创建缓存服务

创建缓存服务接口项目

• 创建myshop-service-redis-api项目,该项目只负责定义接口
• 创建项目的pom.xml:

<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
         xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 https://maven.apache.org/xsd/maven-4.0.0.xsd">
    <modelVersion>4.0.0</modelVersion>
    <parent>
        <groupId>com.oxford</groupId>
        <artifactId>myshop-dependencies</artifactId>
        <version>1.0.0-SNAPSHOT</version>
        <relativePath>../myshop-dependencies/pom.xml</relativePath>
    </parent>

    <artifactId>myshop-service-redis-api</artifactId>
    <packaging>jar</packaging>
</project>

• 定义数据Redis接口RedisService:

package com.oxford.myshop.service.redis.api

public interface RedisService{
	void set(String key,Object value);
	
	void set(String key,Object value,int seconds);

	void del(String key);

	Object get(String key);
}

创建缓存服务提供者项目

• 创建myshop-service-redis-provider项目,该项目用作缓存服务提供者
• 创建项目的pom.xml:

<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
         xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 https://maven.apache.org/xsd/maven-4.0.0.xsd">
    <modelVersion>4.0.0</modelVersion>
    <parent>
        <groupId>com.oxford</groupId>
        <artifactId>myshop-dependencies</artifactId>
        <version>1.0.0-SNAPSHOT</version>
        <relativePath>../myshop-dependencies/pom.xml</relativePath>
    </parent>

    <artifactId>myshop-service-redis-api</artifactId>
    <packaging>jar</packaging>

	<dependencies>
		<!-- Spring Boot Starter Settings-->
		<dependency>
			<groupId>org.springframework.boot</groupId>
			<artifactId>spring-boot-starter-data-redis</artifactId>
		</dependency>

		<dependency>
			<groupId>org.springframework.boot</groupId>
			<artifactId>spring-boot-starter-test</artifactId>
			<scope>test</scope>
		</dependency>


		<!--Common Setting-->
		<dependency>
			<groupId>org.apache.commons</groupId>
			<artifactId>commons-pool2</artifactId>
		</dependency>
		<dependency>
			<groupId>de.javakaffee</groupId>
			<artifactId>kryo-serializers</artifactId>
		</dependency>

		<!--Project Settings-->
		<dependency>
			<groupId>com.oxford</groupId>
			<artifactId>my-shop-commons-dubbo</artifactId>
			<version>${Project.parent.version}</version>
		</dependency>
		<dependency>
			<groupId>com.oxford</groupId>
			<artifactId>my-shop-service-redis-api</artifactId>
			<version>${Project.parent.version}</version>
		</dependency>
	</dependencies>

	<build>
		<plugins>
			<plugin>
				<groupId>org.springframework.boot</groupId>
				<artifactId>spring-boot-maven-plugin</artifactId>
				<configuration>
					<mainClass>com.oxford.myshop.service.redis.provider.MyshopServiceRedisProviderApplication</mainClass>
				</configuration>
			</plugin>
		</plugins>
	</build>
</project>

Redis底层实现的Java的lettuce客户端

• 创建缓存服务接口实现类RedisServiceImpl

package com.oxford.myshop.service.redis.provider.api.impl;

@Service(version="${service.versions.redis.v1}")
public class RedisServiceImpl implements RedisService{
	
	@Override
	public void set(String key,Object value){
		redisTemplate.opsForValue().set(key,value);
	}

	@Override
	public void set(String key,Object value,int seconds){
		redisTemplate.opsForValue().set(key,value,seconds,TimeUnit.SECONDS);
	}

	@Override
	public void del(String key){
		redisTemplate.delete(key);
	}

	@Override
	public Object get(String key){
		return redisTemplate.opsForValue().get(key);
	}
}

• 创建启动类SpringBootApplication

package com.oxford.myshop.service.redis.provider;

import com.alibaba.dubbo.container.Main;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.cloud.netflix.hystrix.EnableHystrix;
import org.springframework.cloud.netflix.hystrix.dashboard.EnableHystrixDashboard;



@EnableHystrix
@EnableHystrixDashboard
public class MyShopServiceRedisrProviderApplication {
    public static void main(String[]args) {
        SpringApplication.run(MyShopServiceRedisProviderApplication.class,args);
        Main.main(args);
    }
}

• 创建配置文件application.yml

spring:
  application:
    name: myshop-service-redis-provider
  redis:
  	lettuce:
      pool:
      	max-active: 8
      	max-idle: 8
      	max-wait: -1ms
      	min-idle: 0
    sentinel:
      master: mymaster
      nodes: 192.168.32.255:26379,192.168.32.255:26380,192.168.32.255:26381
server:
  port: 8503

services:
  version:
    redis:
  	  v1: 1.0.0
    user:
      v1: 1.0.0

dubbo:
  scan:
    basePackages: com.oxford.myshop.service.redis.provider.api.impl
  application:
    id: com.oxford.myshop.service.redis.provider.api
    name: com.oxford.myshop.service.redis.provider.api
    qos-port: 22224
    qos-enable: true
  protocal:
    id: dubbo
    name: dubbo
    port: 20883
    status: server
    serialization: kryo

  regitry:
    id: zookeeper
    address: zookeeper://localhost:2181?backup=192.168.32.255:2182,192.168.32.255:2183

management:
  endpoint:
    dubbo:
      enabled: true
    dubbo-shutdown:
      enabled: true
    dubbo-configs:
      enabled: true
    dubbo-sevicies:
      enabled: true
    dubbo-reference:
      enabled: true
    dubbo-properties:
      enabled: true
  health:
    dubbo:
      status:
        defaults: memory
        extras: load,threadpool

创建缓存服务消费者项目

• 在pom文件中引入redis接口依赖
• 在缓存服务消费者项目的ServiceImpl中调用RedisService

@Reference(version="services.versions.redis.v1")
private RedisService redisService;

MyBatis Redis二级缓存

MyBatis缓存

• 一级缓存:
  • MyBatis会在表示会话的SqlSession对象中建立一个简单的缓存: 将每次查询到的结果缓存起来,当下次查询的时候,如果判断先前有个完全一样的查询,会直接从缓存中直接将结果取出,返回给用户,不需要再进行一次数据库查询
  • 一级缓存是SqlSession级别的缓存:
    • 在操作数据库时需要构造SqlSession对象
    • 对象中有一个(内存区域)数据结构(HashMap)用于存储缓存数据
    • 不同的SqlSession之间的缓存数据区域(HashMap)互不影响,
    • 一级缓存的作用域是同一个SqlSession
    • 在同一个SqlSession中两次执行相同的SQL语句: 第一次执行完毕会将数据库中查询的数据写到缓存(内存),第二次会从缓存中获取数据,将不再从数据库查询,从而提高查询效率
    • 当一个SqlSession结束后该SqlSession中的一级缓存就不存在了
    • MyBatis默认开启一级缓存
• 二级缓存:
  • 二级缓存是Mapper级别的缓存: 多个SqlSession去操作同一个Mapper的SQL语句,多个SqlSession去操作数据库得到数据会存在二级缓存区域,多个SqlSession可以共用二级缓存,二级缓存是跨SqlSession的
  • 二级缓存的作用域是mapper的同一个namespace
  • 不同的SqlSession两次执行相同namespace下的SQL语句且向SQL中传递参数也相同即最终执行相同的SQL语句: 第一次执行完毕会将数据库中查询的数据写到缓存(内存),第二次会从缓存中获取数据将不再从数据库查询,从而提高查询效率
  • MyBatis默认没有开启二级缓存,需要在setting全局参数中配置开启二级缓存

配置MyBatis二级缓存

SpringBoot中开启MyBatis二级缓存

• 在myshop-service-user-provider的配置文件中开启MyBatis二级缓存

spring:
  application:
    name: myshop-service-user-provider
  datasource:
    druid:
      url: jdbc:mysql://localhost:3306/myshop?useUnicode=true&characterEncoding=utf-8&useSSL=false
      username: root
      password: 123456
      initial-size: 1
      min-idle: 1
      main-active: 20
      test-on-borrow: true
      driver-class-name: com.mysql.cj.jdbc.Driver
  redis:
  	lettuce:
      pool:
      	max-active: 8
      	max-idle: 8
      	max-wait: -1ms
      	min-idle: 0
    sentinel:
      master: mymaster
      nodes: 192.168.32.255:26379,192.168.32.255:26380,192.168.32.255:26381

server:
  port: 8501

# MyBatis Config properties
mybatis:
  configuration:
  	cache-enabled: true
  type-aliases-package: com.oxford.myshop.commons.domain
  mapper-location: classpath:mapper/*.xml

services:
  version:
  	redis:
  	  v1: 1.0.0
    user:
      v1: 1.0.0

dubbo:
  scan:
    basePackages: com.oxford.myshop.service.user.provider.api.impl
  application:
    id: com.oxford.myshop.service.user.provider.api
    name: com.oxford.myshop.service.user.provider.api
    qos-port: 22222
    qos-enable: true
  protocal:
    id: dubbo
    name: dubbo
    port: 20001
    status: server
    serialization: kryo

  regitry:
    id: zookeeper
    address: zookeeper://localhost:2181?backup=192.168.32.255:2182,192.168.32.255:2183

management:
  endpoint:
    dubbo:
      enabled: true
    dubbo-shutdown:
      enabled: true
    dubbo-configs:
      enabled: true
    dubbo-sevicies:
      enabled: true
    dubbo-reference:
      enabled: true
    dubbo-properties:
      enabled: true
  health:
    dubbo:
      status:
        defaults: memory
        extras: load,threadpool

• 在myshop-commons-mapper的pom.xml中增加redis依赖:

<dependency>
	<groupId>org.springframework.boot</groupId>
	<artifactId>spring-boot-starter-data-redis</artifacted>
</dependency>

<dependency>
	<groupId>org.apache.commons</groupId>
	<artifactId>commons-pool2</artifacted>
</dependency>

实体类实现序列化接口并声明序列号

private static final long serialVersionUID = 82897704415244673535L

IDEA生成序列号方法:
- 使用GenerateSerialVersionUID插件生成,安装完插件后在实现了序列化接口的类中
- 使用快捷键Alt+Insert即可呼出生成菜单,即可自动生成序列号

实现Mybatis Cache接口,自定义缓存为Redis

• 在myshop-commons项目中创建ApplicationContextHolder类

package com.oxford.myshop.commons.context;

@Component
public class ApplicationContextHolder implements ApplicationContextAware,DisposableBean{

	private static final Logger logger=LoggerFactory.getLogger(ApplicationContext.class);

	private static ApplicationContext applicationContext;

	/**
	 * 获取存储在静态变量中的ApplicationContext
	 */
	 public static ApplicationContext getApplicationContext(){
	 	assertContextInjected();
	 	return applicationContext;
	 }

	/**
	 * 从静态变量applicationContext中获取Bean,自动转型成所赋值对象的类型
	 */
	 public static <T> T getBean(String name){
	 	assertContextInjected();
	 	return (T) applicationContext.getBean(name);
	 }

	/**
	 * 从静态变量applicationContext中获取Bean,自动转型成所赋值对象的类型
	 */
	public static <T> T getBean(Class<T> clazz){
	 	assertContextInjected();
	 	return (T) applicationContext.getBean(clazz);
	 }

	/**
	 * 实现DisposableBean接口,在Context关闭时清理静态变量
	 */
	 public void destroy() throws Exception{
	 	logger.debug("清除 SpringContext 中的 ApplicationContext: {}",applicationContext);
	 	applicationContext=null;
	 }

	/**
	 * 实现ApplicationContextAware接口,注入Context到静态变量中
	 */
	 public void setApplicationContext(ApplicationContext applicationContext) throws BeanException{
	 	ApplicationContext.applicationContext=applicationContext;
	 }

	/**
	 * 断言Context已经注入
	 */
	 private static void assertContextInjected(){
		Validate.validState(applicationContext !=null,"applicationContext 属性未注入,请在配置文件中配置定义ApplicationContextContext");
	}
}

• 在myshop-commons-mapper项目中创建一个RedisCache的工具类

package com.oxford.myshop.commons.utils;

public class RedisCache implements Cache{
	private static final Logger logger=LoggerFactory.getLogger(RedisCache.class);

	private final ReadWriteLock readWriteLock=new ReentranReadWriteLock();
	private final String id;
	private RedisTemplate redisTemplate;

	private static final long EXPIRE_TIME_IN_MINUTES=30		// redis过期时间

	public RedisCache(String id){
		if(id==null){
			throw new IllegalArgumentException("Cache instances require an ID");
		}
		this.id=id;
	}

	@Override
	public String getId(){
		return id;
	}

	/**
	 * Put query result to redis 
	 */
	@Override
	public void putObject(Object key,Object value){
		try{
			RedisTemplate redisTemplate=getRedisTemplate();
			ValueOperations opsForValue=redisTemplate.opsForValue();
			opsForValue.set(key, value, EXPIRE_TIME_IN_MINUTES, TimeUnit.MINUTES);
			logger.debug("Put query result to redis");
		}catch(Throwable t){
			logger.error("Redis put failed",t);
		}
	}

	/**
	 * Get cached query result from redis 
	 */
	 @Override
	 public Object getObject(Object key){
		try{
			RedisTemplate redisTemplate=getRedisTemplate();
			ValueOperations opsForValue=redisTemplate.opsForValue();
			opsForValue.set(key, value, EXPIRE_TIME_IN_MINUTES, TimeUnit.MINUTES);
			logger.debug("Get cache query result from redis");
			return opsForValue.get(key);
		}catch(Throwable t){
			logger.error("Redis get failed, fail over to db");
			return null;
		}
	}

	/**
	 * Get cached query result from redis 
	 */
	 @Override
	 public Object getObject(Object key){
		try{
			RedisTemplate redisTemplate=getRedisTemplate();
			ValueOperations opsForValue=redisTemplate.opsForValue();
			opsForValue.set(key, value, EXPIRE_TIME_IN_MINUTES, TimeUnit.MINUTES);
			logger.debug("Get cache query result from redis");
			return opsForValue.get(key);
		}catch(Throwable t){
			logger.error("Redis get failed, fail over to db");
			return null;
		}
	}

	/**
	 * Remove cached query result from redis 
	 */
	 @Override
	 @SuppressWarnings("unchecked")
	 public Object removeObject(Object key){
		try{
			RedisTemplate redisTemplate=getRedisTemplate();
			redisTemplate.delete(key);
			logger.debug("Remove cached query result from redis");
		}catch(Throwable t){
			logger.error("Redis remove failed");
		}
			return null;
	}

	/**
	 * Clear this cache instance
	 */
	 @Override
	 public void clear(){
	 	RedisTemplate redisTemplate=getRedisTemplate();
	 	redisTemplate.execute((RedisCallback)->{
	 		connection.flushDb();
	 		return null;
	 	});
	 	logger.debug("Clear all the cached query result from redis");
	 }

	@Override
	public int getSize(){
		return 0;
	}
	
	@Override
	public ReadWriteLock getReadWriteLock(){
		return readWriteLock;
	}

	private RedisTemplate getRedisTemplate(){
		if(redisTemplate==null){
			redisTemplate=ApplicationContextHolder.getBean("redisTemplate");
		}
		return redisTemplate;
	}
}

Mapper接口类中标注注解

• 在Mapper接口类上标注注解,声明使用二级缓存

@CacheNamespace(implementation=RedisCache.class)