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
}
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();
}
