CODEWITHSUNDEEP
javaservletsweb.xml
Kirn
Kirn

Reputation: 524

How can I read context parameter/web.xml values in a non-servlet java file?

I've got a regular java file that I use to update and query a mysql database but I need to take configurable options in that file (like host name, password, etc) and put it in the web.xml file (or perhaps another file if that's an option, but ideally in web.xml).

But I don't know how to get access to web.xml values from a regular non-servlet java file.

Or would I need to read the xml (like any other xml file... or is there a shortcut route to this...)

Upvotes: 19

Views: 53080

Answers (5)

Hank
Hank

Reputation: 4696

Implement a ServletContextListener:

package util;

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

public class MyConfigListener implements ServletContextListener {
    @Override
    public void contextInitialized(ServletContextEvent sce) {
        ServletContext ctx = sce.getServletContext();

        String hostname = ctx.getInitParameter("my.config.hostname");

        // now go and do something with that
    }

    @Override
    public void contextDestroyed(ServletContextEvent sce) {}

}

And don't forget to register it in web.xml:

<context-param>
  <param-value>somewhere.example.org</param-value>
  <param-name>my.config.hostname</param-name>
</context-param>
<listener>
  <listener-class>util.MyConfigListener</listener-class>
</listener>

Upvotes: 1

stjohnroe
stjohnroe

Reputation: 3206

You need to put the required parameters in env-entry entries of your web.xml file:

<env-entry> 
    <env-entry-name>dbhost</env-entry-name>
    <env-entry-type>java.lang.String</env-entry-type>
    <env-entry-value>localhost</env-entry-value> 
</env-entry>

and then access them via the jndi context 

import javax.naming.Context;
import javax.naming.InitialContext;
...
// Get the base naming context
Context env = (Context)new InitialContext().lookup("java:comp/env");

// Get a single value
String dbhost = (String)env.lookup("dbhost");

Upvotes: 33

Eugene Kuleshov
Eugene Kuleshov

Reputation: 31795

Create a static class that would be initialized from one of the servlets init.

Upvotes: 0

Ralph
Ralph

Reputation: 120761

You could use context-parameters in your web.xml and a javax.servlet.ServletContextListener to populate some static fields.

In you normal java class you read this this static fields.

<?xml version="1.0" encoding="UTF-8"?>
<web-app version="2.5" xmlns="http://java.sun.com/xml/ns/javaee"
    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd">
...
<context-param>
    <description>Prameter</description>
    <param-name>myParam</param-name>
    <param-value>123456790</param-value>
</context-param>
...
</web-app>

You can access this context parameter with ServletContext.getInitParameter

Upvotes: 11

Jigar Joshi
Jigar Joshi

Reputation: 240860

One way is to read xml file and parse it.

You can put it on some static map in after parsing in ServletContextListener

Upvotes: 3

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