MethodCacheInterceptor.java

package com.jrails.modules.spring.cache.aop;

import java.io.Serializable;

import net.sf.ehcache.Cache;
import net.sf.ehcache.Element;

import org.aopalliance.intercept.MethodInterceptor;
import org.aopalliance.intercept.MethodInvocation;
import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
import org.springframework.beans.factory.InitializingBean;
import org.springframework.util.Assert;

/**
 * 
 * @author arden
 */
public class MethodCacheInterceptor implements MethodInterceptor, InitializingBean
{
    private static final Log logger = LogFactory.getLog(MethodCacheInterceptor.class);

    private Cache cache;

    public void setCache(Cache cache) {
        this.cache = cache;
    }

    public MethodCacheInterceptor() {
        super();
    }

    /**
     * 拦截Service/DAO的方法，并查找该结果是否存在，如果存在就返回cache中的值，
     * 否则，返回数据库查询结果，并将查询结果放入cache
     */
    public Object invoke(MethodInvocation invocation) throws Throwable {
        String targetName = invocation.getThis().getClass().getName();
        String methodName = invocation.getMethod().getName();
        Object[] arguments = invocation.getArguments();
        Object result;

        logger.debug("Find object from cache is " + cache.getName());

        String cacheKey = getCacheKey(targetName, methodName, arguments);
        Element element = cache.get(cacheKey);

        if (element == null) {
            logger.debug("Hold up method , Get method result and create cache........!");
            result = invocation.proceed();
            element = new Element(cacheKey, (Serializable) result);
            cache.put(element);
        }
        return element.getValue();
    }

    /**
     * 获得cache key的方法，cache key是Cache中一个Element的唯一标识
     * cache key包括 包名+类名+方法名，如com.co.cache.service.UserServiceImpl.getAllUser
     */
    private String getCacheKey(String targetName, String methodName, Object[] arguments) {
        StringBuffer sb = new StringBuffer();
        sb.append(targetName).append(".").append(methodName);
        if ((arguments != null) && (arguments.length != 0)) {
            for (int i = 0; i < arguments.length; i++) {
                sb.append(".").append(arguments[i]);
            }
        }
        return sb.toString();
    }

    /**
     * implement InitializingBean，检查cache是否为空
     */
    public void afterPropertiesSet() throws Exception {
        Assert.notNull(cache, "Need a cache. Please use setCache(Cache) create it.");
    }

}