com.ocpsoft.pretty.faces.el.resolver.SpringBeanNameResolver 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.resolver;

import java.lang.reflect.InvocationTargetException;
import java.lang.reflect.Method;

import javax.servlet.ServletContext;

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

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

/**
 * 
 * Implementation of {@link ELBeanNameResolver} that will resolve names of beans
 * managed by Spring.
 * 
 * 
 * This resolver will get the WebApplicationContext from the
 * {@link ServletContext} and then use the getBeanNamesForType(beanClass) method
 * to resolve bean names.
 * 
 * 
 * @author Christian Kaltepoth
 */
public class SpringBeanNameResolver implements ELBeanNameResolver
{

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

   /**
    * FQCN of the WebApplicationContext class
    */
   private final static String WEB_APP_CONTEXT_CLASS = "org.springframework.web.context.WebApplicationContext";

   /**
    * Name of the getBeanNamesForType() class
    */
   private final static String GET_BEAN_NAMES_METHOD = "getBeanNamesForType";

   /**
    * The getBeanNamesForType() method
    */
   private Method getBeanNamesMethod;

   /**
    * The Spring WebApplicationContext
    */
   private Object webAppContext;

   /*
    * Interface implementation
    */
   public boolean init(ServletContext servletContext, ClassLoader classLoader)
   {

      // try to get WebApplicationContext from ServletContext
      webAppContext = servletContext.getAttribute("org.springframework.web.context.WebApplicationContext.ROOT");

      // Not found? Disable resolver!
      if (webAppContext == null)
      {
         if (log.isDebugEnabled())
         {
            log.debug("WebApplicationContext not found in ServletContext. Resolver has been disabled.");
         }
         return false;
      }

      // catch reflection failures
      try
      {
         // get findBeanNamesByType method
         Class webAppContextClass = classLoader.loadClass(WEB_APP_CONTEXT_CLASS);
         getBeanNamesMethod = webAppContextClass.getMethod(GET_BEAN_NAMES_METHOD, Class.class);

         // init successful
         if (log.isDebugEnabled())
         {
            log.debug("Spring detected. Enabling Spring bean name resolving.");
         }
         return true;

      }
      catch (ClassNotFoundException e)
      {
         // will happen when Spring is not on the classpath
         if (log.isDebugEnabled())
         {
            log.debug("WebApplicationContext class could not be found. Resolver has been disabled.");
         }
      }
      catch (NoSuchMethodException e)
      {
         // Spring is expected to offer this methods
         log.warn("Cannot find getBeanNamesByType() method.", e);
      }
      catch (SecurityException e)
      {
         // security issues
         log.warn("Unable to init resolver due to security restrictions", e);
      }

      // resolver will be disabled
      return false;

   }

   /*
    * Interface implementation
    */
   public String getBeanName(Class clazz)
   {

      // catch any reflection exceptions
      try
      {

         // ask for bean names for the supplied type
         String[] names = (String[]) getBeanNamesMethod.invoke(webAppContext, clazz);

         // no beans names returned?
         if (names == null || names.length == 0)
         {

            if (log.isTraceEnabled())
            {
               log.trace("Spring doesn't know a name for class: " + clazz.getName());
            }

            return null;
         }

         // more than one name? Warn the user..
         if (names.length > 1)
         {

            log.warn("Spring returns more than one name for " + clazz.getName()
                  + ". You should place a @URLBeanName annotation on the class.");
            return null;

         }

         // we found the name!!!
         if (log.isTraceEnabled())
         {
            log.trace("Spring returned the name " + names[0] + " for class: " + clazz.getName());
         }

         // return the resolved name
         return names[0];

      }
      catch (IllegalAccessException e)
      {
         // security issues
         log.warn("Unable to call Spring due to security restrictions", e);
      }
      catch (InvocationTargetException e)
      {
         // One of the methods we called has thrown an exception
         log.error("Failed to query Spring for the bean name...", e);
      }

      // we don't know
      return null;
   }

}