ehcache-web缓存的使用和清除

引入jar包

<!--ehcache缓存-->
            <dependency>
                <groupId>net.sf.ehcache</groupId>
                <artifactId>ehcache-web</artifactId>
                <version>2.0.4</version>
            </dependency>

配置ehcache.xml

<ehcache xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
         xsi:noNamespaceSchemaLocation="./ehcache.xsd" updateCheck="true" monitoring="autodetect" dynamicConfig="true">

    <!--自创建的时候起，缓存300秒,300秒后重新查询放入缓存-->
    <cache name="SimplePageCachingFilter"
           maxElementsInMemory="10000"
           eternal="false"
           overflowToDisk="false"
           timeToIdleSeconds="0"
           timeToLiveSeconds="300"
           memoryStoreEvictionPolicy="LFU" />

</ehcache>

配置web.xml

 <!--缓存设置-->
        <filter>
        <filter-name>SimplePageCachingFilter</filter-name>
        <filter-class>com.gome.home.controller.common.CacheFilter</filter-class>
        <init-param>
 <!--缓存线程锁超时间，默认无限期，导致程序永不响应-->
            <param-name>blockingTimeoutMillis</param-name>
            <param-value>500</param-value>
        </init-param>
        <init-param>
 <!--设置的缓存名称 默认为SimplePageCachingFilter-->
            <param-name>cacheName</param-name>
            <param-value>SimplePageCachingFilter</param-value>
        </init-param>

    </filter>

    <!--测试URL-->
    <filter-mapping>
        <filter-name>SimplePageCachingFilter</filter-name>
        <url-pattern>/test</url-pattern>
    </filter-mapping>

当访问/test这个URL的时候,ehcache会把生成的HTML全部放入缓存,再次访问时,从缓存中取出HTML直接输出,响应时间为20毫秒内,不需要缓存时,比如后台修改了部分数据,使用以下方式清空缓存,重新加载.

缓存的位置,默认是内存,速度最快,也可以配置为磁盘文件,如果文件较多,可以配置为磁盘文件,这种方式其实就是页面静态化的工作.而几乎不需作任何开发就实现了

清除缓存

import net.sf.ehcache.CacheManager;
import net.sf.ehcache.Ehcache;
import net.sf.ehcache.Element;
import net.sf.ehcache.constructs.web.PageInfo;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.stereotype.Controller;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.ResponseBody;

import java.io.UnsupportedEncodingException;
import java.util.List;

@Controller()
@RequestMapping("/common/cache")
public class CacheController {
    public static final Logger logger  = LoggerFactory.getLogger(CacheController.class);
    public static final String DEFAULT_CACHE_NAME = "SimplePageCachingFilter";

    private static final CacheManager cacheManager = CacheManager.getInstance();

    @RequestMapping("clean")
    public @ResponseBody Boolean clean(){
        logger.debug("cache clean");
        String[] names = cacheManager.getCacheNames();
        logger.debug("cache names {}",names);
        BlockingCache cache = (BlockingCache)cacheManager.getEhcache(DEFAULT_CACHE_NAME);

        logger.debug("cache.getMemoryStoreSize() {}",cache.getMemoryStoreSize());
        List keys = cache.getKeys();
//for里的Element e = cache.get(k);必须注掉
          for(Object k:keys){
            logger.debug("clean cache key {}", k);

            //BlockingCache 取不到值将加上读写锁的写锁
            //等待写入数据 不写入数据将会死锁 此段代码必须注掉
            Element e = cache.get(k);
            if(e==null)continue;
            PageInfo pageInfo = (PageInfo)e.getObjectValue();
            try {
                if(pageInfo.hasGzippedBody()){
                    logger.debug("pageInfo.getGzippedBody() {}", new String(pageInfo.getUngzippedBody()));
                }
            } catch (Exception e1) {
                e1.printStackTrace();
            }
            //手动释放写锁无效 
            //cache.releaseWriteLockOnKey(k);
        }
        cache.removeAll();

        logger.debug("clean over ");
        return true;
    }
}

默认情况下,SimplePageCachingFilter会对输出的内容进行gzip压缩,这样的结果会导致
nginx SSI失效,解决此问题,可以使用自定义的filter,重新其中的writeContent方法
所有内容全不进行gzip输出即可

import net.sf.ehcache.constructs.web.PageInfo;
import net.sf.ehcache.constructs.web.ResponseHeadersNotModifiableException;
import net.sf.ehcache.constructs.web.ResponseUtil;
import net.sf.ehcache.constructs.web.filter.SimplePageCachingFilter;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.BufferedOutputStream;
import java.io.IOException;
import java.io.OutputStream;

/**
 * Created on 2016/3/15.
 */
public class CacheFilter extends SimplePageCachingFilter {
    public static final Logger logger  = LoggerFactory.getLogger(CacheController.class);

    @Override
    protected void writeContent(final HttpServletRequest request,
                                final HttpServletResponse response, final PageInfo pageInfo)
            throws IOException, ResponseHeadersNotModifiableException {

        logger.debug("customer filter working");

        byte[] body;

        boolean shouldBodyBeZero = ResponseUtil.shouldBodyBeZero(request,
                pageInfo.getStatusCode());
        if (shouldBodyBeZero) {
            body = new byte[0];
        } else {
            body = pageInfo.getUngzippedBody();
        }

        response.setContentLength(body.length);
        OutputStream out = new BufferedOutputStream(response.getOutputStream());
        out.write(body);
        out.flush();
    }
}