分布式数据存储之 Redis(二) —— spring中的缓存抽象

一、spring boot 中的 StringRedisTemplate

1.StringRedisTemplate Demo

第一步：引入redis依赖

最重要的依赖

compile('org.springframework.boot:spring-boot-starter-data-redis')

此依赖为springCloud 父项目依赖（但已添加 redis 依赖）

buildscript {
    ext {
        springBootVersion = '2.1.2.RELEASE'
    }
    repositories {
        mavenLocal() //maven本地仓库
        maven {
            url = "http://maven.aliyun.com/nexus/content/groups/public"
        }
        mavenCentral()//maven中心仓库
    }
    dependencies {
        classpath("org.springframework.boot:spring-boot-gradle-plugin:${springBootVersion}")
    }
}

subprojects {
    apply plugin: 'java'
    apply plugin: 'eclipse'
    apply plugin: 'org.springframework.boot'
    apply plugin: 'io.spring.dependency-management'

    group = 'com.lichuang.kukri'
    version = '1.0.0'
    sourceCompatibility = 1.8

    repositories {
        mavenLocal() //maven本地仓库
        maven {
            url = "http://maven.aliyun.com/nexus/content/groups/public"
        }
        mavenCentral()//maven中心仓库
    }


    ext {
        springCloudVersion = 'Greenwich.RELEASE'
    }

    dependencies {
        compile('org.springframework.boot:spring-boot-starter-actuator')
        compile('org.springframework.boot:spring-boot-starter-web')
        compile('org.springframework.cloud:spring-cloud-starter')
        testCompile('org.springframework.boot:spring-boot-starter-test')
        
        //redis 依赖
        compile('org.springframework.boot:spring-boot-starter-data-redis')
    }

    dependencyManagement {
        imports {
            mavenBom "org.springframework.cloud:spring-cloud-dependencies:${springCloudVersion}"
        }
    }

}

第二步：创建 StringRedisTemplate 的 Bean

由 StringRedisTemplate 的构造函数可知需要 RedisConnectionFactory 的 Bean，又由 RedisConnectionFactory 可知需要 RedisStandaloneConfiguration 的 Bean， RedisStandaloneConfiguration 的构造函数中需要有 hostname 以及 port

@Configuration
@ComponentScan
public class AppConfig {

    //xxxTemplate -> 设计模式之一 模板方法设计模式

    @Bean
    public RedisStandaloneConfiguration redisStandaloneConfiguration(){
        RedisStandaloneConfiguration redisStandaloneConfiguration = new RedisStandaloneConfiguration("hostname",6379);
        return redisStandaloneConfiguration;
    }


    @Bean
    public RedisConnectionFactory redisConnectionFactory(){
        LettuceConnectionFactory connectionFactory = new LettuceConnectionFactory(redisStandaloneConfiguration());

        return connectionFactory;
    }

    @Bean
    public StringRedisTemplate stringRedisTemplate(){
        StringRedisTemplate redisTemplate = new StringRedisTemplate(redisConnectionFactory());

        return redisTemplate;
    }

}

第三步：获取 StringRedisTemplate 进行运用

添加数据至Redis： redisTemplate.opsForValue().set("name","test");
从Redis 获取数据： redisTemplate.opsForValue().get("name")

public class RedisServer {
    public static void main(String[] args) {
        AnnotationConfigApplicationContext applicationContext = new AnnotationConfigApplicationContext(AppConfig.class);

        StringRedisTemplate redisTemplate = applicationContext.getBean(StringRedisTemplate.class);


        redisTemplate.opsForValue().set("name","test");

        //System.out.println(redisTemplate.opsForValue().get("name"));

       /* redisTemplate.watch("name");
        redisTemplate.multi();
        redisTemplate.exec();*/
    }
}

二、 Cache Abstraction

1.核心接口

CachManager

Spring's central cache manager SPI.

方法

Cache getCache(String name);

Collection getCacheNames();

Cache

Interface that defines common cache operations

常见实现类

ConcurrentMapCache
RedisCache
EhCacheCache

KeyGenerator

SimpleKeyGenerator(默认实现类)

2. 常见注解

@Cacheable

如果缓存中有值，则使用缓存中的值；如果没有则执行业务方法并存入缓存中

属性

condition

判断
unless

非

@CachePut

每次都会执行业务方法，并设置缓存

@CacheEvict

每次都会执行业务方法，并删除缓存

3. Cache Abstraction Demo

第一步：引入依赖

dependencies {
    compile('org.springframework.boot:spring-boot-starter-data-redis')
    compile group: 'org.projectlombok', name: 'lombok', version: '1.18.6'
    compile group: 'com.alibaba', name: 'fastjson', version: '1.2.56'
}

第二步：创建 CacheManager 的 Bean

注：

1. GenericFastJsonRedisSerializer 类使 Value 的储存方式为 Josn

@Configuration
@ComponentScan
@MapperScan("com.lichuang.kukri.springcloudproject.config.dao")
@EnableCaching
public class AppConfig {

    //xxxTemplate -> 设计模式之一 模板方法设计模式

    @Bean
    public RedisStandaloneConfiguration redisStandaloneConfiguration(){
        RedisStandaloneConfiguration redisStandaloneConfiguration = new RedisStandaloneConfiguration("hostname",6379);
        return redisStandaloneConfiguration;
    }

    @Bean
    public CacheManager cacheManager(){
        RedisCacheWriter redisCacheWriter = RedisCacheWriter.nonLockingRedisCacheWriter(redisConnectionFactory());

        RedisCacheConfiguration redisCacheConfiguration = RedisCacheConfiguration.defaultCacheConfig()
                .serializeValuesWith(RedisSerializationContext.SerializationPair.fromSerializer(new GenericFastJsonRedisSerializer()));

        RedisCacheManager redisCacheManager = new RedisCacheManager(redisCacheWriter,redisCacheConfiguration);

        return redisCacheManager;
    }

}

第三步：创建 Service

@Service
public class CacheService {

    @CachePut(cacheNames = "person")
    public Person update(int age){
        Person person = new Person();
        person.setPersonName("admin");
        person.setAge(age);
        return person;
    }


    @Cacheable(cacheNames = "person")
    public Person selectP(int age){
        Person person = new Person();
        person.setPersonName("test");
        person.setAge(age);
        return person;
    }

    @Cacheable(cacheNames = "cache")
    public String selectC(int i){
        System.out.println("select");
        return "admin";
    }
}

Person.java(实体类)

public class Person {

    private String personName;

    private int age;

    public String getPersonName() {
        return personName;
    }

    public void setPersonName(String personName) {
        this.personName = personName;
    }

    public int getAge() {
        return age;
    }

    public void setAge(int age) {
        this.age = age;
    }
}

第四步：运行

public class RedisServer {
    public static void main(String[] args) {
        AnnotationConfigApplicationContext applicationContext = new AnnotationConfigApplicationContext(AppConfig.class);

        PersonDao personDao = applicationContext.getBean(PersonDao.class);
        List<Person> people = personDao.select();
        for (int i = 0; i < people.size(); i++) {
            System.out.println(people.get(i).getPersonName() + "-" + people.get(i).getAge());
        }

        /*CacheService cacheService = applicationContext.getBean(CacheService.class);
        for (int i = 0; i < 2; i++) {
            //System.out.println(cacheService.selectC(i));

            cacheService.update(i);
        }*/
    }
}

第五步：在 Redis 中获取

127.0.0.1:6379> get cache::0
""admin""
127.0.0.1:6379> get person::0
"{"@type":"com.bean.Person","age":1,"name":"test"}"

把曾经失去的全部补回来！ ---一位在“生死边缘”徘徊的JAVA程序猿