content: /*
   * Copyright 2002-2005 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 com.alibaba.spring.core.convert.support;
  
  import org.apache.commons.logging.Log;
  import org.apache.commons.logging.LogFactory;
  import org.springframework.beans.factory.config.ConfigurableBeanFactory;
  import org.springframework.beans.factory.config.SingletonBeanRegistry;
  import org.springframework.context.ConfigurableApplicationContext;
  import org.springframework.core.convert.ConversionService;
  import org.springframework.format.support.DefaultFormattingConversionService;
  
  import static com.alibaba.spring.util.BeanUtils.getBeanIfAvailable;
  import static com.alibaba.spring.util.BeanUtils.isBeanPresent;
  import static java.lang.String.format;
  import static org.springframework.context.ConfigurableApplicationContext.CONVERSION_SERVICE_BEAN_NAME;
  
  /**
   * The class to resolve a singleton instance of {@link ConversionService} that may be retrieved from Spring
   * {@link ConfigurableApplicationContext#CONVERSION_SERVICE_BEAN_NAME built-in bean} or create a new one.
   *
   * @see ConversionService
   * @see ConfigurableApplicationContext#CONVERSION_SERVICE_BEAN_NAME
   * @see SingletonBeanRegistry#registerSingleton(String, Object)
   * @since 1.0.6
   */
  public class ConversionServiceResolver {
  
      /**
       * The bean name of a singleton instance of {@link ConversionService} has been resolved
       */
      public static final String RESOLVED_CONVERSION_SERVICE_BEAN_NAME = "resolved-" + CONVERSION_SERVICE_BEAN_NAME;
  
      private final Log logger = LogFactory.getLog(getClass());
  
      private final ConfigurableBeanFactory beanFactory;
  
      public ConversionServiceResolver(ConfigurableBeanFactory beanFactory) {
          this.beanFactory = beanFactory;
      }
  
      public ConversionService resolve() {
          return resolve(true);
      }
  
      public ConversionService resolve(boolean requireToRegister) {
  
          ConversionService conversionService = getResolvedBeanIfAvailable();
  
          if (conversionService == null) { // If not resolved, try to get from ConfigurableBeanFactory
              conversionService = getFromBeanFactory();
          }
  
          if (conversionService == null) { // If not found, try to get the bean from BeanFactory
              debug("The conversionService instance can't be found in Spring ConfigurableBeanFactory.getConversionService()");
              conversionService = getIfAvailable();
          }
          if (conversionService == null) { // If not found, will create an instance of ConversionService as default
              conversionService = createDefaultConversionService();
          }
  
          if (!isBeanPresent(beanFactory, RESOLVED_CONVERSION_SERVICE_BEAN_NAME, ConversionService.class)
                  && requireToRegister) { // To register a singleton into SingletonBeanRegistry(ConfigurableBeanFactory)
              beanFactory.registerSingleton(RESOLVED_CONVERSION_SERVICE_BEAN_NAME, conversionService);
          }
  
          return conversionService;
      }
  
      private ConversionService getResolvedBeanIfAvailable() {
          return getBeanIfAvailable(beanFactory, RESOLVED_CONVERSION_SERVICE_BEAN_NAME, ConversionService.class);
      }
  
      private ConversionService getFromBeanFactory() {
          return beanFactory.getConversionService();
      }
  
      private ConversionService getIfAvailable() {
          return getBeanIfAvailable(beanFactory, CONVERSION_SERVICE_BEAN_NAME, ConversionService.class);
      }
  
      /**
       * Create the instance of {@link DefaultFormattingConversionService} as the default,
       * this method is allow to be override by the sub-class.
       *
       * @return non-null
       */
      protected ConversionService createDefaultConversionService() {
          return new DefaultFormattingConversionService();
      }
  
      private void debug(String message, Object... args) {
          if (logger.isDebugEnabled()) {
              logger.debug(format(message, args));
          }
      }
  }
  