org.springframework.integration.config.IdGeneratorConfigurer.java Source code

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Here is the source code for org.springframework.integration.config.IdGeneratorConfigurer.java

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/*
 * Copyright 2002-2013 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 org.springframework.integration.config;

import java.lang.reflect.Field;
import java.util.HashSet;
import java.util.Set;

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

import org.springframework.beans.factory.BeanDefinitionStoreException;
import org.springframework.beans.factory.NoSuchBeanDefinitionException;
import org.springframework.context.ApplicationContext;
import org.springframework.context.ApplicationListener;
import org.springframework.context.event.ApplicationContextEvent;
import org.springframework.context.event.ContextClosedEvent;
import org.springframework.context.event.ContextRefreshedEvent;
import org.springframework.integration.MessageHeaders;
import org.springframework.integration.MessageHeaders.IdGenerator;
import org.springframework.util.ReflectionUtils;

/**
 * @author Oleg Zhurakousky
 * @author Mark Fisher
 * @author Gary Russell
 * @since 2.0.4
 */
public final class IdGeneratorConfigurer implements ApplicationListener<ApplicationContextEvent> {

    private static final Set<String> generatorContextId = new HashSet<String>();

    private static volatile IdGenerator theIdGenerator;

    private final Log logger = LogFactory.getLog(getClass());

    public synchronized void onApplicationEvent(ApplicationContextEvent event) {
        ApplicationContext context = event.getApplicationContext();
        if (event instanceof ContextRefreshedEvent) {
            boolean contextHasIdGenerator = context.getBeanNamesForType(IdGenerator.class).length > 0;
            if (contextHasIdGenerator) {
                if (this.setIdGenerator(context)) {
                    IdGeneratorConfigurer.generatorContextId.add(context.getId());
                }
            }
        } else if (event instanceof ContextClosedEvent) {
            if (IdGeneratorConfigurer.generatorContextId.contains(context.getId())) {
                if (IdGeneratorConfigurer.generatorContextId.size() == 1) {
                    this.unsetIdGenerator();
                }
                IdGeneratorConfigurer.generatorContextId.remove(context.getId());
            }
        }
    }

    private boolean setIdGenerator(ApplicationContext context) {
        try {
            IdGenerator idGeneratorBean = context.getBean(IdGenerator.class);
            if (logger.isDebugEnabled()) {
                logger.debug("using custom MessageHeaders.IdGenerator [" + idGeneratorBean.getClass() + "]");
            }
            Field idGeneratorField = ReflectionUtils.findField(MessageHeaders.class, "idGenerator");
            ReflectionUtils.makeAccessible(idGeneratorField);
            IdGenerator currentIdGenerator = (IdGenerator) ReflectionUtils.getField(idGeneratorField, null);
            if (currentIdGenerator != null) {
                if (currentIdGenerator.equals(idGeneratorBean)) {
                    // same instance is already set, nothing needs to be done
                    return false;
                } else {
                    if (IdGeneratorConfigurer.theIdGenerator.getClass() == idGeneratorBean.getClass()) {
                        if (logger.isWarnEnabled()) {
                            logger.warn("Another instance of " + idGeneratorBean.getClass()
                                    + " has already been established; ignoring");
                        }
                        return true;
                    } else {
                        // different instance has been set, not legal
                        throw new BeanDefinitionStoreException(
                                "'MessageHeaders.idGenerator' has already been set and can not be set again");
                    }
                }
            }
            if (logger.isInfoEnabled()) {
                logger.info("Message IDs will be generated using custom IdGenerator [" + idGeneratorBean.getClass()
                        + "]");
            }
            ReflectionUtils.setField(idGeneratorField, null, idGeneratorBean);
            IdGeneratorConfigurer.theIdGenerator = idGeneratorBean;
        } catch (NoSuchBeanDefinitionException e) {
            // No custom IdGenerator. We will use the default.
            int idBeans = context.getBeansOfType(IdGenerator.class).size();
            if (idBeans > 1 && logger.isWarnEnabled()) {
                logger.warn("Found too many 'IdGenerator' beans (" + idBeans + ") "
                        + "Will use the existing UUID strategy.");
            } else if (logger.isDebugEnabled()) {
                logger.debug("Unable to locate MessageHeaders.IdGenerator. Will use the existing UUID strategy.");
            }
            return false;
        } catch (IllegalStateException e) {
            // thrown from ReflectionUtils
            if (logger.isWarnEnabled()) {
                logger.warn("Unexpected exception occurred while accessing idGenerator of MessageHeaders."
                        + " Will use the existing UUID strategy.", e);
            }
            return false;
        }
        return true;
    }

    private void unsetIdGenerator() {
        try {
            Field idGeneratorField = ReflectionUtils.findField(MessageHeaders.class, "idGenerator");
            ReflectionUtils.makeAccessible(idGeneratorField);
            idGeneratorField.set(null, null);
            IdGeneratorConfigurer.theIdGenerator = null;
        } catch (Exception e) {
            if (logger.isWarnEnabled()) {
                logger.warn("Unexpected exception occurred while accessing idGenerator of MessageHeaders.", e);
            }
        }
    }

}