How do I load and store global variables in Jersey/Glassfish - glassfish

Question

I am creating a RESTful Web Service that wraps an antiquated vendor API. Some external configuration will be required and will be stored on the server either in a file or rdbms. I'm using Jersey 1.11.1 in Glassfish 3.1.2. This configuration data is all in String key/value format.
My first question is this - where can I store global/instance variables in Jersey so that they will be persisted between requests and available to all resources? If this was a pure Servlet application I would use the ServletContext to accomplish this.
The second part to the question is how can I load my configuration once the Jersey server has loaded? Again, my Servlet analogy would be to find the equivalent to the init() method.

Answer 1

#Singleton #Startup EJB matches your requirements.
#Singleton
#Startup // initialize at deployment time instead of first invocation
public class VendorConfiguration {
#PostConstruct
void loadConfiguration() {
// do the startup initialization here
}
#Lock(LockType.READ) // To allow multiple threads to invoke this method
// simultaneusly
public String getValue(String key) {
}
}
#Path('/resource')
#Stateless
public class TheResource {
#EJB
VendorConfiguration configuration;
// ...
}
EDIT: Added annotation as per Graham's comment

Answer 2

You can use a listener for init the variables and set to the context as attribute before the web application start, something like the following:
package org.paulvargas.shared;
import java.util.HashMap;
import java.util.Map;
import javax.servlet.ServletContext;
import javax.servlet.ServletContextEvent;
import javax.servlet.ServletContextListener;
public class LoadConfigurationListener implements ServletContextListener {
public void contextInitialized(ServletContextEvent sce) {
// read file or rdbms
...
ServletContext context = sce.getServletContext();
// set attributes
...
}
public void contextDestroyed(ServletContextEvent sce) {
ServletContext context = sce.getServletContext();
// remove attributes
...
}
}
This listener is configured in the web.xml.
<listener>
<listener-class>org.paulvargas.shared.LoadConfigurationListener</listener-class>
</listener>
You can use the #Context annotation for inject the ServletContext and retrieving the attribute.
package org.paulvargas.example.helloworld;
import java.util.*;
import javax.servlet.ServletContext;
import javax.ws.rs.*;
import javax.ws.rs.core.*;
#Path("/world")
public class HelloWorld {
#Context
private ServletContext context;
#GET
#Produces("text/plain; charset=UTF-8")
public String getGreeting() {
// get attributes
String someVar = (String) context.getAttribute("someName")
return someVar + " says hello!";
}
}