Package org.springframework.cache.jcache

Source Code of org.springframework.cache.jcache.JCacheCache$NullHolder

/*
* Copyright 2002-2012 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.jcache;

import java.io.Serializable;

import javax.cache.Status;

import org.springframework.cache.Cache;
import org.springframework.cache.support.SimpleValueWrapper;
import org.springframework.util.Assert;

/**
* {@link org.springframework.cache.Cache} implementation on top of a
* {@link javax.cache.Cache} instance.
*
* @author Juergen Hoeller
* @since 3.2
*/
public class JCacheCache implements Cache {

  private static final Object NULL_HOLDER = new NullHolder();

  @SuppressWarnings("rawtypes")
  private final javax.cache.Cache cache;

  private final boolean allowNullValues;


  /**
   * Create an {@link org.springframework.cache.jcache.JCacheCache} instance.
   * @param jcache backing JCache Cache instance
   */
  public JCacheCache(javax.cache.Cache<?,?> jcache) {
    this(jcache, true);
  }

  /**
   * Create an {@link org.springframework.cache.jcache.JCacheCache} instance.
   * @param jcache backing JCache Cache instance
   * @param allowNullValues whether to accept and convert null values for this cache
   */
  public JCacheCache(javax.cache.Cache<?,?> jcache, boolean allowNullValues) {
    Assert.notNull(jcache, "Cache must not be null");
    Status status = jcache.getStatus();
    Assert.isTrue(Status.STARTED.equals(status),
        "A 'started' cache is required - current cache is " + status.toString());
    this.cache = jcache;
    this.allowNullValues = allowNullValues;
  }


  public String getName() {
    return this.cache.getName();
  }

  public javax.cache.Cache<?,?> getNativeCache() {
    return this.cache;
  }

  public boolean isAllowNullValues() {
    return this.allowNullValues;
  }

  @SuppressWarnings("unchecked")
  public ValueWrapper get(Object key) {
    Object value = this.cache.get(key);
    return (value != null ? new SimpleValueWrapper(fromStoreValue(value)) : null);
  }

  @SuppressWarnings("unchecked")
  public void put(Object key, Object value) {
    this.cache.put(key, toStoreValue(value));
  }

  @SuppressWarnings("unchecked")
  public void evict(Object key) {
    this.cache.remove(key);
  }

  public void clear() {
    this.cache.removeAll();
  }


  /**
   * Convert the given value from the internal store to a user value
   * returned from the get method (adapting <code>null</code>).
   * @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</code>).
   * @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 {
  }

}
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