loggersetupservlet.java

我在加拿大学习的一个比较复杂的在线银行程序.

package com.ebusiness.ebank.log;

/**
 * <p>Title: </p>
 * <p>Description: This servlet class is to initiate logger, and it must be loaded on startup.
 *                  Once the Logger has been set up, the instance of the class can be destroyed</p>
 * <p>Copyright: Copyright (c) 2005</p>
 * <p>Company: eBusiness Inc., All right reserved</p>
 * @author unascribed
 * @version 1.0
 */

import javax.servlet.http.HttpServlet;
import javax.servlet.ServletConfig;
import javax.servlet.ServletException;

import org.apache.log4j.PropertyConfigurator;
import org.apache.log4j.Logger;
import org.apache.log4j.MDC;

import java.sql.DriverManager;
import java.sql.Driver;
import java.sql.Connection;
import java.sql.DatabaseMetaData;
import java.sql.SQLException;
import javax.sql.DataSource;
//import java.io.FileInputStream;
import java.util.Properties;

import com.ebusiness.ebank.servicedelegate.ServiceLocator;
import com.ebusiness.ebank.servicedelegate.ServiceLocatorException;
import com.ebusiness.ebank.exception.ErrorMessages;
import com.ebusiness.ebank.util.Constants;

public class LoggerSetupServlet extends HttpServlet
{
    public void init(ServletConfig config)
          throws ServletException
    {
        super.init(config);
        String driverName = config.getInitParameter("driverName");

        //Since Logger has not been set up yet, System.err is used for displaying message
        System.out.println("\nStart to set up Logger...");
        System.err.println("\nStart to set up Logger...");
        System.err.println("\nDriver name: " + driverName);

        //Set up the Driver that Logger might be using
        try
        {
            Driver d = (Driver)(Class.forName(driverName).newInstance());
            DriverManager.registerDriver(d);
            System.err.println("\nDatabase Driver has been registered with: " + driverName);
        }
        catch(Exception e)
        {
            System.err.println(e);
        }

        Properties prop = new Properties();
        try
        {
            prop.load(this.getClass().getResourceAsStream("ebankLogConfig.properties"));
            //prop.load(this.getServletContext().getResourceAsStream("/WEB-INF/ebankLogConfig.properties"));
        }
        catch (Exception e)
        {
            System.out.println("\nFATAL: Log config file does not found");
            System.err.println(e);
        }

        String dbUrl = "";
        String dbUserName = "";
        String dbPassword = "";
        Connection con = null;
        try
        {
            DataSource ds = ServiceLocator.getInstance().getDataSource(Constants.DATASOURCE_EBANK);
            con = ds.getConnection();
            DatabaseMetaData metaData = con.getMetaData();
            dbUrl = metaData.getURL();
            dbUserName = metaData.getUserName();
            System.out.println("\nINFO: Database URL: " + dbUrl);
            System.out.println("\nINFO: Database User Name: " + dbUserName);
        }
        catch (ServiceLocatorException sle)
        {
            System.err.println("\nFATAL: " + ErrorMessages.FAIL_TO_LOOKUP_DATASOURCE + " for " + Constants.DATASOURCE_EBANK);
        }
        catch (SQLException se)
        {
            System.err.println("\nFATAL: " + ErrorMessages.OTHER_DATABASE_ERROR);
        }
        finally
        {
            try
            {
                if (con != null)
                    con.close();
            }
            catch (SQLException se)
            {
                System.err.println("\nFATAL: " + ErrorMessages.FAIL_TO_CLOSE_DATABASE_CONNECTION);
            }
        }

        //The codes below is to avoid the need to reconfigure log properties when the eBank
        //application is promoted from one environment to another environment
        prop.setProperty("log4j.appender.R1.url", dbUrl);
        prop.setProperty("log4j.appender.R1.username", dbUserName);
        prop.setProperty("log4j.appender.JDBC2.url", dbUrl);
        prop.setProperty("log4j.appender.JDBC2.username", dbUserName);

        if (dbUrl.equalsIgnoreCase(prop.getProperty("dev.url"))
            && dbUserName.equalsIgnoreCase(prop.getProperty("dev.username"))) //Dev environment
        {
            prop.setProperty("log4j.logger.com.ebusiness.ebank", prop.getProperty("dev.logTarget"));
            prop.setProperty("log4j.appender.R1.password", prop.getProperty("dev.password"));
            prop.setProperty("log4j.appender.JDBC2.password", prop.getProperty("dev.password"));
        }
        else if (dbUrl.equalsIgnoreCase(prop.getProperty("qa.url"))
            && dbUserName.equalsIgnoreCase(prop.getProperty("qa.username"))) //QA environment
        {
            prop.setProperty("log4j.logger.com.ebusiness.ebank", prop.getProperty("qa.logTarget"));
            prop.setProperty("log4j.appender.R1.password", prop.getProperty("qa.password"));
            prop.setProperty("log4j.appender.JDBC2.password", prop.getProperty("qa.password"));
        }
        else if (dbUrl.equalsIgnoreCase(prop.getProperty("uat.url"))
            && dbUserName.equalsIgnoreCase(prop.getProperty("uat.username"))) //Uat environment
        {
            prop.setProperty("log4j.logger.com.ebusiness.ebank", prop.getProperty("uat.logTarget"));
            prop.setProperty("log4j.appender.R1.password", prop.getProperty("uat.password"));
            prop.setProperty("log4j.appender.JDBC2.password", prop.getProperty("uat.password"));
        }
        else if (dbUrl.equalsIgnoreCase(prop.getProperty("prod.url"))
            && dbUserName.equalsIgnoreCase(prop.getProperty("prod.username"))) //Production environment
        {
            prop.setProperty("log4j.logger.com.ebusiness.ebank", prop.getProperty("prod.logTarget"));
            prop.setProperty("log4j.appender.R1.password", prop.getProperty("prod.password"));
            prop.setProperty("log4j.appender.JDBC2.password", prop.getProperty("prod.password"));
        }
        else if (dbUrl.equalsIgnoreCase(prop.getProperty("dr.url"))
          && dbUserName.equalsIgnoreCase(prop.getProperty("dr.username"))) //DR environment
       {
          prop.setProperty("log4j.logger.com.ebusiness.ebank", prop.getProperty("dr.logTarget"));
          prop.setProperty("log4j.appender.R1.password", prop.getProperty("dr.password"));
          prop.setProperty("log4j.appender.JDBC2.password", prop.getProperty("dr.password"));
       }

        else //No database URL matchs, the Logger will not be able to successfully set up
        {
            System.err.println("\nFATAL: No database URL matchs the eBank connection pool URl. \nPlease reconfigure ebankLogConfig.properties or ebank connection pool URL");
            return;
        }

        PropertyConfigurator.configure(prop);

        //Now that Logger has been set up, Logger can be used to display messages
        Logger log = Logger.getLogger(this.getClass());
        MDC.put("userid", "system");
        log.debug("This is a Logger test.");
        log.info("The Logger has been successfully set up.");

        //Once Logger has been configured, this servlet is no longer needed
        this.destroy();
    }
}