Apache Camel 3.x Upgrade Guide

This document is for helping you upgrade your Apache Camel application from Camel 3.x to 3.y. For example if you are upgrading Camel 3.0 to 3.2, then you should follow the guides from both 3.0 to 3.1 and 3.1 to 3.2.

Upgrading Camel 3.5 to 3.6

UUID Generator

The default UUID Generator in Camel has switched to a faster algorithm based on UUID that were used by Camel Quarkus and Camel K. This generator does not use the hostname as part of the ID generation and avoids any network IO calls during initialization.

The old generator has been renamed and moved into a new package at org.apache.camel.support.ClassicUuidGenerator. The new default generator is now also located in camel-support as org.apache.camel.support.DefaultUuidGenerator where all the out of the box generators reside.

Users that want to use the old UUID generator can configure Camel to use org.apache.camel.support.ClassicUuidGenerator as the generator.

Simple language

The simple language have been optimized to handle numeric and boolean values more naturally. We have also optimized for unneeded type conversions in predicates such as comparing left and right hand side in operators with their given type as-is, or the least amount of conversion when possible.

The contains and not contains operator now handles numerics naturally. For example ${header.numbers} contains '123,456' would return false if the numbers header has the value -123, as the operator now compares numerically. Previously it would compare with String based values.

Bean component

We have now implemented bean scope (singleton, request, and prototype) for all kinds of using the bean component, whether it’s the bean endpoint, bean language (method call), bean EIP, or the bean function in the simple language (eg ${bean:foo}).

The default scope is now singleton. Previously the bean function in simple language would be prototype scope (always lookup the bean on each use). With singleton scope we improve the performance by avoiding the repetitive lookup of the same bean on each usage.

You can use the old behaviour by setting the scope to prototype.

API components upgrade

The camel-braintree, camel-twilio and camel-zendesk has updated to newer versions and regenerated their API signatures in the Camel components which changed a few existing API methods and adding new API methods as well.

API components overhauled

The following API component has been overhauled, by having a new Java source parser to inspect API and fully generate Camel endpoint configuration and documentation gathered from javadoc.

The components affected are:

  • camel-as2

  • camel-box

  • camel-braintree

  • camel-fhir

  • camel-google-calendar

  • camel-google-drive

  • camel-google-email

  • camel-google-sheets

  • camel-olingo2

  • camel-olingo4

  • camel-twilio

  • camel-zendesk


All the out of the box supported languages (simple, bean, groovy, jsonpath, xpath etc.) have been optmized to be singleton which improves performance for concurrent processing that uses those languages that would be resolved on each use. Now the languages are resolved once during startup or first usage.


Expressions built via ExpressionBuilder and similar now often require to be initialized by calling init before use. This is part of an effort to optimize Camel to eager initialize its expression and languages. This only impacts Camel end users whom use the ExpressionBuilder directly. Normal usage of Camel should not be impacted by this change.


Customizers, which are objects used to configure some of the Camel services such as component, language and data formats, that were previously limited to Camel Spring Boot, are now consistently used across runtimes. To make that possible, the interfaces have been changed and they do not use generics anymore.

Impacted interfaces:

  • org.apache.camel.spi.ComponentCustomizer

  • org.apache.camel.spi.LanguageCustomizer

  • org.apache.camel.spi.DataFormatCustomizer

As example the signature of the ComponentCustomizer interface in Camel 3.5 is:

public interface ComponentCustomizer<T extends Component> {
     * Customize the specified {@link Component}.
     * @param component the component to customize
    void customize(T component);

And below the Camel 3.6 version:

public interface ComponentCustomizer {
     * Customize the specified {@link Component}.
     * @param name   the unique name of the component
     * @param target the component to configure
    void configure(String name, Component target);

     * Checks whether this customizer should be applied to the given {@link Component}.
     * @param  name   the unique name of the component
     * @param  target the component to configure
     * @return        <tt>true</tt> if the customizer should be applied
    default boolean isEnabled(String name, Component target) {
        return true;

    default int getOrder() {
        return 0;

As the customizers are now taken into account as part of the standard lifecycle of the CamelContext, to programmatically configure a component, it is enough to register the appropriate customizer in the Registry. For example:

public class Application {

    public static void main(String args) throws Exception {
        Main main = new Main();

    public static class MyConfiguration {
        public ComponentCustomizer logCustomizer() {
            // Use a fluent Component Customizer builder to ease the process of creating an customizer.
            return ComponentCustomizer.builder(LogComponent.class)
                    .build(component -> component.setExchangeFormatter(new DefaultExchangeFormatter()));

As a consequence of this change, the Camel Spring Boot starters have been amended to use Customizers instead of creating instances of components, languages or data formats.

Component Verifiers

Camel components which provides ComponentVerifierExtension should have camel-core-catalog added as dependency at runtime, if the verifier are in use. You will see an exception about camel-core-catalog not found on classpath otherwise.


The API in org.apache.camel.spi.SendDynamicAware has changed and any custom implementations must be updated accordingly. There is a new abstract org.apache.camel.support.component.SendDynamicAwareSupport class which can be used as base for custom implementations.

Stream Caching

If stream caching is enabled and an exception is thrown while converting the message payload to StreamCache then the error handler can now handle this exception (e.g. onException). The exception is regarded as non-recoverable and redelivery is not in use.

Camel Caffeine

To configure the component to use a pre-configured cache, it is no longer required to use the now removed cache option as the component performs a look-up in the registry based on the cacheName URI param.

For example, the following code:


Should be replaced by:


Camel Karaf

The following feature has been removed due to being no longer compatible with OSGi: camel-atmosphere-websocket.


The class CamelFileDataSource has moved from camel-http-common package org.apache.camel.http.common to camel-attachments package org.apache.camel.attachment.

If your code directly depends on this class, you will need to update the package reference to the new location.

Message History

When message history is enabled then there is a slight performance overhead as the history data is now stored in a java.util.concurrent.CopyOnWriteArrayList due to the need of being thread safe.

Default limit set on decompressed file size

From Apache Camel 3.6.0, a default limit is enforced on the maximum size of a decompressed file, to prevent possible denial of service attacks. This applies to the camel-zipfile and camel-tarfile data formats. This can be configured as follows:

ZipFileDataFormat maxDecompressedSizeZip = new ZipFileDataFormat();


The default value if not specified corresponds to one gigabyte. An IOException will be thrown if the decompressed size exceeds this amount. Set to -1 to disable setting a maximum decompressed size.

Camel RabbitMQ

The camel-rabbitmq server component properties have been changed. The properties prefix rabbitmq. was replaced by CamelRabbitmq.


The options username, iconUrl and iconEmoji have been deprecated and they will be removed in 3.7.0.


This component has been removed.