Modify Servlet parameters

Question

Hi guys,

I've a GWT Servlet running in a Tomcat 6.0 server. This server acts as a proxy to another service. This final service may be running in different IPs and/or ports in my network.

How can I configure my GWT Servlet to connect to any of my services without manually modifying the web.xml file?

I'm initializing my servlet with:

  <!-- Servlets -->
  <servlet>
    <servlet-name>MyServlet</servlet-name>
    <servlet-class>com.proxy.MyServletServiceImpl</servlet-class>
    <init-param>
        <param-name>serverAddress</param-name>
        <param-value>192.168.1.10</param-value>
    </init-param>
    <init-param>
        <param-name>serverPort</param-name>
        <param-value>55005</param-value>
    </init-param>
  </servlet>

From inside my MyServletSerciveImpl.java file I'm doing

private void loadConfig() {
    ServletConfig config = this.getServletConfig();
    serverAddress = config.getInitParameter("serverAddress");
    serverPort = Integer.valueOf(config.getInitParameter("serverPort"));
}

My ideal case would be that this configuration is the default, but applying some configuration file (a properpies file, xml, ini, cfg, .....) I could overwrite the default web.xml values.

Any idea how to do that?

Thanks.

Answer 1

For true dynamic configuration, you can expose a configuration object as a jmx bean, and have your servlet use that bean.

An intermediate solution is to put the configuration in a different file, as xml or properties, or in a db table, and read from it periodically in a background thread.

Answer 2

For completeness:

public class MyServiceImpl extends RemoteServiceServlet implements
        MyService {

    private void loadConfig() {     
        InputStream inStream = this.getServletContext().getResourceAsStream("/WEB-INF/config.properties");
        Properties properties = new Properties();
        try {
            properties.load(inStream);
            // properties.getProperty("myValue");

        } catch (IOException e) {
            Log.error(e.getMessage());
            e.printStackTrace();
        }
    }
....
}