Easys Excel的表格导入(读)导出(写)-----java

一,EasyExcel官网:

可以学习一些新知识:

EasyExcel官方文档 - 基于Java的Excel处理工具 | Easy Excel

二,为什么要使用easyexcle

excel的一些优点和缺点

java解析excel的框架有很多 ：

poi jxl,存在问题：非常的消耗内存，

easyexcel 我们遇到再大的excel都不会出现内存溢出的问题 能够将一个原本3M excel文件，poi来操作将会占用内存

100MB，使用easyexcel减低到几Mb,使用起来更加简单

poi读 1、创建xsshworkbook/hssfworkbook（inputstream in）

2、读取sheet

3、拿到当前sheet所有行row

4、通过当前行去拿到对应的单元格的值

---

easyexcel拟解决的问题

1.excel读写时内存溢出

2.使用简单

3.excel格式解析

---

工作原理

三，项目的步骤

依赖包：

基本上要用的的依赖包:

       <!--		mybatis-plus-->
        <dependency>
            <groupId>com.baomidou</groupId>
            <artifactId>mybatis-plus-boot-starter</artifactId>
            <version>3.3.2</version>
        </dependency>
        <!--	mysql	-->
        <dependency>
            <groupId>mysql</groupId>
            <artifactId>mysql-connector-java</artifactId>
            <version>8.0.28</version>
        </dependency>
        <dependency>
            <groupId>com.alibaba</groupId>
            <artifactId>fastjson</artifactId>
            <version>1.2.28</version>
        </dependency>
        <!--        reds依赖-->
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-data-redis-reactive</artifactId>
        </dependency>
        <!--     连接池依赖   -->
        <!-- https://mvnrepository.com/artifact/org.apache.commons/commons-pool2 -->
        <dependency>
            <groupId>org.apache.commons</groupId>
            <artifactId>commons-pool2</artifactId>
            <version>2.11.1</version>
        </dependency>
<!--        数据池-->
        <!-- https://mvnrepository.com/artifact/com.alibaba/druid -->
        <dependency>
            <groupId>com.alibaba</groupId>
            <artifactId>druid</artifactId>
            <version>1.1.14</version>
        </dependency>
<!--    mapper    -->
        <!-- https://mvnrepository.com/artifact/tk.mybatis/mapper -->
        <dependency>
            <groupId>tk.mybatis</groupId>
            <artifactId>mapper</artifactId>
            <version>4.0.2</version>
        </dependency>

        <!--    easyexcel依赖    -->
        <dependency>
            <groupId>com.alibaba</groupId>
            <artifactId>easyexcel</artifactId>
            <version>2.1.3</version>
        </dependency>
        <!--log4j -->
        <dependency>
            <groupId>log4j</groupId>
            <artifactId>log4j</artifactId>
            <version>1.2.17</version>
        </dependency>

一，导出(写)流程写法:

1. Server接口:

package com.example.excel01.generator.service;

import com.example.excel01.generator.domain.Excel;
import com.baomidou.mybatisplus.extension.service.IService;

import java.util.List;

/**
* @author zeng
* @description 针对表【excel】的数据库操作Service
* @createDate 2023-08-02 11:10:56
*/
public interface ExcelService extends IService<Excel> {
    public Integer getCount(); //总条数
    public List<Excel> getListBYPage(Integer pageOn); //分页查询

}

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2. 2.ServiceImpl类：

package com.example.excel01.generator.service.impl;

import com.baomidou.mybatisplus.extension.service.impl.ServiceImpl;
import com.example.excel01.generator.domain.Excel;
import com.example.excel01.generator.mapper.ExcelMapper;
import com.example.excel01.generator.service.ExcelService;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Service;
import org.springframework.transaction.annotation.Propagation;
import org.springframework.transaction.annotation.Transactional;

import java.util.List;

/**
* @author zeng
* @description 针对表【excel】的数据库操作Service实现
* @createDate 2023-08-02 11:10:56
*/
@Service
@Transactional
public class ExcelServiceImpl extends ServiceImpl<ExcelMapper, Excel>
    implements ExcelService {
    @Autowired
    private ExcelMapper excelMapper;
    @Transactional(propagation = Propagation.SUPPORTS)
    @Override
    public Integer getCount() {
        return excelMapper.selectCount(null);
    }
    @Transactional(propagation = Propagation.SUPPORTS)
    @Override
    public List<Excel> getListBYPage(Integer pageOn) {
        Integer begin=(pageOn-1)*50000+1;
        //第几页显示多少数据
        return excelMapper.ListPage(begin,50000);
    }
}

---

3. 3.Test测试：

    /**
     * 写数据
     * */
    @Test
    void contextLoads4(){
        //保存路径
        String path="E:\\aaa\\ciy2.xls";
        //查询数据总条数
        Integer count = excelService.getCount();
        //创建easyexcel的写出类构造器 参数 告诉构造器 我的excel将来要写到哪里 以及excel中数据是基于哪个java对象模板创建的
        ExcelWriter excelWriter = EasyExcel.write(path, Excel.class).build();
        //判断一页能放多少条数据
        Integer sheetNum = count % 50000 == 0 ? count / 50000 : count / 50000 + 1;
        log.info("sheetNum=={}",sheetNum);
        for(int i=1;i<sheetNum;i++){
            log.info("第"+i+"批次");
            //分页查询数据库
            List<Excel> listPage = excelService.getListBYPage(i);
            //创建sheet构造器
            WriteSheet sheet = EasyExcel.writerSheet("test").build();
            //使用excel对象将数据写入到创建的sheet当中
            excelWriter.write(listPage,sheet);
        }
        excelWriter.finish();
        log.info("导出成功");
    }

二,导入(读)流程写法

1. 监听器:

读取数据要通过监听器来实现，监听读取的每一条数据：

---

监听器:

package com.example.excel01.generator.listenner;

import com.alibaba.excel.context.AnalysisContext;
import com.alibaba.excel.event.AnalysisEventListener;
import com.example.excel01.generator.domain.FmAddress;
import com.example.excel01.generator.service.FmAddressService;
import lombok.extern.slf4j.Slf4j;

/**
 * 监听器
 */

@Slf4j
public class EasyExcelListenner extends AnalysisEventListener<FmAddress> {

    static Integer a = 0;

    @Override
    public void invoke(FmAddress fmAddress, AnalysisContext analysisContext) {
        ++a;
        log.info("a={}",a);
        if (a == 1000) {
            try {
                a=0;
                Thread.sleep(500);
            } catch (InterruptedException e) {
                throw new RuntimeException(e);
            }
        }
        log.info(String.valueOf(fmAddress));
        //获取bean
        FmAddressService fmAddressService = SpringJobBeanFactory.getBean(FmAddressService.class);
        fmAddressService.insert(fmAddress);
    }

    @Override
    public void doAfterAllAnalysed(AnalysisContext analysisContext) {

    }
}

---

a. 知识点普及：

1.监听器我们是继承Excel中的AnalysisEventListener方法来

2.该监听器是不被Spring (bean) 容器管理的，我要手动注入容器

---

2. 手动将监听器注入Spring容器：

package com.example.excel01.generator.listenner;

import org.springframework.beans.BeansException;
import org.springframework.context.ApplicationContext;
import org.springframework.context.ApplicationContextAware;
import org.springframework.stereotype.Component;

/**
 * @ClassName: SpringJobBeanFactory*/
@Component
public class SpringJobBeanFactory implements ApplicationContextAware {
    private static ApplicationContext applicationContext;

    @Override
    public void setApplicationContext(ApplicationContext applicationContext) throws BeansException {
        SpringJobBeanFactory.applicationContext=applicationContext;

    }
    public static ApplicationContext getApplicationContext() {
        return applicationContext;
    }
    @SuppressWarnings("unchecked")
    public static <T> T getBean(String name) throws BeansException {
        if (applicationContext == null){
            return null;
        }
        return (T)applicationContext.getBean(name);
    }

    public static <T> T getBean(Class<T>  name) throws BeansException {
        if (applicationContext == null){
            return null;
        }
        return applicationContext.getBean(name);
    }
}

a. 普及知识点：

手动注入bean 调用的是ApplicationContextAware接口

---

3.Test测试类：

    /**
     * 读数据
     */
    @Test
    void contextLoads5(){
        //保存路径
        String path="E:\\aaa\\ciy.xls";
        ExcelReader build = EasyExcel.read(path, FmAddress.class, new EasyExcelListenner()).build();
        ReadSheet build1 = EasyExcel.readSheet(0).build();
        log.info("build1={}",build1);
        build.read(build1);
        build.finish();

    }