nodejs review-02

30 Receive POST data

• POST接受JSON数据处理;

//req. res都是可读的stream;http.createServer(function (req, res) {
var json_data = ''; req.on('readable', function () {
var d = req.read(); if(typeof d === 'string') {
json_data += d;
} else if(typeof d === 'object' && d instanceof Buffer) { //可以简化使用Buffer.isBuffer/util.isBuffer判断;
json_data += d.toString('utf8');
}
}); req.on('end', function () {
var out = ''; if(!json_data) {
out = 'No JSON';
} else {
var json;
try {
json = JSON.parse(json_data); //判断是否为字符串化的JSON数据
} catch(e) {} if(!json) out = 'Invalid JSON';
else out = 'Valid Data JSON: ' + json_data;
}
res.end(out);
});
}).listen(3000);//curl的postcurl -i -X POST -H 'Content-Type: application/json' -d '{"name": "jinks" , "age": 25}' http://localhost:3000


• POST接受query处理

var qs = require('querystring');
...
req.on('end', function () {
var out = '';
if(!form_data) {
out = 'No JSON';
} else {
var json = qs.parse(form_data);
if(!json) out = 'Invalid form_data';
else out = 'Valid Data form_data: ' + JSON.stringify(json);
}
res.end(out);
});
...//--data 即 -dcurl -i -X POST --data 'name=jinks&age=25' http://localhost:3000


• 处理查询字符串的注意:如果同一个键有多个值,其值会以数组形式返回，实际业务中需要做判断

32 Use npm the node package manager

• npm查找包

npm search


• npm全局安装的地方/nodejs最底层查找包的地方;

/usr/local/lib/node_modules


• 包映射

npm link; //允许后将当前包映射到/usr/local/lib/node_modules中,每次当前包变化,相应机会变化;
npm link package; //可以将/usr/local/lib/node_modules中的包映射到当前node_modules中,也会相应变化;


37 Investigate Node js streams

• 读取数据流

var ws = fs.createWriteStream('test.js');function read_file(filename, callback) {
var rs = fs.createReadStream(filename);
var content = ''; rs.on('readable', function () {
var d = rs.read();
if(typeof d === 'string') {
content += b;
} else if(Buffer.isBuffer(d)) {
content += d.toString('utf8')
}
}); rs.on('end', function () {
callback(null, content);
});
};read_file('example.txt', function (err, contents) {
if(err) return console.log(err);
return ws.write(contents);
});//扩展
//1.使用data事件取代readable rs.on('data', function (chunk) {
content += chunk.toString('utf8');
});//2.将全部读取完后写入改成边写边读function read_file(filename, callback) {
var rs = fs.createReadStream(filename);
var content = ''; rs.on('data', function (chunk) {
ws.write(chunk) === false && rs.pause();
}); rs.on('end', function () {
ws.end();
}); ws.on('drain', function () {
rs.resume();
}); rs.on('err', function () {
callback(err);
}); ws.on('err', function () {
callback(err);
});
};//3.使用pipe
fs.createReadStream('example.txt')
.pipe(fs.createWriteStream('copy.txt'))
.on('error', function () {});


• string,buffer的长度关系

var b = new Buffer(100);
var s = 'string';
b.write(s);
console.log(s.length, b.length, Buffer.byteLength(s)); //6, 100, 6var b2 = new Buffer(100);
var c = '字符串';
b2.write(c);
console.log(c.length, b2.length, Buffer.byteLength(c)); //3, 100, 9


38 Serve static files from our server

• server中使用数据库

http.createServer(function (req, res) {
var rs = fs.createReadStream('example.txt');
rs.on('error', function (err) {
res.writeHead(404);
res.end(JSON.stringify(err));
})
.on('open', function () {
res.writeHead(202);
})
.on('data', function (chunk) {
res.write(chunk) === false && rs.pause();
})
.on('drain', function () {
rs.resume();
})
.on('end', function () {
res.end();
});
}).listen(3000);//
http.createServer(function (req, res) {
var rs = fs.createReadStream('example.txt');
rs.on('error', function (err) {
res.writeHead(404);
res.end(JSON.stringify(err));
});
rs.on('open', function () {
res.writeHead(202);
});
rs.pipe(res);
}).listen(3000);

• Buffer类型的处理

//
var fs = require('fs');
var rs = fs.createReadStream('example.txt');
var data = '';
rs.on("data", function (chunk){
data += chunk; //隐藏操作data = data.toString() + chunk.toString();
});
rs.on("end", function () {
console.log(data);
});//对于中文处理
rs.setEncoding('utf8'); //初始化声明;而然存在问题//Buffer拼接
var chunks = [], size = 0;
res.on('data', function (chunk) {
chunks.push(chunk);
size += chunk.length;
};res.on('end', function () {
var buf = Buffer.concat(chunks, size); //省略第二个参数时，Node内部会计算出这个值，然后再据此进行合并运算。因此，显式提供这个参数，能提供运行速度。
console.log(buf.toString('utf8'));
});//相当于
res.on('end', function () {
var buffer = new Buffer(size), pos = 0;
for(var i = 0, l = chunks.length; i < l; i++) {
var buf = chunks[i];
buf.copy(buffer, pos);
pos += buf.length;
};
console.log(buffer.toString('utf8'));
});