Memcached —— 下载、配置、使用

清疚 2022-06-09 01:42 451阅读 0赞

主要了解Memcached 与其其中一个java客户端XMemcached。

**一、基础了解**

Memcahed 是一套分布式高速缓存系统。简言之，它是用于缓存数据的服务。在并发访问web服务器时，为减少直接访问数据库的次数，降低数据库服务器的负载，首次从数据库查询某数据后，我们将其放入缓存系统中，在一定时间内对该相同数据的再次访问，便可直接从缓存系统中拿取，而无需操作数据库。

缓存系统由两部分组成：

1、服务端，即Memcached，使用c语言编写；

2、客户端，即我们编程时所使用的一套用于缓存数据的一套API。Memcached 的java客户端有3种版本：

（1）、memcached client for Java：[https://github.com/gwhalin/Memcached-Java-Client/downloads][https_github.com_gwhalin_Memcached-Java-Client_downloads]

（2）、spymemcached；

（3）、xmemcached。

360百科：[https://baike.so.com/doc/5380534-5616808.html][https_baike.so.com_doc_5380534-5616808.html]

**二、Memcached下载**

官网：[http://memcached.org/][http_memcached.org]

Memcached服务端下载地址：[https://github.com/memcached/memcached/releases][https_github.com_memcached_memcached_releases]

说明：此链接下载的为源代码，可编译为.exe文件后再安装为服务，或从其它站点下载可执行文件。

附一个不错的链接：

XMemcached 中文用户指南：[https://github.com/killme2008/xmemcached/wiki/Xmemcached%20%E4%B8%AD%E6%96%87%E7%94%A8%E6%88%B7%E6%8C%87%E5%8D%97\#spring-30%E5%92%8Cbuilder%E9%85%8D%E7%BD%AE][https_github.com_killme2008_xmemcached_wiki_Xmemcached_20_E4_B8_AD_E6_96_87_E7_94_A8_E6_88_B7_E6_8C_87_E5_8D_97_spring-30_E5_92_8Cbuilder_E9_85_8D_E7_BD_AE]

**三、配置**

1、安装Memcache 服务端。

下载memcached.exe后，cmd进入其所在目录，将其安装为系统服务：memcached.exe -d install

2、项目中使用XMemcached 进行数据缓存。

方式一：与Spring 整合使用

（1）、导入xmemcached-2.\*.jar与其依赖包slf4j-\*.jar；

（2）、spring容器中配置上下文对象：

（一）通过XMemcachedClientFactoryBean类配置：

（简单配置）

（详细配置）

<bean name="server1" class="java.net.InetSocketAddress">
    		<constructor-arg>
    			<value>host1</value>
    		</constructor-arg>
    		<constructor-arg>
    			<value>port1</value>
    		</constructor-arg>
    </bean>
    <bean name="memcachedClient"
                    class="net.rubyeye.xmemcached.utils.XMemcachedClientFactoryBean" destroy-method="shutdown">
    	<property name="servers">
            	<value>host1:port,host2:port host3:port,host4:port</value>
            </property>
            
            <property name="weights">
            	<list>
                    	<value>1</value>
                    	<value>2</value>
                    	<value>3</value>
                    </list>
            </property>
            
    	<property name="authInfoMap">
    		<map>
    			<entry key-ref="server1">
    				<bean class="net.rubyeye.xmemcached.auth.AuthInfo" factory-method="typical">
    					<constructor-arg index="0">
    						<value>cacheuser</value>
    					</constructor-arg>
    					<constructor-arg index="1">
    						<value>123456</value>
    					</constructor-arg>
    				</bean>
    			</entry>
    		</map>
    	</property>
            
            <property name="connectionPoolSize" value="2"></property>
            
            <property name="commandFactory">
            	<bean class="net.rubyeye.xmemcached.command.BinaryCommandFactory"></bean>
            </property>
            
            <property name="sessionLocator">
                    <bean class="net.rubyeye.xmemcached.impl.KetamaMemcachedSessionLocator"></bean>
            </property>
            
            <property name="transcoder">
                    <bean class="net.rubyeye.xmemcached.transcoders.SerializingTranscoder" />
            </property>
            
            <property name="bufferAllocator">
                    <bean class="net.rubyeye.xmemcached.buffer.SimpleBufferAllocator"></bean>
            </property>
            
            <property name="failureMode" value="false"/>
     </bean>

属性说明：

servers：memcached服务器节点列表；

weights：与servers对应的节点的权重，权重大小控制缓存对象的多少；

authInfoMap 授权验证信息，仅在xmemcached 1.2.5及以上版本有效；

connectionPoolSize ：nio连接池大小，默认为1

commandFactory：协议工厂，net.rubyeye.xmemcached.command.BinaryCommandFactory，TextCommandFactory(默认)，KestrelCommandFactory；

sessionLocator：分布策略，一致性哈希net.rubyeye.xmemcached.impl.KetamaMemcachedSessionLocator或者ArraySessionLocator(默认)

transcoder：序列化转换器，默认使用net.rubyeye.xmemcached.transcoders.SerializingTranscoder，更多选项参见javadoc；

bufferAllocator ：IoBuffer分配器，默认为net.rubyeye.xmemcached.buffer.SimpleBufferAllocator，可选CachedBufferAllocator(不推荐)；

failureMode：是否启用failure模式，true为启用，默认不启用。

（二）在Spring3.0中通过Builder配置

Spring 3.0修改了查找destroy method的方式，所以上述配置将出错，可采用下面配置。

<bean name="memcachedClientBuilder" class="net.rubyeye.xmemcached.XMemcachedClientBuilder">
                    
                    <constructor-arg>
                            <list>
                                    <bean class="java.net.InetSocketAddress">
                                            <constructor-arg>
                                                    <value>localhost</value>
                                            </constructor-arg>
                                            <constructor-arg>
                                                    <value>12000</value>
                                            </constructor-arg>
                                    </bean>
                                    <bean class="java.net.InetSocketAddress">
                                            <constructor-arg>
                                                    <value>localhost</value>
                                            </constructor-arg>
                                            <constructor-arg>
                                                    <value>12001</value>
                                            </constructor-arg>
                                    </bean>
                            </list>
                    </constructor-arg>
                    <constructor-arg>
                            <list>
                                    <value>1</value>
                                    <value>2</value>
                            </list>
                    </constructor-arg>
                    <property name="authInfoMap">
    			<map>
    				<entry key-ref="server1">
    					<bean class="net.rubyeye.xmemcached.auth.AuthInfo"
    						factory-method="typical">
    						<constructor-arg index="0">
    							<value>cacheuser</value>
    						</constructor-arg>
    						<constructor-arg index="1">
    							<value>123456</value>
    						</constructor-arg>
    					</bean>
    				</entry>
    			</map>
    		</property>
                    <property name="connectionPoolSize" value="2"></property>
                    <property name="commandFactory">
                            <bean class="net.rubyeye.xmemcached.command.TextCommandFactory"></bean>
                    </property>
                    <property name="sessionLocator">
                            <bean class="net.rubyeye.xmemcached.impl.KetamaMemcachedSessionLocator"></bean>
                    </property>
                    <property name="transcoder">
                            <bean class="net.rubyeye.xmemcached.transcoders.SerializingTranscoder" />
                    </property>
            </bean>
            
            <bean name="memcachedClient3" factory-bean="memcachedClientBuilder"
                    factory-method="build" destroy-method="shutdown"/>

authInfoMap保存的是以memcached服务器地址为键的键值对，暂时对其作用不太了解，此属性可不用配置。

最终，可通过自动装配使用XMemcached进行数据缓存：

@Autowired
    private MemcachedClient memcachedClient3;
    
    ……
    	//存数据
    	String data = ……//首次查数据库
    	String key = "key";
    	if(memcachedClient3.get(key)==null){
    		memcachedClient3.add(key,10000,data);//参数列表为键、缓存时间、缓存数据
    	}
    	//查数据
    	String data = memcachedClient3.get("key");
    	if(data!=null){
    		return data;
    	}else{
    		//查数据库
    	}
    ……

方式二：项目中直接使用

假设memcached 服务安装在本地（其默认端口为11211），则示例代码：

MemcachedClientBuilder builder = new XMemcachedClientBuilder(
    					AddrUtil.getAddresses("localhost:11211"));
        MemcachedClient memcachedClient = builder.build();
        try {
    		memcachedClient.set("hello", 0, "Hello,xmemcached");
    		String value = memcachedClient.get("hello");
    		System.out.println("hello=" + value);
    		memcachedClient.delete("hello");
    		value = memcachedClient.get("hello");
    		System.out.println("hello=" + value);
        } catch (MemcachedException e) {
    		System.err.println("MemcachedClient operation fail");
    		e.printStackTrace();
        } catch (TimeoutException e) {
    		System.err.println("MemcachedClient operation timeout");
    		e.printStackTrace();
        } catch (InterruptedException e) {
    		// ignore
        }
        try {
                  //close memcached client
          		memcachedClient.shutdown();
        } catch (IOException e) {
            	System.err.println("Shutdown MemcachedClient fail");
    		e.printStackTrace();
        }

XMemcached详细了解：  
[https://github.com/killme2008/xmemcached/wiki/Xmemcached%20%E4%B8%AD%E6%96%87%E7%94%A8%E6%88%B7%E6%8C%87%E5%8D%97][https_github.com_killme2008_xmemcached_wiki_Xmemcached_20_E4_B8_AD_E6_96_87_E7_94_A8_E6_88_B7_E6_8C_87_E5_8D_97]

[https_github.com_gwhalin_Memcached-Java-Client_downloads]: https://github.com/gwhalin/Memcached-Java-Client/downloads
[https_baike.so.com_doc_5380534-5616808.html]: https://baike.so.com/doc/5380534-5616808.html
[http_memcached.org]: http://memcached.org/
[https_github.com_memcached_memcached_releases]: https://github.com/memcached/memcached/releases
[https_github.com_killme2008_xmemcached_wiki_Xmemcached_20_E4_B8_AD_E6_96_87_E7_94_A8_E6_88_B7_E6_8C_87_E5_8D_97_spring-30_E5_92_8Cbuilder_E9_85_8D_E7_BD_AE]: https://github.com/killme2008/xmemcached/wiki/Xmemcached%20%E4%B8%AD%E6%96%87%E7%94%A8%E6%88%B7%E6%8C%87%E5%8D%97#spring-30%E5%92%8Cbuilder%E9%85%8D%E7%BD%AE
[https_github.com_killme2008_xmemcached_wiki_Xmemcached_20_E4_B8_AD_E6_96_87_E7_94_A8_E6_88_B7_E6_8C_87_E5_8D_97]: https://github.com/killme2008/xmemcached/wiki/Xmemcached%20%E4%B8%AD%E6%96%87%E7%94%A8%E6%88%B7%E6%8C%87%E5%8D%97