setCommon处理所有中间件

import { Log, accessLogger } from "../utils/api_log.js";
const log = new Log("setCommon");

//配置traceId追踪
import { randomBytes } from "crypto";

• 必备中间件

//POS请求解析
import bodyParser from "koa-bodyparser";

//模板渲染
import views from "koa-views";

//静态文件服务
import serve from "koa-static-server";

• 可选优化中间件

//协商缓存
import conditional from "koa-conditional-get";
import etag from "koa-etag";

//文件压缩
import compress from "koa-compress";

//允许跨域
import cors from "@koa/cors";

//安全加固
//import helmet from "koa-helmet";

//管理用户session，用于配合csrf，但已弃用
import session from "koa-session";

函数主体

const setCommon = async (app)=>{
    log.info("middleware set common");

    app.use(async (ctx, next) => {
        try {
            await next();
            switch (ctx.status) {
                case 404:
                    ctx.throw(404);
                    break;
                case 500:
                    ctx.throw(500);
                    break;
                default:
            }
        } catch (err) {
            switch (err.status) {
                case 404:
                    await ctx.render("errors/404")
                    break;
                case 500:
                    await ctx.render("errors/500")
                    break;
                default:
            }
        }
    });

    app.use(async (ctx, next) => {
        ctx.traceId = randomBytes(4).toString('hex');
        await next();
    });

    app.use(async (ctx, next) => {
        const start = new Date();
        await next();
        const ms = new Date() - start;
        accessLogger(ctx, ms);
    });

    app.use(cors());
    // app.use(helmet())

    app.use(bodyParser({
        enableTypes: ['json', 'form', 'text'],
        extendTypes: {
            text: ['text/xml', 'application/xml']
        },
        jsonLimit: '10mb',
        textLimit: '10mb',
        formLimit: '10mb'
    }));

    app.keys = [process.env.NEW_SESSION_KEY,process.env.OLD_SESSION_KEY];
    app.use(session(app))
    
    app.use(conditional());
    app.use(etag());

    let zlib = await import('zlib');
    app.use(compress({
        filter (content_type) {
            return /text|javascript|css/.test(content_type)
        },
        threshold: 512,
        gzip: {
          flush: zlib.default.constants.Z_SYNC_FLUSH
        },
        deflate: {
          flush: zlib.default.constants.Z_SYNC_FLUSH,
        }
    }));

    app.use(serve({
        rootDir:'static', 
        rootPath:'/static', 
        maxage: 10 * 1000
    }));

    app.use(views('views',{
        map: {html: 'ejs'}
    }))

    app.on('error', (err) => {
        log.error(err);
    })
}

export default setCommon;