Java设计实现一个针对各种类型的缓存_开发_开发者

1. 设计顶层接口

// 定义为一个泛型接口,提供给抽象类使用
public interface CacheManager<T> {
    // 获取所有的缓存item
    List<T> getAll();
    // 根据条件获取某些缓存item
    List<T> get(Predicate<T> predicate);
    // 设置缓存
    boolean set(T t);
    // 设置缓存list
    boolean set(List<T> tList);
}

有接口必定有实现类或者抽象类，实现接口。

那为了更好地控制子类的行为，可以做一个抽象类，控制子类行为。

分析：

抽象类作为缓存管理的话，那么就需要提供安全访问数据
需要考虑线程安全问题。
花絮：不仅要满足上述需求，而且让代码尽量简洁。

2. 设计抽象类 – AbstractCacheManager

属性设计：

需要一个缓存
需要一个线程安全机制方案

行为设计：

自己的行为：

利用线程安全机制控制缓存的读写。
权限：仅自己可访问

后代的行为：

访问一些简单api方法即可实现安全访问缓存
权限：公共访问

设计模式：

包裹思想，将后代行为方法中，包裹一层安全访问的行为。

Java Code：

 // properties design:
protected ConcurrentMap<String, T> cache;

private ReentrantReadwriteLock lock = new ReentrantReadWriteLock();

// subclass to implements these abstract methods.

protected abstract List<T> getAllByCache();

protected abstract void setByCache(T t);

protected abstract void setByCache(List<T> tList);

protected abstract List<T> getByCache(Predicate<T> predicate);

// next content needs to consider safety of multithreads. following methods do implements.
// entry to use
@Override
public final List<T> getAll() {
   return thijavascripts.readLockThenGet(() -> this.getAllByCache());
}

@Override
public final List<T> get(Predicate<T> predicate) {
   return this.readLockThenGet(pre -> getByCache(pre), predicate);
}

@Override
public final boolean set(T t) {
   return this.writeLockThenSet((Consumer<T>) obj -> set(obj), t);
}

@Override
public final boolean set(List<T> tList) {
   return this.writeLockThenSet((Consumer<List<T>>) list -> set(list), tList);
}

// current abstract class Access cache object.
private boolean writeLockThenSet(Consumer consumer, Object object){
    boolean wLock = false;
    try {
        if (!(wLock = lock.writeLock().tryLock(100, TimeUnit.MICROSECONDS))) {
            return false;
        }
        consumer.accept(object);
        return true;
    } catch (Exception e) {
        return false;
    } finally {
        if(wLock) {
            lock.writeLock().unlock();
        }
    }
}

private List<T> readLockThenGet(Supplier<List<T>> supplier){
    boolean rLock = false;
    try{
        if(!(rLock = lock.readLock().tryLock(100, TimeUnit.MICROSECONDS))){
            return null;
        }
        return supplier.get();
    }catch (Exception e){
        return null;
    }finally {
        if(rLock) {
            lock.readLock().unlock();
        }
    }
}

private List<T> readLockThenGet(Function<Predicate<T>, List<T>> function, Predicate<T> predicate){
    boolean rLock = false;
    try{
        if(!(rLock = lock.readLock().tryLock(100, TimeUnit.MICROSECONDS))){
            return null;
        }
        return function.apply(predicate);
    }catch (Exception e){
        return null;
    }finally {
        if(rLock) {
            lock.readLock().unlock();
        }
    }
}

3. 具体子类

3.1 – AlertRuleItemExpCacheManager

@Component("alertRuleItemExpCacheManager")
public class AlertRuleItemExpCacheManager<T extends AlertRuleItemExpCache> extends AbstractCacheManager<AlertRuleItemExpCache> {
   @Resource
   private AlertRuleItemExpDao alertRuleItemExpDao;

   @Override
   protected List<AlertRuleItemExpCache> getAllByCache() {
       if (null == cache) {
           List<AlertRuleItemExp> alertRuleItemSrcList =
                   alertRuleItemExpDao.selectList(Wrappers.<AlertRuleItemExp>lambdaQuery().eq(AlertRuleItemExp::getDeleted, 0));
           cache = alertRuleItemSrcList.stream().map(entity -> entity.toCache())
                   .collect(Collectors.toConcurrentMap(cache -> cache.getId().toString(), cache -> cache));
       }
       return cache.values().stream()
               .sorted(Comparator.comparing(AlertRuleItemExpCache::getId))
               .collect(Collectors.toList());
   }

   @Override
   protected void setByCache(AlertRuleItemExpCache alertRuleItemExpCache) {
       cache.put(alertRuleItemExpCache.getId().toString(), alertRuleItemExpCache);
   }

   @Override
   protected void setByCache(List<AlertRuleItemExpCache> alertRuleItesFGdkLmExpCacheList) {
       alertRuleItemExpCacheList.parallelStream().forEach(alertRuleItemExpCache ->
               cache.put(alertRuleItemExpCache.getId().toString(), alertRuleItemExpCache));
   }

   @Override
   protected List<AlertRuleItemExpCache> getByCache(Predicate<AlertRuleItemExpCache> predicate) {
       return getAllByCache().stream().filter(cache -> predicate.test(cache)).collect(Collectors.toList());
   }
}

3.2 – AlertRuleItemSrcCacheManager

@Component("alertRuleItemSrcCacheManager")
public class AlertRuleItemSrcCacheManager<T extends AlertRuleItemSrcCache> extends AbstractCacheManager<AlertRuleItemSrcCache> {
   @Resource
   private AlertRuleItemSrcDao alertRuleItemSrcDao;

   @Override
   protected List<AlertRuleItemSrcCache> getAllByCache() {
       if (null == cache) {
           List<AlertRuleItemSrc> alertRuleItemSrcList =
                   alertRuleItemSrcsFGdkLDao.selectList(Wrappers.<AlertRuleItemSrc>lambdaQuery().eq(AlertRuleItemSrc::getDeleted, 0));
           cache = alertRuleItemSrcList.stream().map(entity -> entity.toCache())
                   .collect(Collectors.toConcurrentMap(cache -> cache.getId().toString(), cache -> cache));
       }
       return cache.values().stream()
               .sorted(Comparator.comparing(AlertRuleItemSrcCache::getId))
               .collect(Collectors.toList());
   }

   @Override
   protected void setByCache(AlertRuleItemSrcCache alertRuleItemSrcCache) {
       cache.put(alertRuleItemSrcCache.getId().toString(), alertRuleItemSrcCache);
   }

   @Override
   protected void setByCache(List<AlerjstRuleItemSrcCache> alejsrtRuleItemSrcCacheList) {
       alertRuleItemSrcCacheList.parallelStream().forEach(alertRuleItemSrcCache ->
               cache.put(alertRuleItemSrcCache.getId().toString(), alertRuleItemSrcCache));
   }

   @Override
   protected List<AlertRuleItemSrcCache> getByCache(Predicate<AlertRuleItemSrcCache> predicate) {
       return getAllByCache().stream().filter(cache -> predicate.test(cache)).collect(Collectors.toList());
   }
}