com.github.exper0.efilecopier.ftp.DynamicFtpChannelResolver.java Source code

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/*
 * Copyright 2002-2012 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.github.exper0.efilecopier.ftp;

import java.util.HashMap;
import java.util.LinkedHashMap;
import java.util.Map;
import java.util.Map.Entry;
import java.util.Properties;

import org.springframework.context.ConfigurableApplicationContext;
import org.springframework.context.support.AbstractApplicationContext;
import org.springframework.context.support.ClassPathXmlApplicationContext;
import org.springframework.context.support.GenericApplicationContext;
import org.springframework.core.env.PropertiesPropertySource;
import org.springframework.core.env.StandardEnvironment;
import org.springframework.integration.ftp.session.DefaultFtpSessionFactory;
import org.springframework.messaging.MessageChannel;

/**
 * Demonstrates how a dynamic Spring Integration flow snippet can be used
 * to send files to dynamic destinations.
 *
 * @author Gary Russell
 * @author Amol Nayak
 * @since 2.1
 *
 */
public class DynamicFtpChannelResolver {

    //In production environment this value will be significantly higher
    //This is just to demonstrate the concept of limiting the max number of
    //Dynamically created application contexts we'll hold in memory when we execute
    //the code from a junit
    public static final int MAX_CACHE_SIZE = 2;
    private Map<String, AbstractApplicationContext> roots;

    public DynamicFtpChannelResolver() {
        this.roots = new HashMap<String, AbstractApplicationContext>();
    }

    private final LinkedHashMap<String, MessageChannel> channels = new LinkedHashMap<String, MessageChannel>() {

        private static final long serialVersionUID = 1L;

        @Override
        protected boolean removeEldestEntry(Entry<String, MessageChannel> eldest) {
            //This returning true means the least recently used
            //channel and its application context will be closed and removed
            boolean remove = size() > MAX_CACHE_SIZE;
            if (remove) {
                MessageChannel channel = eldest.getValue();
                ConfigurableApplicationContext ctx = contexts.get(channel);
                if (ctx != null) { //shouldn't be null ideally
                    ctx.close();
                    contexts.remove(channel);
                }
            }
            return remove;
        }

    };

    private final Map<MessageChannel, ConfigurableApplicationContext> contexts = new HashMap<MessageChannel, ConfigurableApplicationContext>();

    /**
     * Resolve a customer to a channel, where each customer gets a private
     * application context and the channel is the inbound channel to that
     * application context.
     *
     * @param customer
     * @return a channel
     */
    public MessageChannel resolve(String customer) {
        MessageChannel channel = this.channels.get(customer);
        if (channel == null) {
            channel = createNewCustomerChannel(customer);
        }
        return channel;
    }

    private synchronized MessageChannel createNewCustomerChannel(String customer) {
        MessageChannel channel = this.channels.get(customer);
        if (channel == null) {
            ReportSettings settings = new FtpReportSettings();
            settings.setPassword("demo");
            settings.setUser("demo");
            settings.setHost("localhost");
            settings.setPort(4444);
            ConfigurableApplicationContext ctx = new ClassPathXmlApplicationContext(
                    new String[] { "/META-INF/spring/integration/dynamic-ftp-outbound-adapter-context.xml" }, false,
                    getContext(settings));
            this.setEnvironmentForCustomer(ctx, customer);
            ctx.refresh();
            channel = ctx.getBean("toFtpChannel", MessageChannel.class);
            this.channels.put(customer, channel);
            //Will works as the same reference is presented always
            this.contexts.put(channel, ctx);
        }
        return channel;
    }

    /**
     * Use Spring 3.1. environment support to set properties for the
     * customer-specific application context.
     *
     * @param ctx
     * @param customer
     */
    private void setEnvironmentForCustomer(ConfigurableApplicationContext ctx, String customer) {

        StandardEnvironment env = new StandardEnvironment();
        Properties props = new Properties();
        // populate properties for customer
        props.setProperty("remote.directory", "/");
        props.setProperty("session.factory", "session.factory");
        PropertiesPropertySource pps = new PropertiesPropertySource("ftpprops", props);
        env.getPropertySources().addLast(pps);
        ctx.setEnvironment(env);
    }

    private AbstractApplicationContext getContext(ReportSettings settings) {
        final String key = String.format("%s:%d", settings.getHost(), settings.getPort());
        AbstractApplicationContext context = roots.get(key);
        if (context == null) {
            context = new GenericApplicationContext();
            DefaultFtpSessionFactory factory = new DefaultFtpSessionFactory();
            factory.setUsername(settings.getUser());
            factory.setPassword(settings.getPassword());
            factory.setHost(settings.getHost());
            factory.setPort(settings.getPort());
            context.getBeanFactory().registerSingleton("session.factory", factory);
            context.refresh();
        }
        return context;
    }
}