java類比資料庫緩衝

標籤：pre   壓力   code   map   try   private   寫鎖   類比   nal   

實現緩衝一些資料到本地，避免重複查詢資料庫，對資料庫造成壓力，代碼如下：

package threadLock;import java.util.HashMap;import java.util.Map;import java.util.concurrent.locks.ReadWriteLock;import java.util.concurrent.locks.ReentrantReadWriteLock;public class CatheDemo {    private Map<String, Object> map = new HashMap<String, Object>();        private ReadWriteLock rwl = new ReentrantReadWriteLock(); //定義讀寫鎖        public Object getData(String key){        rwl.readLock().lock();        Object value = null;        try {            value = map.get(key);            if (value ==  null) {                rwl.readLock().unlock();                rwl.writeLock().lock();                try {                    if(value == null)                        value = "dqwdwqd"; //從資料庫中尋找資料                } catch (Exception e) {                    e.printStackTrace();                }finally{                    rwl.writeLock().unlock();                    rwl.readLock().lock();                }                                            }        } catch (Exception e) {            e.printStackTrace();        }finally{            rwl.readLock().unlock();        }        return value;    }}

 

java類比資料庫緩衝