JConsole

The JConsole graphical user interface is a monitoring tool that complies to the Java Management Extensions (JMX) specification. JConsole uses the extensive instrumentation of the Java Virtual Machine (Java VM) to provide information about the performance and resource consumption of applications running on the Java platform.

Starting JConsole

The jconsole executable can be found in JDK_HOME/bin, where JDK_HOME is the directory in which the Java Development Kit (JDK) is installed. 

If this directory is in your system path, you can start JConsole by simply typing jconsole in a command (shell) prompt. Otherwise, you have to type the full path to the executable file.

Command Syntax

You can use JConsole to monitor both local applications and  remote applications.

Setting up Local Monitoring

You start JConsole by typing the following command at the command line.

% jconsole

When JConsole starts, you will be given a choice of all the Java applications that are running locally that JConsole can connect to.

If you want to monitor a specific application, and you know that application's process ID, then you can also start JConsole so that it connects to that application. This application must be running with the same user ID as JConsole. The command syntax to start JConsole for local monitoring of a specific application is the following.

% jconsole processID

For example, if you determined that the process ID of the Notepad application is 2956, then you would start JConsole with the following command.

% jconsole 2956

Both JConsole and the application must by executed by the same user. The management and monitoring system uses the operating system's file permissions. If you do not specify a process ID, JConsole will automatically detect all local Java applications, and display a dialog box that lets you select which one you want to monitor.

Setting up Remote Monitoring

To start JConsole for remote monitoring, you use the following command syntax.

% jconsole hostName:portNum

In the command above, hostName is the name of the system running the application and portNum is the port number you specified when you enabled the JMX agent when you started the Java VM.

If you do not specify a host name/port number combination, then JConsole will display a connection dialog box to enable you to enter a host name and port number.