通用化本地缓存设计及其实现框架

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简介

在实际业务开发过程中，有许多需要使用本地缓存的场景，如热点数据缓存、不变数据缓存等。
在这里实现一个通用化的本地缓存框架(类型)，起到数据缓存、缓存定时清理等作用。

设计

失效缓存清理

程序流程图:

说明:

  • 缓存类内部实现缓存数据模型，包含缓存数据、缓存时刻。 
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private class CacheModel {
    private VALUE object;
    private Long createTime;

    CacheModel(VALUE object) {
        this.createTime = System.currentTimeMillis();
        this.object = object;
    }

    VALUE getObject() {
        return object;
    }

    Long getCreateTime() {
        return createTime;
    }
}
  • 遍历缓存数据对象，使用当前时间与该对象缓存时刻进行对比，若超过设置的缓存失效时间，则清理该对象。

数据按需加载

程序流程图:

说明:

  • 从缓存获取数据，首先判断缓存数据是否存在，若存在，直接返回缓存数据。
  • 缓存数据不存在，则调用缓存对象初始化时候配置的数据获取对象，获取对应数据。 
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public interface CacheAcquireOperation<KEY, VALUE> {
    VALUE acquire(KEY key);
}

核心代码片段

缓存清理

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private void initCacheCleanTask(String name) {
    new Thread(() -> {
        while (!shutdown.get()) {
            sleep(10_000);
            checkCleanCache();
        }
    }, name).start();
}

private void checkCleanCache() {
    try {
        lock.get(6000);
        List<KEY> invalidKeys = new ArrayList<>();
        for (Map.Entry<KEY, CacheModel> entry : cacheMap.entrySet()) {
            KEY key = entry.getKey();
            CacheModel cacheModel = entry.getValue();
            if (System.currentTimeMillis() - cacheModel.getCreateTime() >= cacheTimeMillis) {
                invalidKeys.add(key);
            }
        }
        sleep(100);
        invalidKeys.forEach(cacheMap::remove);
    } catch (Exception e) {
        logger.warn(e.getMessage(), e);
    } finally {
        lock.release();
    }
}

缓存获取

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public VALUE get(KEY key) {
    if (cacheMap.containsKey(key)) {
        return cacheMap.get(key).getObject();
    }
    if (cacheAcquireOperation != null) {
        VALUE value = null;
        try {
            value = cacheAcquireOperation.acquire(key);
        } catch (Exception e) {
            logger.warn(e.getMessage(), e);
        }
        if (value != null) {
            put(key, value);
            return value;
        }
    }
    return null;
}

用法示例

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public static void main(String[] args) throws Exception {
    LocalCache<String, String> localCache = new LocalCache<String, String>("test-cache")
            .cacheTimeSeconds(20)
            .cacheAcquireOperation(key -> {
                String value = key + "-" + System.currentTimeMillis();
                System.out.println(String.format("Cache acquire operation, key: %s, value: %s", key, value));
                return value;
            });

    for (int i = 0; i < 10; i++) {
        System.out.println(localCache.get(i + "-name"));
    }
    TimeUnit.MILLISECONDS.sleep(10_000);
    System.out.println("----------------------");
    for (int i = 0; i < 10; i++) {
        System.out.println(localCache.get(i + "-name"));
    }
    TimeUnit.MILLISECONDS.sleep(15_000);
    System.out.println("----------------------");
    for (int i = 0; i < 10; i++) {
        System.out.println(localCache.get(i + "-name"));
    }
    TimeUnit.MILLISECONDS.sleep(10_000);
    localCache.close();
}

输出结果

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Cache acquire operation, key: 0-name, value: 0-name-1569833192414
0-name-1569833192414
Cache acquire operation, key: 1-name, value: 1-name-1569833192436
1-name-1569833192436
Cache acquire operation, key: 2-name, value: 2-name-1569833192437
2-name-1569833192437
Cache acquire operation, key: 3-name, value: 3-name-1569833192437
3-name-1569833192437
Cache acquire operation, key: 4-name, value: 4-name-1569833192438
4-name-1569833192438
Cache acquire operation, key: 5-name, value: 5-name-1569833192438
5-name-1569833192438
Cache acquire operation, key: 6-name, value: 6-name-1569833192438
6-name-1569833192438
Cache acquire operation, key: 7-name, value: 7-name-1569833192439
7-name-1569833192439
Cache acquire operation, key: 8-name, value: 8-name-1569833192439
8-name-1569833192439
Cache acquire operation, key: 9-name, value: 9-name-1569833192439
9-name-1569833192439
----------------------
0-name-1569833192414
1-name-1569833192436
2-name-1569833192437
3-name-1569833192437
4-name-1569833192438
5-name-1569833192438
6-name-1569833192438
7-name-1569833192439
8-name-1569833192439
9-name-1569833192439
----------------------
Cache acquire operation, key: 0-name, value: 0-name-1569833217448
0-name-1569833217448
Cache acquire operation, key: 1-name, value: 1-name-1569833217449
1-name-1569833217449
Cache acquire operation, key: 2-name, value: 2-name-1569833217449
2-name-1569833217449
Cache acquire operation, key: 3-name, value: 3-name-1569833217450
3-name-1569833217450
Cache acquire operation, key: 4-name, value: 4-name-1569833217450
4-name-1569833217450
Cache acquire operation, key: 5-name, value: 5-name-1569833217450
5-name-1569833217450
Cache acquire operation, key: 6-name, value: 6-name-1569833217450
6-name-1569833217450
Cache acquire operation, key: 7-name, value: 7-name-1569833217450
7-name-1569833217450
Cache acquire operation, key: 8-name, value: 8-name-1569833217450
8-name-1569833217450
Cache acquire operation, key: 9-name, value: 9-name-1569833217451
9-name-1569833217451

代码仓库

https://github.com/johnsonmoon/commons/blob/master/src/main/java/com/github/johnsonmoon/commons/LocalCache.java