startuplistener.java

Struts数据库项目中的一个实例

package com.relationinfo.webapp.listener;

import java.util.HashMap;
import java.util.Map;

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

import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
import com.relationinfo.Constants;
import com.relationinfo.service.LookupManager;
import org.springframework.context.ApplicationContext;
import org.springframework.web.context.ContextLoaderListener;
import org.springframework.web.context.support.WebApplicationContextUtils;

/**
 * StartupListener class used to initialize and database settings
 * and populate any application-wide drop-downs.
 *
 * @author caoguangxin www.relationinfo.com
 *
 * @web.listener
 */
public class StartupListener extends ContextLoaderListener
    implements ServletContextListener {
    
    private static final Log log = LogFactory.getLog(StartupListener.class);

    public void contextInitialized(ServletContextEvent event) {
        if (log.isDebugEnabled()) {
            log.debug("initializing context...");
        }

        // call Spring's context ContextLoaderListener to initialize
        // all the context files specified in web.xml
        super.contextInitialized(event);

        ServletContext context = event.getServletContext();
        String daoType = context.getInitParameter(Constants.DAO_TYPE);

        // if daoType is not specified, use DAO as default
        if (daoType == null) {
            log.warn("No 'daoType' context carameter, using hibernate");
            daoType = Constants.DAO_TYPE_HIBERNATE;
        }

        // Orion starts Servlets before Listeners, so check if the config
        // object already exists
        Map config = (HashMap) context.getAttribute(Constants.CONFIG);

        if (config == null) {
            config = new HashMap();
        }

        // Create a config object to hold all the app config values
        config.put(Constants.DAO_TYPE, daoType);
        context.setAttribute(Constants.CONFIG, config);

        // output the retrieved values for the Init and Context Parameters
        if (log.isDebugEnabled()) {
            log.debug("daoType: " + daoType);
            log.debug("populating drop-downs...");
        }

        setupContext(context);
    }

    public static void setupContext(ServletContext context) {
        ApplicationContext ctx = 
            WebApplicationContextUtils.getRequiredWebApplicationContext(context);

        LookupManager mgr = (LookupManager) ctx.getBean("lookupManager");

        // get list of possible roles
        context.setAttribute(Constants.AVAILABLE_ROLES, mgr.getAllRoles());

        if (log.isDebugEnabled()) {
            log.debug("drop-down initialization complete [OK]");
        }
    }
}