Java本地缓存解决方案---使用Google的CacheBuilder

一、背景

当业务实现上需要用到本地缓存，来解决一些数据量相对较小但是频繁访问数据的场景，可以采用Google的CacheBuilder解决方案。

二、代码实现

1. 首先在maven中引入下面的包

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

2. 代码测试案例

import com.google.common.cache.CacheBuilder;
import com.google.common.cache.CacheLoader;
import com.google.common.cache.LoadingCache;

import java.util.concurrent.TimeUnit;

public class LocalCacheTest {
    // 测试类
    public static void main(String[] args) throws Exception {
        CacheService us = new CacheService();
        for (int i = 0; i < 6; i++) {
            System.out.println(us.getName("1001"));
            TimeUnit.SECONDS.sleep(1);
        }
    }

    // 实现类
    public static class CacheService {
        private final LoadingCache<String, String> cache;

        public CacheService() {
            /**
             * 创建本地缓存，当本地缓存不命中时，调用load方法，返回结果，再缓存结果, 3秒自动过期
             */
            cache = CacheBuilder.newBuilder().expireAfterWrite(3, TimeUnit.SECONDS)
                    .build(new CacheLoader<String, String>() {
                public String load(String id) throws Exception {
                    System.out.println("load()method invoke, 执行查询数据库, 等其他复杂的逻辑");
                    TimeUnit.MILLISECONDS.sleep(100);
                    return "User:" + id;
                }
            });
        }

        public String getName(String id) throws Exception {
            long start = System.currentTimeMillis();
            String result = cache.get(id);
            System.out.println("查询 "+id +" 耗时："+ (System.currentTimeMillis()-start) + " ms");
            return result;
        }
    }
}

3. 控制台输出

从控制台输出，可以看出，当本地缓存不命中时，调用load方法，通过数据库查询结果，返回结果，再缓存结果, 耗时较长。如果命中查询速度非常快，可达0ms，3秒自动过期后，重复上述操作。

load()method invoke, 执行查询数据库, 等其他复杂的逻辑
查询 1001 耗时：124 ms
User:1001
查询 1001 耗时：0 ms
User:1001
查询 1001 耗时：0 ms
User:1001
load()method invoke, 执行查询数据库, 等其他复杂的逻辑
查询 1001 耗时：108 ms
User:1001
查询 1001 耗时：0 ms
User:1001
查询 1001 耗时：0 ms
User:1001

Process finished with exit code 0

4. 附工具类

import com.google.common.cache.Cache;
import com.google.common.cache.CacheBuilder;

import java.util.concurrent.TimeUnit;

public final class JvmCacheUtil {

    public static final String JVM_CACHE_SPECIFY_GEO = "cache_specify_geo";

    public static final String JVM_CACHE_BUILD_SQL = "cache_build_sql";

    public static final int DEFAULT_CAPACITY = 50;

    public static final long DEFAULT_CACHE_EXP = 12L;

    public static final long DEFAULT_CACHE_ENTRY_EXP = 900L;
    
    /**
    * 12小时后过期
    */
    private static Cache<String,
        Cache> cacheManager = CacheBuilder.newBuilder()
            .maximumSize(DEFAULT_CAPACITY)
            .expireAfterAccess(12L, TimeUnit.HOURS)
            .expireAfterWrite(12L, TimeUnit.HOURS)
            .initialCapacity(10)
            .build();

    public static Cache getCache(String cacheName) {
        return getCache(cacheName, DEFAULT_CAPACITY, DEFAULT_CACHE_ENTRY_EXP, TimeUnit.SECONDS);
    }

    public static Cache getCache(String cacheName, long expire, TimeUnit timeUnit) {
        return getCache(cacheName, DEFAULT_CAPACITY, expire, timeUnit);
    }

    public static Cache getCache(String cacheName, int capacity, long expire, TimeUnit timeUnit) {
        Cache cache = cacheManager.getIfPresent(cacheName);
        if (null == cache) {
            cache = CacheBuilder.newBuilder()
                .maximumSize(DEFAULT_CAPACITY)
                .expireAfterAccess(expire, timeUnit)
                .expireAfterWrite(expire, timeUnit)
                .initialCapacity(capacity)
                .build();
            cacheManager.put(cacheName, cache);
        }
        return cache;
    }

    public static Object get(String cacheName, String key) {
        Cache cache = getCache(cacheName);
        return cache.getIfPresent(key);
    }

    public static void put(String cacheName, String key, Object val) {
        Cache cache = getCache(cacheName);
        cache.put(key, val);
    }

    public static void put(String cacheName, String key, Object val, long expire, TimeUnit timeUnit) {
        Cache cache = getCache(cacheName, expire, timeUnit);
        cache.put(key, val);
    }