spring-projects/spring-boot · error · MojoExecutionException

Failed to connect to MBean server at port {jmxPort}

Error message

Failed to connect to MBean server at port {jmxPort}

What it means

Catch-all Exception handler in waitForSpringApplication for unexpected errors contacting the MBean server. Distinct from [48] which catches IOException specifically; this catches any other Throwable reaching the connection attempt.

Source

Thrown at build-plugin/spring-boot-maven-plugin/src/main/java/org/springframework/boot/maven/StartMojo.java:171

	private void waitForSpringApplication() throws MojoFailureException, MojoExecutionException {
		try {
			getLog().debug("Connecting to local MBeanServer at port " + this.jmxPort);
			try (JMXConnector connector = execute(this.wait, this.maxAttempts, new CreateJmxConnector(this.jmxPort))) {
				if (connector == null) {
					throw new MojoExecutionException("JMX MBean server was not reachable before the configured "
							+ "timeout (" + (this.wait * this.maxAttempts) + "ms");
				}
				getLog().debug("Connected to local MBeanServer at port " + this.jmxPort);
				MBeanServerConnection connection = connector.getMBeanServerConnection();
				doWaitForSpringApplication(connection);
			}
		}
		catch (IOException ex) {
			throw new MojoFailureException("Could not contact Spring Boot application via JMX on port " + this.jmxPort
					+ ". Please make sure that no other process is using that port", ex);
		}
		catch (Exception ex) {
			throw new MojoExecutionException("Failed to connect to MBean server at port " + this.jmxPort, ex);
		}
	}

	private void doWaitForSpringApplication(MBeanServerConnection connection)
			throws MojoExecutionException, MojoFailureException {
		final SpringApplicationAdminClient client = new SpringApplicationAdminClient(connection, this.jmxName);
		try {
			Callable<@Nullable Boolean> isReady = () -> (client.isReady() ? true : null);
			execute(this.wait, this.maxAttempts, isReady);
		}
		catch (ReflectionException ex) {
			throw new MojoExecutionException("Unable to retrieve 'ready' attribute", ex.getCause());
		}
		catch (Exception ex) {
			throw new MojoFailureException("Could not invoke shutdown operation", ex);
		}
	}

View on GitHub (pinned to 270dfe353f)

Solutions

1. Inspect the wrapped exception in the stack trace to identify the real class
2. Confirm jmxPort and jmxName configuration match the running application
3. Retry on a fresh port and re-run with mvn -X for verbose JMX diagnostics

try { waitForSpringApplication(); } catch (MojoExecutionException ex) { log.error("Unexpected JMX connection error on port {}", jmxPort, ex); throw ex; }

When it happens

Trigger: Non-IO exception while establishing the MBean connection (e.g. runtime exception during connector construction, malformed JMX URL, NPE in client code).

Common situations: JMX client library version mismatch between plugin and JVM; malformed JMX service URL; unexpected null from connector factory.

Related errors

• Could not contact Spring Boot application via JMX on port {j
• Unexpected: attribute 'Ready' not available
• Failed to retrieve Ready attribute
• Shutdown failed
• Could not invoke shutdown operation

AI-assisted analysis of spring-projects/spring-boot@270dfe353f (2026-08-11). Data as JSON: /api/errors/34c2fca877244501. Report an issue: GitHub.