My Java Notebook

The toString() method in the Java Collection invokes the toString() method of each item using Iterator.
In a multi-threaded environment a call to toString() should be synchronized to prevent ConcurrentModificationException.

Eclipse BIRT report viewer can be deployed on a J2EE Server

In order to use a JDBC driver in the BIRT viewer, the driver jar file needs to be in the viewer drivers directory. On BIRT 2.2.2 it is:
/WEB-INF/platform/plugins/org.eclipse.birt.report.data.oda.jdbc_2.2.2.r22x_v20071206/drivers
On BIRT 2.3 it is:
/WEB-INF/platform/plugins/org.eclipse.birt.report.data.oda.jdbc_2.3.0.v20080610/drivers


If you are using Firefox 3 you might have noticed the Version Mismatch error. In this case you will need to use a different browser or to upgrade your BIRT version to 2.3

Prerequisites:

The Eclipse tptp Agent Controller is compiled using libstdc++-libc6.2-2.so.3. If we don't have it under /usr/lib, then we need to install it:

sudo apt-get install libstdc++2.10-glibc2.2

Using Ubuntu Hardy 8.04? take a look here on how to install libstdc++2.10-glibc2.2

Agent Controller Installation:

$ sudo mkdir /opt/agntctrl.linux_ia32-TPTP-4.4.1
$ sudo ln -s /opt/agntctrl.linux_ia32-TPTP-4.4.1 /opt/tptpAC
$ cd /opt/tptpAC/
$ sudo unzip /home/shimi/agntctrl.linux_ia32-TPTP-4.4.1.zip

Run the configuration script. The script will create the Eclipse tptp Agent Controller configuration file /opt/tptpAC/config/serviceconfig.xml

$ cd bin
$ sudo SetConfig.sh

Add the following lines to ~/.bashrc

PATH=$PATH:/opt/tptpAC/bin
LD_LIBRARY_PATH=$LD_LIBRARY_PATH:/opt/tptpAC/lib
TEMP=/tmp


Change the first line in the scripts ACStart.sh and ACStop.sh from
#!/bin/sh
to
#!/bin/bash

Object identity in Terracotta is based on a combination of classloader name and object reference. When using Terracotta to share an object between different applications where the object class is loaded by classloaders with different names, exception is thrown. In my case I shared an object between deployed ear application on JBoss (app-ee.ear) and a console application.

Exception in thread "Thread-10" com.tc.exception.TCClassNotFoundException: java.lang.ClassNotFoundException: No registered loader for description: JBoss.UnifiedClassLoader3:deploy/app-ee.ear, trying to load org.terracotta.datagrid.workmanager.routing.RoutableWorkItem
at com.tc.object.bytecode.ManagerUtil.lookupObject(ManagerUtil.java:335)
at java.util.concurrent.LinkedBlockingQueue$Node.getItem(LinkedBlockingQueue.java:65)
at java.util.concurrent.LinkedBlockingQueue.extract(LinkedBlockingQueue.java:139)
at java.util.concurrent.LinkedBlockingQueue.poll(LinkedBlockingQueue.java:386)
at org.terracotta.datagrid.workmanager.routing.RoutingAwareWorker.start(RoutingAwareWorker.java:46)
at com.shimi.example.StartRoutingWorker$1.run(StartRoutingWorker.java:20)
Caused by: java.lang.ClassNotFoundException: No registered loader for description: JBoss.UnifiedClassLoader3:deploy/app-ee.ear, trying to load org.terracotta.datagrid.workmanager.routing.RoutableWorkItem
at com.tc.object.loaders.StandardClassProvider.getClassFor(StandardClassProvider.java:43)
at com.tc.object.ClientObjectManagerImpl.lookup(ClientObjectManagerImpl.java:522)
at com.tc.object.ClientObjectManagerImpl.lookupObject(ClientObjectManagerImpl.java:423)
at com.tc.object.ClientObjectManagerImpl.lookupObject(ClientObjectManagerImpl.java:412)
at com.tc.object.bytecode.ManagerImpl.lookupObject(ManagerImpl.java:651)
at com.tc.object.bytecode.ManagerUtil.lookupObject(ManagerUtil.java:333)
... 5 more


In order to solve the problem, all the VMs which are synchronized by Terracotta needs to load the shared class with the same classloader name. Since the name of the classloader which loaded the class on JBoss was JBoss.UnifiedClassLoader3:deploy/app-ee.ear, I needed to load the class on the console application using a classloader with the same name. I used a wrapper main class around the application main class. The wrapper class rename the system classloader using Terracotta NamedClassLoader and start the application.

import java.lang.reflect.Method;
import java.net.URL;
import java.net.URLClassLoader;
import com."com/caucho/loader/EnvironmentClassLoader"tc.object.bytecode.hook.impl.ClassProcessorHelper;
import com.tc.object.loaders.NamedClassLoader;

public class CustomLoader {

    // usage: java CustomLoader com.example.MyRealMainClass [arg1] [arg2]

    public static void main(String[] args) throws Exception {
        URL[] systemURLs = ((URLClassLoader) ClassLoader.getSystemClassLoader()).getURLs();

        ClassLoader loader = new URLClassLoader(systemURLs, ClassLoader
                .getSystemClassLoader().getParent());

        // here is the custom classloader name
        ((NamedClassLoader) loader).__tc_setClassLoaderName("JBoss.UnifiedClassLoader3:deploy/app-ee.ear");
        ClassProcessorHelper.registerGlobalLoader((NamedClassLoader) loader);

        Thread.currentThread().setContextClassLoader(loader);
        Class mainClass = loader.loadClass(args[0]);

        Method main = mainClass.getMethod("main", new Class[] { args.getClass() });

        String[] nextArgs = new String[args.length - 1];
        System.arraycopy(args, 0, nextArgs, 0, nextArgs.length);
        main.invoke(null, new Object[] { nextArgs });
    }
}

In order to configure Firefox with installed JRE, a link needs to be created in the browser plugins directory to the JRE plugin directory

cd ~/.mozilla/plugins/
ln -s /usr/lib/jvm/java-6-sun/jre/plugin/i386/ns7/libjavaplugin_oji.so


I have been trying to remote monitoring my application which was running on Ubuntu server using Jconsole and I kept on getting connection failure.
When I run the same application on my Ubuntu desktop I did managed to connect to it using Jconsole.

I wrote a small program to help me investigate the problem:

public class JmxTest {
 public static void main(String[] args) {

   try {
       Thread.sleep(Integer.MAX_VALUE);
   } catch (InterruptedException e) {
       e.printStackTrace();
   }
 }
}

java.rmi.ConnectException: Connection refused to host: 127.0.1.1; nested exception is:
java.net.ConnectException: Connection refused: connect
at sun.rmi.transport.tcp.TCPEndpoint.newSocket(TCPEndpoint.java:574)
at sun.rmi.transport.tcp.TCPChannel.createConnection(TCPChannel.java:185)
at sun.rmi.transport.tcp.TCPChannel.newConnection(TCPChannel.java:171)
at sun.rmi.server.UnicastRef.invoke(UnicastRef.java:94)
at javax.management.remote.rmi.RMIServerImpl_Stub.newClient(Unknown Source)
at javax.management.remote.rmi.RMIConnector.getConnection(RMIConnector.java:2239)
at javax.management.remote.rmi.RMIConnector.connect(RMIConnector.java:271)
at javax.management.remote.JMXConnectorFactory.connect(JMXConnectorFactory.java:248)
at org.mc4j.console.connection.JSR160ConnectionNode.connect(JSR160ConnectionNode.java:132)
at org.mc4j.console.connection.ReconnectAction.performAction(ReconnectAction.java:47)
at org.openide.util.actions.NodeAction$3.run(NodeAction.java:440)
at org.openide.util.actions.CallableSystemAction$ActionRunnable.actionPerformed(CallableSystemAction.java:247)
at org.netbeans.core.ModuleActions.invokeAction(ModuleActions.java:74)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
at java.lang.reflect.Method.invoke(Method.java:585)
at org.openide.util.actions.CallableSystemAction.invokeAction(CallableSystemAction.java:179)
at org.openide.util.actions.CallableSystemAction.access$000(CallableSystemAction.java:31)
at org.openide.util.actions.CallableSystemAction$ActionRunnable.doRun(CallableSystemAction.java:241)
at org.openide.util.actions.CallableSystemAction$2.run(CallableSystemAction.java:111)
at org.openide.util.Task.run(Task.java:136)
at org.openide.util.RequestProcessor$Task.run(RequestProcessor.java:330)
at org.openide.util.RequestProcessor$Processor.run(RequestProcessor.java:686)
Caused by: java.net.ConnectException: Connection refused: connect
at java.net.PlainSocketImpl.socketConnect(Native Method)
at java.net.PlainSocketImpl.doConnect(PlainSocketImpl.java:333)
at java.net.PlainSocketImpl.connectToAddress(PlainSocketImpl.java:195)
at java.net.PlainSocketImpl.connect(PlainSocketImpl.java:182)
at java.net.SocksSocketImpl.connect(SocksSocketImpl.java:366)
at java.net.Socket.connect(Socket.java:520)
at java.net.Socket.connect(Socket.java:470)
at java.net.Socket.<init>(Socket.java:367)
at java.net.Socket.<init>(Socket.java:180)
at sun.rmi.transport.proxy.RMIDirectSocketFactory.createSocket(RMIDirectSocketFactory.java:22)
at sun.rmi.transport.proxy.RMIMasterSocketFactory.createSocket(RMIMasterSocketFactory.java:128)
at sun.rmi.transport.tcp.TCPEndpoint.newSocket(TCPEndpoint.java:569)
[catch] ... 23 more

 java.rmi.ConnectException: Connection refused to host: 127.0.0.1; nested exception is: java.net.ConnectException: Connection refused: connect
at sun.rmi.transport.tcp.TCPEndpoint.newSocket(TCPEndpoint.java:574)
at sun.rmi.transport.tcp.TCPChannel.createConnection(TCPChannel.java:185)
at sun.rmi.transport.tcp.TCPChannel.newConnection(TCPChannel.java:171)
at sun.rmi.server.UnicastRef.invoke(UnicastRef.java:94)
at javax.management.remote.rmi.RMIServerImpl_Stub.newClient(Unknown Source)
at javax.management.remote.rmi.RMIConnector.getConnection(RMIConnector.java:2239)
at javax.management.remote.rmi.RMIConnector.connect(RMIConnector.java:271)
at javax.management.remote.JMXConnectorFactory.connect(JMXConnectorFactory.java:248)
at org.mc4j.console.connection.JSR160ConnectionNode.connect(JSR160ConnectionNode.java:132)
at org.mc4j.console.connection.ReconnectAction.performAction(ReconnectAction.java:47)
at org.openide.util.actions.NodeAction$3.run(NodeAction.java:440)
at org.openide.util.actions.CallableSystemAction$ActionRunnable.actionPerformed(CallableSystemAction.java:247)
at org.netbeans.core.ModuleActions.invokeAction(ModuleActions.java:74)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
at java.lang.reflect.Method.invoke(Method.java:585)
at org.openide.util.actions.CallableSystemAction.invokeAction(CallableSystemAction.java:179)
at org.openide.util.actions.CallableSystemAction.access$000(CallableSystemAction.java:31)
at org.openide.util.actions.CallableSystemAction$ActionRunnable.doRun(CallableSystemAction.java:241)
at org.openide.util.actions.CallableSystemAction$2.run(CallableSystemAction.java:111)
at org.openide.util.Task.run(Task.java:136)
at org.openide.util.RequestProcessor$Task.run(RequestProcessor.java:330)
at org.openide.util.RequestProcessor$Processor.run(RequestProcessor.java:686)
Caused by: java.net.ConnectException: Connection refused: connect
at java.net.PlainSocketImpl.socketConnect(Native Method)
at java.net.PlainSocketImpl.doConnect(PlainSocketImpl.java:333)
at java.net.PlainSocketImpl.connectToAddress(PlainSocketImpl.java:195)
at java.net.PlainSocketImpl.connect(PlainSocketImpl.java:182)
at java.net.SocksSocketImpl.connect(SocksSocketImpl.java:366)
at java.net.Socket.connect(Socket.java:520)
at java.net.Socket.connect(Socket.java:470)
at java.net.Socket.<init>(Socket.java:367)
at java.net.Socket.<init>(Socket.java:180)
at sun.rmi.transport.proxy.RMIDirectSocketFactory.createSocket(RMIDirectSocketFactory.java:22)
at sun.rmi.transport.proxy.RMIMasterSocketFactory.createSocket(RMIMasterSocketFactory.java:128)
at sun.rmi.transport.tcp.TCPEndpoint.newSocket(TCPEndpoint.java:569)
[catch] ... 23 more

Command line properties are very helpful when running JMeter in non-gui mode.

Passing a property value to the test plan:
-J[prop name]=[value]

Accessing the property value from the test plan:
${__P(prop name,default-value)}
The first value is the property name. The second value is the default value if the test was started without passing a value to the property.

For example, if we want to configure the host name and port number of the server that we want to test, we can write ${__P(server.host,localhost)} in the server name and ${__P(server.port,80)} in the port number of the test plan HTTP Request Defaults config element.
The command line will look like this:
./jmeter -t testplan.jmx -n -Jserver.host=differenthostname -Jserver.port=8080

HDFS permissions is a new feature in Hadoop 0.16.0
The default value for the HDFS permissions in hadoop 0.16.0 is true. In order to disable it you need to add the following block to your Hadoop configuration file (hadoop-site.xml):

<property>
<name>dfs.permissions</name>
<value>false</value>
</property>

To enable Java with JMX Agent we need to add the following line to the application VM arguments:
-Dcom.sun.management.jmxremote

This will enable only local monitoring. To enable remote JMX connection we need to specify the port which the JMX server will listen for remote connection.
-Dcom.sun.management.jmxremote.port=9004 (or any other port number)

The JMX remote connection is secured by default. To disable the authentication or the SSL in the JMX remote connection:
-Dcom.sun.management.jmxremote.authenticate=false -Dcom.sun.management.jmxremote.ssl=false

much more information about monitoring and management using JMX can be found here