Memcached安装教程及使用

Memcached

Memcached 是一个高性能的分布式内存对象缓存系统，用于动态Web应用以减轻数据库负载

Table of contents

• 安装
• 使用
• 在spring中使用

安装

1. 下载下来memcached.exe
2. 切换到memcached.exe所在路径
3. 输入memcached -d install
4. win + r 输入 services.msc打开window服务
5. 随便选中一个输入memcached就可以查看到安装好的服务,右击启动它,然后关闭窗口

使用

1. 新建java工程或者maven工程

2. 导入三个必备的依赖,fastjson-1.2.3,slf4j-api-1.7.5,xmemcached-2.3.2

3. main方法中加入

   MemcachedClientBuilder builder = new XMemcachedClientBuilder(AddrUtil.getAddresses("127.0.0.1:11211"));
   builder.setSessionLocator(new KetamaMemcachedSessionLocator());
   try {
   MemcachedClient memcachedClient =builder.build();

   //在这里写入测试代码

   memcachedClient.shutdown();
   } catch (IOException e) {
   e.printStackTrace();
   } catch (InterruptedException e) {
   e.printStackTrace();
   } catch (MemcachedException e) {
   e.printStackTrace();
   } catch (TimeoutException e) {
   e.printStackTrace();
   }

• 测试一定时间后数据是否还能取出来
• 永久时间,测试重启服务之后先前存储的数据是否还能取出来
• delete
• 自动增长

时效

memcachedClient.set("testTime",2,"testTimeValue");
String testTime = memcachedClient.get("testTime");
System.out.println("testTime = " + testTime);
TimeUnit.SECONDS.sleep(4);
System.out.println("4s 过去了");
String valueExist = memcachedClient.get(testTime);
System.out.println("valueExist = " + valueExist);

输出:
testTime = testTimeValue
4s 过去了
valueExist = null

恢复

//存储,然后关闭掉服务
memcachedClient.set("test",0,"testValue");
String testTime=memcachedClient.get("test");
System.out.println("testTime="+testTime);
System.out.println("存储成功");

输出:
testTime = testValue
存储成功

//关闭掉服务后的重启
String testTime = memcachedClient.get("test");
System.out.println("testTime = " + testTime);
System.out.println("取值失败");

输出:
testTime = null
取值失败

delete

memcachedClient.set("test",0,"testValue");
String getVal = memcachedClient.get("test");
System.out.println("getVal = " + getVal);
memcachedClient.delete("test");
System.out.println("after delete ...");
getVal = memcachedClient.get("test");
System.out.println("getVal = " + getVal);

输出:
getVal = testValue
after delete ...
getVal = null

自动增长

//三个参数,第一个指定键,第二个指定递增的幅度大小,第三个指定当key不存在的情况下的初始值
for (int i = 0; i < 5; i++) {
memcachedClient.incr("博客的赞",1,20);
String point = memcachedClient.get("博客的赞");
System.out.println("point = " + point);
}

输出:
point = 20
point = 21
point = 22
point = 23
point = 24

关于incr的用法,值得警惕的是,它的值虽然看起来是一个数字,实际上正如代码中的String point = memcachedClient.get("博客的赞");
其实是一个字符串,所以会出现如下错误

memcachedClient.set("博客的赞1",0,10);
int str = memcachedClient.get("博客的赞1");
System.out.println("str1 = " + str);
memcachedClient.incr("博客的赞1",2,22);
str = memcachedClient.get("博客的赞1");
System.out.println("str2 = " + str);

输出:
net.rubyeye.xmemcached.exception.MemcachedClientException: cannot increment or decrement non-numeric value,key=博客的赞1
at net.rubyeye.xmemcached.command.Command.decodeError(Command.java:267)
..
at com.google.code.yanf4j.nio.impl.NioController.onRead(NioController.java:157)
at com.google.code.yanf4j.nio.impl.Reactor.dispatchEvent(Reactor.java:323)
at com.google.code.yanf4j.nio.impl.Reactor.run(Reactor.java:180)
str1 = 10

输出的顺序不同,注意输出的异常栈信息的第一条和后面的几条就指明nio.impl.Reactor.run,线程的,这儿就不深入展开了

spring

• 新建一个maven工程
• pom.xml
• 在resource中新建sping-config.xml
• spring单元测试代码骨架
• 测试代码

骨架

@RunWith(SpringJUnit4ClassRunner.class)
@ContextConfiguration(locations = "classpath:spring-config.xml")
public class TestMem {
@Autowired
private MemcachedClient memcachedClient;

@Test
public void test1(){
//测试代码部分
}

}

测试代码

memcachedClient.set("springData",3,"dataVal");
String str = memcachedClient.get("springData");
System.out.println("str = " + str);

输出:
str = dataVal

还可以存储对象,不过该对象必须实现Serializable接口,不然会报错java.io.NotSerializableException: Teacher,

实现接口后

import lombok.Data;
import java.io.Serializable;
@Data
public class Teacher implements Serializable {
private int age;
private String name;
}

关于@Data关我在另一篇博客中有介绍lombok

Teacher teacher = new Teacher();
teacher.setAge(3);
teacher.setName("23");

memcachedClient.set("te", 0, teacher);
Teacher teacher1 = memcachedClient.get("te");
System.out.println("teacher1 = " + teacher1);

输出:
teacher1 = Teacher(age=3, name=23)

pom.xml

4.0.0

com.selton
DemoMemSpring
1.0

org.projectlombok
lombok
1.18.0
provided

org.springframework
spring-context
4.3.11.RELEASE

com.googlecode.xmemcached
xmemcached
2.0.0


org.springframework
spring-context

org.springframework
spring-test
4.3.11.RELEASE

junit
junit
4.12
test

config

127.0.0.1:11211




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