Jolokia Starter

The Jolokia Starter integrates Jolokia agent configuration in Spring Boot, wrapping the Jolokia Spring Support with default configurations to let the application work out-of-the-box without manually declaring Jolokia servers.

This starter can be considered an alternative to the Jolokia JVM agent. When enabled, it exposes the Jolokia endpoint at http://0.0.0.0:8778/jolokia.

Maven Dependency

<dependency>
    <groupId>org.apache.camel.springboot</groupId>
    <artifactId>camel-jolokia-starter</artifactId>
</dependency>

Configuration Options

The following configuration options are available under the camel.component.jolokia prefix:

Option Default Description

enabled

true

Enable the component.

lookup-config

false

If true, Spring’s application context is searched for additional SpringJolokiaConfigHolder beans to configure the agent.

lookup-services

false

If true, Spring’s application context is searched for additional JolokiaService beans to add to Jolokia’s internal context.

system-properties-mode

never

Specifies how system properties with jolokia. prefix affect configuration. Values: never, fallback, override.

expose-application-context

false

If true, adds SpringRequestHandler to the agent allowing Spring bean operations via Jolokia protocol.

use-camel-restrictor

true

Use the Camel restrictor that allows only operations on Camel domain MBeans.

config-from-properties-first

true

When using custom bean configuration, prefer values from properties over values from bean.

kubernetes-discover

true

Auto-configure for Kubernetes/OpenShift environments (sets protocol=https, enables client authentication).

kubernetes-use-default-ca

true

Use the default Kubernetes CA file at /var/run/secrets/kubernetes.io/serviceaccount/service-ca.crt.

server-config

Map of Jolokia server configuration options (e.g., server-config.port=8779).

For detailed server configuration options, see the Jolokia JVM agent configuration documentation.

Usage Example

@SpringBootApplication
public class MyApplication {
    // The Jolokia agent is auto-configured when the starter is on the classpath
    // and camel.component.jolokia.enabled=true (default)
}

Configure in application.properties:

# Change the default port
camel.component.jolokia.server-config.port=8779

# Enable discovery for Hawtio
camel.component.jolokia.server-config.discoveryEnabled=true

Security Restrictor

To avoid exposing all JMX MBeans (see Security considerations), a default Jolokia Restrictor is provided that allows only Camel related data and some basic information from Java.

You can disable the restrictor with camel.component.jolokia.use-camel-restrictor=false or use your own custom one with camel.component.jolokia.server-config.restrictorClass=org.example.MyRestrictor.

An example to extend the provided restrictor:

public class MyRestrictor extends CamelRestrictor {

    @Override
    protected List<String> getAllowedDomains() {
        final List<String> newDomains = new ArrayList<>(getDefaultDomains());
        newDomains.add("my.domain");
        return newDomains;
    }
}

Custom Configuration

The starter creates a default configuration according to the provided properties, but you can provide a custom SpringJolokiaConfigHolder implementation by declaring a Bean named camelConfigHolder:

@Bean("camelConfigHolder")
public SpringJolokiaConfigHolder myConfigHolder() {
    final SpringJolokiaConfigHolder myConfig = new SpringJolokiaConfigHolder();
    myConfig.setConfig(Map.of("threadNr", "5", "executor", "fixed"));
    return myConfig;
}

The executor configuration will be taken from the custom Bean if the same properties are not defined in application.properties. This behaviour is configurable with camel.component.jolokia.config-from-properties-first=false, meaning the configuration uses the Bean value when the key is present in both places. If the keys from properties and beans do not override each other, they will be merged.

Logging Configuration

The starter provides a log configuration using the slf4j implementation. You can change this by providing a Bean named camelLogHandlerHolder:

@Bean
@ConditionalOnMissingBean(name = "camelLogHandlerHolder")
public SpringJolokiaLogHandlerHolder myLogHandlerHolder() {
    final SpringJolokiaLogHandlerHolder stdoutHandlerHolder = new SpringJolokiaLogHandlerHolder();
    stdoutHandlerHolder.setType("stdout");
    return stdoutHandlerHolder;
}

The logging category for the Camel Spring Boot starter is org.apache.camel.component.jolokia, while the core Jolokia server uses org.jolokia:

logging.level.org.apache.camel.component.jolokia=TRACE
logging.level.org.jolokia=TRACE

Kubernetes Support

The starter provides default configurations for Kubernetes environments. It checks for the existence of a certification authority file at /var/run/secrets/kubernetes.io/serviceaccount/service-ca.crt and, if present, initializes the server using TLS protocol and client authentication. The endpoint becomes https://0.0.0.0:8778/jolokia.

You can disable this behaviour with camel.component.jolokia.kubernetes-discover=false.

Spring Boot Actuator Integration

The wrapped Jolokia Spring Support library provides integration with Spring Boot Actuator, where it is possible to retrieve information about the Jolokia server. As with any other actuator endpoint, it can be excluded or disabled.

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