guava LoadingCache 的用法

這段代碼主要功能是實現使用guava的LoadingCache記錄一個ip在一段時間類反覆登錄失敗的次數，如果超過10次則在規定時間(expiration=1800)內禁止登錄(Blocked);使用方式比較簡單，沒事學習用的。

引入的pom文件：

<dependency>
    <groupId>com.google.guava</groupId>
    <artifactId>guava</artifactId>
    <version>22.0</version>
</dependency>

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Java實現代碼:
package com.merce.woven.service;

import com.google.common.cache.CacheBuilder;
import com.google.common.cache.CacheLoader;
import com.google.common.cache.LoadingCache;
import org.springframework.stereotype.Service;

import javax.annotation.PostConstruct;
import java.util.concurrent.ExecutionException;
import java.util.concurrent.TimeUnit;

@Service
public class LoginAttemptService {

   //緩存有效期1800秒
    private int expiration = 1800;

    private final int MAX_ATTEMPT = 10;
    private LoadingCache<String, Integer> attemptsCache;

   //服務啓動的時候初始化value值爲0;這樣如果給的的key不存在，則能取到初始化值0
    @PostConstruct
    private void init(){
        attemptsCache = CacheBuilder.newBuilder().
                expireAfterWrite(expiration, TimeUnit.SECONDS).build(new CacheLoader<String, Integer>() {
            public Integer load(String key) {
                return 0;
            }
        });
    }

    //刪除對應key的內容信息
    public void loginSucceeded(String key) {
        attemptsCache.invalidate(key);
    }

   //每個key loginFailed一次，則對應value+1
    public void loginFailed(String key) {
        int attempts = 0;
        try {
            attempts = attemptsCache.get(key);
        } catch (ExecutionException e) {
            attempts = 0;
        }
        attempts++;
        attemptsCache.put(key, attempts);
    }

    //如果給的key的value值大於了MAX_ATTEMPT 則表示blocked
    public boolean isBlocked(String key) {
        try {
            return attemptsCache.get(key) >= MAX_ATTEMPT;
        } catch (ExecutionException e) {
            return false;
        }
    }
}