com.github.hugh.support.instance.Instance Maven / Gradle / Ivy

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package com.github.hugh.support.instance;

import com.github.hugh.support.cache.GuavaCache;
import com.github.hugh.util.common.AssertUtils;
import com.google.common.cache.CacheLoader;
import com.google.common.cache.LoadingCache;

import java.util.concurrent.ExecutionException;

/**
 * 实例工具类
 *
 * @author hugh
 * @since 1.2.1
 */
public class Instance { 

    private static volatile Instance instance;

    /**
     * 懒汉式获取单例对象
     *
     * @return Instance 实例
     */
    public static Instance getInstance() {
        if (instance == null) {//懒汉式
            synchronized (Instance.class) {
                if (instance == null) {//二次检查
                    instance = new Instance();
                }
            }
        }
        return instance;
    }

    //实例加载缓存
    private static CacheLoader INSTANCE_CACHE_LOADER = CacheLoader
            .from(key -> {
                try {
                    return Class.forName(key).newInstance();//根据 key(包名)创建实体
                } catch (InstantiationException | IllegalAccessException | ClassNotFoundException e) {
                    e.printStackTrace();
                }
                return null;
            });

    /**
     * Guava 缓存策略
     */
    public static LoadingCache SINGLETON_CACHE = GuavaCache.create(INSTANCE_CACHE_LOADER);

    /**
     * 根据Class 创建实体
     *
     * @param tClass class
     * @param     泛型
     * @return T 实体类型
     */
    @SuppressWarnings("unchecked")
    public  T singleton(Class tClass) {
        AssertUtils.notNull(tClass, "class");
        String fullClassName = tClass.getName();
        try {
            return (T) SINGLETON_CACHE.get(fullClassName);
        } catch (ExecutionException e) {
            e.printStackTrace();
            return null;
        }
    }
}