springboot 整合GuavaCache缓存

Guava Cache是一种本地缓存机制，之所以叫本地缓存，是因为它不会把缓存数据放到外部文件或者其他服务器上，而是存放到了应用内存中。

Guava Cache的优点是：简单、强大、轻量级。

GuavaCache适用场景：

1.某些接口或者键值会被查询多次以上；

2.愿意使用或牺牲一些内存空间来提升访问或者计算速度；

3.缓存内容或者结果值较小，不会超过内存总容量；

GuavaCache中基于注解的声明式缓存操作    

@Cacheable 触发缓存逻辑

Spring 在执行 @Cacheable 标注的方法前先查看缓存中是否有数据，如果有数据，则直接返回缓存数据；若没有数据，执行该方法并将方法返回值放进缓存。

参数： value缓存名、 key缓存键值、 condition满足缓存条件、unless否决缓存条件

@CacheEvict

触发缓存逐出逻辑

方法执行成功后会从缓存中移除相应数据。

参数： value缓存名、 key缓存键值、 condition满足缓存条件、 unless否决缓存条件、 allEntries是否移除所有数据 （设置为true时会移除所有缓存）

@CachePut

和 @Cacheable 类似，但会把方法的返回值放入缓存中, 主要用于数据新增和修改方法。

pom.xml配置文件：

<dependency>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-starter-cache</artifactId>
    <version>1.5.9.RELEASE</version>
</dependency>

<dependency>
    <groupId>com.google.guava</groupId>
    <artifactId>guava</artifactId>
    <version>19.0</version>
</dependency>

GuavaCacheConfig：

/**
 * Copyright (c) 2020, All Rights Reserved.
 *
*/

package com.demo.server.config;

import java.util.concurrent.TimeUnit;

import org.springframework.cache.CacheManager;
import org.springframework.cache.annotation.EnableCaching;
import org.springframework.cache.guava.GuavaCacheManager;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;

import com.google.common.cache.CacheBuilder;

@Configuration
@EnableCaching
public class GuavaCacheConfig {

    @Bean
    public CacheManager cacheManager() {
        GuavaCacheManager cacheManager = new GuavaCacheManager();
        cacheManager.setCacheBuilder(
            CacheBuilder.newBuilder().
            expireAfterWrite(10, TimeUnit.SECONDS). //存活时间10秒
            maximumSize(1000));     //最大线程数
        return cacheManager;
    }

}

CacheController：

/**
 * Copyright (c) 2020, All Rights Reserved.
 *
*/

package com.demo.server.guava;

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RequestMethod;
import org.springframework.web.bind.annotation.RestController;

@RestController
@RequestMapping(value = "/guava")
public class CacheController {

    @Autowired
    private CacheService cacheService;

    /**
     * 查询方法
     */
    @RequestMapping(value = "/get", method = RequestMethod.GET)
    public String getByCache() {
        Long startTime = System.currentTimeMillis();
        long timestamp = this.cacheService.getByCache();
        Long endTime = System.currentTimeMillis();
        System.out.println("耗时: " + (endTime - startTime));
        return timestamp+"";
    }

    /**
     * 保存方法
     */
    @RequestMapping(value = "/save", method = RequestMethod.POST)
    public void save() {
        this.cacheService.save();
    }

    /**
     * 删除方法
     */
    @RequestMapping(value = "delete", method = RequestMethod.DELETE)
    public void delete() {
        this.cacheService.delete();
    }
}

CacheService：

/**
 * Copyright (c) 2020, All Rights Reserved.
 *
*/

package com.demo.server.guava;

import java.sql.Timestamp;

import org.springframework.cache.annotation.CacheEvict;
import org.springframework.cache.annotation.CachePut;
import org.springframework.cache.annotation.Cacheable;
import org.springframework.stereotype.Service;

@Service
public class CacheService {

    @CachePut(value = "guavacache")
    public long save() {
        long timestamp = new Timestamp(System.currentTimeMillis()).getTime();
        System.out.println("进行缓存：" + timestamp);
        return timestamp;
    }

    @CacheEvict(value = "guavacache")
    public void delete() {
        System.out.println("删除缓存");
    }

    @Cacheable(value = "guavacache")
    public long getByCache() {
        try {
            Thread.sleep(3 * 1000);
        } catch (InterruptedException e) {
            e.printStackTrace();
        }
        return new Timestamp(System.currentTimeMillis()).getTime();
    }

}

Application：

package com.demo;

import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.boot.Banner;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;

@SpringBootApplication
public class Application {
    private static final Logger LOG = LoggerFactory.getLogger(Application.class);

    public static void main(String[] args) {
        SpringApplication app = new SpringApplication(Application.class);
        app.setBannerMode(Banner.Mode.OFF);
        app.setWebEnvironment(true);
        app.run(args);
        LOG.info("**************** Startup Success ****************");
    }
}