使用EasyExcel添加多级分类功能

绪论

当面对很多数据要处理，并且需要导入导出Excel表格时。在使用POI时发现非常耗内存，这时GitHub上的阿里开源项目Easy Excel可以解决此类问题，它是基于java的读写Excel，十分省内存。本篇博文主要是总结其简单使用以及关于添加分类功能的实现。

快速入门

1. 创建项目导入依赖（此依赖依靠PIO模块，项目还需要导入PIO模块）

   <dependency>
          <groupId>com.alibaba</groupId>
          <artifactId>easyexcel</artifactId>
          <version>2.1.4</version>
   </dependency>
   

2. 创建测试的实体类DemoData

   @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;
   }
   

   其中index对应excel表格中的列，value是列的名称

3. 写操作

     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 = "D:\\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. 读操作

       public static void main(String[] args) {
          
           //实现excel读操作
           String filename = "D:\\write.xlsx";
           EasyExcel.read(filename,DemoData.class,new ExcelListener()).sheet().doRead();
       }
   

   这里我们需要创建一个读取excel监听器：

   //创建读取excel监听器
   public class ExcelListener extends AnalysisEventListener<DemoData> {
          
   
       //一行一行读取excel内容
       @Override
       public void invoke(DemoData demoData, AnalysisContext analysisContext) {
          
           System.out.println("****"+demoData);
       }
       
       //读取表头内容
       @Override
       public void invokeHeadMap(Map<Integer, String> headMap, AnalysisContext analysisContext) {
          
           System.out.println("表头："+headMap);
       }
       
       //读取完之后
       @Override
       public void doAfterAllAnalysed(AnalysisContext analysisContext) {
          
   
       }
   }
   

   以上是EsayExcel的一些基本使用，具体可以去看官方的文档。

应用场景（课程多分类的添加）

1. 表结构

   DROP TABLE IF EXISTS `edu_subject`;
   CREATE TABLE `edu_subject`  (
     `id` char(19) CHARACTER SET utf8mb4 COLLATE utf8mb4_0900_ai_ci NOT NULL COMMENT '课程类别ID',
     `title` varchar(10) CHARACTER SET utf8mb4 COLLATE utf8mb4_0900_ai_ci NOT NULL COMMENT '类别名称',
     `parent_id` char(19) CHARACTER SET utf8mb4 COLLATE utf8mb4_0900_ai_ci NOT NULL DEFAULT '0' COMMENT '父ID',
     `sort` int(0) UNSIGNED NOT NULL DEFAULT 0 COMMENT '排序字段',
     `gmt_create` datetime(0) NOT NULL COMMENT '创建时间',
     `gmt_modified` datetime(0) NOT NULL COMMENT '更新时间',
     PRIMARY KEY (`id`) USING BTREE,
     INDEX `idx_parent_id`(`parent_id`) USING BTREE
   ) ENGINE = InnoDB CHARACTER SET = utf8mb4 COLLATE = utf8mb4_0900_ai_ci COMMENT = '课程科目' ROW_FORMAT = Compact;
   
   

2. 实体类EduSubject 和分类实体类SubjectData

   @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")
       private Date gmtCreate;
   
       @ApiModelProperty(value = "更新时间")
       private Date gmtModified;
   }
   

   @Data
   public class SubjectData {
          
   
       @ExcelProperty(index = 0)
       private String oneSubjectName;  //一级分类
       @ExcelProperty(index = 1)
       private String twoSubjectName;  //二级分类
   }
   
   

3. 监听类SubjectExcelListener

   public class SubjectExcelListener extends AnalysisEventListener<SubjectData> {
          
   
       //因为SubjectExcelListener不能交给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
       //我们这里通过一个有参构造进行传值
       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 eduOneSubject =  this.existOneSubject(subjectService,subjectData.getOneSubjectName());
           if(eduOneSubject == null){
           //没有相同的一级分类，进行添加
               eduOneSubject = new EduSubject();
               eduOneSubject.setParentId("0");
               eduOneSubject.setTitle(subjectData.getOneSubjectName());
               subjectService.save(eduOneSubject);
           }
   
           //获取一级分类id值
           String pid = eduOneSubject.getId();
   
           //添加二级分类
           //判断二级分类是否重复
           EduSubject eduTwoSubject = this.existTwoSubject(subjectService, subjectData.getTwoSubjectName(), pid);
           if(eduTwoSubject == null) {
          
               eduTwoSubject = new EduSubject();
               eduTwoSubject.setParentId(pid);
               eduTwoSubject.setTitle(subjectData.getTwoSubjectName());//二级分类名称
               subjectService.save(eduTwoSubject);
           }
       }
   
       //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) {
          
   
       }
   }
   

4. 实现类EduSubjectServiceImpl

   @Service
   public class EduSubjectServiceImpl extends ServiceImpl<EduSubjectMapper, EduSubject> implements EduSubjectService {
          
   
       //添加课程分类
       @Override
       public void saveSubject(MultipartFile file,EduSubjectService subjectService) {
          
   
           try {
          
               //文件输入流
               InputStream in = file.getInputStream();
               EasyExcel.read(in, SubjectData.class,new SubjectExcelListener(subjectService)).sheet().doRead();
           } catch (IOException e) {
          
               e.printStackTrace();
           }
   
       }
   }
   

5. Controller层EduSubjectController

   @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();
       }
   }
   

6. 测试
   （1）excel表中信息：
   
   （2）运行项目，用Swagger测试
   
   （3）查看数据库中是否添加成功
   

课程多分类添加整合前端

这里用的是elementUI的一个后台管理模板，项目地址：element，把项目下载下来用npm 安装运行。

1. 添加路由在index.js中

    {
          
       path: '/subject',
       component: Layout,
       redirect: '/subject/list',
       name: '课程分类管理',
       meta: {
           title: '课程分类管理', icon: 'example' },
       children: [
         {
          
           path: 'list',
           name: '课程分类列表',
           component: () => import('@/views/edu/subject/list'),
           meta: {
           title: '课程分类列表', icon: 'table' }
         },
         {
          
           path: 'save',
           name: '添加课程分类',
           component: () => import('@/views/edu/subject/save'),
           meta: {
           title: '添加课程分类', icon: 'tree' }
         }
       ]
     }
   

2. 创建路由对应的页面save.vue

   <template>
     <div class="app-container">
       <el-form label-width="120px">
         <el-form-item label="Excel模板描述">
           <el-tag type="info">excel模版说明</el-tag>
           <el-tag>
             <i class="el-icon-download"/>
             <a :href="'/static/01.xlsx'">点击下载模版</a>
           </el-tag>
   
         </el-form-item>
   
         <el-form-item label="选择Excel文件">
           <el-upload
             ref="upload"
             :auto-upload="false"
             :on-success="fileUploadSuccess"
             :on-error="fileUploadError"
             :disabled="importBtnDisabled"
             :limit="1"
             :action="BASE_API+'/eduservice/subject/addSubject'"
             name="file"
             accept="application/vnd.ms-excel">
             <el-button slot="trigger" size="small" type="primary">选取文件</el-button>
             <el-button
               :loading="loading"
               style="margin-left: 10px;"
               size="small"
               type="success"
               @click="submitUpload">上传</el-button>
           </el-upload>
         </el-form-item>
       </el-form>
     </div>
   </template>
   
   <script>
   export default {
          
       data() {
          
           return {
          
               BASE_API: process.env.BASE_API, // 接口API地址
               importBtnDisabled: false, // 按钮是否禁用,
               loading: false
           }
       },
       created() {
          
   
       },
       methods:{
          
           //点击按钮上传文件到接口里面
           submitUpload() {
          
               this.importBtnDisabled = true
               this.loading = true
               // js: document.getElementById("upload").submit()
               this.$refs.upload.submit()
           },
           //上传成功
           fileUploadSuccess(response) {
          
               //提示信息
               this.loading = false
               this.$message({
          
                   type: 'success',
                   message: '添加课程分类成功'
               })
               //跳转课程分类列表
               //路由跳转
               this.$router.push({
          path:'/subject/list'})
           },
           //上传失败
           fileUploadError() {
          
               this.loading = false
               this.$message({
          
                   type: 'error',
                   message: '添加课程分类失败'
               })
           }
       }
   }
   </script>
   

3. 展示
   

总节

EsayExcel在各方面性能还是很不错的，后期可以根据官方的API进行深入学习。