背景
这是我的（简化的）GenericDao接口，可以通过任何DomainDao实现：
GenericDao.java
@NoRepositoryBean
public interface GenericDao<E extends Persistable<K>, K extends Serializable> extends JpaRepository<E, K> {
public List<E> findAll();
public E persist(E entity);
}
GenericDaoImpl.java
public class GenericDaoImpl<E extends Persistable<K>, K extends Serializable> extends SimpleJpaRepository<E, K> implements GenericDao<E, K> {
private final JpaEntityInformation<E, ?> entityInformation;
private final EntityManager em;
private final Class<E> type;
public GenericDaoImpl(JpaEntityInformation<E, ?> entityInformation, EntityManager em) {
super(entityInformation, em);
this.entityInformation = entityInformation;
this.em = em;
this.type = entityInformation.getJavaType();
}
@Override
public List<E> findAll() {
return super.findAll();
}
@Override
@Transactional
public E persist(E entity) {
if (entityInformation.isNew(entity) || !EntityUtils.isPrimaryKeyGenerated(type) && !em.contains(entity)) {
em.persist(entity);
}
return entity;
}
}
例如，要管理域
Foo和Bar，只需创建两个接口，如下所示：FooDao.java
public interface FooDao extends GenericDao<Foo, Integer> {
}
BarDao.java
public interface BarDao extends GenericDao<Bar, Integer> {
}
@Autowired的Spring注释将自动实例化具有良好实体和主键类型的GenericDaoImpl。问题
我现在正在尝试使用EhCache和EhCache Spring Annotations模型在DAO上添加一个缓存过程。
GenericDao.java
@NoRepositoryBean
public interface GenericDao<E extends Persistable<K>, K extends Serializable> extends JpaRepository<E, K> {
@Cacheable(cacheName = "dao")
public List<E> findAll();
@TriggersRemove(cacheName = "dao")
public E persist(E entity);
}
applicationContext.xml
<ehcache:annotation-driven cache-manager="ehCacheManager" />
<bean id="ehCacheManager" class="org.springframework.cache.ehcache.EhCacheManagerFactoryBean" />
ehcache.xml
<cache name="dao"
eternal="false"
maxElementsInMemory="10000"
overflowToDisk="false"
timeToIdleSeconds="86400"
timeToLiveSeconds="86400"
memoryStoreEvictionPolicy="LFU" />
使用
GenericDao的问题在于，缓存应该彼此独立地管理每个DomainDao。例如，在当前配置下，如果我先调用fooDao.findAll()，然后再调用barDao.persist(new Bar())，则由于使用了相同的缓存（即fooDao.findAll()），因此将重置<cache name="dao" />生成的缓存，因为没错步道
我尝试实现自己的
CacheKeyGenerator，这将考虑调用DomainDao的类型：applicationContext.xml
<ehcache:annotation-driven cache-manager="ehCacheManager" default-cache-key-generator="daoCacheKeyGenerator" />
<bean id="ehCacheManager" class="org.springframework.cache.ehcache.EhCacheManagerFactoryBean" />
<bean id="daoCacheKeyGenerator" class="myapp.dao.support.DaoCacheKeyGenerator" />
DaoCacheKeyGenerator.java
public class DaoCacheKeyGenerator implements CacheKeyGenerator<DaoCacheKey> {
@Override
public DaoCacheKey generateKey(MethodInvocation methodInvocation) {
Class<?> clazz = methodInvocation.getThis().getClass().getInterfaces()[0];
Method method = methodInvocation.getMethod();
String methodName = method.getName();
Class<?>[] parameterClasses = method.getParameterTypes();
return new DaoCacheKey(clazz, methodName, parameterClasses);
}
@Override
public DaoCacheKey generateKey(Object... data) {
return null;
}
}
DaoCacheKey.java
public class DaoCacheKey implements Serializable {
private static final long serialVersionUID = 338466521373614710L;
private Class<?> clazz;
private String methodName;
private Class<?>[] parameterClasses;
public DaoCacheKey(Class<?> clazz, String methodName, Class<?>[] parameterClasses) {
this.clazz = clazz;
this.methodName = methodName;
this.parameterClasses = parameterClasses;
}
@Override
public boolean equals(Object obj) { // <-- breakpoint
if (obj instanceof DaoCacheKey) {
DaoCacheKey other = (DaoCacheKey) obj;
if (clazz.equals(other.clazz)) {
// if @TriggersRemove, reset any cache generated by a find* method of the same DomainDao
boolean removeCache = !methodName.startsWith("find") && other.methodName.startsWith("find");
// if @Cacheable, check if the result has been previously cached
boolean getOrCreateCache = methodName.equals(other.methodName) && Arrays.deepEquals(parameterClasses, other.parameterClasses);
return removeCache || getOrCreateCache;
}
}
return false;
}
@Override
public int hashCode() { // <-- breakpoint
return super.hashCode();
}
}
上述
DaoCacheKey的问题在于，equals方法永远不会被调用（程序至少不会中断），而hashCode方法却不会调用，因此该算法无法应用。题
有没有人已经管理过这样的缓存？如果是，怎么办？我的尝试是否有意义？如果是，如何调用
equals方法而不是hashCode方法？通过扩展现有的CacheKeyGenerator？如果是，那一个？ 最佳答案
这是我最终采用的工作解决方案。精度很低：我的域都实现了Spring的Persistable接口。而且，由于我正在使用反射，因此我不确定缓存过程所节省的时间不会减少多少...
applicationContext.xml
<ehcache:annotation-driven cache-manager="ehCacheManager" default-cache-key-generator="daoCacheKeyGenerator" />
<bean id="ehCacheManager" class="org.springframework.cache.ehcache.EhCacheManagerFactoryBean" />
<bean id="daoCacheKeyGenerator" class="myapp.dao.support.cache.DaoCacheKeyGenerator" />
DaoCacheKeyGenerator.java（使用gentyref库）
public class DaoCacheKeyGenerator implements CacheKeyGenerator<DaoCacheKey> {
@SuppressWarnings("unchecked")
@Override
public DaoCacheKey generateKey(MethodInvocation methodInvocation) {
Method method = methodInvocation.getMethod();
Class<? extends GenericDao<?, ?>> daoType = (Class<? extends GenericDao<?, ?>>) methodInvocation.getThis().getClass().getInterfaces()[0];
Class<? extends Persistable<?>> domainType = getDomainType(daoType);
String methodName = method.getName();
Class<?>[] parameterTypes = method.getParameterTypes();
Object[] parameters = methodInvocation.getArguments();
return new DaoCacheKey(domainType, methodName, parameterTypes, parameters);
}
@SuppressWarnings("unchecked")
private Class<? extends Persistable<?>> getDomainType(Class<?> daoType) {
Type baseDaoType = GenericTypeReflector.getExactSuperType(daoType, GenericDao.class);
ParameterizedType parameterizedBaseDaoType = (ParameterizedType) baseDaoType;
return (Class<? extends Persistable<?>>) parameterizedBaseDaoType.getActualTypeArguments()[0];
}
@Override
public DaoCacheKey generateKey(Object... data) {
return null;
}
}
DaoCacheKey.java
public class DaoCacheKey implements Serializable {
private static final long serialVersionUID = 338466521373614710L;
private Class<? extends Persistable<?>> domainType;
private String methodName;
private Class<?>[] parameterTypes;
private Object[] parameters;
public DaoCacheKey(Class<? extends Persistable<?>> domainType, String methodName, Class<?>[] parameterTypes, Object[] parameters) {
this.domainType = domainType;
this.methodName = methodName;
this.parameterTypes = parameterTypes;
this.parameters = parameters;
}
public Class<? extends Persistable<?>> getDomainType() {
return domainType;
}
@Override
public boolean equals(Object obj) {
return this == obj || obj instanceof DaoCacheKey && hashCode() == obj.hashCode();
}
@Override
public int hashCode() {
return Arrays.hashCode(new Object[] { domainType, methodName, Arrays.asList(parameterTypes), Arrays.asList(parameters) });
}
}
ehcache.xml
<cache name="dao"
eternal="false"
maxElementsInMemory="10000"
overflowToDisk="false"
timeToIdleSeconds="86400"
timeToLiveSeconds="86400"
memoryStoreEvictionPolicy="LFU">
<cacheEventListenerFactory class="myapp.dao.support.cache.DaoCacheEventListenerFactory" />
</cache>
DaoCacheEventListenerFactory.java
public class DaoCacheEventListenerFactory extends CacheEventListenerFactory {
@Override
public CacheEventListener createCacheEventListener(Properties properties) {
return new DaoCacheEventListener();
}
}
DaoCacheEventListener.java
public class DaoCacheEventListener implements CacheEventListener {
@SuppressWarnings("unchecked")
@Override
public void notifyElementRemoved(Ehcache cache, Element element) throws CacheException {
DaoCacheKey daoCachekey = (DaoCacheKey) element.getKey();
List<Class<? extends Persistable<?>>> impacts = getOneToManyImpacts(daoCachekey.getDomainType());
for (DaoCacheKey daoCachedkey : (List<DaoCacheKey>) cache.getKeys()) {
if (impacts.contains(daoCachedkey.getDomainType())) {
cache.remove(daoCachedkey);
}
}
}
@SuppressWarnings("unchecked")
private List<Class<? extends Persistable<?>>> getOneToManyImpacts(Class<? extends Persistable<?>> domainType) {
List<Class<? extends Persistable<?>>> impacts = new ArrayList<Class<? extends Persistable<?>>>();
impacts.add(domainType);
for (Method method : domainType.getDeclaredMethods()) {
if (method.isAnnotationPresent(OneToMany.class)) {
ParameterizedType parameterizedType = (ParameterizedType) method.getGenericReturnType();
Class<? extends Persistable<?>> impactedDomainType = (Class<? extends Persistable<?>>) parameterizedType.getActualTypeArguments()[0];
if (!impacts.contains(impactedDomainType)) {
impacts.addAll(getOneToManyImpacts(impactedDomainType));
}
}
}
return impacts;
}
@Override
public void notifyElementPut(Ehcache cache, Element element) throws CacheException {
}
@Override
public void notifyElementUpdated(Ehcache cache, Element element) throws CacheException {
}
@Override
public void notifyElementExpired(Ehcache cache, Element element) {
}
@Override
public void notifyElementEvicted(Ehcache cache, Element element) {
}
@Override
public void notifyRemoveAll(Ehcache cache) {
}
@Override
public void dispose() {
}
@Override
public Object clone() throws CloneNotSupportedException {
return super.clone();
}
}
希望对您有所帮助
关于java - 尝试通过Spring和扩展了Hibernate的JpaRepository的自定义GenericDao接口(interface)使用EhCache，我们在Stack Overflow上找到一个类似的问题：https://stackoverflow.com/questions/14259165/