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
