用springboot，vue，mybatis和elementUI实现上传PDF文件到数据库，需要上传到数据库的内容有文件名，文件上传时间，文件路径，上传者的编号。请给我domain代码，controller代码，service代码，前端vue和element代码，mybatis代码和数据库建表语句，并用注释讲解

非常感谢您的问题，以下是代码和注释：

1. 首先是domain代码，用于定义上传文件的属性：

public class UploadFile {
    private Integer id; // 文件id
    private String fileName; // 文件名
    private String filePath; // 文件路径
    private Date uploadTime; // 上传时间
    private Integer uploaderId; // 上传者编号

    // getter和setter方法
}

2. 接下来是controller代码，用于处理上传文件的请求：

@RestController
@RequestMapping("/upload")
public class UploadController {
    @Autowired
    private UploadService uploadService;

    @PostMapping("/pdf")
    public Result uploadPdf(@RequestParam("file") MultipartFile file, Integer uploaderId) {
        return uploadService.uploadPdf(file, uploaderId);
    }
}

3. 然后是service代码，用于处理上传文件的业务逻辑：

@Service
public class UploadServiceImpl implements UploadService {
    @Autowired
    private UploadMapper uploadMapper;

    @Override
    public Result uploadPdf(MultipartFile file, Integer uploaderId) {
        // 生成文件名
        String fileName = file.getOriginalFilename();
        // 生成文件路径
        String filePath = "/pdf/" + fileName;
        // 生成上传时间
        Date uploadTime = new Date();
        // 将文件信息保存到数据库
        UploadFile uploadFile = new UploadFile();
        uploadFile.setFileName(fileName);
        uploadFile.setFilePath(filePath);
        uploadFile.setUploadTime(uploadTime);
        uploadFile.setUploaderId(uploaderId);
        uploadMapper.insert(uploadFile);
        // 保存文件到服务器
        try {
            file.transferTo(new File(filePath));
        } catch (IOException e) {
            e.printStackTrace();
            return Result.error("文件上传失败");
        }
        return Result.success("文件上传成功");
    }
}

4. 接下来是前端vue和element代码，用于实现上传文件的界面：

<template>
  <div>
    <el-upload
      class="upload-demo"
      action="/upload/pdf"
      :headers="{Authorization: token}"
      :data="{uploaderId: uploaderId}"
      :on-success="handleSuccess"
      :before-upload="beforeUpload"
      :file-list="fileList"
      multiple>
      <el-button size="small" type="primary">点击上传</el-button>
      <div slot="tip" class="el-upload__tip">只能上传pdf文件</div>
    </el-upload>
  </div>
</template>

<script>
export default {
  data() {
    return {
      fileList: [],
      uploaderId: 1, // 上传者编号
      token: "Bearer " + localStorage.getItem("token") // token
    };
  },
  methods: {
    handleSuccess(response, file, fileList) {
      this.$message.success("文件上传成功");
    },
    beforeUpload(file) {
      const isPdf = file.type === "application/pdf";
      if (!isPdf) {
        this.$message.error("只能上传pdf文件");
      }
      return isPdf;
    }
  }
};
</script>

5. 最后是mybatis代码和数据库建表语句，用于实现文件信息的存储和查询：

<!-- UploadMapper.xml -->
<mapper namespace="com.example.mapper.UploadMapper">
    <insert id="insert" parameterType="com.example.domain.UploadFile">
        insert into upload_file (file_name, file_path, upload_time, uploader_id)
        values (#{fileName}, #{filePath}, #{uploadTime}, #{uploaderId})
    </insert>
    <select id="selectById" parameterType="int" resultType="com.example.domain.UploadFile">
        select * from upload_file where id = #{id}
    </select>
</mapper>

-- upload_file表的建表语句
CREATE TABLE `upload_file` (
  `id` int(11) NOT NULL AUTO_INCREMENT,
  `file_name` varchar(255) NOT NULL,
  `file_path` varchar(255) NOT NULL,
  `upload_time` datetime NOT NULL,
  `uploader_id` int(11) NOT NULL,
  PRIMARY KEY (`id`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8mb4;

希望以上代码和注释能够对您有所帮助，如果还有什么问题，请随时提出。