koa中間層 文件下載的請求轉發

背景：

前端用a標簽發起下載文檔的get請求

node中間層接到get請求后將請求轉發到java后端

java后端返回文檔流傳遞給node中間層

 

好處：

后端的java業務邏輯層接口、數據庫不向外部暴露，node中間層進行安全驗證及請求轉發

 

 

1.前端發起請求

 <a download={`${filename}文件.doc`} href={`${domain}/api/word/download?a=${fileid}&b=${filename}>
    下載文件
</a>

 

2.koa 中間層轉發

router.get('/word/download',async (ctx,next)=>{
    let {a,b,date} = ctx.query;
    date = date || timeStamp2String(false,'short');
    let file = await request({
        uri:'word',
        qs:{
            orgNo:a
        }
    });
    let s = new Readable;
    s.push(file);
    s.push(null);
    let docx = 'application/vnd.openxmlformats-officedocument.wordprocessingml.document';
    let doc = 'application/msword';
    ctx.set('content-type',docx);
    ctx.set('content-disposition',`attachment;filename*=UTF-8''${encodeURIComponent(b)}.docx`);
    ctx.body = s;
});

 

3.request方法請求java后端

import request from 'request-promise';
function reqGetStreamData(params){
    let {uri,qs} = params;
    return new Promise((resolve,reject)=>{
        request({
            uri:`${domain}api/jgs/${uri}`,
            qs,
            encoding:null,
            headers: {
                'User-Agent': 'Request-Promise',
                'Content-type':docx
            },
            json: false
        }).then(data => {
            resolve(data);
        }, err => {
            let errData = {
                status:1,
                data:err,
                statusInfo:'失敗'
            }
            reject(errData);
        }).catch(err => {
            let obj = {
                status: 1,
                data: err,
                statusInfo: '未知錯誤！'
            };
            reject(obj);
        });
    });
}

 

 

原理就是：將java后端返回的文件流被request轉換為buffer對象，然后用stream.Readable將buffer對象轉換為流，直接返回給前端即可