理一理ehcache-spring-annotations快取的Key生成
阿新 • • 發佈：2019-02-02
pom.xml
<!-- ehcache -->
<dependency>
<groupId>com.googlecode.ehcache-spring-annotations</groupId>
<artifactId>ehcache-spring-annotations</artifactId>
<version>1.2.0</version>
</dependency>
<dependency 說明:
本文說的不是Spring Cache, ehcache-spring-annotations需要配合ehcache使用. 在程式碼中只是加註解(@Cacheable)而已
@Cacheable(cacheName="myCache" @Cacheable的全名: com.googlecode.ehcache.annotations.Cacheable,不要跟Spring Cache的同名註解(org.springframework.cache.annotation.Cacheable)混為一體
@Cacheable
@Target(value = {ElementType.METHOD})
@Retention(value = RetentionPolicy.RUNTIME)
@Inherited
@Documented
public @interface Cacheable {
public String cacheName();
public boolean cacheNull() default true;
public DecoratedCacheType decoratedCacheType() default DecoratedCacheType.NONE;
@Deprecated
public boolean selfPopulating() default false;
public int selfPopulatingTimeout() default 0;
public long refreshInterval() default 60000L;
public String keyGeneratorName() default "";
public String exceptionCacheName() default "";
public KeyGenerator keyGenerator() default @KeyGenerator(name = "");
public String cacheableInteceptorName() default "";
public String resolverFactoryName() default "";
public ResolverFactory resolverFactory() default @ResolverFactory(name = "");
}說明:
keyGeneratorName和keyGenerator在下一篇中詳細說說.refreshInterval預設是一分鐘(60000L).一般只需要為cacheName設定一個值
快取的Key
記憶體快取大多都是key-value鍵值儲存,註解中的keyGeneratorName和keyGenerator是可以指定一個自定義key生成策略.不指定預設使用的是:com.googlecode.ehcache.annotations.key.HashCodeCacheKeyGenerator
package com.googlecode.ehcache.annotations.key;
/**
* @author Eric Dalquist
* @version $Revision: 656 $
*/
public class HashCodeCacheKeyGenerator extends AbstractHashingCacheKeyGenerator<HashCodeCacheKeyGenerator.LongGenerator, Long> {}這裡都不一一列出類的層次結構了.有興趣的可以翻牆去下原始碼.下面是具體作生成的方法
package com.googlecode.ehcache.annotations.key;
import java.io.Serializable;
import java.lang.reflect.Method;
import java.util.IdentityHashMap;
import java.util.Map;
import org.aopalliance.intercept.MethodInvocation;
/**
* Base class for cache key generators. Handles common logic for including/excluding the method
* signature from key generation. Also provides support for avoiding circular references for key
* generators that traverse the argument object graph via the {@link #register(Object)} and
* {@link #unregister(Object)} APIs
*
* @author Eric Dalquist
* @version $Revision: 656 $
*/
public abstract class AbstractCacheKeyGenerator<T extends Serializable> implements CacheKeyGenerator<T> {
//ETC
/* (non-Javadoc)
* @see com.googlecode.ehcache.annotations.key.CacheKeyGenerator#generateKey(org.aopalliance.intercept.MethodInvocation)
*/
public T generateKey(MethodInvocation methodInvocation) {
final Object[] arguments = methodInvocation.getArguments();
if (this.includeMethod) {
final Method method = methodInvocation.getMethod();
final Class<?> declaringClass = method.getDeclaringClass();
final String name = method.getName();
final Class<?> returnType = method.getReturnType();
if (this.includeParameterTypes) {
final Class<?>[] parameterTypes = method.getParameterTypes();
return this.generateKey(declaringClass, name, returnType, parameterTypes, arguments);
}
return this.generateKey(declaringClass, name, returnType, arguments);
}
try {
return this.generateKey(arguments);
}
finally {
if (this.checkforCycles) {
//Cleanup our thread local data
REGISTRY.remove();
}
}
}
}說明:
MethodInvocation 在aopalliance-1.0.jar中的org.aopalliance.intercept包下,MethodInvocation 繼承了Invocation可以拿到方法的引數值(getArguments),其它的都是反射包下的Method可以拿到的
method.getName()返回方法的名字
method.getReturnType()返回方法的返回值型別
method.getParameterTypes()返回方法的引數型別
在程式碼中定位一個方法的元素都有了:類全名 + 方法的簽名(返回值 + 方法名 + 引數列表 )
引數的值不同也可以生成唯一的key
package com.googlecode.ehcache.annotations.interceptor;
/**
* Intercepter that handles invocations on methods annotated with {@link Cacheable} or {@link TriggersRemove}.
*
* @author Eric Dalquist
* @version $Revision: 681 $
*/
public class EhCacheInterceptor implements MethodInterceptor {
//ETC
/**
* Creates a {@link Serializable} cache key from the {@link MethodInvocation} and configuration attributes.
*
* @param methodInvocation Invocation to build the key for
* @param methodAttribute Configuration for the invoked method
* @return Generated cache key, must not return null.
*/
protected Serializable generateCacheKey(MethodInvocation methodInvocation, final MethodAttribute methodAttribute) {
final CacheKeyGenerator<? extends Serializable> cacheKeyGenerator = methodAttribute.getCacheKeyGenerator();
final ParameterMask parameterMask = methodAttribute.getCacheKeyParameterMask();
if (parameterMask.shouldMask()) {
methodInvocation = new ParameterFilteringMethodInvocation(methodInvocation, parameterMask);
}
final Serializable cacheKey = cacheKeyGenerator.generateKey(methodInvocation);
this.logger.debug("Generated key '{}' for invocation: {}", cacheKey, methodInvocation);
return cacheKey;
}
}debug日誌
Generated key '-27052115907236245' for invocation: ReflectiveMethodInvocation:
public net.htage.forum.entity.ForumPermissions net.htage.forum.impl.service.spring.EhcacheCacheBox.getPermissions(net.htage.forum.entity.define.GlobalPermissionEnum);
target is of class [net.htage.forum.impl.service.spring.EhcacheCacheBox]
Generated key '-27052113702228882' for invocation: ReflectiveMethodInvocation:
public net.htage.forum.entity.ForumPermissions net.htage.forum.impl.service.spring.EhcacheCacheBox.getPermissions(net.htage.forum.entity.define.GlobalPermissionEnum);
target is of class [net.htage.forum.impl.service.spring.EhcacheCacheBox]ReflectiveMethodInvocation :
可見性修飾符(public) +
返回值型別(net.htage.forum.entity.ForumPermissions) +
方法全名(net.htage.forum.impl.service.spring.EhcacheCacheBox.getPermissions) +
( +
引數型別列表(net.htage.forum.entity.define.GlobalPermissionEnum) +
);
也說明如果一個方法沒有引數，第一次呼叫生成key並快取，以後的N次呼叫都是同一份快取. 在debug日誌中只能搜到一份記錄
Generated key '-937817555943' for invocation: ReflectiveMethodInvocation:
public java.util.List net.htage.forum.impl.service.spring.EhcacheCacheBox.getAllLevel();
target is of class [net.htage.forum.impl.service.spring.EhcacheCacheBox]對於全域性的配置來說沒問題, N次呼叫後都是一樣的結果. 但是？具有時間性的方法(同時它沒有引數)則不然。第二次呼叫到第100呼叫之間資料肯定有變化的.哪這個預設的key生成策略還能用嗎？