Lookup datasource with custom variable in runtime

Question

I have context.xml defined in META-INF as follow:

<Context path="/7Restaurant">
<Resource name="datasource"
      type="javax.sql.DataSource"
      auth="Container"
      maxActive="10"
      maxIdle="3"
      maxWait="10000"
      username="work"
      password=""
      driverClassName="org.postgresql.Driver"
      url="jdbc:postgresql://127.0.0.1:5432/7restaurant"/>
</Context>

I am about to deploy my web app (Servlet, in Tomcat 7). The only problem is that, how can I change the url, username, etc. to match that with the environment the WAR package is deployed.

So, in essence, how could such a file is modified; or any other technique so that user can finely connect to the database in the environment it will be deployed on.

I am so new in web-app eclipse, tomcat, postgresql stack; so I expect my question to be wrong, if that's the case; please let me know any other way to solve this.

My context initializer in Java:

package com.restaurant.web;

import java.io.File;
import java.io.InputStream;
import java.io.StringWriter;
import java.net.URL;

import javax.naming.*;
import javax.servlet.*;
import javax.sql.*;
import javax.xml.parsers.DocumentBuilder;
import javax.xml.parsers.DocumentBuilderFactory;
import javax.xml.transform.Result;
import javax.xml.transform.Source;
import javax.xml.transform.Transformer;
import javax.xml.transform.TransformerFactory;
import javax.xml.transform.dom.DOMSource;
import javax.xml.transform.stream.StreamResult;

import org.w3c.dom.*;

import com.restaurant.dao.dbpostgres.DBDAO;
import com.restaurant.setup.GeneralConfigurerSetup;
import com.restaurant.web.Logger;

import sun.java2d.loops.DrawGlyphListAA.General;

public class Database implements ServletContextListener {
    private void contextInitialized2(ServletContext servletContext) throws Exception
    {
        /*
        //prepare META-INF/context.xml
        DocumentBuilder docbldr = DocumentBuilderFactory.newInstance().newDocumentBuilder();
        Document doc = docbldr.newDocument();
        Element context = doc.createElement("Context");
        context.setAttribute("path", "/7Restaurant");
        Element resource = doc.createElement("Resource");
        resource.setAttribute("name", "datasource");
        resource.setAttribute("type", "javax.sql.DataSource");
        resource.setAttribute("auth", "Container");
        resource.setAttribute("maxActive", "10");
        resource.setAttribute("maxIdle", "3");
        resource.setAttribute("maxWait", "10000");
        resource.setAttribute("username", Configurer.get(GeneralConfigurerSetup.DB_USERNAME));
        resource.setAttribute("password", Configurer.get(GeneralConfigurerSetup.DB_PASSWORD));
        resource.setAttribute("driverClassName", Configurer.get(GeneralConfigurerSetup.DB_CLASS));
        resource.setAttribute("url", Configurer.get(GeneralConfigurerSetup.DB_JDBCURL));
        context.appendChild(resource);
        doc.appendChild(context);

        System.out.println(System.getProperty("java.class.path"));

        File fOut = new File("META-INF/context.xml");       
        System.out.println(fOut.getAbsolutePath());
        if (fOut.exists()) fOut.delete();
        TransformerFactory tff = TransformerFactory.newInstance();
        Transformer tf = tff.newTransformer();
        Source input = new DOMSource(doc);
        Result output = new StreamResult(fOut);
        tf.transform(input, output);        
        */

        //META-INF/context
        InitialContext enc = new InitialContext();
        Context compContext = (Context) enc.lookup("java:comp/env");
        DataSource dataSource = (DataSource) compContext.lookup("datasource");
        DBDAO.setDataSource(dataSource);
    }

    public void contextInitialized(ServletContextEvent sce) {
        ServletContext servletContext = sce.getServletContext();
        try {
            contextInitialized2(servletContext);
        } catch(Exception e) {
            Logger.error("Initializing failed: " + e.getMessage());
            System.exit(-1);
        }       
    }

    public void contextDestroyed(ServletContextEvent sce) {

    }
}

Answer 1

Remove context.xml from your build (just to be safe), and put it in your tomcat folder under conf/Catalina/localhost. Rename it so it's whatever you want your app context name to be (like myapp.xml).

As you can see, that allows each environment to have different myapp.xml files, and when you deploy the war, it will pick that up instead of using an internal one.