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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