OSCache是當(dāng)前運(yùn)用最廣的緩存方案，JBoss,Hibernate,Spring等都對(duì)其有支持，
下面簡單介紹一下OSCache的配置和使用過程。
1.安裝過程
從
http://www.opensymphony.com/oscache/download.html
下載合適的OSCache版本，
我下載的是oscache-2.0.2-full版本。
解壓縮下載的文件到指定目錄
從解壓縮目錄取得oscache.jar 文件放到 /WEB-INF/lib 或相應(yīng)類庫目錄 目錄中，
jar文件名可能含有版本號(hào)和該版本的發(fā)布日期信息等，如oscache-2.0.2-22Jan04.jar
如果你的jdk版本為1.3.x,建議在lib中加入Apache Common Lib 的commons-collections.jar包。
如jdk是1.4以上則不必
從src或etc目錄取得oscache.properties 文件，放入src根目錄或發(fā)布環(huán)境的/WEB-INF/classes 目錄
如你需要建立磁盤緩存，須修改oscache.properties 中的cache.path信息 (去掉前面的#注釋)。
win類路徑類似為c:\\app\\cache
unix類路徑類似為/opt/myapp/cache
拷貝OSCache標(biāo)簽庫文件oscache.tld到/WEB-INF/classes目錄。
現(xiàn)在你的應(yīng)用目錄類似如下：
$WEB_APPLICATION\WEB-INF\lib\oscache.jar
$WEB_APPLICATION\WEB-INF\classes\oscache.properties
$WEB_APPLICATION\WEB-INF\classes\oscache.tld
將下列代碼加入web.xml文件中
<taglib>
<taglib-uri>oscache</taglib-uri>
<taglib-location>/WEB-INF/classes/oscache.tld</taglib-location>
</taglib>
為了便于調(diào)試日志輸出，須加入commons-logging.jar和log4j-1.2.8.jar到當(dāng)前類庫路徑中
在src目錄加入下面兩個(gè)日志輸出配置文件：
log4j.properties 文件內(nèi)容為：
log4j.rootLogger=DEBUG,stdout,file
log4j.appender.stdout=org.apache.log4j.ConsoleAppender
log4j.appender.stdout.layout=org.apache.log4j.PatternLayout
log4j.appender.stdout.layout.ConversionPattern=[start]%d{yyyy/MM/dd/ HH:mm:ss}[DATE]%n%p[PRIORITY]%n%x[NDC]%n%t[THREAD] n%c[CATEGORY]%n%m[MESSAGE]%n%n
?
log4j.appender.file=org.apache.log4j.RollingFileAppender
log4j.appender.file.File=oscache.log
log4j.appender.file.MaxFileSize=100KB
log4j.appender.file.MaxBackupIndex=5
log4j.appender.file.layout=org.apache.log4j.PatternLayout
log4j.appender.file.layout.ConversionPattern=[start]%d{yyyy/MM/dd/ HH:mm:ss}[DATE]%n%p[PRIORITY]%n%x[NDC]%n%t[THREAD] n%c[CATEGORY]%n%m[MESSAGE]%n%n
log4j.logger.org.apache.commons=ERROR
log4j.logger.com.opensymphony.oscache.base=INFO
commons-logging.properties 文件內(nèi)容為
org.apache.commons.logging.Log=org.apache.commons.logging.impl.Log4JCategoryLog
2.oscache.properties 文件配置向?qū)?
cache.memory
值為true 或 false ，默認(rèn)為在內(nèi)存中作緩存，
如設(shè)置為false，那cache只能緩存到數(shù)據(jù)庫或硬盤中，那cache還有什么意義：）
cache.capacity
緩存元素個(gè)數(shù)
cache.persistence.class
持久化緩存類，如此類打開，則必須設(shè)置cache.path信息
cache.cluster 相關(guān)
為集群設(shè)置信息。
如
cache.cluster.multicast.ip為廣播IP地址
cache.cluster.properties為集群屬性
3.OSCache的基本用法
cache1.jsp 內(nèi)容如下
<%@ page import="java.util.*" %>
<%@ taglib uri="oscache" prefix="cache" %>
<html>
<body>
沒有緩存的日期: <%= new Date() %><p>
<!--自動(dòng)刷新-->
<cache:cache time="30">
每30秒刷新緩存一次的日期: <%= new Date() %>
</cache:cache>
<!--手動(dòng)刷新-->
<cache:cache key="testcache">
手動(dòng)刷新緩存的日期: <%= new Date() %> <p>
</cache:cache>
<a href="/cache2.jsp">手動(dòng)刷新</a>
</body>
</html>
cache2.jsp 執(zhí)行手動(dòng)刷新頁面如下
<%@ taglib uri="oscache" prefix="cache" %>
<html>
<body>
緩存已刷新...<p>
<cache:flush key="testcache" scope="application"/>
<a href="/cache1.jsp">返回</a>
</body>
</html>
OSCache庫提供的flush標(biāo)記能夠刷新緩沖內(nèi)容。我們可以把下面的代碼加入到處理用戶動(dòng)作且可能影響這一區(qū)域的頁面之中：
<cache:flush key="testcache" scope="application"/>
當(dāng)用戶下次訪問它時(shí)，testcache緩沖塊將被刷新
你也可以通過下面語句定義Cache的有效范圍,如不定義scope,scope默認(rèn)為Applcation
<cache:cache time="30" scope="session">
...
</cache:cache>
4. 緩存過濾器 CacheFilter
package com.lvke.company.common;
import com.opensymphony.oscache.base.Cache;
import com.opensymphony.oscache.base.EntryRefreshPolicy;
import com.opensymphony.oscache.base.NeedsRefreshException;
import com.opensymphony.oscache.web.ServletCacheAdministrator;
import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
import java.io.IOException;
import javax.servlet.*;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.jsp.PageContext;
import com.opensymphony.oscache.web.filter.CacheHttpServletResponseWrapper;
import com.opensymphony.oscache.web.filter.ICacheGroupsProvider;
import com.opensymphony.oscache.web.filter.ICacheKeyProvider;
import com.opensymphony.oscache.web.filter.ExpiresRefreshPolicy;
import com.opensymphony.oscache.web.filter.ResponseContent;
public class CacheFilter implements Filter, ICacheKeyProvider, ICacheGroupsProvider {
??? // Header
??? public static final String HEADER_LAST_MODIFIED = "Last-Modified";
??? public static final String HEADER_CONTENT_TYPE = "Content-Type";
??? public static final String HEADER_CONTENT_ENCODING = "Content-Encoding";
??? public static final String HEADER_EXPIRES = "Expires";
??? public static final String HEADER_IF_MODIFIED_SINCE = "If-Modified-Since";
??? public static final String HEADER_CACHE_CONTROL = "Cache-Control";
??? public static final String HEADER_ACCEPT_ENCODING = "Accept-Encoding";
??? // Fragment parameter
??? public static final int FRAGMENT_AUTODETECT = -1;
??? public static final int FRAGMENT_NO = 0;
??? public static final int FRAGMENT_YES = 1;
??? // No cache parameter
??? public static final int NOCACHE_OFF = 0;
??? public static final int NOCACHE_SESSION_ID_IN_URL = 1;
??? // Last Modified parameter
??? public static final long LAST_MODIFIED_OFF = 0;
??? public static final long LAST_MODIFIED_ON = 1;
??? public static final long LAST_MODIFIED_INITIAL = -1;
??? // Expires parameter
??? public static final long EXPIRES_OFF = 0;
??? public static final long EXPIRES_ON = 1;
??? public static final long EXPIRES_TIME = -1;
??? // Cache Control
??? public static final long MAX_AGE_NO_INIT = Long.MIN_VALUE;
??? public static final long MAX_AGE_TIME = Long.MAX_VALUE;
??? // request attribute to avoid reentrance
??? private final static String REQUEST_FILTERED = "__oscache_filtered";
??? // the policy for the expires header
??? private EntryRefreshPolicy expiresRefreshPolicy;
??? // the logger
??? private final Log log = LogFactory.getLog(this.getClass());
??? // filter variables
??? private FilterConfig config;
??? private ServletCacheAdministrator admin = null;
??? private int cacheScope = PageContext.APPLICATION_SCOPE; // filter scope - default is APPLICATION
??? private int fragment = FRAGMENT_AUTODETECT; // defines if this filter handles fragments of a page - default is auto detect
??? private int time = 60 * 60; // time before cache should be refreshed - default one hour (in seconds)
??? private String cron = null; // A cron expression that determines when this cached content will expire - default is null
??? private int nocache = NOCACHE_OFF; // defines special no cache option for the requests - default is off
??? private long lastModified = LAST_MODIFIED_INITIAL; // defines if the last-modified-header will be sent - default is intial setting
??? private long expires = EXPIRES_ON; // defines if the expires-header will be sent - default is on
??? private long cacheControlMaxAge = -60; // defines which max-age in Cache-Control to be set - default is 60 seconds for max-age
??? private ICacheKeyProvider cacheKeyProvider = this; // the provider of the cache key - default is the CacheFilter itselfs
??? private ICacheGroupsProvider cacheGroupsProvider = this; // the provider of the cache groups - default is the CacheFilter itselfs
??? /**
???? * Filter clean-up
???? */
??? public void destroy() {
??????? //Not much to do...
??? }
??? public void doFilter(ServletRequest request, ServletResponse response, FilterChain chain) throws ServletException, IOException {
??????? if (log.isInfoEnabled()) {
??????????? log.info("<cache>: filter in scope " + cacheScope);
??????? }
??????? // avoid reentrance (CACHE-128) and check if request is cacheable
??????? if (isFilteredBefore(request) || !isCacheable(request)) {
??????????? chain.doFilter(request, response);
??????????? return;
??????? }
??????? request.setAttribute(REQUEST_FILTERED, Boolean.TRUE);
??????? HttpServletRequest httpRequest = (HttpServletRequest) request;
??????? // checks if the response will be a fragment of a page
??????? boolean fragmentRequest = isFragment(httpRequest);
??????? // avoid useless session creation for application scope pages (CACHE-129)
??????? Cache cache;
??????? if (cacheScope == PageContext.SESSION_SCOPE) {
??????????? cache = admin.getSessionScopeCache(httpRequest.getSession(true));
??????? } else {
??????????? cache = admin.getAppScopeCache(config.getServletContext());
??????? }
??????? // generate the cache entry key
??????? String key = cacheKeyProvider.createCacheKey(httpRequest, admin, cache);
??????? try {
??????????? ResponseContent respContent = (ResponseContent) cache.getFromCache(key, time, cron);
??????????? if (log.isInfoEnabled()) {
??????????????? log.info("<cache>: Using cached entry for " + key);
??????????? }
??????????? boolean acceptsGZip = false;
??????????? if ((!fragmentRequest) && (lastModified != LAST_MODIFIED_OFF)) {
??????????????? long clientLastModified = httpRequest.getDateHeader(HEADER_IF_MODIFIED_SINCE); // will return -1 if no header...
??????????????? // only reply with SC_NOT_MODIFIED
??????????????? // if the client has already the newest page and the response isn't a fragment in a page
??????????????? if ((clientLastModified != -1) && (clientLastModified >= respContent.getLastModified())) {
??????????????????? ((HttpServletResponse) response).setStatus(HttpServletResponse.SC_NOT_MODIFIED);
??????????????????? return;
??????????????? }
??????????????? acceptsGZip = respContent.isContentGZiped() && acceptsGZipEncoding(httpRequest);
??????????? }
??????????? respContent.writeTo(response, fragmentRequest, acceptsGZip);
??????????? // acceptsGZip is used for performance reasons above; use the following line for CACHE-49
??????????? // respContent.writeTo(response, fragmentRequest, acceptsGZipEncoding(httpRequest));
??????? } catch (NeedsRefreshException nre) {
??????????? boolean updateSucceeded = false;
??????????? try {
??????????????? if (log.isInfoEnabled()) {
??????????????????? log.info("<cache>: New cache entry, cache stale or cache scope flushed for " + key);
??????????????? }
??????????????? CacheHttpServletResponseWrapper cacheResponse = new CacheHttpServletResponseWrapper((HttpServletResponse) response, fragmentRequest, time * 1000L, lastModified, expires, cacheControlMaxAge);
??????????????? chain.doFilter(request, cacheResponse);
??????????????? cacheResponse.flushBuffer();
??????????????? // Only cache if the response is cacheable
??????????????? if (isCacheable(cacheResponse)) {
??????????????????? // get the cache groups of the content
??????????????????? String[] groups = cacheGroupsProvider.createCacheGroups(httpRequest, admin, cache);
??????????????????? // Store as the cache content the result of the response
??????????????????? cache.putInCache(key, cacheResponse.getContent(), groups, expiresRefreshPolicy, null);
??????????????????? updateSucceeded = true;
??????????????? }
??????????? } finally {
??????????????? if (!updateSucceeded) {
??????????????????? cache.cancelUpdate(key);
??????????????? }
??????????? }
??????? }
??? }
??? public void init(FilterConfig filterConfig) {
??????? //Get whatever settings we want...
??????? config = filterConfig;
??????? admin = ServletCacheAdministrator.getInstance(config.getServletContext());
??????? // filter parameter time
??????? try {
??????????? time = Integer.parseInt(config.getInitParameter("time"));
??????? } catch (Exception e) {
??????????? log.info("Could not get init parameter 'time', defaulting to one hour.");
??????? }
??????? // setting the refresh period for this cache filter
??????? expiresRefreshPolicy = new ExpiresRefreshPolicy(time);
??????? // filter parameter scope
??????? try {
??????????? String scopeString = config.getInitParameter("scope");
??????????? if (scopeString.equals("session")) {
??????????????? cacheScope = PageContext.SESSION_SCOPE;
??????????? } else if (scopeString.equals("application")) {
??????????????? cacheScope = PageContext.APPLICATION_SCOPE;
??????????? } else if (scopeString.equals("request")) {
??????????????? cacheScope = PageContext.REQUEST_SCOPE;
??????????? } else if (scopeString.equals("page")) {
??????????????? cacheScope = PageContext.PAGE_SCOPE;
??????????? }
??????? } catch (Exception e) {
??????????? log.info("Could not get init parameter 'scope', defaulting to 'application'.");
??????? }
??????? // filter parameter cron
??????? cron = config.getInitParameter("cron");
??????? // filter parameter fragment
??????? try {
??????????? String fragmentString = config.getInitParameter("fragment");
??????????? if (fragmentString.equals("no")) {
??????????????? fragment = FRAGMENT_NO;
??????????? } else if (fragmentString.equals("yes")) {
??????????????? fragment = FRAGMENT_YES;
??????????? } else if (fragmentString.equalsIgnoreCase("auto")) {
??????????????? fragment = FRAGMENT_AUTODETECT;
??????????? }
??????? } catch (Exception e) {
??????????? log.info("Could not get init parameter 'fragment', defaulting to 'auto detect'.");
??????? }
??????? // filter parameter nocache
??????? try {
??????????? String nocacheString = config.getInitParameter("nocache");
??????????? if (nocacheString.equals("off")) {
??????????????? nocache = NOCACHE_OFF;
??????????? } else if (nocacheString.equalsIgnoreCase("sessionIdInURL")) {
??????????????? nocache = NOCACHE_SESSION_ID_IN_URL;
??????????? }
??????? } catch (Exception e) {
??????????? log.info("Could not get init parameter 'nocache', defaulting to 'off'.");
??????? }
??????? // filter parameter last modified
??????? try {
??????????? String lastModifiedString = config.getInitParameter("lastModified");
??????????? if (lastModifiedString.equals("off")) {
??????????????? lastModified = LAST_MODIFIED_OFF;
??????????? } else if (lastModifiedString.equals("on")) {
??????????????? lastModified = LAST_MODIFIED_ON;
??????????? } else if (lastModifiedString.equalsIgnoreCase("initial")) {
??????????????? lastModified = LAST_MODIFIED_INITIAL;
??????????? }
??????? } catch (Exception e) {
??????????? log.info("Could not get init parameter 'lastModified', defaulting to 'initial'.");
??????? }
??????? // filter parameter expires
??????? try {
??????????? String expiresString = config.getInitParameter("expires");
??????????? if (expiresString.equals("off")) {
??????????????? expires = EXPIRES_OFF;
??????????? } else if (expiresString.equals("on")) {
??????????????? expires = EXPIRES_ON;
??????????? } else if (expiresString.equalsIgnoreCase("time")) {
??????????????? expires = EXPIRES_TIME;
??????????? }
??????? } catch (Exception e) {
??????????? log.info("Could not get init parameter 'expires', defaulting to 'on'.");
??????? }
??????? // filter parameter Cache-Control
??????? try {
??????????? String cacheControlMaxAgeString = config.getInitParameter("max-age");
??????????? if (cacheControlMaxAgeString.equals("no init")) {
??????????????????? cacheControlMaxAge = MAX_AGE_NO_INIT;
??????????? } else if (cacheControlMaxAgeString.equals("time")) {
??????????????????? cacheControlMaxAge = MAX_AGE_TIME;
??????????? } else {
??????????????????? cacheControlMaxAge = Long.parseLong(cacheControlMaxAgeString);
??????????????????? if (cacheControlMaxAge >= 0) {
??????????????????????????? // declare the cache control as a constant
??????????????????????????? cacheControlMaxAge = - cacheControlMaxAge;
??????????????????? } else {
??????????????????? log.warn("Init parameter 'max-age' must be at least a positive integer, defaulting to 'time'. ");
??????????????????????? cacheControlMaxAge = 60;
??????????????????? }
??????????? }
??????? } catch (Exception e) {
??????????? log.info("Could not get init parameter 'max-age', defaulting to 'time'.");
??????? }
??????? // filter parameter ICacheKeyProvider
??????? ICacheKeyProvider cacheKeyProvider = (ICacheKeyProvider)instantiateFromInitParam("ICacheKeyProvider", ICacheKeyProvider.class, this.getClass().getName());
??????? if (cacheKeyProvider != null) {
??????????? this.cacheKeyProvider = cacheKeyProvider;
??????? }
??????? // filter parameter ICacheGroupsProvider
??????? ICacheGroupsProvider cacheGroupsProvider = (ICacheGroupsProvider)instantiateFromInitParam("ICacheGroupsProvider", ICacheGroupsProvider.class, this.getClass().getName());
??????? if (cacheGroupsProvider != null) {
??????????? this.cacheGroupsProvider = cacheGroupsProvider;
??????? }
??????? // filter parameter EntryRefreshPolicy
??????? EntryRefreshPolicy expiresRefreshPolicy = (EntryRefreshPolicy)instantiateFromInitParam("EntryRefreshPolicy", EntryRefreshPolicy.class, this.expiresRefreshPolicy.getClass().getName());
??????? if (expiresRefreshPolicy != null) {
??????????? this.expiresRefreshPolicy = expiresRefreshPolicy;
??????? }
??? }
??? private Object instantiateFromInitParam(String classInitParam, Class interfaceClass, String defaultClassName) {
??????????????? String className = config.getInitParameter(classInitParam);
??????????????? if (className == null) {
??????????????????????? log.info("Could not get init parameter '" + classInitParam + "', defaulting to " + defaultClassName + ".");
??????????????????????? return null;
??????????????? } else {
??????????????????????? try {
??????????????????????????????? Class clazz = Class.forName(className);
??????????????????????????????? if (!interfaceClass.isAssignableFrom(clazz)) {
??????????????????????????????????????? log.error("Specified class '" + className + "' does not implement" + interfaceClass.getName() + ". Using default " + defaultClassName + ".");
??????????????????????????????????????? return null;
??????????????????????????????? } else {
??????????????????????????????????????? return clazz.newInstance();
??????????????????????????????? }
??????????????????????? } catch (ClassNotFoundException e) {
??????????????????????????????? log.error("Class '" + className + "' not found. Defaulting to " + defaultClassName + ".", e);
??????????????????????? } catch (InstantiationException e) {
??????????????????????????????? log.error("Class '" + className + "' could not be instantiated because it is not a concrete class. Using default class " + defaultClassName + ".", e);
??????????????????????? } catch (IllegalAccessException e) {
??????????????????????????????? log.error("Class '"+ className+ "' could not be instantiated because it is not public. Using default class " + defaultClassName + ".", e);
??????????????????????? }
??????????????????????? return null;
??????????????? }
??????? }
??? public String createCacheKey(HttpServletRequest httpRequest, ServletCacheAdministrator scAdmin, Cache cache) {
??????? return scAdmin.generateEntryKey(null, httpRequest, cacheScope);
??? }
??? public String[] createCacheGroups(HttpServletRequest httpRequest, ServletCacheAdministrator scAdmin, Cache cache) {
??????? return null;
??? }
??? protected boolean isFragment(HttpServletRequest request) {
??????? if (fragment == FRAGMENT_AUTODETECT) {
??????????? return request.getAttribute("javax.servlet.include.request_uri") != null;
??????? } else {
??????????? return (fragment == FRAGMENT_NO) ? false : true;
??????? }
??? }
??? protected boolean isFilteredBefore(ServletRequest request) {
??????? return request.getAttribute(REQUEST_FILTERED) != null;
??? }
??? protected boolean isCacheable(ServletRequest request) {
??????? // TODO implement CACHE-137 and CACHE-141 here
??????? boolean cachable = request instanceof HttpServletRequest;
??????? if (cachable) {
??????????? HttpServletRequest requestHttp = (HttpServletRequest) request;
??????????? if (nocache == NOCACHE_SESSION_ID_IN_URL) { // don't cache requests if session id is in the URL
??????????????? cachable = !requestHttp.isRequestedSessionIdFromURL();
??????????? }
??????? }
??????? if (log.isDebugEnabled()) {
??????????? log.debug("<cache>: the request " + ((cachable) ? "is" : "is not") + " cachable.");
??????? }
??????? return cachable;
??? }
??? protected boolean isCacheable(CacheHttpServletResponseWrapper cacheResponse) {
??????? // TODO implement CACHE-137 and CACHE-141 here
??????? // Only cache if the response was 200
??????? boolean cachable = cacheResponse.getStatus() == HttpServletResponse.SC_OK;
??????? if (log.isDebugEnabled()) {
??????????? log.debug("<cache>: the response " + ((cachable) ? "is" : "is not") + " cachable.");
??????? }
??????? return cachable;
??? }
??? protected boolean acceptsGZipEncoding(HttpServletRequest request) {
??????? String acceptEncoding = request.getHeader(HEADER_ACCEPT_ENCODING);
??????? return? (acceptEncoding != null) && (acceptEncoding.indexOf("gzip") != -1);
??? }
}
你可以在web.xml中定義緩存過濾器，定義特定資源的緩存。
<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>
上面定義將緩存所有.jsp頁面，緩存刷新時(shí)間為60秒，緩存作用域?yàn)镾ession
?
注意，CacheFilter只捕獲Http頭為200的頁面請(qǐng)求，即只對(duì)無錯(cuò)誤請(qǐng)求作緩存，
而不對(duì)其他請(qǐng)求（如500,404,400）作緩存處理
OSCache - Tags
：
http://www.opensymphony.com/oscache/wiki/JSP%20Tags.html
??
??注：本文引自
http://www.zhanglihai.com/
????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????? 13:11:20 12-22-2006