在Node.js应用中使用Redis的方法简介

在开始本文之前请确保安装好 Redis 和 Node.js 以及 Node.js 的 Redis 扩展 —— node_redis

首先创建一个新文件夹并新建文本文件 app.js 文件内容如下：

var redis = require("redis")

, client = redis.createClient();

client.on("error", function (err) {

console.log("Error " + err);

});

client.on("connect", runSample);

function runSample() {

// Set a value

client.set("string key", "Hello World", function (err, reply) {

console.log(reply.toString());

});

// Get a value

client.get("string key", function (err, reply) {

console.log(reply.toString());

});

}

当连接到 Redis 后会调用 runSample 函数并设置一个值，紧接着便读出该值，运行的结果如下：

OK

Hello World

我们也可以使用 EXPIRE 命令来设置对象的失效时间，代码如下：

var redis = require('redis')

, client = redis.createClient();

client.on('error', function (err) {

console.log('Error ' + err);

});

client.on('connect', runSample);

function runSample() {

// Set a value with an expiration

client.set('string key', 'Hello World', redis.print);

// Expire in 3 seconds

client.expire('string key', 3);

// This timer is only to demo the TTL

// Runs every second until the timeout

// occurs on the value

var myTimer = setInterval(function() {

client.get('string key', function (err, reply) {

if(reply) {

console.log('I live: ' + reply.toString());

} else {

clearTimeout(myTimer);

console.log('I expired');

client.quit();

}

});

}, 1000);

}

注意: 上述使用的定时器只是为了演示 EXPIRE 命令，你必须在 Node.js 项目中谨慎使用定时器。

运行上述程序的输出结果是：

Reply: OK

I live: Hello World

I live: Hello World

I live: Hello World

I expired

接下来我们检查一个值在失效之前存留了多长时间：

var redis = require('redis')

, client = redis.createClient();

client.on('error', function (err) {

console.log('Error ' + err);

});

client.on('connect', runSample);

function runSample() {

// Set a value

client.set('string key', 'Hello World', redis.print);

// Expire in 3 seconds

client.expire('string key', 3);

// This timer is only to demo the TTL

// Runs every second until the timeout

// occurs on the value

var myTimer = setInterval(function() {

client.get('string key', function (err, reply) {

if(reply) {

console.log('I live: ' + reply.toString());

client.ttl('string key', writeTTL);

} else {

clearTimeout(myTimer);

console.log('I expired');

client.quit();

}

});

}, 1000);

}

function writeTTL(err, data) {

console.log('I live for this long yet: ' + data);

}

运行结果：

Reply: OK

I live: Hello World

I live for this long yet: 2

I live: Hello World

I live for this long yet: 1

I live: Hello World

I live for this long yet: 0

I expired