springboot实现内存缓存

题记：实现缓存大部分可以使用redis实现，简单、便捷，redis在针对应用部署多服务器是很好的，但如果针对单一服务器，内存缓存更好。

1、创建CacheLoader.java

import java.util.Iterator;
import java.util.Map;

/**
 * Created by Tisa on 2018/5/9.
 * 将数据库表记录加载到jvm
 */
public class CacheLoader<V,T> {
    /**
     * 将数据库中的记录加载到jvm缓存，使用Map存储
     *
     * @param from 从数据库load出的记录
     * @param to
     */
    public void loadCache(Map<V, T> from, Map<V, T> to) {
        if (!from.isEmpty()) {
            Iterator<V> iterator = to.keySet().iterator();
            while (iterator.hasNext()) {
                V key = iterator.next();
                if (to.containsKey(key)) {
                    to.remove(key);
                }
            }
            to.putAll(from);
        } else {
            to.clear();
        }
    }
}

2、在springboot启动项目时加载进内存，创建ProvinceAppkeyAndSecretCache.java 

import com.entity.ProvinceAppkeyAndAppsecret;
import com.entity.ProvinceInfo;
import com.mapper.ProvinceAppkeyAndSecretMapper;
import com.mapper.ProvinceInfoMapper;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Component;

import javax.annotation.PostConstruct;
import java.util.*;
import java.util.concurrent.ConcurrentHashMap;

/**
 * @author:yangwj
 */
@Component
public class ProvinceAppkeyAndSecretCache {
    private static final Map<String, ProvinceAppkeyAndAppsecret> provinceAppkeyAndSecretCache = new ConcurrentHashMap<>();
    @Autowired
    private ProvinceAppkeyAndSecretMapper provinceAppkeyAndSecretMapper;

    @PostConstruct
    public void init() {
        Map<String, ProvinceAppkeyAndAppsecret> provinceAppkeyAndSecretMap = loadProvinceInfo();
        CacheLoader<String, ProvinceAppkeyAndAppsecret> loader = new CacheLoader<String, ProvinceAppkeyAndAppsecret>();
        loader.loadCache(provinceAppkeyAndSecretMap, provinceAppkeyAndSecretCache);
    }

    private Map<String, ProvinceAppkeyAndAppsecret> loadProvinceInfo() {
        Map<String, ProvinceAppkeyAndAppsecret> map = new HashMap<>();
        List<ProvinceAppkeyAndAppsecret> list = provinceAppkeyAndSecretMapper.selectAll();
        if (list == null) {
            return Collections.emptyMap();
        }
        Iterator<ProvinceAppkeyAndAppsecret> iterator = list.iterator();
        while (iterator.hasNext()) {
            ProvinceAppkeyAndAppsecret next = iterator.next();
            map.put(next.getAppkey(), next);
        }
        return map;
    }

    public ProvinceAppkeyAndAppsecret get(String appkey) {
        return provinceAppkeyAndSecretCache.get(appkey);
    }
}

3、在controller中调用

@RestController
@RequestMapping("Cache")
public class CacheController extends BaseOrderController {
        private static final Logger LOGGER = LoggerFactory.getLogger(com.controller.CacheController.class);

        @Autowired
        private ProvinceAppkeyAndSecretCache provinceAppkeyAndSecretCache;

        @RequestMapping("/cache")
        public String orderRelationUpdateNotify(HttpServletRequest request) {
            String appKey = request.getParameter("appKey");
            //从内存中获取
            ProvinceAppkeyAndAppsecret provinceAppkeyAndAppsecret =provinceAppkeyAndSecretCache.get(appKey);
        }
}