One of the drawbacks of JMX is the lack of cluster support, you have
to invoke the operation in each one of the servers. The solution? use a
JMX client that does that for you, as jManage.
You setup the servers as in any other administration console and then
you can group them in clusters, allowing you to see the value of the
properties in each one of the servers in the cluster and invoke operations
in all of them getting the results of each server in a single page.

Download jManage version 0.5.3.

Go to jmanage-0.5.3/modules/jboss and copy there the following jars from jboss installation.

• jboss-4.0.2/client/jbossall-client.jar
• jboss-4.0.2/lib/jboss-jmx.jar

Start JBoss servers with the java option  -Djava.rmi.server.hostname=hostname (you can set JAVA_OPTS environment variable)

Run jManage with jmanage-0.5.3/bin/startup.sh, you’ll be asked for a password (123456 by default). Then you can login at http://localhost:9090 with username/password admin/123456

When working at a client site we decided to enable Hibernate
statistics, so we can access all this information about cache
hits/misses, transactions, entities,… and all kind of cool stuff
through a JMX interface at runtime, allowing runtime configuration
changes and monitoring.

But seems that not many people is using this feature, because we
got the frustrating NullPointerException. After debugging a bit through
the Hibernate sources (if you have ever tried you know that it’s a PITA) I found the errors, same exception in two places,
and told JBoss support (the client was paying for it). Anyway I fixed them
locally while they fixed them in CVS, see the cvs diff or the JIRA issue. This bugs are present in hibernate 3.0.5 when using TreeCache.

Now we can get a lot of useful information at runtime, through a JMX console, I really like jManage,
mostly due to it’s cluster support, but you’ll need some tricks to make
it run with JBoss 4, that I’ll post in a separate entry.

I really like dbUnit for unit tests, but I like it more for other
tasks, as exporting data from the database in xml or Excel formats with
a few lines of code and without bothering about writing xml tags or
interacting with POI to write Excel cells.

For
instance the next code can be used to export the result of a query into
an Excel file.

public class Report {

    private DataSource dataSource;

    public void exportData() throws Exception {

        IDatabaseConnection connection = new DatabaseConnection(dataSource
                .getConnection());

        try {

            // partial database export
            QueryDataSet partialDataSet = new QueryDataSet(connection);

            String query =
                    "SELECT a, b FROM t WHERE a = 'whatever'");

            partialDataSet.addTable("Report", query);
            XlsDataSet.write(partialDataSet, new FileOutputStream(
                    "report.xls"));

        } finally {
            connection.close();
        }

    }

In relation to Rick Hightower entry on annotations and inheritance I also checked if annotations on implemented interfaces are accesible
from the class implementing them. The answer is NO, neither using the
@Inherited annotation on the annotation class. The only way is getting
the implemented interfaces and iterate over them to see if they have
annotations.

public class AnnotationTest extends TestCase {

    @Retention(RetentionPolicy.RUNTIME) // This makes the annotation available at runtime
    @Inherited
    public static @interface Developer {
        String name();

        String email() default “[email protected]”;

        int rank() default 1;
    }

    // Using the annotation to decorate a class and a method
    @Developer(name = “RickHightower”)
    interface MyInterface {
        @Developer(name = “ScottFauerbach”, email = “[email protected]”)
        void myMethod();
    }

    class MyClassSub implements MyInterface {
        
        public void myMethod() {
            // …
        }
    }

    // Testing the annotation
    public void testAnnotation() throws Exception {
        assertFalse (MyClassSub.class.isAnnotationPresent(Developer.class));
        Method method2 = MyClassSub.class.getMethod(“myMethod”, (Class[]) null);
        assertFalse (method2.isAnnotationPresent(Developer.class));
        
        Class[] interfaces = MyClassSub.class.getInterfaces();
        boolean annotationPresent = false;
        for (Class iClass : interfaces) {
            if (iClass.isAnnotationPresent(Developer.class)) {
                   
annotationPresent = true;
                    break;
            }
        }
        assertTrue(annotationPresent);
    }
}