */
@Data
@NoArgsConstructor
@AllArgsConstructor
@Builder
public class User implements Serializable {
    @ExcelProperty(value = {"用户基本信息","用户名"},index = 1)
    @ExcelIgnore
    private String userName;
    @ExcelProperty(value = {"用户基本信息","年龄"},index = 2)
    private Integer age;
    @ExcelProperty(value = {"用户基本信息","地址"} ,index = 4)
    private String address;
    @ExcelProperty(value = {"用户基本信息","生日"},index = 3)
    //注意：日期格式注解由alibaba.excel提供
    @DateTimeFormat("yyyy/MM/dd HH:mm")
    private Date birthday;
}

?效果：

3.4 设置单元格大小

@Data
@NoArgsConstructor
@AllArgsConstructor
@Builder
@HeadRowHeight(value = 35) // 表头行高
@ContentRowHeight(value = 25) // 内容行高
@ColumnWidth(value = 50) // 列宽
public class User implements Serializable {
    @ExcelProperty(value = {"用户基本信息","用户名"},index = 1)
    @ExcelIgnore
    private String userName;
    @ExcelProperty(value = {"用户基本信息","年龄"},index = 2)
    private Integer age;
    @ExcelProperty(value = {"用户基本信息","地址"} ,index = 4)
    private String address;
    @ExcelProperty(value = {"用户基本信息","生日"},index = 3)
    //注意：日期格式注解由alibaba.excel提供
    @DateTimeFormat("yyyy/MM/dd HH:mm")
    private Date birthday;
}

?效果：

4、EasyExcel导入数据

    /**
     * excel数据格式必须与实体类定义一致，否则数据读取不到
     */
    @Test
    public void readExcel(){
        ArrayList<User> users = new ArrayList<>();
        //读取数据
        EasyExcel.read("C:\\Users\\46035\\Desktop\\ex\\用户.xls", User.class, new AnalysisEventListener<User>() {
            @Override
            public void invoke(User o, AnalysisContext analysisContext) {
                System.out.println(o);
                users.add(o);
            }
            @Override
            public void doAfterAllAnalysed(AnalysisContext analysisContext) {
                System.out.println("完成。。。。");
            }
        }).sheet().doRead();
        System.out.println(users);
    }

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