java 读取各种类型的文件 （五）

后端java，springboot 、前端vue： 对 csv 文件的读写，以及前端预览

一、后端读

            public void readCSV() {
                CSVReader reader = null;
                try {
                    reader = new CSVReader(new InputStreamReader(new FileInputStream(xxx), "GBK"));
                    String[] lineData = null;
                    while((lineData = reader.readNext()) != null)
                    {
                            fileData.put(lineData);
                    }
                } catch (Exception e) {
                    try {
                        reader.close();
                    } catch (Exception e1) {
                    }
                    LOGGER.error("读取CVS文件失败{}",e);
                }
            }

二、前后台配合预览
　　1、controller
public ResponseEntity<byte[]> previewFile(@RequestBody FileVO fileVO) {

        if(fileVO == null || fileVO.getId() == null){
            return null;
        }
        String filename = fileVO.getFileName();
        byte[] buffer = getCSVBytes(fileVO,30); 

 　 　　HttpHeaders headers = new HttpHeaders();

        //防止中文名乱码
        //filename = new String(filename.getBytes(StandardCharsets.UTF_8), StandardCharsets.ISO_8859_1);
        try {
            headers.setContentDispositionFormData("attachment",  filename=java.net.URLEncoder.encode(filename, "UTF-8"));
        } catch (UnsupportedEncodingException e) {
            e.printStackTrace();
        }
        headers.add(HttpHeaders.CONTENT_TYPE,"application/octet-stream;charset=UTF-8");
        headers.add("file-type",smsTaskFile.getFileType());
        //返回
        return new ResponseEntity<byte[]>(buffer, headers, HttpStatus.CREATED);
    }

　private byte[] getCSVBytes(SmsTaskFile smsTaskFile, int preLines) {
    byte[] fileBuffer = null;
    int readLine = 0;
    CSVReader reader = null;
    try {
        StringBuilder content = new StringBuilder("");
        reader = new CSVReader(new InputStreamReader(new FileInputStream(smsTaskFile.getFilePath()), "GBK"));
        String[] lineData = null;
        while((lineData = reader.readNext()) != null && readLine < preLines)
        {
            for (String lineStr:lineData) {
                content.append(lineStr).append(" ");
            }
            content.append("\n");
            readLine++;
        }
        fileBuffer = content.toString().getBytes(StandardCharsets.UTF_8);
    } catch (Exception e) {
        try {
            reader.close();
        } catch (Exception e1) {
        }
        LOGGER.error("读取CSV文件失败{}",e);
    }
    return fileBuffer;
}
　　2、vue
<el-button v-if="item.key == 'operate'" @click.stop="taskfilePreview(scope.row)" type="text" size="small">预览</el-button>
<el-dialog-side :visible="showPreviewFile" @close="showPreviewFile = false;fileContent=''">

  <h1>只预览文件前30行</h1><br>
  <el-card>
    <el-input v-if="fileContent"
              v-model="fileContent"
              show-word-limit
              :autosize="{ minRows: 12}"
              type="textarea"
    ></el-input>
  </el-card>
</el-dialog-side>

taskfilePreview(row){
  const reader = new FileReader();

  //通过readAsArrayBuffer将blob转换为ArrayBuffer对
  Actions.previewFile(row).then(res => {
    if (res.data) {
      reader.readAsText(res.data) // 这里的res.data是blob文件流
      reader.onload = (event) => {
        var data = event.target.result;
        this.showPreviewFile = true
        this.fileContent = data
      }
    }
  })
}