hashing-based cache

hashing-based cache.

傳統以hashing實作的Cache有很多種類, 最簡單地實作, 就是Java所內建提供的HashMap, TreeMap類別, 或是它們的執行緒安全(Thread-Safed)版本ConcurrentHashMap, ConcurrentSkipListMap. 若想以這些類別來儲存Eva的查詢結果時, 我們需將條件物件包裝成ConditionKey型別來能正確地執行, 例如下面的例子.


package example7;



import java.util.HashMap;

import java.util.Map;



import com.logntw.eva.bean.condition.ConditionObj;

import com.logntw.eva.condition.OP;

import com.logntw.eva.hb.ConditionKey;

import com.logntw.eva.orm.DBConnectionProvider;

import com.logntw.eva.orm.ORMapper;

import com.logntw.eva.orm.ORMappers;

import com.logntw.eva.orm.defo.DefaultTableCreator;

import com.logntw.eva.orm.defo.DefoORMappers;

import com.logntw.eva.orm.defo.conn.HSQLDB_1_8ConnectionProvider;



import example6.EntityS;



public class ConditionKeyExample

{

  public static void main(String[] args) throws Exception

  {

    DBConnectionProvider db = new HSQLDB_1_8ConnectionProvider("dbName");

    ORMappers mappers = DefoORMappers.getInstance(db);

    DefaultTableCreator.create(mappers, EntityS.class);

    ORMapper<EntityS> mapper = mappers.getMapper(EntityS.class);

    Map<ConditionKey, Object> cache = new HashMap<ConditionKey, Object>();

    

    ConditionObj<EntityS> condition = mapper.newCondition();

    condition.If(OP.EQUAL).setId1("10");

    condition.Or();

    condition.If(OP.EQUAL).setId1("20");

    

    ConditionKey key = new ConditionKey(condition);

    cache.put(key, "STR");

    Object obj = cache.get(key); // "STR"      

  }

}