在Node.js应用中读写Redis数据库的简单方法

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