com.headissue.pigeon.PigeonBootstrapListener.java Source code

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Here is the source code for com.headissue.pigeon.PigeonBootstrapListener.java

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/*
 * Copyright (C) 2013 headissue GmbH (www.headissue.com)
 *
 * Source repository: https://github.com/headissue/pigeon
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU Affero General Public License as
 * published by the Free Software Foundation, either version 3 of the
 * License, or (at your option) any later version.
 *
 * This patch is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU Affero General Public License for more details.
 *
 * You should have received a copy of the GNU Affero General Public License
 * along with this patch.  If not, see <http://www.gnu.org/licenses/agpl.txt/>.
 */
package com.headissue.pigeon;

import com.google.inject.Guice;
import com.google.inject.Injector;
import com.google.inject.Module;
import com.google.inject.servlet.GuiceServletContextListener;
import com.headissue.pigeon.util.ClassUtils;
import com.headissue.pigeon.util.LogUtils;
import org.apache.commons.lang.StringUtils;
import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;

import javax.servlet.ServletContext;
import javax.servlet.ServletContextEvent;

/**
 * Creates the Guice Injector. The parameter "com.headissue.pigeon.guice.Module" stores
 * the module for the injector to load.
 *
 * @see PigeonModule
 */
public class PigeonBootstrapListener extends GuiceServletContextListener {

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

    static final String INIT_PARAM_GUICE_MODULE = "com.headissue.pigeon.guice.Module";

    private ServletContext context;

    @Override
    public void contextInitialized(ServletContextEvent servletContextEvent) {
        LogUtils.debug(log, "Pigeon listener is starting");
        context = servletContextEvent.getServletContext();
        super.contextInitialized(servletContextEvent);
    }

    @Override
    protected Injector getInjector() {
        try {
            return Guice.createInjector(findAndCreateModule(this.context));
        } catch (Exception e) {
            LogUtils.warn(log, e, "create injector failed");
            if (e instanceof PigeonException) {
                throw (PigeonException) e;
            }
            throw new PigeonException("create injector failed", e);
        }
    }

    /**
     * try finding the classname of the Guice module.
     */
    static Module findAndCreateModule(ServletContext context) {
        String className = getParam(context, INIT_PARAM_GUICE_MODULE);
        if (StringUtils.isEmpty(className)) {
            throw new PigeonException("missing  parameter '" + INIT_PARAM_GUICE_MODULE + "'");
        }
        return ClassUtils.newInstance(className, Module.class);
    }

    static String getParam(ServletContext _context, String _name) {
        String s = _context.getInitParameter(_name);
        if (StringUtils.isNotEmpty(s)) {
            LogUtils.debug(log, "found in servlet:   '%s'=%s", _name, s);
            return s;
        }
        String _envName = _name.replaceAll("\\.", "_");
        s = System.getenv(_envName);
        if (StringUtils.isNotEmpty(s)) {
            LogUtils.debug(log, "found in env param: '%s'=%s", _envName, s);
            return s;
        }
        s = System.getProperty(_name);
        if (StringUtils.isNotEmpty(s)) {
            LogUtils.debug(log, "found in sys prop:  '%s'=%s", _name, s);
        }
        return s;
    }
}