/*
* Copyright 2002-2014 the original author or authors.
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package org.springframework.cache.guava;
import java.io.Serializable;
import java.util.concurrent.Callable;
import java.util.concurrent.ExecutionException;
import org.springframework.cache.Cache;
import org.springframework.cache.support.SimpleValueWrapper;
import org.springframework.util.Assert;
/**
* Spring {@link Cache} adapter implementation on top of a
* Guava {@link com.google.common.cache.Cache} instance.
*
* <p>Requires Google Guava 12.0 or higher.
*
* @author Juergen Hoeller
* @author Stephane Nicoll
* @since 4.0
*/
public class GuavaCache implements Cache {
private static final Object NULL_HOLDER = new NullHolder();
private final String name;
private final com.google.common.cache.Cache<Object, Object> cache;
private final boolean allowNullValues;
/**
* Create a {@link GuavaCache} instance with the specified name and the
* given internal {@link com.google.common.cache.Cache} to use.
* @param name the name of the cache
* @param cache the backing Guava Cache instance
*/
public GuavaCache(String name, com.google.common.cache.Cache<Object, Object> cache) {
this(name, cache, true);
}
/**
* Create a {@link GuavaCache} instance with the specified name and the
* given internal {@link com.google.common.cache.Cache} to use.
* @param name the name of the cache
* @param cache the backing Guava Cache instance
* @param allowNullValues whether to accept and convert {@code null}
* values for this cache
*/
public GuavaCache(String name, com.google.common.cache.Cache<Object, Object> cache, boolean allowNullValues) {
Assert.notNull(name, "Name must not be null");
Assert.notNull(cache, "Cache must not be null");
this.name = name;
this.cache = cache;
this.allowNullValues = allowNullValues;
}
@Override
public final String getName() {
return this.name;
}
@Override
public final com.google.common.cache.Cache<Object, Object> getNativeCache() {
return this.cache;
}
public final boolean isAllowNullValues() {
return this.allowNullValues;
}
@Override
public ValueWrapper get(Object key) {
Object value = this.cache.getIfPresent(key);
return toWrapper(value);
}
@Override
@SuppressWarnings("unchecked")
public <T> T get(Object key, Class<T> type) {
Object value = fromStoreValue(this.cache.getIfPresent(key));
if (value != null && type != null && !type.isInstance(value)) {
throw new IllegalStateException("Cached value is not of required type [" + type.getName() + "]: " + value);
}
return (T) value;
}
@Override
public void put(Object key, Object value) {
this.cache.put(key, toStoreValue(value));
}
@Override
public ValueWrapper putIfAbsent(Object key, final Object value) {
try {
PutIfAbsentCallable callable = new PutIfAbsentCallable(value);
Object result = this.cache.get(key, callable);
return (callable.called ? null : toWrapper(result));
}
catch (ExecutionException ex) {
throw new IllegalStateException(ex);
}
}
@Override
public void evict(Object key) {
this.cache.invalidate(key);
}
@Override
public void clear() {
this.cache.invalidateAll();
}
/**
* Convert the given value from the internal store to a user value
* returned from the get method (adapting {@code null}).
* @param storeValue the store value
* @return the value to return to the user
*/
protected Object fromStoreValue(Object storeValue) {
if (this.allowNullValues && storeValue == NULL_HOLDER) {
return null;
}
return storeValue;
}
/**
* Convert the given user value, as passed into the put method,
* to a value in the internal store (adapting {@code null}).
* @param userValue the given user value
* @return the value to store
*/
protected Object toStoreValue(Object userValue) {
if (this.allowNullValues && userValue == null) {
return NULL_HOLDER;
}
return userValue;
}
private ValueWrapper toWrapper(Object value) {
return (value != null ? new SimpleValueWrapper(fromStoreValue(value)) : null);
}
@SuppressWarnings("serial")
private static class NullHolder implements Serializable {
}
private class PutIfAbsentCallable implements Callable<Object> {
private final Object value;
private boolean called;
public PutIfAbsentCallable(Object value) {
this.value = value;
}
@Override
public Object call() throws Exception {
this.called = true;
return toStoreValue(this.value);
}
}
}