org.springmodules.cache.guava.GuavaCache.java Source code

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Here is the source code for org.springmodules.cache.guava.GuavaCache.java

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/*
 * Copyright 2013 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.springmodules.cache.guava;

import com.google.common.cache.CacheBuilder;
import com.google.common.cache.CacheBuilderSpec;
import org.springframework.cache.Cache;
import org.springframework.cache.support.SimpleValueWrapper;

import java.io.Serializable;

import static com.google.common.base.Preconditions.checkNotNull;

/**
 * Simple {@link Cache} implementation backed by {@link com.google.common.cache.Cache}.
 * @author Omar Irbouh
 * @since 1.0
 */
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> store;

    private final boolean allowNullValues;

    /**
     * Create a new GuavaCache with the specified name.
     * @param name the name of the cache
     */
    public GuavaCache(String name) {
        this(name, CacheBuilder.newBuilder(), true);
    }

    /**
     * Create a new GuavaCache with the specified name.
     * @param name the name of the cache
     * @param allowNullValues whether to accept and convert null values for this cache
     */
    public GuavaCache(String name, boolean allowNullValues) {
        this(name, CacheBuilder.newBuilder(), allowNullValues);
    }

    /**
     * Create a new GuavaCache using the specified name and {@link CacheBuilderSpec specification}
     * @param name the name of the cache
     * @param spec the cache builder specification to use to build he cache
     */
    public GuavaCache(String name, CacheBuilderSpec spec, boolean allowNullValues) {
        this(name, CacheBuilder.from(spec), allowNullValues);
    }

    /**
     * Create a new GuavaCache using the specified name and {@link CacheBuilderSpec specification}
     * @param name the name of the cache
     * @param builder the cache builder to use to build the cache
     */
    public GuavaCache(String name, CacheBuilder<Object, Object> builder, boolean allowNullValues) {
        this.name = checkNotNull(name, "name is required");
        this.allowNullValues = allowNullValues;
        this.store = builder.build();
    }

    @Override
    public String getName() {
        return this.name;
    }

    public boolean isAllowNullValues() {
        return allowNullValues;
    }

    @Override
    public com.google.common.cache.Cache<Object, Object> getNativeCache() {
        return this.store;
    }

    @Override
    public ValueWrapper get(Object key) {
        Object value = this.store.getIfPresent(key);
        return (value != null ? new SimpleValueWrapper(fromStoreValue(value)) : null);
    }

    @Override
    public void put(Object key, Object value) {
        this.store.put(key, toStoreValue(value));
    }

    @Override
    public void evict(Object key) {
        this.store.invalidate(key);
    }

    @Override
    public void clear() {
        this.store.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;
    }

    @SuppressWarnings("serial")
    private static class NullHolder implements Serializable {

    }

}