Memcached 简明教程

Memcached - Increment Decrement Data

Memcached incr 和 decr 命令用于增加或减少现有密钥的数值。如果未找到该密钥，则它将返回 NOT_FOUND 。如果该密钥不是数字，则它将返回 CLIENT_ERROR cannot increment or decrement non-numeric value 。否则，将返回 ERROR 。

Memcached incr and decr commands are used to increment or decrement the numeric value of an existing key. If the key is not found, then it returns NOT_FOUND. If the key is not numeric, then it returns CLIENT_ERROR cannot increment or decrement non-numeric value. Otherwise, ERROR is returned.

Syntax - incr

Memcached incr 命令的基本语法如下所示：

The basic syntax of Memcached incr command is as shown below −

incr key increment_value

Example

在此示例中，我们使用 visitors 作为密钥，并最初在其中设置 10，然后将其增加 5。

In this example, we use visitors as key and set 10 initially into it, thereafter we increment the visitors by 5.

set visitors 0 900 2
10
STORED
get visitors
VALUE visitors 0 2
10
END
incr visitors 5
15
get visitors
VALUE visitors 0 2
15
END

Syntax - decr

Memcached decr 命令的基本语法如下所示：

The basic syntax of Memcached decr command is as shown below

decr key decrement_value

Example

set visitors 0 900 2
10
STORED
get visitors
VALUE visitors 0 2
10
END
decr visitors 5
5
get visitors
VALUE visitors 0 1
5
END

Incr/Decr Using Java Application

若要在 Memcached 服务器中增加或减少数据，您需要分别使用 Memcached incr or decr 方法。

To increment or decrement data in a Memcached server, you need to use Memcached incr or decr methods respectively.

Example

import net.spy.memcached.MemcachedClient;
public class MemcachedJava {
   public static void main(String[] args) {

      // Connecting to Memcached server on localhost
      MemcachedClient mcc = new MemcachedClient(new
      InetSocketAddress("127.0.0.1", 11211));
      System.out.println("Connection to server sucessfully");
      System.out.println("set status:"+mcc.set("count", 900, "5").isDone());

      // Get value from cache
      System.out.println("Get from Cache:"+mcc.get("count"));

      // now increase the stored value
      System.out.println("Increment value:"+mcc.incr("count", 2));

      // now decrease the stored value
      System.out.println("Decrement value:"+mcc.decr("count", 1));

      // now get the final stored value
      System.out.println("Get from Cache:"+mcc.get("count"));
   }
}

Output

编译并执行该程序后，您可以看到以下输出：

On compiling and executing the program, you get to see the following output −

Connection to server successfully
set status:true
Get from Cache:5
Increment value:7
Decrement value:6
Get from Cache:6