EasyExcel的用法
https://www.cnblogs.com/liuyi13535496566/p/12634898.html
EasyExcel的用法
一.Excel导入导出的应用场景
1.数据导入：减轻录入的工作量
2.数据导出：统计信息归档
3.数据传输：异构系统之间数据传输
二。EasyExcel简介
1.EasyExcel特点
Java领域解析，生成Excel比较有名的框架有Apache poi,jxl等，但他们都存在一个严重的问题就是非常的耗内存，如果你的系统并发量不大的话可能还行，但是一旦并发上来后一定会OOM或者JVM频繁的full gc.
EasyExcel是阿里巴巴开源的一个excel处理框架，以使用简单，节省内存著称，EasyExcel能大大减少占用内存的主要原因是在解析Excel时没有将文件数据一次性全部加载到内存中，而是从磁盘上一行行读取数据，逐个解析。
EasyExcel采用一行一行的解析模式，并将一行的解析结果以观察者的模式通知处理（AnalysisEventListener）。
1.导入maven依赖，主要还需要poi的依赖，并且版本要对应上
<!-- https://mvnrepository.com/artifact/com.alibaba/easyexcel -->
<dependency>
<groupId>com.alibaba</groupId>
<artifactId>easyexcel</artifactId>
<version>2.1.1</version>
</dependency>
<!--xls-->
<dependency>
<groupId>org.apache.poi</groupId>
<artifactId>poi</artifactId>
<version>3.17</version>
</dependency>
<dependency>
<groupId>org.apache.poi</groupId>
<artifactId>poi-ooxml</artifactId>
<version>3.17</version>
</dependency>
2.编写entity对象类
@Data
public class DemoData {
//设置excel表头名称
@ExcelProperty(value = "学生编号",index = 0)
private Integer sno;
@ExcelProperty(value = "学生姓名",index = 1)
private String sname;
}
3.写操作
public class TestEasyExcelWrite {
public static void main(String[] args) {
//实现excel写的操作
//1 设置写入文件夹地址和excel文件名称
String filename = "C:\\Users\\aus\\write.xlsx";
// 2 调用easyexcel里面的方法实现写操作
// write方法两个参数：第一个参数文件路径名称，第二个参数实体类class
EasyExcel.write(filename,DemoData.class).sheet("学生列表").doWrite(getData());
}
//创建方法返回list集合
private static List<DemoData> getData() {
List<DemoData> list = new ArrayList<>();
for (int i = 0; i < 10; i++) {
DemoData data = new DemoData();
data.setSno(i);
data.setSname("lucy"+i);
list.add(data);
}
return list;
}
}
4.最终效果
5.读取excel需要先写一个监听器继承AnalysisEventListener
public class ExcelListener extends AnalysisEventListener<DemoData> {
//一行一行读取excel内容
@Override
public void invoke(DemoData data, AnalysisContext analysisContext) {
System.out.println("****"+data);
}
//读取表头内容
@Override
public void invokeHeadMap(Map<Integer, String> headMap, AnalysisContext context) {
System.out.println("表头："+headMap);
}
//读取完成之后
@Override
public void doAfterAllAnalysed(AnalysisContext analysisContext) { }
}
6.读取excel代码
public class TestEasyExcelRead {
public static void main(String[] args) {
//实现excel读操作
String filename = "C:\\Users\\aus\\write.xlsx";
EasyExcel.read(filename,DemoData.class,new ExcelListener()).sheet().doRead();
}
}
打印效果见下图：
实际项目中开发
entity
@Data
@EqualsAndHashCode(callSuper = false)
@Accessors(chain = true)
@ApiModel(value="EduSubject对象", description="课程科目")
public class EduSubject implements Serializable {
private static final long serialVersionUID = 1L;
@ApiModelProperty(value = "课程类别ID")
@TableId(value = "id", type = IdType.ID_WORKER_STR)
private String id;
@ApiModelProperty(value = "类别名称")
private String title;
@ApiModelProperty(value = "父ID")
private String parentId;
@ApiModelProperty(value = "排序字段")
private Integer sort;
@ApiModelProperty(value = "创建时间")
@TableField(fill = FieldFill.INSERT)
private Date gmtCreate;
@ApiModelProperty(value = "更新时间")
@TableField(fill = FieldFill.INSERT)
private Date gmtModified;
}
@Data
public class SubjectData {
@ExcelProperty(index = 0)
private String oneSubjectName;
@ExcelProperty(index = 1)
private String twoSubjectName;
}
Controller层
@RestController
@RequestMapping("/eduservice/subject")
@CrossOrigin
public class EduSubjectController {
@Autowired
private EduSubjectService subjectService;
//添加课程分类
//获取上传过来文件，把文件内容读取出来
@PostMapping("addSubject")
public R addSubject(MultipartFile file) {
//上传过来excel文件
subjectService.saveSubject(file,subjectService);
return R.ok();
}
}
service层
@Service
public class EduSubjectServiceImpl extends ServiceImpl<EduSubjectMapper, EduSubject> implements EduSubjectService {
@Override
public void saveSubject(MultipartFile file, EduSubjectService subjectService) {
try{
InputStream in = file.getInputStream();
EasyExcel.read(in, SubjectData.class,new SubjectExcelListener(subjectService)).sheet().doRead();
} catch (Exception e) {
e.printStackTrace();
}
}
}
5.监听器继承AnalysisEventListener，这里需要注意的点，因为业务层的SubjectExcelListener 并没有交给Spring容器来管理，所以监听器代码无法注入EduSubjectService ，
这里通过构造方法的方式传过来，从而完成对数据库的操作。
public class SubjectExcelListener extends AnalysisEventListener<SubjectData> {
//因为SubjectExcelListener不交给spring进行管理，需要自己new，不能注入其他对象
//不能实现数据库操作
public EduSubjectService subjectService;
public SubjectExcelListener() {}
public SubjectExcelListener(EduSubjectService subjectService) {
this.subjectService = subjectService;
}
//读取excel内容，一行一行进行读取
@Override
public void invoke(SubjectData subjectData, AnalysisContext analysisContext) {
if(subjectData == null) {
throw new GuliException(20001,"文件数据为空");
}
//一行一行读取，每次读取有两个值，第一个值一级分类，第二个值二级分类
//判断一级分类是否重复
EduSubject existOneSubject = this.existOneSubject(subjectService, subjectData.getOneSubjectName());
if(existOneSubject == null) { //没有相同一级分类，进行添加
existOneSubject = new EduSubject();
existOneSubject.setParentId("0");
existOneSubject.setTitle(subjectData.getOneSubjectName());//一级分类名称
subjectService.save(existOneSubject);
}
//获取一级分类id值
String pid = existOneSubject.getId();
//添加二级分类
//判断二级分类是否重复
EduSubject existTwoSubject = this.existTwoSubject(subjectService, subjectData.getTwoSubjectName(), pid);
if(existTwoSubject == null) {
existTwoSubject = new EduSubject();
existTwoSubject.setParentId(pid);
existTwoSubject.setTitle(subjectData.getTwoSubjectName());//二级分类名称
subjectService.save(existTwoSubject);
}
}
//判断一级分类不能重复添加
private EduSubject existOneSubject(EduSubjectService subjectService,String name) {
QueryWrapper<EduSubject> wrapper = new QueryWrapper<>();
wrapper.eq("title",name);
wrapper.eq("parent_id","0");
EduSubject oneSubject = subjectService.getOne(wrapper);
return oneSubject;
}
//判断二级分类不能重复添加
private EduSubject existTwoSubject(EduSubjectService subjectService,String name,String pid) {
QueryWrapper<EduSubject> wrapper = new QueryWrapper<>();
wrapper.eq("title",name);
wrapper.eq("parent_id",pid);
EduSubject twoSubject = subjectService.getOne(wrapper);
return twoSubject;
}
@Override
public void doAfterAllAnalysed(AnalysisContext analysisContext) {
}
}
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