Scope of variables in a class implementing webservice - web-services

Question

This may be stupid question, but i want to know the root cause.
I am implementing a simple webservice using jersey. I have declared a global variable i and initialised to 0;
I set i to 10 in sayPlainTextHello() method but when i display i in sayXMLHello() it is still 0 ; What is the reason behind this behavior.
server side code
#Path("/hello")
public class Hello
{
int i = 0;
#GET
#Path("/string")
#Produces(MediaType.TEXT_PLAIN)
public String sayPlainTextHello()
{
i = 10;
System.out.println("string hello");
System.out.println("i in string " + i);
return "Hello";
}
#GET
#Path("/xml")
#Produces(MediaType.TEXT_XML)
public String sayXMLHello()
{
System.out.println("i in xml"+i);
System.out.println("xml hello");
return "<?xml version=\"1.0\"?>" + "<hello> Hello Jersey" + " </hello>";
}
This is my web.xml file
<?xml version="1.0" encoding="UTF-8"?>
<web-app xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns="http://java.sun.com/xml/ns/javaee" xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-app_3_0.xsd" id="WebApp_ID" version="3.0">
<display-name>com.vogella.jersey.first</display-name>
<welcome-file-list>
<welcome-file>home.jsp</welcome-file>
</welcome-file-list>
<servlet>
<servlet-name>Jersey REST Service</servlet-name>
<servlet-class> com.sun.jersey.spi.container.servlet.ServletContainer</servlet-class>
<!-- Register resources and providers under com.vogella.jersey.first package. -->
<init-param>
<param-name>jersey.config.server.provider.packages</param-name>
<param-value>com.spaneos.webservices</param-value>
</init-param>
<load-on-startup>1</load-on-startup>
</servlet>
<servlet-mapping>
<servlet-name>Jersey REST Service</servlet-name>
<url-pattern>/rest/*</url-pattern>
</servlet-mapping>
<servlet-mapping>
<servlet-name>default</servlet-name>
<url-pattern>*.js</url-pattern>
</servlet-mapping>
</web-app>

Answer 1

The default scope of resource classes is per-request (or request scoped). For each request a new resource instance will created to handle that particular request.
You can make your classes singleton scoped, meaning only one object will be created for the entire application, but that may not be desired for a few reasons.
If you do want to make your resource class singleton scoped, then you can just annotate your Hello class with #com.sun.jersey.spi.resource.Singleton
That said, unless you have a direct requirement to make the resource class stateful, I would aim to keep the classes stateless.
See more at Life-cycle of Root Resource Classes