hibernate 2級快取 + cluster

hibernate 二級快取 + cluster

原文出自：http://mmmmtodd.blogspot.com/2012/03/hibernate-cluster.html

?

result as below

我們相同嗎 ? true  我是一級快取

結果顯示 : from 良格葛 -- 第二次查詢資料時，在快取中找到資料物件，於是直接返回，這與第一次查詢到的資料物件是同一個實例，所以會顯示 true 的結果。

那要怎麼將快取清掉呢?
可以透過evict()將某個物件從快取中移去，或使用clear()清除快取中的所有物件，
例如 :

public String firstCache() {    Users userA = usersService.getById(1L);    // session.clear() || session.evict(userA);    Users userB = usersService.getById(1L);    System.out.println("我們相同嗎 ? " + (userA == userB));        System.out.println("我是一級快取");    return SUCCESS;  }

則答案就會變成 false

我們相同嗎 ? false  我是一級快取

小結：當讀取的資料很大時，每一次 request 進來就去讀取一次，會造成相當的負擔，所以有了二級快取這個東西。
簡單講就是當資料沒有修改時，不管讀幾次，只要有設定二級快取，session 就算關閉了以後，二級快取裡如果有的話，也不會對 DB select。


以下開始介紹二級快取：

首先，先來看一下程式片段：

public String noCache() {    Users uA = usersService.getByAccount("markyeh");    System.out.println("我沒有 快取 : " + uA.getUpdateTime());    return SUCCESS;  }

然後我對點了這個連結兩次 http://localhost:8080/Cache/noCache.do

result as below：

Hibernate:     /* FROM    Users WHERE    account = ? */ select        users0_.id as id0_,        users0_.account as account0_,        users0_.address as address0_,        users0_.area1 as area4_0_,        users0_.area2 as area5_0_,        users0_.create_time as create6_0_,        users0_.email as email0_,        users0_.icon as icon0_,        users0_.mobile as mobile0_,        users0_.name as name0_,        users0_.password as password0_,        users0_.reg_ip as reg12_0_,        users0_.reg_random_code as reg13_0_,        users0_.roc_id as roc14_0_,        users0_.score as score0_,        users0_.state as state0_,        users0_.update_time as update17_0_     from        users users0_     where        users0_.account=?我沒有 快取 : 2012-03-15 10:37:41.395Hibernate:     /* FROM    Users WHERE    account = ? */ select        users0_.id as id0_,        users0_.account as account0_,        users0_.address as address0_,        users0_.area1 as area4_0_,        users0_.area2 as area5_0_,        users0_.create_time as create6_0_,        users0_.email as email0_,        users0_.icon as icon0_,        users0_.mobile as mobile0_,        users0_.name as name0_,        users0_.password as password0_,        users0_.reg_ip as reg12_0_,        users0_.reg_random_code as reg13_0_,        users0_.roc_id as roc14_0_,        users0_.score as score0_,        users0_.state as state0_,        users0_.update_time as update17_0_     from        users users0_     where        users0_.account=?我沒有 快取 : 2012-03-15 10:37:41.395

執行結果：hibernate 對 db 進行了兩次的 select，但明明相同的東西，怎麼做才能只對 db select 一次就好呢？


這裡就開始說明如何設定 hibernate 的二級快取：
我的環境如下
struts2 + hibernate + spring + ehcache(第三方實作 cache　的套件)


1. 在 spring 設定檔中，在 hibernate 注入的 bean 裡，增加二級快取的設定

<bean id="sessionFactory"    ref="ihergoSqlDataSource" />    <property name="hibernateProperties">      <props>        <!--         <prop key="hibernate.dialect">org.hibernate.dialect.MySQLInnoDBDialect</prop>        -->        <prop key="hibernate.dialect">org.hibernate.dialect.PostgreSQLDialect</prop>        <prop key="hibernate.connection.characterEncoding">utf-8</prop>        <prop key="hibernate.show_sql">true</prop>        <prop key="hibernate.format_sql">true</prop>        <prop key="hibernate.use_sql_comments">true</prop>        <prop key="hibernate.cache.use_second_level_cache">true</prop> <!-- 要不要使用二級快取 -->        <prop key="hibernate.cache.provider_class">org.hibernate.cache.EhCacheProvider</prop> <!-- 指定為 EHCache -->        <prop key="hibernate.cache.region.factory_class">net.sf.ehcache.hibernate.SingletonEhCacheRegionFactory</prop>         <prop key="hibernate.cache.use_query_cache">true</prop> <!-- query 也要快取-->        <prop key="hibernate.hbm2ddl.auto">update</prop>      </props>    </property>    <property name="packagesToScan">      <list>        <value>mt.buyer.db.entity</value>      </list>    </property>  </bean>

2. 設定 entity (以 annotation 為例)

@Entity@Cache(usage = CacheConcurrencyStrategy.READ_WRITE) // <---這裡, 只定為 read_write@Table(name = "users")public class Users implements Serializable {  @Id  @GeneratedValue(strategy = GenerationType.AUTO)  private long id;  /**   * 帳號   */  @Column(name = "account", length = 20, nullable = false)  private String account;  ...}

3. 編寫 dao

// 快取  public Users getByAccountUserCache(final String account) {    final String hql = "FROM Users WHERE account = :account ";        List memberList = getHibernateTemplate().executeFind(        new HibernateCallback>() {          public List doInHibernate(Session hbmSs)              throws HibernateException, SQLException {            // TODO Auto-generated method stub            Query query = hbmSs.createQuery(hql);            query.setString("account", account);            query.setCacheable(true); // <---- 這裡            return query.list();          }        });    if (memberList != null && memberList.size() > 0) {      return (Users) memberList.get(0);    }    return null;  }  // 沒有快取  public Users getByAccount(String account) {    final String hql = "FROM Users WHERE account = ?";    List memberList = getHibernateTemplate().find(hql, account);    if (memberList != null && memberList.size() > 0) {      return (Users) memberList.get(0);    }    return null;  }

4. 增加設定檔 ehcache.xml 並放在 src 下(預設讀取入徑, 也可用 spring 注入)

<?xml version="1.0" encoding="UTF-8"?><ehcache><diskStore path="java.io.tmpdir" /><defaultCache maxElementsInMemory="10000" eternal="false"overflowToDisk="true" timeToIdleSeconds="300" timeToLiveSeconds="180"diskPersistent="false" diskExpiryThreadIntervalSeconds="120" /><!-- Hibernate --><cache name="org.hibernate.cache.StandardQueryCache"maxElementsInMemory="5" eternal="false" timeToLiveSeconds="120"overflowToDisk="true"></cache><cache name="org.hibernate.cache.UpdateTimestampsCache"maxElementsInMemory="5000" eternal="true" overflowToDisk="true"></cache></ehcache>

5. 測試程式 (action)

public String cache() {    Users uA = usersService.getByAccountUserCache("markyeh");    Users uB = usersService.getByAccountUserCache("markyeh");    System.out.println("快取 : " + uA.getUpdateTime());    System.out.println("快取 : " + uB.getUpdateTime());    return SUCCESS;  }

6. 執行連結 : http://localhost:8080/Cache/cache.do

Hibernate:     /* FROM    Users WHERE    account = :account  */ select        users0_.id as id0_,        users0_.account as account0_,        users0_.address as address0_,        users0_.area1 as area4_0_,        users0_.area2 as area5_0_,        users0_.create_time as create6_0_,        users0_.email as email0_,        users0_.icon as icon0_,        users0_.mobile as mobile0_,        users0_.name as name0_,        users0_.password as password0_,        users0_.reg_ip as reg12_0_,        users0_.reg_random_code as reg13_0_,        users0_.roc_id as roc14_0_,        users0_.score as score0_,        users0_.state as state0_,        users0_.update_time as update17_0_     from        users users0_     where        users0_.account=?快取 : 2012-03-15 10:37:41.395快取 : 2012-03-15 10:37:41.395

7. 可以發現, 第二次的查詢就已經沒有再進 db search 了, 如果再執行相同連結一次(也就是再發一個 request 到後台)

快取 : 2012-03-15 10:37:41.395快取 : 2012-03-15 10:37:41.395

可以看到，都是從二級快取的地方取得資料，這時，大家會問，那修改時怎麼判斷要不要取得新資料 8. 我們加入下面的程式碼：

public String update() {    // Users u = usersService.getByAccountUserCache("markyeh");    Users u = usersService.getByAccount("markyeh");    u.setArea1(3);    u.setUpdateTime(new Date());    usersService.update(u);    System.out.println("我修改了 : " + u.getUpdateTime());        return SUCCESS;  }

9. 分別依順序執行 3 個連結 a) http://localhost:8080/Cache/cache.do b) http://localhost:8080/Cache/update.do c) http://localhost:8080/Cache/cache.do

// a) selectHibernate:     /* FROM    Users WHERE    account = :account  */ select        users0_.id as id0_,        users0_.account as account0_,        users0_.address as address0_,        users0_.area1 as area4_0_,        users0_.area2 as area5_0_,        users0_.create_time as create6_0_,        users0_.email as email0_,        users0_.icon as icon0_,        users0_.mobile as mobile0_,        users0_.name as name0_,        users0_.password as password0_,        users0_.reg_ip as reg12_0_,        users0_.reg_random_code as reg13_0_,        users0_.roc_id as roc14_0_,        users0_.score as score0_,        users0_.state as state0_,        users0_.update_time as update17_0_     from        users users0_     where        users0_.account=?快取 : 2012-03-15 16:39:16.944快取 : 2012-03-15 16:39:16.944第一次執行, 結果一樣, 不會撈兩次// b) updateHibernate:     /* FROM    Users WHERE    account = ? */ select        users0_.id as id0_,        users0_.account as account0_,        users0_.address as address0_,        users0_.area1 as area4_0_,        users0_.area2 as area5_0_,        users0_.create_time as create6_0_,        users0_.email as email0_,        users0_.icon as icon0_,        users0_.mobile as mobile0_,        users0_.name as name0_,        users0_.password as password0_,        users0_.reg_ip as reg12_0_,        users0_.reg_random_code as reg13_0_,        users0_.roc_id as roc14_0_,        users0_.score as score0_,        users0_.state as state0_,        users0_.update_time as update17_0_     from        users users0_     where        users0_.account=?Hibernate:     /* update        mt.buyer.db.entity.Users */ update            users         set            account=?,            address=?,            area1=?,            area2=?,            create_time=?,            email=?,            icon=?,            mobile=?,            name=?,            password=?,            reg_ip=?,            reg_random_code=?,            roc_id=?,            score=?,            state=?,            update_time=?         where            id=?我修改了 : Thu Mar 15 16:40:19 CST 2012// c) selectHibernate:     /* FROM    Users WHERE    account = :account  */ select        users0_.id as id0_,        users0_.account as account0_,        users0_.address as address0_,        users0_.area1 as area4_0_,        users0_.area2 as area5_0_,        users0_.create_time as create6_0_,        users0_.email as email0_,        users0_.icon as icon0_,        users0_.mobile as mobile0_,        users0_.name as name0_,        users0_.password as password0_,        users0_.reg_ip as reg12_0_,        users0_.reg_random_code as reg13_0_,        users0_.roc_id as roc14_0_,        users0_.score as score0_,        users0_.state as state0_,        users0_.update_time as update17_0_     from        users users0_     where        users0_.account=?快取 : 2012-03-15 16:40:19.524快取 : 2012-03-15 16:40:19.524

可以發現，ehcache 會自動判斷 cache 裡的東西跟 db 的記錄是不是不一樣了，如果不一樣會再 select 一次放入二級快取裡


小結: ehcache.xml 可以設定的方式很多，這裡只是 demo，而我也還在學習，官方表示還可以做到 tx　的管理，所以還是去看一下文件比較好。

參考文件:

http://www.ehcache.org/documentation/user-guide/hibernate

http://renren.it/a/JAVAbiancheng/Spring/20101022/55282.html

http://caterpillar.onlyfun.net/Gossip/HibernateGossip/SecondLevelCache.html





進階，因公司架構 tomcat 為 cluster ，那...二級快取有辦法共用嗎? 答案是可以的


以下介紹 cluster　環境下怎麼共用二級快取的資料：

參考了官方文件後，必須加入第三方的套件 terracotta 先來看看官方的說明:

http://terracotta.org/documentation/enterprise-ehcache/get-started

其這套件就是一個 server ，經由這個 server 幫你控管各 session

而我測試的流程大概如下

1. 先裝 2 個tomcat，分別設定 port 為 8080, 8081

2. 加入相關 jar 檔

3. 修改 ehcache.xml

4. depoly 程式

5. 將 terracotta server run 起來

6. 測試



就從第二點開始：

2. ehcache　官網有寫，要做到For Terracotta clustering, download a full Ehcache distribution. 所以先下載好檔案，並解壓縮，內容會長這樣
將相關的 lib 加入 ap 裡: ehcache-terracotta-2.5.1.jar terracotta-toolkit-1.4-runtime-4.1.0.jar ... 3.

<?xml version="1.0" encoding="UTF-8"?><ehcache xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"xsi:noNamespaceSchemaLocation="ehcache.xsd" updateCheck="true"monitoring="autodetect"><terracottaConfig url="localhost:9510" /> <!-- 連接到 terracotta server 的 ip 與 port --><defaultCache maxElementsInMemory="10000" eternal="false"overflowToDisk="false" timeToIdleSeconds="300" timeToLiveSeconds="180"diskPersistent="false" diskExpiryThreadIntervalSeconds="120" /> <!-- diskPersistent 必須設成 false --><!-- Hibernate --><cache name="org.hibernate.cache.StandardQueryCache"maxElementsInMemory="5" eternal="false" timeToLiveSeconds="120"overflowToDisk="false"> <!-- overflowToDisk 必須設成 false --><terracotta /></cache><cache name="org.hibernate.cache.UpdateTimestampsCache"maxElementsInMemory="5000" eternal="true" overflowToDisk="false"> <!-- overflowToDisk 必須設成 false --><terracotta /></cache></ehcache>

5. 在剛那個資料夾裡, 找到 \ehcache-2.5.1\terracotta\bin\start-tc-server.bat 並執行, 將 server run 起來
6. 測試: 分別執行 a) http://localhost:8080/Cache/cache.do b) http://localhost:8081/Cache/cache.do 成功...這裡就不貼圖了 提供程式下載的連結 https://www.asuswebstorage.com/navigate/share/GYYVXWYN7Y
...
補充 :

分散式 cache 參考連結
http://www.informit.com/guides/content.aspx?g=java&seqNum=630
http://bbs.51osos.com/thread-4570-1-1.html
http://terracotta.org/documentation/enterprise-ehcache/configuration-guide

然後許多東西都沒有講, 如: terracotta 也可以加入 xml 設定檔, 設定 port, 而且 terracotta 本身也可以做 cluster
反正看一下官網就對了

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