com.ocpsoft.pretty.faces.el.resolver.SpringBeanNameResolver.java Source code

Introduction

Here is the source code for com.ocpsoft.pretty.faces.el.resolver.SpringBeanNameResolver.java

Source

/*
 * 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;

/**
 * <p>
 * Implementation of {@link ELBeanNameResolver} that will resolve names of beans
 * managed by Spring.
 * </p>
 * <p>
 * This resolver will get the WebApplicationContext from the
 * {@link ServletContext} and then use the getBeanNamesForType(beanClass) method
 * to resolve bean names.
 * </p>
 * 
 * @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;
    }

}