KOA基础篇（一）

起步

npm i koa复制代码

路由

npm i koa-router复制代码

const Koa = require('koa');
const Router = require('koa-router');

let app = new Koa();
let router = new Router();

app.get('/',async ctx => {
    ctx.body = 'Index Page';
})
app.use(router.routes());
app.listen(3000);复制代码

嵌套路由

const Koa = require('koa');
const Router = require('koa-router');

let app = new Koa();
let router = new Router();

let userRouter = new Router();
userRouter.get('/', async ctx=>{
    ctx.body = 'user';
})
    let company = new Router();
    company.get('a',ctx=>{
        ctx.body = 'company Page';
    })

    let admin = new Router();
    admin.get('b',ctx=>{
        ctx.body = 'admin Page';
    })

userRouter.use(company.routes());
userRouter.use(admin.routes());

router.use(userRouter.routes());

app.use(router.routes());
app.listen(3000);复制代码

路由参数

const Koa = require('koa');
const Router = require('koa-router');

let app = new Koa();
let router = new Router();

app.get('/user/:id',async ctx => {
    // 参数能够从ctx中的params中获取
    console.log(ctx.params);
    
    //获取id的值
    let { id } = ctx.params;

    console.log(id);
})
app.use(router.routes());
app.listen(3000);复制代码

urlencoded传路由参数与params传路由参数

urlencoded格式: http://www.baidu.com/user?id=xxx

获取urlencoded路由的参数

const Koa = require('koa');
const Router = require('koa-router');

let app = new Koa();
let router = new Router();

app.get('/user/',async ctx => {
    // urlencoded传参数能够从ctx中的query中获取
    console.log(ctx.query);
    
    //获取id的值
    let { id } = ctx.query;

    console.log(id);
})
app.use(router.routes());
app.listen(3000);复制代码

params格式: http:/www.baidu.com/user/12 12=>:id

app.context

app.context是app服务中ctx的原型，若是须要添加全局组件，或者全局变量，能够使用app.context来设置全局

const Koa = require('koa');
const Router = require('koa-router');

let app = new Koa();

// 将数据库设置为全局
app.context.db = mysql.createPool();
let router = new Router();

app.get('/',async ctx => {
   ctx.db.query('xxxxxxxx');
})

app.use(router.routes());
app.listen(3000);复制代码

ctx中经常使用的信息

• ctx.method   //请求方式
• ctx.url    //url
• ctx.path    
• ctx.params    //路由参数
• ctx.query    //get提交的参数
• ctx.ip    //客户端ip
• ctx.headers    //请求头

ctx中经常使用的方法

• ctx.throw(state,msg)  //处理错误方法,state为状态码，msg为提示信息

const Koa = require('koa');
const Router = require('koa-router');

let app = new Koa();

// 将数据库设置为全局
app.context.db = mysql.createPool();
let router = new Router();

app.get('/login',async ctx => {
   let { username,password } = ctx.query;
    if( !username || !password ){
        ctx.throw(404,'username and password are required');
    }
})

app.use(router.routes());
app.listen(3000);复制代码

• ctx.assert(条件,state,msg)

const Koa = require('koa');
const Router = require('koa-router');

let app = new Koa();

// 将数据库设置为全局
app.context.db = mysql.createPool();
let router = new Router();

app.get('/login',async ctx => {
    ctx.assert(ctx.query.username,404,'username is required');
    ctx.assert(ctx.query.password,404,'password is required');

    ctx.body= ' success ';
})

app.use(router.routes());
app.listen(3000);复制代码

• ctx.state

ctx.state = 404复制代码

• ctx.attachment()
• ctx.redireact()

ctx.redireact('/register');
ctx.redireact('http://www.baidu.com');复制代码

static

koa不自带static，须要安装koa-static

npm i koa-static复制代码

const Koa = require('koa');
const Router = require('koa-router');
const static = require('koa-static');

let app = new Koa();

let router = new Router();

app.use(static('./static',{
    maxage: 17*86400*100; //缓存时间
    index: 'index.html'; //跟文件
})

app.use(router.routes());
app.listen(3000);复制代码

const Koa=require('koa');
const Router=require('koa-router');
const static=require('koa-static');

let server=new Koa();
server.listen(8080);

//
let router=new Router();

router.get('/user', async ctx=>{
});

server.use(router.routes());

let staticRouter=new Router();
staticRouter.all(/(\.jpg|\.png|\.gif)$/i, static('./static', {
  maxage: 60*86400*1000
}));
staticRouter.all(/(\.css)$/i, static('./static', {
  maxage: 1*86400*1000
}));
staticRouter.all(/(\.html|\.htm|\.shtml)$/i, static('./static', {
  maxage: 20*86400*1000
}));
staticRouter.all('', static('./static', {
  maxage: 30*86400*1000
}));

server.use(staticRouter.routes());复制代码

koa-better-body中间件

koa-better-body可以解析上传的文件以及普通的post数据

const Koa=require('koa');
const Router=require('koa-router');
const body=require('koa-better-body');

let server=new Koa();
server.listen(8080);

server.use(body({
  // 文件上传的路径
  uploadDir: './static/upload'
}));

server.use(async ctx=>{
  //文件和post数据信息都在ctx.request.fields里面
  console.log(ctx.request.fields);

  ctx.body='aaa';
});
复制代码

cookie

koa自带cookie

const Koa=require('koa');
const Router=require('koa-router');

let server=new Koa();
server.listen(8080);

// 循环秘钥
server.keys=[
  'sdfasdfasdfsadfasddfsdaf',
  'gutryurtyhfddyt8uytug',
  'tyutryur687tyuyujghjkhj',
];
server.use(async ctx=>{
  ctx.cookies.set('user', 'blue', {
    signed: true
    // 还能够加httpOnly,domain,maxAge等等
    });

  console.log(ctx.cookies.get('user', {
    // 校验cookie
    signed: true
  }));
});
复制代码

session

npm i koa-session复制代码

const Koa=require('koa');
const Router=require('koa-router');
const session=require('koa-session');

let server=new Koa();
server.listen(8080);

// 循环秘钥
server.keys=[
  'asdfasdfasdfasdfasdf',
  'hghjfgjghjkyggfytyurt',
  'hjghjkfguig8ygyi8t78i8',
];

server.use(session({
  maxAge: 20*60*1000,   //有效期
  renew: true           //自动续期
}, server));


server.use(async ctx=>{
  // session信息能够在ctx.session中寻找
  if(!ctx.session['view']){
    ctx.session['view']=0;
  }

  ctx.session['view']++;

  ctx.body=`欢迎你第${ctx.session.view}次来访`;
});
复制代码

MySQL

database.js

const mysql=require('mysql');
const co=require('co-mysql');

let conn=mysql.createPool({
  host: 'localhost',
  user: 'root',
  password: '',
  database: '20181101'
});
let db=co(conn);

module.exports=db;
复制代码

app.js

const Koa=require('koa');
const Router=require('koa-router');

let server=new Koa();
server.listen(8080);

server.context.db=require('./libs/database');

server.use(async (ctx, next)=>{
    try{
        let data = await ctx.db.query('SELECT * FROM user');
        console.log(data);
    }catch(err){
        console.log(err);
    }
    
});

server.use(router.routes());复制代码

错误处理

const Koa=require('koa');
const Router=require('koa-router');

let server=new Koa();
server.listen(8080);

server.context.db=require('./libs/database');

/*
    在全部的use以前，处理普通的错误，由于执行了next(),全部下面全部的错误都会在该处被捕获
*/
server.use(async (ctx, next)=>{
  try{
    await next();
  }catch(e){
    ctx.body='错了';
  }
});


let router=new Router();

/*
    在全部路由以前，处理路由错误，* 表示全部路由
*/
router.all('*', async ctx=>{
  try{
    await next();
  }catch(e){
    ctx.body='错了-router';
  }
});

router.get('/a', async ctx=>{
  ctx.body=div.title;
});

server.use(router.routes());
复制代码