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marlonyao 's List: Java Cache

Mindmapping, concept mapping and information organisation software

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java cache on 2009-01-09 and saved by 4 people
- Ableverse
  Product:
  WoW (Web of Web)
Isolation (database systems) - Wikipedia, the free encyclopedia

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java cache on 2009-01-08 and saved by 3 people
- serializability requires that range locks are acquired when a query uses a ranged WHERE clause.
- however, if the SELECT statement contains any ranged WHERE clauses, phantom reads may occur
- 6 more annotations...
- - All data records retrieved by a SELECT statement cannot be changed
  - acquires read locks on all retrieved data
  - but does not acquire range locks
  - write locks are released at the end of the transaction
  - read locks are acquired on selected data but they are released immediately
  - However, the definitions above have been criticised in the paper A Critique of ANSI SQL Isolation Levels as being ambiguous
19.2. The Second Level Cache

www.hibernate.org/...performance-cache.html - Preview

java cache on 2009-01-08
- This cache strategy should never be used if serializable transaction isolation level is required
- only occasionally needs to update data
- 1 more annotations...
- - it is extremely unlikely that two
    transactions would try to update the same item simultaneously
OptimisticCache (Hibernate API Documentation)

www.hibernate.org/...OptimisticCache.html - Preview

java cache hibernate on 2009-01-12
- only utilized for
  the entity cache region
- all the methods
  here will only ever be called from access scenarios where versioned
  data is actually a possiblity
CacheConcurrencyStrategy (Hibernate API Documentation)

www.hibernate.org/...CacheConcurrencyStrategy.html - Preview

java cache hibernate on 2009-01-12
- updates to the cache are written
  to the cache inside the transaction
- items are merely "soft locked" during the
  transaction and then updated during the "after transaction completion"
  phase
- 3 more annotations...
- - In terms of entity cache
  - In terms of collection caches
  - query result caching does not go through a concurrency strategy
ReadWriteCache (Hibernate API Documentation)

www.hibernate.org/...ReadWriteCache.html - Preview

hibernate cache java on 2009-01-12
- asynchronous
- underlying cache implementation does not do
  asynchronous replication
- 4 more annotations...
- - that state has been fully replicated as soon
    as the lock is released
  - get(Object key, long txTimestamp)
  - Do not return an item whose timestamp is later than the current
    transaction timestamp
  - It is also possible
    to overwrite changes made and committed by another transaction
    after the current transaction read the item from the cache.
Cache Insight - 企业应用 - Java - JavaEye论坛

www.javaeye.com/21727 - Preview

java cache on 2009-01-12 and saved by 5 people
- 3. Eviction Policy 清除策略
- 4. 命中率
- 25 more annotations...
- - 6. 分布式Cach
  - 锁，事务，数据同步
  - memcached主要使用在Shared Nothing Architecture中
  - 同一个key对应的数据，只存在于一台memcached server的一份内存中
  - Memcached通过key的hashcode来判断从哪台memcached server上存取数据数据
  - JBoss Cache提出了POJO Cache的概念，意思是数据不是Serializable，一样能够在Cluster中同步
  - JBoss POJO Cache通过AOP机制，支持对象同步，支持对象属性的同步，支持关联对象的Cache，支持继承，集合，Query，并支持不同级别的事务
  - put的时候，放进去的是个干干净净的POJO，出来的时候，就是Enhanced Object，里面夹杂了很多Interceptor代码，监听对象的方法
  - Cluster之间的Cache同步有多种实现方法。比如，JMS，RMI，Client Server Socket等方法，用的最多的，支持最广的方法是JGroups开源项目实现的Multicast
  - Cluster Cache来说，读操作（get）肯定是Local方法
  - Put这个写方法，可以是Local，也可以是Remote的
  - Local Put比起Remote Put的优势很明显，所以，通常的Cluster Cache都采用Local Put的策略
  - Center vs Cluster
  - Local get/put在关联对象的组装和分拆方面，优势比较明显
  - 不要把没有Commit的修改数据放入到缓存中
  - 如果readTime > removeTime，这个put才能成功，数据才能够进入缓存
  - db.commt(); cache.remove(key); 这两步调用之间，有很小的可能发生另外的事务。这段极小的时间内，可能无法保证Read Committed，可能出现很短期的过期数据
  - 这么短期的几乎不可能发生的小概率事件，都不能容忍，那么可以，db.commt()之前，给Cache加一个悲观锁，不让别的事务，把数据Put进入Cache，就可以防止这个小概率、微影响的事件
  - ORM Cache一般分为两种。一种是ID Cache（ORM文档中称为二级Cache），用来存放Entity ID对应的Entity对象；一种是Query Cache，用来存放一条查询语句对应的查询结果集。
  - equals方法需要比较很长的Query String。如果没有命中，Query String不相等，那么开销很小，因为通常来说，不相等的String长度都不同，或者前面的字符串都不相同。开销最大的是命中的时候，Query String相等，那么需要把String从头比到尾。
  - 最好直接使用最外面的HQL, EQL, OQL作为Query Key，而不是采用生成的SQL结果。
  - WHL提到的方案中，我觉得，还没有支持任何的事务相关语义。
  - Cache位处Client-DB之间，它的一些行为使得Client的事务语义不能得到保证
  - READ_COMMITED需要 cache remove after update commit + time lock 共同实现
  - Repatable Read 和 Serializable 由JDBC来保证。Cache根本不需要考虑
Cache Insight - 企业应用 - Java - JavaEye论坛

www.javaeye.com/...21727 - Preview

java cache on 2009-01-12
- 这个字段变化如此之频繁，我只好对这个字段进行单独处理，积累很久才update db一次，只update这一个字段，并且不清楚ID Cache和Query Cache。
关于Hibernate Cache - Hibernate - Java - JavaEye论坛

www.javaeye.com/6593 - Preview

java hibernate cache on 2009-01-13
- 而Session.find()的数据获取与CACHE没有关系, 完全由JDBC来操办
- 最后只是把从JDBC获得的对象注入CACHE. 通过关系查找对象的过程和Session.find()没有异样, 甚至CACHE还报出对象已存在的消息
Remote Cache, Transaction - buaawhl - JavaEye技术网站

buaawhl.javaeye.com/21631 - Preview

cache on 2009-02-15
- 中心Cache，和Cluster Cache

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marlonyao

10 items | 20 visits

Updated on 2009-02-15
Created on 2009-01-12

Category: Computers & Internet

java cache

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marlonyao 's List: Java Cache

Mindmapping, concept mapping and information organisation software

Isolation (database systems) - Wikipedia, the free encyclopedia

19.2. The Second Level Cache

OptimisticCache (Hibernate API Documentation)

CacheConcurrencyStrategy (Hibernate API Documentation)

ReadWriteCache (Hibernate API Documentation)

Cache Insight - 企业应用 - Java - JavaEye论坛

Cache Insight - 企业应用 - Java - JavaEye论坛

关于Hibernate Cache - Hibernate - Java - JavaEye论坛

Remote Cache, Transaction - buaawhl - JavaEye技术网站

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