在Node.js应用中读写Redis数据库的简单方法

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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：

OKHello 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: OKI live: Hello WorldI live: Hello WorldI live: Hello WorldI 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: OKI live: Hello WorldI live for this long yet: 2I live: Hello WorldI live for this long yet: 1I live: Hello WorldI live for this long yet: 0I expired

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