guavacache mysql_java使用guava cache實作本地緩存

cache = CacheBuilder.newBuilder()

.recordStats()

.maximumSize(5000000)

.expireAfterWrite(1, TimeUnit.MINUTES)

.build(

new CacheLoader() {

@Override

public Integer load(String key) throws Exception {

//僞代碼：

//查詢資料庫并傳回existFlag

//return existFlag;

//資料庫中查詢不到，傳回null

return null;

}

}

);

}

```

#### 手動加載緩存方式

代碼示例：

```java

import com.google.common.cache.Cache;

import com.google.common.cache.CacheBuilder;

import org.slf4j.Logger;

import org.slf4j.LoggerFactory;

import org.springframework.stereotype.Component;

import java.util.concurrent.TimeUnit;

@Component

public class VehicleNumCache {

private static Logger logger = LoggerFactory.getLogger(VehicleNumCache.class);

private final Integer existFlag = new Integer(1);

private Cachecache = CacheBuilder.newBuilder()

.recordStats()

.maximumSize(5000000)

.expireAfterWrite(1, TimeUnit.MINUTES)

.build();

public Integer get(String vehicleNum){

logger.info(cache.stats().toString());

return cache.getIfPresent(vehicleNum);

}

public void put(String vehicleNum){

cache.put(vehicleNum,existFlag);

}

}

```

#### 如何調用

代碼示例：

```java

Integer flag = vehicleNumCache.get(vehicleNum);

//緩存不存在

if(flag == null){

filterVehicleList.add(v);

}

```

調用前記得注入緩存類vehicleNumCache