OSCache使用指南

OSCache是当前运用最广的缓存方案，JBoss,Hibernate,Spring等都对其有支持，
下面简单介绍一下OSCache的配置和使用过程。
1.安装过程
从[url]http://www.opensymphony.com/oscache/download.html[/url]下载合适的OSCache版本,我下载的是最新版本oscache-2.4.1-full.zip，然后解压缩到指定的目录。
把解压缩文件中的oscache-2.4.1.jar放入你的项目的/WEB-INF/lib中。
注：如果你的jdk版本为1.3.x,建议在lib中加入Apache Common Lib 的commons-collections.jar包。如jdk是1.4以上则不必 。
从src或etc目录取得oscache.properties 文件，放入你项目中的src根目录或发布环境的/WEB-INF/classes 目录下。
如你需要建立磁盘缓存，须修改oscache.properties 中的cache.path信息 (去掉前面的#注释)。
win类路径类似为c:\\app\\cache
unix类路径类似为/opt/myapp/cache
oscache.properties文件：

# CACHE IN MEMORY
#
# If you want to disable memory caching, just uncomment this line.
#
cache.memory=true


# CACHE KEY
#
# This is the key that will be used to store the cache in the application
# and session scope.
#
# If you want to set the cache key to anything other than the default
# uncomment this line and change the cache.key
#
# cache.key=__oscache_cache


# USE HOST DOMAIN NAME IN KEY
#
# Servers for multiple host domains may wish to add host name info to
# the generation of the key.  If this is true, then uncomment the
# following line.
#
# cache.use.host.domain.in.key=true


# CACHE LISTENERS
#
# These hook OSCache events and perform various actions such as logging
# cache hits and misses, or broadcasting to other cache instances across a cluster.
# See the documentation for further information.
#
# cache.event.listeners=com.opensymphony.oscache.plugins.clustersupport.JMSBroadcastingListener,  \
#                       com.opensymphony.oscache.extra.CacheEntryEventListenerImpl,               \
#                       com.opensymphony.oscache.extra.CacheMapAccessEventListenerImpl,           \
#                       com.opensymphony.oscache.extra.ScopeEventListenerImpl,                    \
#                       com.opensymphony.oscache.extra.StatisticListenerImpl


# CACHE PERSISTENCE CLASS
#
# Specify the class to use for persistence. If you use the supplied DiskPersistenceListener,
# don't forget to supply the cache.path property to specify the location of the cache
# directory.
# 
# If a persistence class is not specified, OSCache will use memory caching only.
#
cache.persistence.class=com.opensymphony.oscache.plugins.diskpersistence.HashDiskPersistenceListener
# cache.persistence.class=com.opensymphony.oscache.plugins.diskpersistence.HashDiskPersistenceListener

# CACHE OVERFLOW PERSISTENCE
# Use persistent cache in overflow or not. The default value is false, which means
# the persistent cache will be used at all times for every entry.  true is the recommended setting.
#
cache.persistence.overflow.only=true

# CACHE DIRECTORY
#
# This is the directory on disk where caches will be stored by the DiskPersistenceListener.
# it will be created if it doesn't already exist. Remember that OSCache must have
# write permission to this directory.
#
# Note: for Windows machines, this needs \ to be escaped
# ie Windows:
cache.path=d:\\myapp\\cache
# or *ix:
# cache.path=/opt/myapp/cache
#
# cache.path=c:\\app\\cache


# CACHE ALGORITHM
#
# Default cache algorithm to use. Note that in order to use an algorithm
# the cache size must also be specified. If the cache size is not specified,
# the cache algorithm will be Unlimited cache.
#
# cache.algorithm=com.opensymphony.oscache.base.algorithm.LRUCache
# cache.algorithm=com.opensymphony.oscache.base.algorithm.FIFOCache
# cache.algorithm=com.opensymphony.oscache.base.algorithm.UnlimitedCache

# THREAD BLOCKING BEHAVIOR
#
# When a request is made for a stale cache entry, it is possible that another thread is already
# in the process of rebuilding that entry. This setting specifies how OSCache handles the
# subsequent 'non-building' threads. The default behaviour (cache.blocking=false) is to serve
# the old content to subsequent threads until the cache entry has been updated. This provides
# the best performance (at the cost of serving slightly stale data). When blocking is enabled,
# threads will instead block until the new cache entry is ready to be served. Once the new entry
# is put in the cache the blocked threads will be restarted and given the new entry.
# Note that even if blocking is disabled, when there is no stale data available to be served
# threads will block until the data is added to the cache by the thread that is responsible
# for building the data.
#
# cache.blocking=false

# CACHE SIZE
#
# Default cache size in number of items. If a size is specified but not
# an algorithm, the cache algorithm used will be LRUCache.
#
cache.capacity=5000


# CACHE UNLIMITED DISK
# Use unlimited disk cache or not. The default value is false, which means
# the disk cache will be limited in size to the value specified by cache.capacity.
#
# cache.unlimited.disk=false


# JMS CLUSTER PROPERTIES
#
# Configuration properties for JMS clustering. See the clustering documentation
# for more information on these settings.
#
#cache.cluster.jms.topic.factory=java:comp/env/jms/TopicConnectionFactory
#cache.cluster.jms.topic.name=java:comp/env/jms/OSCacheTopic
#cache.cluster.jms.node.name=node1


# JAVAGROUPS CLUSTER PROPERTIES
#
# Configuration properites for the JavaGroups clustering. Only one of these
# should be specified. Default values (as shown below) will be used if niether
# property is set. See the clustering documentation and the JavaGroups project
# (www.javagroups.com) for more information on these settings.
#
#cache.cluster.properties=UDP(mcast_addr=231.12.21.132;mcast_port=45566;ip_ttl=32;\
#mcast_send_buf_size=150000;mcast_recv_buf_size=80000):\
#PING(timeout=2000;num_initial_members=3):\
#MERGE2(min_interval=5000;max_interval=10000):\
#FD_SOCK:VERIFY_SUSPECT(timeout=1500):\
#pbcast.NAKACK(gc_lag=50;retransmit_timeout=300,600,1200,2400,4800;max_xmit_size=8192):\
#UNICAST(timeout=300,600,1200,2400):\
#pbcast.STABLE(desired_avg_gossip=20000):\
#FRAG(frag_size=8096;down_thread=false;up_thread=false):\
#pbcast.GMS(join_timeout=5000;join_retry_timeout=2000;shun=false;print_local_addr=true)
#cache.cluster.multicast.ip=231.12.21.132

拷贝OSCache标签库文件oscache.tld到/WEB-INF/classes目录。
现在你的应用目录类似如下：
$WEB_APPLICATION\WEB-INF\lib\oscache.jar
$WEB_APPLICATION\WEB-INF\classes\oscache.properties
$WEB_APPLICATION\WEB-INF\classes\oscache.tld


将下列代码加入web.xml文件中

<taglib> 
<taglib-uri>oscache</taglib-uri> 
<taglib-location>/WEB-INF/classes/oscache.tld</taglib-location> 
</taglib> 

2.oscache.properties 文件配置向导

cache.memory
值为true 或 false ，默认为在内存中作缓存，
如设置为false，那cache只能缓存到数据库或硬盘中，那cache还有什么意义：）

cache.capacity
缓存元素个数

cache.persistence.class
持久化缓存类，如此类打开，则必须设置cache.path信息

cache.cluster 相关
为集群设置信息。
如
cache.cluster.multicast.ip为广播IP地址
cache.cluster.properties为集群属性
3.OSCache的基本用法

cache1.jsp 内容如下

<%@ page import="java.util.*" %> 
<%@ taglib uri="oscache" prefix="cache" %> 

<html> 
<body> 

没有缓存的日期: <%= new Date() %><p> 
<!--自动刷新--> 
<cache:cache time="30"> 
每30秒刷新缓存一次的日期: <%= new Date() %> 
</cache:cache> 
<!--手动刷新--> 
<cache:cache key="testcache"> 
手动刷新缓存的日期: <%= new Date() %> <p> 
</cache:cache> 
<a href="cache2.jsp">手动刷新</a> 

</body> 
</html> 

cache2.jsp 执行手动刷新页面如下

<%@ taglib uri="oscache" prefix="cache" %> 

<html> 
<body> 

缓存已刷新...<p> 

<cache:flush key="testcache" scope="application"/> 

<a href="cache1.jsp">返回</a> 

</body> 
</html> 


你也可以通过下面语句定义Cache的有效范围,如不定义scope,scope默认为Applcation 
<cache:cache time="30" scope="session"> 
... 
</cache:cache> 

4. 缓存过滤器 CacheFilter

你可以在web.xml中定义缓存过滤器，定义特定资源的缓存。

<filter> 
<filter-name>CacheFilter</filter-name> 
<filter-class>com.opensymphony.oscache.web.filter.CacheFilter</filter-class> 
<init-param> 
<param-name>time</param-name> 
<param-value>60</param-value> 
</init-param> 
<init-param> 
<param-name>scope</param-name> 
<param-value>session</param-value> 
</init-param> 
</filter> 
<filter-mapping> 
<filter-name>CacheFilter</filter-name> 
<url-pattern>*.jsp</url-pattern> 
</filter-mapping> 

注：上面定义将缓存所有.jsp页面，缓存刷新时间为60秒，缓存作用域为Session
或者在web.xml先设置页面级缓存处理

<!--页面级缓存处理 -->
	<filter>
		<filter-name>CacheFilter</filter-name>
		<filter-class>
			com.opensymphony.oscache.web.filter.CacheFilter
		</filter-class>
		<init-param>
			<param-name>time</param-name>
			<param-value>1200</param-value>
		</init-param>
		<init-param>
			<param-name>disableCacheOnMethods</param-name>
			<param-value>POST,PUT,DELETE</param-value>
		</init-param>
		<init-param>
			<param-name>oscache-properties-file</param-name>
			<param-value>
				/WEB-INF/classes/oscache.properties
			</param-value>
		</init-param>
	</filter>

然后再在web.xml中设置要缓存的页面

<!-- 设置oscache -->

	<filter-mapping>
		<filter-name>CacheFilter</filter-name>
       <!-- 
		<url-pattern>/manager/cust/syscs.action</url-pattern>

		<url-pattern>/tool_bar/*</url-pattern>

		<url-pattern>/common/css/*</url-pattern>
		 -->	
		<!-- 
		<url-pattern>/common/js/*</url-pattern>

		<url-pattern>/news/css/*</url-pattern>
		<url-pattern>/news/js/*</url-pattern>
		<url-pattern>/dwr/util.js</url-pattern>
		 -->	
		<url-pattern>/dwrdsfsdf/util.js</url-pattern>
	</filter-mapping>

注意：CacheFilter只捕获Http头为200的页面请求，即只对无错误请求作缓存，
而不对其他请求（如500,404,400）作缓存处理。