基于Java实现Redis多级缓存方法

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<dependency>

     <groupId>com.github.ben-manes.caffeine</groupId>

     <artifactId>caffeine</artifactId>

     <version>3.0.5</version>

 </dependency>

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package com.erick.cache;

import com.github.benmanes.caffeine.cache.Cache;

import com.github.benmanes.caffeine.cache.Caffeine;

import java.time.Duration;

public final class CacheUtil {

    private static int expireSeconds = 2;

    public static Cache<String, String> cacheWithExpireSeconds;

    private static int maxPairs = 1;

    public static Cache<String, String> cacheWithMaxPairs;

    static {

        /*过期策略，写完60s后过期*/

        cacheWithExpireSeconds = Caffeine.newBuilder()

                .expireAfterWrite(Duration.ofSeconds(expireSeconds))

                .build();

        /*过期策略，达到最大值后删除

         * 1. 并不会立即删除，等一会儿才会删除

         * 2. 会将之前存储的数据删除掉*/

        cacheWithMaxPairs = Caffeine.newBuilder()

                .maximumSize(maxPairs)

                .build();

    }

    /*从缓存中获取数据

     * 1. 如果缓存中有，则直接从缓存中返回

     * 2. 如果缓存中没有，则去数据查询并返回结果*/

    public static String getKeyWithExpire(String key) {

        return cacheWithExpireSeconds.get(key, value -> {

            return getResultFromDB();

        });

    }

    public static String getKeyWithMaxPair(String key) {

        return cacheWithMaxPairs.get(key, value -> {

            return getResultFromDB();

        });

    }

    private static String getResultFromDB() {

        System.out.println("数据库查询");

        return "db result";

    }

}

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package com.erick.cache;

import java.util.concurrent.TimeUnit;

public class Test {

    @org.junit.Test

    public void test01() throws InterruptedException {

        CacheUtil.cacheWithExpireSeconds.put("name", "erick");

        System.out.println(CacheUtil.getKeyWithExpire("name"));

        TimeUnit.SECONDS.sleep(3);

        System.out.println(CacheUtil.getKeyWithExpire("name"));

    }

    @org.junit.Test

    public void test02() throws InterruptedException {

        CacheUtil.cacheWithMaxPairs.put("name", "erick");

        CacheUtil.cacheWithMaxPairs.put("age", "12");

        System.out.println(CacheUtil.getKeyWithMaxPair("name"));

        System.out.println(CacheUtil.getKeyWithMaxPair("age"));

        TimeUnit.SECONDS.sleep(2);

        System.out.println(CacheUtil.getKeyWithMaxPair("name")); // 查询不到了

        System.out.println(CacheUtil.getKeyWithMaxPair("age"));

    }

}