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   /*
    * Copyright 2012 The Netty Project
    *
    * The Netty Project licenses this file to you 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.jboss.netty.handler.codec.serialization;
  
  import java.lang.ref.Reference;
  import java.util.HashMap;
  import java.util.concurrent.ConcurrentHashMap;
  
  public final class ClassResolvers {
  
      /**
       * cache disabled
       * @param classLoader - specific classLoader to use, or null if you want to revert to default
       * @return new instance of class resolver
       */
      public static ClassResolver cacheDisabled(ClassLoader classLoader) {
          return new ClassLoaderClassResolver(defaultClassLoader(classLoader));
      }
  
      /**
       * non-agressive non-concurrent cache
       * good for non-shared default cache
       *
       * @param classLoader - specific classLoader to use, or null if you want to revert to default
       * @return new instance of class resolver
       */
      public static ClassResolver weakCachingResolver(ClassLoader classLoader) {
          return new CachingClassResolver(
                  new ClassLoaderClassResolver(defaultClassLoader(classLoader)),
                  new WeakReferenceMap<String, Class<?>>(new HashMap<String, Reference<Class<?>>>()));
      }
  
      /**
       * agressive non-concurrent cache
       * good for non-shared cache, when we're not worried about class unloading
       *
       * @param classLoader - specific classLoader to use, or null if you want to revert to default
       * @return new instance of class resolver
       */
      public static ClassResolver softCachingResolver(ClassLoader classLoader) {
          return new CachingClassResolver(
                  new ClassLoaderClassResolver(defaultClassLoader(classLoader)),
                  new SoftReferenceMap<String, Class<?>>(new HashMap<String, Reference<Class<?>>>()));
      }
  
      /**
       * non-agressive concurrent cache
       * good for shared cache, when we're worried about class unloading
       *
       * @param classLoader - specific classLoader to use, or null if you want to revert to default
       * @return new instance of class resolver
       */
      public static ClassResolver weakCachingConcurrentResolver(ClassLoader classLoader) {
          return new CachingClassResolver(
                  new ClassLoaderClassResolver(defaultClassLoader(classLoader)),
                  new WeakReferenceMap<String, Class<?>>(new ConcurrentHashMap<String, Reference<Class<?>>>()));
      }
  
      /**
       * agressive concurrent cache
       * good for shared cache, when we're not worried about class unloading
       *
       * @param classLoader - specific classLoader to use, or null if you want to revert to default
       * @return new instance of class resolver
       */
      public static ClassResolver softCachingConcurrentResolver(ClassLoader classLoader) {
          return new CachingClassResolver(
                  new ClassLoaderClassResolver(defaultClassLoader(classLoader)),
                  new SoftReferenceMap<String, Class<?>>(new ConcurrentHashMap<String, Reference<Class<?>>>()));
      }
  
      static ClassLoader defaultClassLoader(ClassLoader classLoader) {
          if (classLoader != null) {
              return classLoader;
          }
  
          final ClassLoader contextClassLoader = Thread.currentThread().getContextClassLoader();
          if (contextClassLoader != null) {
              return contextClassLoader;
          }
  
          return ClassResolvers.class.getClassLoader();
      }
  
      private ClassResolvers() {
          // Unused
     }
 }