谷粒学院EasyExcel | 课程分类模块
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文章目录
一、EasyExcel 简介
1、Excel导入导出的应用场景
- 数据导入：减轻录入工作量
- 数据导出：统计信息归档
- 数据传输：异构系统之间数据传输
2、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)。
3、案例1:EasyExcel进行Excel写操作
1、pom中引入xml相关依赖
<dependencies>
<!-- https://mvnrepository.com/artifact/com.alibaba/easyexcel -->
<dependency>
<groupId>com.alibaba</groupId>
<artifactId>easyexcel</artifactId>
<version>2.1.1</version>
</dependency>
<!-- 因为EasyExcel底层是Poi所以需要引入poi的依赖 -->
<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>
</dependencies>
2、创建实体类
@Data
public class WriteData
//设置excel表头名称
@ExcelProperty("学生编号")
private Integer sno;
@ExcelProperty("学生姓名")
private String sname;
3、实现写操作
public static void testWrite()
//实现excel的写操作
//1.设置写入文件夹地址和excel名称
String filename = "F:\\\\write.xlsx";
//2.调用easyexcel里面的方法实现写操作
EasyExcel.write(filename, WriteData.class).sheet("学生列表").doWrite(getData());
public static List <WriteData> getData()
List <WriteData> list = new ArrayList <>();
for(int i = 0;i < 10;i++)
String sname = "lucy"+i;
list.add(new WriteData(i, sname));
return list;
4、案例2:EasyExcel进行Excel读操作
1、创建实体类并标记对应列关系
@Data
public class ReadData
//设置excel表头名称
@ExcelProperty(index = 0)
private Integer sno;
@ExcelProperty(index = 1)
private String sname;
2、创建监听器进行excel文件读取
public class ExcelListner extends AnalysisEventListener<ReadData>
List<ReadData> list = new ArrayList<ReadData>();
//一行一行的去读取
@Override
public void invoke(ReadData readData, AnalysisContext analysisContext)
System.out.println("****"+readData);
list.add(readData);
//读取Excel表头信息
@Override
public void invokeHeadMap(Map <Integer, String> headMap, AnalysisContext context)
System.out.println("表头信息:"+headMap);
//读取完成之后执行
@Override
public void doAfterAllAnalysed(AnalysisContext analysisContext)
3、进行读操作
public static void testRead()
String filename = "F:\\\\write.xlsx";
EasyExcel.read(filename,ReadData.class,new ExcelListner()).sheet().doRead();
二、课程分类添加功能(后端)
核心:EasyExcel读取excel内容实现
1、引入easyexcel依赖
2、使用代码生成器把课程分类代码生成
3、创建实体类和excel对应关系
@Data
public class SubjectData
@ExcelProperty(index = 0)
private String oneSujectName;
@ExcelProperty(index = 1)
private String twoSujectName;
4、编写 EduSubjectController 类
@Api(description = "课程分类")
@RestController
@RequestMapping("/eduservice/subject")
@CrossOrigin
public class EduSubjectController
@Autowired
private EduSubjectService eduSubjectService;
//添加课程分类
@ApiOperation(value = "添加课程分类")
@PostMapping("addSubjects")
public R addSubjects(MultipartFile file)
boolean flag = eduSubjectService.saveSubjects(file);
if(flag)
return R.ok().message("文件导入成功!");
else
return R.error().message("文件导入失败!");
5、编写EduSubjectServiceImpl 类
@Service
public class EduSubjectServiceImpl extends ServiceImpl<EduSubjectMapper, EduSubject> implements EduSubjectService
@Autowired
private EduSubjectService eduSubjectService;
//添加课程分类
@Override
public boolean saveSubjects(MultipartFile file)
try
InputStream inputStream = file.getInputStream();
//进行excel文件读取
EasyExcel.read(inputStream, SubjectData.class, new SubjectExcelListner(eduSubjectService)).sheet().doRead();
return true;
catch (Exception e)
e.printStackTrace();
return false;
6、创建读取Excel监听器
public class SubjectExcelListner extends AnalysisEventListener<SubjectData>
//因为SubjectExcelListner在EduSubjectServiceImpl每次会被new的形式使用,所以SubjectExcelListner不能交给
//Spring进行管理,也就不能使用@Autowird或@Resource注解注入对象.
//但是该类需要调用service中的方法进行数据库操作,该如何使用呢?
//可以通过构造方法传递参数的形式,使用service对象.
private EduSubjectService eduSubjectService;
public SubjectExcelListner(EduSubjectService eduSubjectService)
this.eduSubjectService = eduSubjectService;
public SubjectExcelListner()
//一行一行的去读取
@Override
public void invoke(SubjectData subjectData, AnalysisContext analysisContext)
if(subjectData==null)
throw new GuLiException(20001,"数据为空!");
//添加一级分类
EduSubject oneSubject = this.existOneSubject(subjectData.getOneSubjectName());
if(oneSubject==null)//没有相同的一级分类
oneSubject = new EduSubject();
oneSubject.setTitle(subjectData.getOneSubjectName());
oneSubject.setParentId("0");
eduSubjectService.save(oneSubject);
//获取一级分类id
String pid = oneSubject.getId();
//添加二级分类
EduSubject twoSubject = this.existTwoSubject(subjectData.getTwoSubjectName(), pid);
if(twoSubject==null)
twoSubject = new EduSubject();
twoSubject.setTitle(subjectData.getTwoSubjectName());
twoSubject.setParentId(pid);
eduSubjectService.save(twoSubject);
//读取Excel表头
@Override
public void invokeHeadMap(Map <Integer, String> headMap, AnalysisContext context)
System.out.println("表头信息:"+headMap);
//读取完成后的操作
@Override
public void doAfterAllAnalysed(AnalysisContext analysisContext)
//判断一级分类是否重复
private EduSubject existOneSubject(String name)
QueryWrapper <EduSubject> wrapper = new QueryWrapper <>();
wrapper.eq("title", name).eq("parent_id",0);
EduSubject subject = eduSubjectService.getOne(wrapper);
return subject;
//判断二级分类是否重复
private EduSubject existTwoSubject(String name,String pid)
QueryWrapper <EduSubject> wrapper = new QueryWrapper <>();
wrapper.eq("title", name).eq("parent_id", pid);
EduSubject subject = eduSubjectService.getOne(wrapper);
return subject;
7、重启oss服务，Swagger中测试文件上传
http://localhost:8001/swagger-ui.html
三、课程分类添加功能(前端)
1、添加课程分类路由
/src/router/index.js:
path: '/subject',
component: Layout, //布局
redirect: '/subject/table',
name: 'SubjectSort',
meta: title: '课程分类管理', icon: 'nested' ,
children: [
path: 'list',
name: 'EduSubjectList',
component: () =>
import ('@/views/edu/subject/list'),
meta: title: '课程分类列表', icon: 'table'
,
path: 'import',
name: 'EduSubjectImport',
component: () =>
import ('@/views/edu/subject/import'),
meta: title: '导入课程分类', icon: 'tree'
]
2、创建课程分类页面，修改路由对应的页面路径
3、在添加课程分类页面实现效果
编写页面:
<template>
<div class="app-container">
<el-form label-width="120px">
<el-form-item label="信息描述">
<el-tag type="info">excel模版说明</el-tag>
<el-tag>
<i class="el-icon-download"/>
<a :href="OSS_PATH + '/excel/template.xlsx'">点击下载模版</a>
</el-tag>
</el-form-item>
<el-form-item label="选择Excel">
<el-upload
ref="upload"
:auto-upload="false"
:on-success="fileUploadSuccess"
:on-error="fileUploadError"
:disabled="importBtnDisabled"
:limit="1"
:action="BASE_API+'/eduservice/subject/addSubjects'"
name="file"
accept="application/vnd.ms-excel">
<el-button slot="trigger" size="small" type="primary">选取文件</el-button>
<el-button
:loading="false"
style="margin-left: 10px;"
size="small"
type="success"
@click="submitUpload"> fileUploadBtnText </el-button>
</el-upload>
</el-form-item>
</el-form>
</div>
</template>
编写js方法:
<script>
export default
data()
return
BASE_API: process.env.BASE_API, // 接口API地址
OSS_PATH: process.env.OSS_PATH, // 阿里云OSS地址
fileUploadBtnText: '上传到服务器', // 按钮文字
importBtnDisabled: false, // 按钮是否禁用,
loading: false
,
created()
,
methods:
//上传成功调用的方法
fileUploadSuccess(response)
if (response.success === true)
this.fileUploadBtnText = '导入成功'
this.loading = false
this.$message(
type: 'success',
message: response.message
)
//跳转到列表页面
this.$router.push(path:'/subject/list')
,
//上传失败调用的方法
fileUploadError(response)
if(response.success === false)
this.fileUploadBtnText = '导入失败'
this.loading = false
this.$message(
type: 'error',
message: response.message
)
//跳转到列表页面
this.$router.push(path:'/subject/list')
,
//点击按钮上传文件到接口
submitUpload()
this.importBtnDisabled = true //上传按钮禁用
this.loading = true
this.$refs.upload.submit()
</script>
4、启动服务测试
四、课程分类列表(后端）
1、根据返回数据创建对应实体类
//一级分类
@Data
public class OneSubject
private String id;
private String title;
//一个一级分类里面有多个二级分类
private List<TwoSubject> children = new ArrayList<>();
//二级分类
@Data
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