com.github.cosycode.ext.io.cache.MapCacheChain Maven / Gradle / Ivy

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扩展模块, 用于存放一些非常用的工具或模块的扩展类, 例如在poi基础上扩展的excel的导入模块, 模拟按键模块
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package com.github.cosycode.ext.io.cache;

import com.github.cosycode.common.lang.BaseRuntimeException;
import lombok.AllArgsConstructor;
import lombok.NonNull;
import lombok.extern.slf4j.Slf4j;

import java.util.Iterator;
import java.util.List;
import java.util.Objects;
import java.util.function.Supplier;

/**
 * Description :  改对象维持一个 ICacheStack 的对象列表,
 * 获取元素的时候从头开始, 从 ICacheStack 的实例对象里面获取数据.
 * 获取到则直接返回, 获取不到则到下一个 ICacheStack 的实例对象里面获取元素, 直到获取到元素为止.
 * 获取到之后, 还会讲元素存储到前面的 ICacheStack 实例中去.
 * 
 * created in  2022/12/8
 * 
 *
 * @author CPF
 * @since 0.2.2
 **/
@Slf4j
@AllArgsConstructor
public class MapCacheChain {

    final List> cacheHandlerList;

    public T getData(String key) {
        Objects.requireNonNull(cacheHandlerList);
        if (cacheHandlerList.isEmpty()) {
            throw new BaseRuntimeException("cacheHandlerList is empty");
        }
        AbstractMapCacheHandler firstHandler = cacheHandlerList.get(0);
        T t = firstHandler.get(key);
        if (t == null || !firstHandler.validate(key, t)) {
            synchronized (cacheHandlerList) {
                t = firstHandler.get(key);
                if (t == null || ! firstHandler.validate(key, t)) {
                    Iterator> iterator = cacheHandlerList.iterator();
                    return getData(key, iterator, null);
                }
            }
        }
        return t;
    }

    public T getData(String key, Supplier supplier) {
        Objects.requireNonNull(cacheHandlerList);
        if (cacheHandlerList.isEmpty()) {
            throw new BaseRuntimeException("cacheHandlerList is empty");
        }
        AbstractMapCacheHandler firstHandler = cacheHandlerList.get(0);
        T t = firstHandler.get(key);
        if (t == null || !firstHandler.validate(key, t)) {
            synchronized (cacheHandlerList) {
                t = firstHandler.get(key);
                if (t == null || ! firstHandler.validate(key, t)) {
                    Iterator> iterator = cacheHandlerList.iterator();
                    return getData(key, iterator, supplier);
                }
            }
        }
        return t;
    }

    /**
     * 该方法不应该返回 null, 在调用该方法之前, 请确保 iterator 中的最后一个 AbstractCacheHandler 对象实例一定可以获取到合法的对象实例.
     *
     * @param iterator 迭代器
     * @return 从 iterator 里面获取到的对象.
     */
    private T getData(String key, @NonNull Iterator> iterator, Supplier supplier) {
        if (! iterator.hasNext()) {
            if (supplier != null) {
                return supplier.get();
            }
            // 假如说最后 一级从 http 上面获取, 那么若该级别的 get 获取不到合法数据, 那么还应该有下一级.
            throw new BaseRuntimeException("The cacheHandlerList is empty. Please make sure that the last AbstractCacheHandler instance object can correctly obtain the element.");
        }
        /* 若是获取到元素则返回, */
        AbstractMapCacheHandler item = iterator.next();
        T pop = item.get(key);
        if (pop != null) {
            boolean validate = item.validate(key, pop);
            if (validate) {
                return pop;
            } else {
                log.debug("{}[{}] clear the invalid element", item.getClass(), item.getTag());
                item.clear(key);
            }
        }
        pop = getData(key, iterator, supplier);
        // 从下一个 AbstractCacheHandler 获取到的元素不应该为 null
        Objects.requireNonNull(pop);
        log.debug("Get the valid elements and cache them in {}[{}]", item.getClass(), item.getTag());
        item.put(key, pop);
        return pop;
    }

}