利用spring的拦截器自定义缓存的实现实例代码

本文研究的主要是利用spring的拦截器自定义缓存的实现，具体实现代码如下所示。

Memcached 是一个高性能的分布式内存对象缓存系统，用于动态Web应用以减轻数据库负载。它通过在内存中缓存数据和对象来减少读取数据库的次数，从而提高动态、数据库驱动网站的速度。本文利用Memcached 的实例和spring的拦截器实现缓存自定义的实现。利用拦截器读取自定义的缓存标签，key值的生成策略。

自定义的Cacheable

package com.jeex.sci;
@Target(ElementType.METHOD)
@Retention(RetentionPolicy.RUNTIME)
@Inherited
@Documented
public @interface Cacheable {
	String namespace();
	String key() default "";
	int[] keyArgs() default {
	}
	;
	String[] keyProperties() default {
	}
	;
	String keyGenerator() default "";
	int expires() default 1800;
}

自定义的CacheEvict

package com.jeex.sci;
@Target(ElementType.METHOD)
@Retention(RetentionPolicy.RUNTIME)
@Inherited
@Documented
public @interface CacheEvict {
	String namespace();
	String key() default "";
	int[] keyArgs() default {
	}
	;
	String[] keyProperties() default {
	}
	;
	String keyGenerator() default "";
}

spring如果需要前后通知的话，一般会实现MethodInterceptor public Object invoke(MethodInvocation invocation) throws Throwable

public Object invoke(MethodInvocation invoction) throws Throwable {
	Method method = invoction.getMethod();
	Cacheable c = method.getAnnotation(Cacheable.class);
	if (c != null) {
		return handleCacheable(invoction, method, c);
	}
	CacheEvict ce = method.getAnnotation(CacheEvict.class);
	if (ce != null) {
		return handleCacheEvict(invoction, ce);
	}
	return invoction.proceed();
}

处理cacheable标签

private Object handleCacheable(MethodInvocation invoction, Method method,
    Cacheable c) throws Throwable {
	String key = getKey(invoction, KeyInfo.fromCacheable(c));
	if (key.equals("")) {
		if (log.isDebugEnabled()){
			log.warn("Empty cache key, the method is " + method);
		}
		return invoction.proceed();
	}
	long nsTag = (long) memcachedGet(c.namespace());
	if (nsTag == null) {
		nsTag = long.valueOf(System.currentTimeMillis());
		memcachedSet(c.namespace(), 24*3600, long.valueOf(nsTag));
	}
	key = makeMemcachedKey(c.namespace(), nsTag, key);
	Object o = null;
	o = memcachedGet(key);
	if (o != null) {
		if (log.isDebugEnabled()) {
			log.debug("CACHE HIT: Cache Key = " + key);
		}
	} else {
		if (log.isDebugEnabled()) {
			log.debug("CACHE MISS: Cache Key = " + key);
		}
		o = invoction.proceed();
		memcachedSet(key, c.expires(), o);
	}
	return o;
}

处理cacheEvit标签

private Object handleCacheEvict(MethodInvocation invoction,
    CacheEvict ce) throws Throwable {
  String key = getKey(invoction, KeyInfo.fromCacheEvict(ce));    

  if (key.equals("")) {
    if (log.isDebugEnabled()) {
      log.debug("Evicting " + ce.namespace());
    }
    memcachedDelete(ce.namespace());
  } else {
    Long nsTag = (Long) memcachedGet(ce.namespace());
    if (nsTag != null) {
      key = makeMemcachedKey(ce.namespace(), nsTag, key);
      if (log.isDebugEnabled()) {
        log.debug("Evicting " + key);
      }
      memcachedDelete(key);
    }
  }
  return invoction.proceed();
} 

根据参数生成key

//使用拦截到方法的参数生成参数
private String getKeyWithArgs(Object[] args, int[] argIndex) {
  StringBuilder key = new StringBuilder();
  boolean first = true;
  for (int index: argIndex) {
    if (index < 0 || index >= args.length) {
      throw new IllegalArgumentException("Index out of bound");
    }
    if (!first) {
      key.append(':');
    } else {
      first = false;
    }
    key = key.append(args[index]);
  }
  return key.toString();
} 

根据属性生成key

private String getKeyWithProperties(Object o, String props[])
    throws Exception {
  StringBuilder key = new StringBuilder();
  boolean first = true;
  for (String prop: props) {
    //把bean的属性转为获取方法的名字
    String methodName = "get"
        + prop.substring(0, 1).toUpperCase()
        + prop.substring(1);
    Method m = o.getClass().getMethod(methodName);
    Object r = m.invoke(o, (Object[]) null);
    if (!first) {
      key.append(':');
    } else {
      first = false;
    }
    key = key.append(r);
  }
  return key.toString();
} 

利用自定义的生成器生成key

//使用生成器生成key
private String getKeyWithGenerator(MethodInvocation invoction, String keyGenerator)
    throws Exception {
  Class<?> ckg = Class.forName(keyGenerator);
  CacheKeyGenerator ikg = (CacheKeyGenerator)ckg.newInstance();
  return ikg.generate(invoction.getArguments());
} 

保存key信息的帮助类

private static class KeyInfo {
	String key;
	int[] keyArgs;
	String keyProperties[];
	String keyGenerator;
	static KeyInfo fromCacheable(Cacheable c) {
		KeyInfo ki = new KeyInfo();
		ki.key = c.key();
		ki.keyArgs = c.keyArgs();
		ki.keyGenerator = c.keyGenerator();
		ki.keyProperties = c.keyProperties();
		return ki;
	}
	static KeyInfo fromCacheEvict(CacheEvict ce) {
		KeyInfo ki = new KeyInfo();
		ki.key = ce.key();
		ki.keyArgs = ce.keyArgs();
		ki.keyGenerator = ce.keyGenerator();
		ki.keyProperties = ce.keyProperties();
		return ki;
	}
	String key() {
		return key;
	}
	int[] keyArgs() {
		return keyArgs;
	}
	String[] keyProperties() {
		return keyProperties;
	}
	String keyGenerator() {
		return keyGenerator;
	}
}

参数的设置

//使用参数设置key
@Cacheable(namespace="BlackList", keyArgs={0, 1})
public int anotherMethond(int a, int b) {
  return 100;
} 

测试类：

package com.jeex.sci.test;
import net.spy.memcached.MemcachedClient;
import org.junit.Test;
import org.springframework.context.ApplicationContext;
import org.springframework.context.support.FileSystemXmlApplicationContext;
public class TestMain {
	public static void main(String args[]) throws InterruptedException{
		ApplicationContext ctx = new FileSystemXmlApplicationContext("/src/test/resources/beans.xml");
		MemcachedClient mc = (MemcachedClient) ctx.getBean("memcachedClient");
		BlackListDaoImpl dao = (BlackListDaoImpl)ctx.getBean("blackListDaoImpl");
		while (true) {
			System.out.println("################################GETTING START######################");
			mc.flush();
			BlackListQuery query = new BlackListQuery(1, "222.231.23.13");
			dao.searchBlackListCount(query);
			dao.searchBlackListCount2(query);
			BlackListQuery query2 = new BlackListQuery(1, "123.231.23.14");
			dao.anotherMethond(333, 444);
			dao.searchBlackListCount2(query2);
			dao.searchBlackListCount3(query2);
			dao.evict(query);
			dao.searchBlackListCount2(query);
			dao.evictAll();
			dao.searchBlackListCount3(query2);
			Thread.sleep(300);
		}
	}
}

总结

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