利用spring的拦截器自定义缓存的实现

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);
}
}
}