传统jsp项目中实现excel的导出
利用后端服务返回输出流，添加header,设置content-type
```
response.addHeader("Content-Disposition", "attachment;filename="+fileName)
response.setContentType("application/ynd.ms-excel;charset=UTF-8");
## 前后端分离导出
js对象Blob能存储大量的二进制数据，利用这个特性将后端服务返回的流存储到blob
```
import axios from 'axios'
export function exportExcel(url,param,fileName) {
axios({
method: "GET",
url: url,
params: param || {},
responseType: 'blob'
}).then(r => {
let blob = new Blob([r.data], {type: 'application/vnd.ms-excel'});
window.URL = window.URL || window.webkitURL;
let href = URL.createObjectURL(blob);
let downA = document.createElement("a");
downA.href = href;//
downA.download = fileName;
downA.click();
window.URL.revokeObjectURL(href);
})
}
```
