com.ocpsoft.pretty.faces.el.LazyBeanNameFinder Maven / Gradle / Ivy

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/*
 * Copyright 2010 Lincoln Baxter, III
 * 
 * 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.ocpsoft.pretty.faces.el;

import java.util.ArrayList;
import java.util.Iterator;
import java.util.List;

import javax.servlet.ServletContext;

import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;

import com.ocpsoft.pretty.faces.spi.ELBeanNameResolver;
import com.ocpsoft.pretty.faces.util.ServiceLoader;

/**
 * 
 * Class implementing lazy resolving of bean names.
 * 
 * 
 * This class is typically created once and is than supplied to
 * {@link LazyExpression} instances in the
 * {@link LazyExpression#LazyExpression(LazyBeanNameFinder, Class, String)}
 * constructor.
 * 
 * 
 * @author Christian Kaltepoth
 */
public class LazyBeanNameFinder
{

   private final static Log log = LogFactory.getLog(LazyBeanNameFinder.class);

   /**
    * List of all resolvers. Initialized once on object creation
    */
   private final List resolvers = new ArrayList();

   /**
    * Creates a new {@link LazyBeanNameFinder}. The constructor will find all
    * implementations of {@link ELBeanNameResolver} by using the
    * {@link ServiceLoader} mechanism.
    * 
    * @param servletContext The servlet context
    */
   public LazyBeanNameFinder(ServletContext servletContext)
   {

      // we use the context classloader
      ClassLoader classLoader = Thread.currentThread().getContextClassLoader();

      // fallback, if no context classloader exists
      if (classLoader == null)
      {
         classLoader = this.getClass().getClassLoader();
      }

      // find resolvers via ServiceLoader
      Iterator beanNameFinderIterator = ServiceLoader.load(ELBeanNameResolver.class).iterator();

      // call init() method on all resolvers
      while (beanNameFinderIterator.hasNext())
      {

         // log resolver name
         ELBeanNameResolver resolver = beanNameFinderIterator.next();
         if (log.isTraceEnabled())
         {
            log.trace("Initializing BeanNameResolver: " + resolver.getClass().getName());
         }

         try
         {

            // call the resolver's init() method
            boolean initialized = resolver.init(servletContext, classLoader);

            // register resolver, if his initialization has completed
            if (initialized)
            {
               resolvers.add(resolver);
            }

         }
         catch (ClassFormatError e)
         {
            /*
             * Seems to happen for CDI classes when using GWT
             * In this case just ignore the resolver
             * See: http://code.google.com/p/prettyfaces/issues/detail?id=101
             */
            log.warn("Failed to initialize "+resolver.getClass().getSimpleName()+": "+e.getMessage());
         }
      }
   }

   /**
    * Find the bean name of the supplied class. This method will try to resolve
    * the bean name by calling all registered implementations of
    * {@link ELBeanNameResolver}. This method will either return the resolved name
    * or throw an {@link IllegalStateException}, if no resolver knows the name
    * of the bean.
    * 
    * @param clazz The class of the bean
    * @return The resolved bean name
    * @throws IllegalStateException If the name of the bean cannot be resolved
    */
   public String findBeanName(Class clazz) throws IllegalStateException
   {

      // process all resolvers
      for (ELBeanNameResolver resolver : resolvers)
      {

         // try to resolve bean name with current resolver
         String name = resolver.getBeanName(clazz);

         // return the bean name, if the resolver was successful
         if (name != null)
         {
            return name;
         }

      }

      // No resolver knows the name of the bean
      throw new IllegalStateException("Cannot find name of bean '" + clazz.getName()
            + "'! You should place a @URLBeanName annotation on this class to let PrettyFaces know its name.");

   }

}