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Subject: RE: What happens to Java objects when Axis is reloaded by Tomcat?
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Date: Thu, 22 Jul 2004 12:49:36 +0100
Message-ID: <D13035D3AF60894998961578840C8CD8826F72@pegasus.axiom.com>
Thread-Topic: What happens to Java objects when Axis is reloaded by Tomcat?
Thread-Index: AcRvUhGkDMgULnuqSE+4MP4APbyD5wAj1p5Q
From: "Keith Hatton" <khatton@axiomsystems.com>
To: <axis-user@ws.apache.org>

You could register a ServletContextListener (in web.xml) that calls some =
cleanup code on your singleton when the web-app is destroyed. But I =
don't know how this would affect your other threads, as a new =
ClassLoader is created when Axis is reloaded (this is why you get =
"another" singleton). If your singleton threw an exception if a method =
was called after the context had been destroyed, at least you would know =
what was happening.

Keith


-----Original Message-----
From: Donald Gorgonzola [mailto:donzola@hotmail.com]
Sent: 21 July 2004 19:39
To: axis-user@ws.apache.org
Subject: What happens to Java objects when Axis is reloaded by Tomcat?


>From a web service call I access a singleton, so subsequent web service=20
calls can access the same object.  Things work fine until Axis is =
reloaded=20
(by Tomcat web app manager).  I can no longer get a handle on the =
original=20
singleton, instead a new singleton is created.

I wouldn't mind this behavior if the original singleton was cleaned up, =
but=20
instead it sticks around.  I know this because I have threads that are =
still=20
able to see the original singleton.  So what I end up with is multiple=20
singletons, one for every time Axis is reloaded and no way of getting a=20
handle on the old singletons.  The only way I can get rid of them is to=20
restart Tomcat.

What happens when Axis is reloaded by Tomcat?
Is there any way to have the singleton objects and threads that were=20
associated with Axis before the reload get cleaned up?  Or a way to get =
a=20
handle on these old objects?

I am using Axis 1.1 with Tomcat 5.0.25 and Java 1.4.2.

Here  is some code that calls a web service that accesses a singleton.


/*
* SingletonTest.jws
* Tests accessing a singleton from a web service call.
*/

public class SingletonTest
{
    /** Shows the current value of the singleton and updates with the =
new=20
value. */
    public String
    showAndSet (String newValue)
    {
        String originalValue =3D Singleton.getInstance().getValue();
        Singleton.getInstance().setValue(newValue);
        return (originalValue);
    }
}


/** Singleton.java */
public class Singleton
{
    private static Singleton singleton =3D null;
    private String value =3D "unset";

    /** Singleton so constructor is private. */
    private
    Singleton()
    {
    }

    public static Singleton
    getInstance()
    {
        if (singleton =3D=3D null) {
            singleton =3D new Singleton();
        }
        return (singleton);
    }

    public String
    getValue()
    {
        return (value);
    }

    public void
    setValue (String newValue)
    {
        value =3D newValue;
    }
}


/*
* SingletonTestClient.java
* Test client used to test SingletonTest.jws.
*/
import org.apache.axis.client.Call;
import org.apache.axis.client.Service;
import org.apache.axis.encoding.XMLType;
import javax.xml.rpc.ParameterMode;

public class SingletonTestClient
{
    public static void
    main(String [] args)
        throws Exception
    {
        String endpoint =3D =
"http://localhost:8080/axis/SingletonTest.jws";

        if (args =3D=3D null || args.length < 1) {
            System.err.println("Usage: SingletonTestClient <name>");
            return;
        }

        String value =3D args[0];
        String retStr =3D null;
        Object [] objs =3D null;

        Service  service =3D new Service();
        Call     call    =3D (Call) service.createCall();

        call.addParameter ("showAndSet", XMLType.XSD_STRING,=20
ParameterMode.IN );
        objs =3D new Object [] { value };

        call.setTargetEndpointAddress( new java.net.URL(endpoint) );
        call.setOperationName("showAndSet");
        call.setReturnType(XMLType.XSD_STRING);

        retStr =3D (String) call.invoke(objs);
        System.out.println("Result: " + retStr);
    }
}

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