This is a quick post about a coding problem that took longer than expected to solve. I have put an example solution here as a reference for myself or others, hopefully speeding up the task. I needed to create a dialog to connect to a local or remote JMX process. Essentially this would be very similar to the JConsole “New Connection” dialog. Initially I thought this would just be a standard component, but instead it took some trial and error (as well as digging through Sun documentation) to get the required functionality working.
The problematic parts are discovering which Java processes are running on the local computer and connecting to a local or remote JMX process. The code below will find local JMX processes, by finding any JVMs running and trying to attach to them. Note that this code requires Sun’s JVM Tool Interface which is in tools.jar in the JDK lib folder (at least for JDK6 - not sure where it is in different versions).
Map<String, VirtualMachine> result = new HashMap<String, VirtualMachine>();
List<VirtualMachineDescriptor> list = VirtualMachine.list();
for (VirtualMachineDescriptor vmd: list) {
String desc = vmd.toString();
try {
result.put(desc, VirtualMachine.attach(vmd));
} catch (IOException e) {
e.printStackTrace();
} catch (AttachNotSupportedException e) {
e.printStackTrace();
}
}To connect to a local JMX process after the VirtualMachine class for that process has been acquired, do the following:
private JMXConnector getLocalConnection(VirtualMachine vm) throws Exception {
Properties props = vm.getAgentProperties();
String connectorAddress = props.getProperty(CONNECTOR_ADDRESS_PROPERTY);
if (connectorAddress == null) {
props = vm.getSystemProperties();
String home = props.getProperty("java.home");
String agent = home + File.separator + "lib" + File.separator + "management-agent.jar";
vm.loadAgent(agent);
props = vm.getAgentProperties();
connectorAddress = props.getProperty(CONNECTOR_ADDRESS_PROPERTY);
}
JMXServiceURL url = new JMXServiceURL(connectorAddress);
return JMXConnectorFactory.connect(url);
}The resulting JMXConnector can be used in the normal way to retrieve
data from JMX calls. For instance, if the JMX process exposed a no-arg
function functionName on object objectName, the call would be:
MBeanServerConnection mbsc = connector.getMBeanServerConnection();
String result = (String)mbsc.invoke(new ObjectName("objectName"),
"functionName", new Object[] {}, new String[] {});Finding remote JMX processes is something you’ll need to work out yourself, but assuming the host, port, user and password are known, the code to get a JMXConnector is:
private JMXConnector getRemoteConnection(String host, int port, String user, String password) throws Exception {
JMXServiceURL url = new JMXServiceURL("service:jmx:rmi:///jndi/rmi://"+host+":"+port+"/jmxrmi");
final Map<String, String[]> environment = new HashMap<String, String[]>();
environment.put(JMXConnector.CREDENTIALS, new String[] {user, password} );
return JMXConnectorFactory.connect(url, environment);
}The resulting JMXConnector can be used in the same manner as before. So
with the above code it is just a matter of adding some GUI glue to
create the required dialog. Excuse the main method and dodgy exception
handling (and anything else) - this is just a quick example class.
import java.awt.BorderLayout;
import java.awt.Component;
import java.awt.Container;
import java.awt.Dimension;
import java.awt.FlowLayout;
import java.awt.Frame;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.awt.event.KeyEvent;
import java.awt.event.KeyListener;
import java.awt.event.WindowAdapter;
import java.awt.event.WindowEvent;
import java.io.File;
import java.io.IOException;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
import java.util.Properties;
import javax.management.remote.JMXConnector;
import javax.management.remote.JMXConnectorFactory;
import javax.management.remote.JMXServiceURL;
import javax.swing.BoxLayout;
import javax.swing.ButtonGroup;
import javax.swing.JButton;
import javax.swing.JComboBox;
import javax.swing.JDialog;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JOptionPane;
import javax.swing.JPanel;
import javax.swing.JPasswordField;
import javax.swing.JRadioButton;
import javax.swing.JTextField;
import com.sun.tools.attach.AttachNotSupportedException;
import com.sun.tools.attach.VirtualMachine;
import com.sun.tools.attach.VirtualMachineDescriptor;
// requires Sun's default-tools.jar
public class JmxConnectorDialog extends JDialog implements ActionListener, KeyListener {
private static final long serialVersionUID = 1L;
private static final String CONNECTOR_ADDRESS_PROPERTY = "com.sun.management.jmxremote.localConnectorAddress";
private final JRadioButton localButton = new JRadioButton("Local Process");
private final JRadioButton remoteButton = new JRadioButton("Remote Process");
private final Map<String, VirtualMachine> localEngines = findEngines();
private final JComboBox typeList = new JComboBox(localEngines.keySet().toArray());
private final JTextField hostField = new JTextField(20);
private final JTextField portField = new JTextField(20);
private final JTextField userField = new JTextField(20);
private final JPasswordField passField = new JPasswordField(20);
private JMXConnector connector = null;
private String errorString = "";
public static void main(String[] args) {
JFrame frame = new JFrame("Graph Explorer");
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
JmxConnectorDialog jmxDialog = JmxConnectorDialog.showDialog(frame);
JMXConnector connector = jmxDialog.getConnector();
if (connector==null) {
JOptionPane.showMessageDialog(frame,
"Can't connect to JMX server: "+jmxDialog.getError(),
"Connection error", JOptionPane.ERROR_MESSAGE);
} else {
JOptionPane.showMessageDialog(frame, "Selected real Java process");
}
/*
MBeanServerConnection mbsc = connector.getMBeanServerConnection();
String result = (String)mbsc.invoke(new ObjectName("objectName"),
"functionName", new Object[] {}, new String[] {});
*/
}
public static JmxConnectorDialog showDialog(Component frameComp) {
Frame frame = JOptionPane.getFrameForComponent(frameComp);
JmxConnectorDialog dialog = new JmxConnectorDialog(frame);
dialog.setVisible(true);
return dialog;
}
public JmxConnectorDialog(Frame frame) {
super(frame, "JMX Connection", true);
addWindowListener(new WindowAdapter() {
@Override public void windowClosing(WindowEvent e) {
errorString="User cancelled";
setVisible(false);
}
});
Container contentPane = getContentPane();
JPanel content = new JPanel();
content.setLayout(new BoxLayout(content, BoxLayout.Y_AXIS));
contentPane.add(content);
content.add(createLocalPanel());
content.add(createRemotePanel());
content.add(createButtonPanel());
ButtonGroup group = new ButtonGroup();
group.add(localButton);
group.add(remoteButton);
pack();
}
private JPanel createLocalPanel() {
JPanel localPanel = new JPanel(new FlowLayout(FlowLayout.LEADING));
localButton.setPreferredSize(new Dimension(150, 50));
localButton.setSelected(true);
localPanel.add(localButton);
typeList.addActionListener(new ActionListener() {
@Override public void actionPerformed(ActionEvent e) {
localButton.setSelected(true);
}
});
JPanel listPanel = new JPanel(new FlowLayout());
listPanel.add(typeList, BorderLayout.SOUTH);
localPanel.add(listPanel);
return localPanel;
}
private JPanel createRemotePanel() {
JPanel remotePanel = new JPanel(new FlowLayout(FlowLayout.LEADING));
remoteButton.setPreferredSize(new Dimension(150, 50));
remotePanel.add(remoteButton);
JPanel remoteOptionPanel = new JPanel();
remoteOptionPanel.setLayout(new BoxLayout(remoteOptionPanel, BoxLayout.Y_AXIS));
remoteOptionPanel.add(createField("Host", hostField));
remoteOptionPanel.add(createField("Port", portField));
remoteOptionPanel.add(createField("User", userField));
remoteOptionPanel.add(createField("Password", passField));
remotePanel.add(remoteOptionPanel);
return remotePanel;
}
private JPanel createButtonPanel() {
JPanel buttonPanel = new JPanel(new FlowLayout());
JButton connectButton = new JButton("Connect");
getRootPane().setDefaultButton(connectButton);
connectButton.addActionListener(this);
buttonPanel.add(connectButton);
JButton cancelButton = new JButton("Cancel");
cancelButton.addActionListener(new ActionListener() {
public void actionPerformed(ActionEvent e) {
errorString="User cancelled";
setVisible(false);
}
});
buttonPanel.add(cancelButton);
return buttonPanel;
}
private JPanel createField(String label, JTextField field) {
JPanel fieldPanel = new JPanel(new FlowLayout(FlowLayout.LEADING, 5, 1));
JLabel labelComponent = new JLabel(label);
labelComponent.setPreferredSize(new Dimension(60, 10));
fieldPanel.add(labelComponent);
fieldPanel.add(field);
field.addKeyListener(this);
return fieldPanel;
}
private Map<String, VirtualMachine> findEngines() {
Map<String, VirtualMachine> result = new HashMap<String, VirtualMachine>();
List<VirtualMachineDescriptor> list = VirtualMachine.list();
for (VirtualMachineDescriptor vmd: list) {
String desc = vmd.toString();
try {
result.put(desc, VirtualMachine.attach(vmd));
} catch (IOException e) {
e.printStackTrace();
} catch (AttachNotSupportedException e) {
e.printStackTrace();
}
}
return result;
}
private JMXConnector getLocalConnection(VirtualMachine vm) {
try {
Properties props = vm.getAgentProperties();
String connectorAddress = props.getProperty(CONNECTOR_ADDRESS_PROPERTY);
if (connectorAddress == null) {
props = vm.getSystemProperties();
String home = props.getProperty("java.home");
String agent = home + File.separator + "lib" + File.separator + "management-agent.jar";
vm.loadAgent(agent);
props = vm.getAgentProperties();
connectorAddress = props.getProperty(CONNECTOR_ADDRESS_PROPERTY);
}
JMXServiceURL url = new JMXServiceURL(connectorAddress);
return JMXConnectorFactory.connect(url);
} catch (Exception e) {
e.printStackTrace();
errorString = e.getMessage();
return null;
}
}
private JMXConnector getRemoteConnection(String host, int port, String user, String password) {
try {
JMXServiceURL url = new JMXServiceURL("service:jmx:rmi:///jndi/rmi://"+host+":"+port+"/jmxrmi");
final Map<String, String[]> environment = new HashMap<String, String[]>();
environment.put(JMXConnector.CREDENTIALS, new String[] {user, password} );
return JMXConnectorFactory.connect(url, environment);
} catch (Exception e) {
e.printStackTrace();
errorString = e.getMessage();
return null;
}
}
public JMXConnector getConnector() {
return connector;
}
public String getError() {
return errorString;
}
@Override
public void actionPerformed(ActionEvent e) {
if (localButton.isSelected()) {
connector = getLocalConnection(localEngines.get(typeList.getSelectedItem()));
} else {
try {
int port = Integer.parseInt(portField.getText());
String password = String.valueOf(passField.getPassword());
connector = getRemoteConnection(hostField.getText(), port, userField.getText(), password);
} catch (NumberFormatException nfe) {
JOptionPane.showMessageDialog(JOptionPane.getRootFrame(), "Invalid port number",
"Connection error", JOptionPane.ERROR_MESSAGE);
return;
}
}
setVisible(false);
}
@Override
public void keyPressed(KeyEvent e) {
remoteButton.setSelected(true);
}
@Override
public void keyReleased(KeyEvent e) {
remoteButton.setSelected(true);
}
@Override
public void keyTyped(KeyEvent e) {
remoteButton.setSelected(true);
}
}