= Apache Camel 2.x to 3.0 Migration Guide

This document is intended to help you migrate your Apache Camel applications
from version 2.x to 3.0.

IMPORTANT: If you are upgrading Camel 3.x to 3.y then use the
xref:camel-3x-upgrade-guide.adoc[Camel 3.x Upgrade Guide].

== Java versions

Camel 3 supports Java 11. Support for Java 8 is best effort for early versions of Camel 3. However at some time in the 3.x lifeline we will drop support for Java 8.

In Java 11 the JAXB modules have been **removed** from the JDK, therefore you will need to add them as Maven dependencies (if you use JAXB such as when using XML DSL or the camel-jaxb component):

[source,xml]
----
<dependency>
    <groupId>javax.xml.bind</groupId>
    <artifactId>jaxb-api</artifactId>
    <version>2.3.1</version>
</dependency>

<dependency>
    <groupId>com.sun.xml.bind</groupId>
    <artifactId>jaxb-core</artifactId>
    <version>2.3.0.1</version>
</dependency>

<dependency>
    <groupId>com.sun.xml.bind</groupId>
    <artifactId>jaxb-impl</artifactId>
    <version>2.3.2</version>
</dependency>
----

== Modularization of camel-core

One of the biggest changes is the modularization of camel-core.
In Camel 2.x camel-core was one JAR file, it has now been split up into many JARs as follows:

- camel-api
- camel-base
- camel-caffeine-lrucache
- camel-cloud
- camel-core
- camel-jaxp
- camel-main
- camel-management-api
- camel-management
- camel-support
- camel-util
- camel-util-json

Maven users of Apache Camel can keep using the dependency `camel-core` which has transitive dependencies on all of its modules, except for `camel-main`, and therefore no migration is needed.
However, users who want to trim the size of the classes on the classpath, can use fine grained Maven dependencies on only the modules needed.
You may find how to do that in the examples.

We have also modularized many of the core components and moved them out of `camel-core` to individual components:

- camel-attachments
- camel-bean
- camel-browse
- camel-controlbus
- camel-dataformat
- camel-dataset
- camel-direct
- camel-directvm
- camel-file
- camel-language
- camel-log
- camel-mock
- camel-ref
- camel-rest
- camel-saga
- camel-scheduler
- camel-seda
- camel-stub
- camel-timer
- camel-validator
- camel-vm
- camel-xpath
- camel-xslt
- camel-xslt-saxon
- camel-zip-deflater

== Spring Boot starters Maven coordinate change

The Maven `groupId` for the Spring Boot starters changed to: `org.apache.camel.springboot`.

Instead of:

[source,xml]
----
<dependency>
  <groupId>org.apache.camel</groupId>
  <artifactId>camel-component-starter</artifactId>
</dependency>
----

Use:

[source,xml]
----
<dependency>
  <groupId>org.apache.camel.springboot</groupId>
  <artifactId>camel-component-starter</artifactId>
</dependency>
----

== Multiple CamelContexts per application not supported

Support for multiple CamelContexts has been removed and only 1 CamelContext per deployment is supported.
The latter was not recommended anyway and was also not 100% implemented (for example in camel-cdi).
For Camel 3 only 1 CamelContext per deployment is recommended and supported.

The `context` attribute on the various Camel annotations such as `@EndpointInject`, `@Produce`, `@Consume` etc. has therefore been removed.

== Migrating custom components

You should depend on `camel-support` and not `camel-core` directly.

The classes from `org.apache.camel.impl` that are intended to support Camel developers building custom components have been moved out of `camel-core` into `camel-support` into the `org.apache.camel.support` package. For example classes such as `DefaultComponent`, `DefaultEndpoint` etc. have been moved and migration is necessary.

== Migrating custom languages

The `LanguageAnnotation` annotation class has been moved from package `org.apache.camel.language` to `org.apache.camel.support.language`.

== Migrating DefaultShutdownStrategy

The `DefaultShutdownStrategy` class has been moved from package `org.apache.camel.impl` to `org.apache.camel.impl.engine`.

== Deprecated APIs and Components

All deprecated APIs and components from Camel 2.x have been removed in Camel 3.

== Migrating Camel applications

=== Main class

The Camel `Main` class has been moved out of `camel-core` into `camel-main` so you should add that as dependency if you use Main.

=== Properties component

The `properties` component has configuring custom prefix and suffix tokens removed as if in use, they had potential issues with clashing with simple languages and elsewhere. The default tokens are now hardcoded and always in use.

The `properties` component has some advanced options removed: `propertyPrefix`, `propertySuffix`, and `fallbackToUnaugmented`; these options was never really useable for end users anyway. The option `propertiesResolver` has also been removed as you should use `PropertiesSource` instead.

The properties component will now use OS environment variables as preferred value. This means you can set an OS environment variable which will override any property values that has been set in property files, JVM system properties etc. You can configure this with the `environmentVariableMode` option on the properties component.

The `properties` component no longer support using endpoints, such as `properties:myKey`. The properties component is now only a property placeholder service.
You can therefore no longer lookup the properties component via `camelContext.getComponent("properties")`.
Instead you can use `camelContext.getPropertiesComponent()`, which also returns an interface of the properties component as `org.apache.camel.spi.PropertiesComponent`.
The implementation is still named `org.apache.camel.component.properties.PropertiesComponent`, however it should rarely be used, as you should favour using the interface instead.


=== Removed components

We have removed all deprecated components from Camel 2.x, including the old `camel-http`, `camel-hdfs`, `camel-mina`, `camel-mongodb`, `camel-netty`, `camel-netty-http`, `camel-quartz`, `camel-restlet` and `camel-rx` components.

We removed `camel-jibx` component which wasn't working on JDK 8.

We removed `camel-boon` dataformat which wasn't working on JDK 9 and later.

We removed the `camel-linkedin` component as the Linkedin API 1.0 is no longer https://engineering.linkedin.com/blog/2018/12/developer-program-updates[supported]. Support for the new 2.0 API is tracked by https://issues.apache.org/jira/browse/CAMEL-13813[CAMEL-13813].

The `camel-zookeeper` has its route policy functionality removed, instead use `ZooKeeperClusterService` or the `camel-zookeeper-master` component.

The `camel-jetty` component no longer supports producer (eg to) which has been removed, use `camel-http` component instead.

The `twitter-streaming` component has been removed as it relied on the deprecated Twitter Streaming API and is no longer functional.

=== Renamed components

The `test` component has been renamed to `dataset-test` and moved out of `camel-core` into `camel-dataset` JAR.

The `http4` component has been renamed to `http`, and it's corresponding component package from `org.apache.camel.component.http4` to `org.apache.camel.component.http`. The supported schemes are now only `http` and `https`.

The `hdfs2` component has been renamed to `hdfs`, and it's corresponding component package from `org.apache.camel.component.hdfs2` to `org.apache.camel.component.hdfs`. The supported scheme is now `hdfs`.

The `mina2` component has been renamed to `mina`, and it's corresponding component package from `org.apache.camel.component.mina2` to `org.apache.camel.component.mina`. The supported scheme is now `mina`.

The `mongodb3` component has been renamed to `mongodb`, and it's corresponding component package from `org.apache.camel.component.mongodb3` to `org.apache.camel.component.mongodb`. The supported scheme is now `mongodb`.

The `netty4-http` component has been renamed to `netty-http`, and it's corresponding component package from `org.apache.camel.component.netty4.http` to `org.apache.camel.component.netty.http`. The supported scheme is now `netty-http`.

The `netty4` component has been renamed to `netty`, and it's corresponding component package from `org.apache.camel.component.netty4` to `org.apache.camel.component.netty`. The supported scheme is now `netty`.

The `quartz2` component has been renamed to `quartz`, and it's corresponding component package from `org.apache.camel.component.quartz2` to `org.apache.camel.component.quartz`. The supported scheme is now `quartz`.

The `rxjava2` component has been renamed to `rxjava`, and it's corresponding component package from `org.apache.camel.component.rxjava2` to `org.apache.camel.component.rxjava`.

We have also renamed `camel-jetty9` to `camel-jetty`. The supported scheme is now `jetty`.

=== Hystrix EIP

The Hystrix EIP has been generalized as circuit breaker to allow to plugin other implementations.

In the Java DSL you need to migrate from `.hystrix()` to `.circuitBreaker()`.
And in XML DSL `<hystrix>` should be `<circuitBreaker>`.


=== Using endpoint options with consumer. prefix

Endpoints with `consumer.` prefix such as `consumer.delay=5000` are no longer supported (deprecated in latest Camel 2.x) and you should just use the option without the `consumer.` prefix, eg `delay=5000`.

=== Calling a processor as an endpoint

Calling a processor as an endpoint from a route such as:

[source,java]
----
from("jms:cheese")
  .to("myProcessor");
----

Is no longer supported. Instead either use the bean component to call the processor or use `process`:

[source,java]
----
from("jms:cheese")
  .to("bean:myProcessor");
----

Or

[source,java]
----
from("jms:cheese")
  .process("myProcessor");
----

=== Tracing

A new tracer has been implemented and the old tracer has been removed.
The new tracer logs messages at the `org.apache.camel.Tracing` logger name which is hardcoded. The format of the output is also updated to make it better. The tracer can be customized.

In JMX the `BacklogTracer` is no longer enabled by default, which you need to enable by setting `backlogTracing=true` on CamelContext. The backlog tracer and tracer are not the same. The former is used for capturing a backlog of traced messages which you can poll via JMX (needed for 3rd party tooling), where as tracer is writing to the log. Neither of them are enabled by default, and they must be enabled to be in use.

=== <setHeader> and <setProperty> in XML DSL

We have renamed the attribute `headerName` and `propertyName` in the XML DSL for the `<setHeader>` and `<setProperty`> EIPs, to be just `name`.

So migrate

[source,xml]
----
<setHeader headerName="foo"><simple>Hello ${body}</simple></setHeader>
----

To

[source,xml]
----
<setHeader name="foo"><simple>Hello ${body}</simple></setHeader>
----

And the same for `<setProperty>`.

=== <aggregate> EIP in XML DSL

The aggregte EIP have renamed the expressions (not the attributes) for setting correlation size/timeout to avoid a name clash, so migrate:

[source,xml]
----
<completionSize>
  <header>mySize</header>
</completionSize>
----

To

[source,xml]
----
<completionSizeExpression>
  <header>mySize</header>
</completionSizeExpression>
----

And the same for `<completionTimeout>`.

==== camel-cdi

Support for multiple CamelContexts has been removed, and therefore `@ContextName` has been removed. Instead use standard CDI annotations such as `@Named` and `@ApplicationScoped`.

=== javax.script

The `camel-script` component has been removed and there is no support for javax.script, which is also deprecated in the JDK and to be removed from Java 11 onwards.

=== Attachments API on Message

The attachments API (javax.activation) has been moved out of `org.apache.camel.message` into an extension `org.apache.camel.attachment.AttachmentMessage` from the `camel-attachments` JAR.

To use this API you can get it via the `getMessage` method on `Exchange`:

  AttachmentMessage am = exchange.getMessage(AttachmentMessage.class);
  am.addAttachment("myAtt", new DataHandler(...));

=== Fault API on Message

The fault API has been removed from `org.apache.camel.Message` as it was only used for SOAP-WS fault message. The `camel-cxf` and `camel-spring-ws` components for SOAP-WS has been modified to support fault messages from their components. The option `handleFault` has also been removed and you now need to turn this on as endpoint or component option on `camel-cxf` or `camel-spring-ws`.

=== getOut on Exchange

The `hasOut` and `getOut` methods on `Exchange` has been deprecated in favour of using `getMessage` instead. (Side note: Camel-core is still using these methods in a few places to be backwards compatible and relies on this logic as Camel was initially designed with the concept of IN and OUT messages inspired by the JBI and SOAP-WS specifications.)

=== OUT message removed from Simple language and Mock component

The simple language has removed the OUT message concepts eg `${out.body}`.
Also the mock component has removed OUT message from its assertion API, eg

  mock.message(0).outBody()...

Also the `@OutHeaders` annotation for bean parameter binding has been removed, instead use `@Headers` instead.

=== Mock component

The `mock` component has been moved out of `camel-core` and as part of this work, we had to remove a number of methods on its _assertion clause builder_ that were seldom in use.

=== ActiveMQ

If you are using the `activemq-camel` component, then you should migrate to use `camel-activemq` component, where the component name has changed from `org.apache.activemq.camel.component.ActiveMQComponent` to `org.apache.camel.component.activemq.ActiveMQComponent`.

=== AWS

The component `camel-aws` has been split into multiple components:

- camel-aws-cw
- camel-aws-ddb (which contains both ddb and ddbstreams components)
- camel-aws-ec2
- camel-aws-iam
- camel-aws-kinesis (which contains both kinesis and kinesis-firehose components)
- camel-aws-kms
- camel-aws-lambda
- camel-aws-mq
- camel-aws-s3
- camel-aws-sdb
- camel-aws-ses
- camel-aws-sns
- camel-aws-sqs
- camel-aws-swf

So you'll have to add explicitly the dependencies for these components. From the OSGi perspective, there is still a `camel-aws` Karaf feature, which includes all the components features.

=== FHIR

The camel-fhir component has upgraded it's hapi-fhir dependency to 4.1.0; Karaf support has been dropped until the hapi-fhir Karaf features are fixed and released.
The default FHIR version has been changed to R4. Therefore if DSTU3 is desired it has to be explicitly set.

=== Kafka

The `camel-kafka` component has removed the options `bridgeEndpoint` and `circularTopicDetection` as this is no longer needed as the component is acting as bridging would work on Camel 2.x. In other words `camel-kafka` will send messages to the topic from the endpoint uri. To override this use the `KafkaConstants.OVERRIDE_TOPIC` header with the new topic. See more details in the `camel-kafka` component documentation.

=== Telegram

The `camel-telegram` component has moved the authorization token from uri-path to a query parameter instead, e.g. migrate

    telegram:bots/myTokenHere

to

    telegram:bots?authorizationToken=myTokenHere

=== JMX

If you run Camel standalone with just `camel-core` as a dependency, and you want JMX enabled out of the box, then you need to add `camel-management` as a dependency.

For using `ManagedCamelContext` you now need to get this an extension from `CamelContext` as follows:

    ManagedCamelContext managed = camelContext.getExtension(ManagedCamelContext.class);

=== XSLT

The XSLT component has moved out of camel-core into `camel-xslt` and `camel-xslt-saxon`. The component is separated so `camel-xslt` is for using the JDK XSTL engine (Xalan), and `camel-xslt-saxon` is when you use Saxon.
This means that you should use `xslt` and `xslt-saxon` as component name in your Camel endpoint URIs.
If you are using XSLT aggregation strategy, then use `org.apache.camel.component.xslt.saxon.XsltSaxonAggregationStrategy` for Saxon support.
And use `org.apache.camel.component.xslt.saxon.XsltSaxonBuilder` for Saxon support if using xslt builder. Also notice that `allowStax` is also only supported in `camel-xslt-saxon` as this is not supported by the JDK XSLT.

=== camel-sql

The `JdbcAggregationRepository` optimistic locking feature has been fixed to work on a distributed environment and every database.
There is a new `version` column that is required and must be added to the repository:

[source,sql]
----
CREATE TABLE aggregation (
 id varchar(255) NOT NULL,
 exchange blob NOT NULL,
 version BIGINT NOT NULL,
 constraint aggregation_pk PRIMARY KEY (id)
);
CREATE TABLE aggregation_completed (
 id varchar(255) NOT NULL,
 exchange blob NOT NULL,
 version BIGINT NOT NULL,
 constraint aggregation_completed_pk PRIMARY KEY (id)
);
----

=== Configuring global options on CamelContext

In Camel 2.x we have deprecated `getProperties` on `CamelContext` in favour of `getGlobalOptions`, so you should migrate to:

[source,java]
----
context.getGlobalOptions().put("CamelJacksonEnableTypeConverter", "true");
context.getGlobalOptions().put("CamelJacksonTypeConverterToPojo", "true");
----

and in XML:

[source,xml]
----
<globalOptions>
  <globalOption key="CamelJacksonEnableTypeConverter" value="true"/>
  <globalOption key="CamelJacksonTypeConverterToPojo" value="true"/>
</globalOptions>
----

=== Main class

The `Main` class from `camel-core`, `camel-spring` and `camel-cdi` has been modified to only support a single `CamelContext` which was really its intention, but there was some old crufty code for multiple Camels. The methods `getCamelContextMap` and `getCamelContexts` have been removed, and there is just a `getCamelContext` method now.

=== POJO annotations

The `ref` attribute on `@Consume`, `@Produce` and `@EndpointInject` has been removed. Instead use the ref component in the `uri` attribute, eg `uri = "ref:myName"`.

The uri attribute has been deprecated, instead use value, which allows a shorthand style, from using `@Consume(uri = "jms:cheese")` to `@Consume("jms:cheese")`.

=== Routes with multiple inputs

In Camel 2.x you could have 2 or more inputs to Camel routes, however this was not supported in all use-cases in Camel, and this functionality is seldom in use. This has
also been deprecated in Camel 2.x. In Camel 3 we have removed the remaining code for specifying multiple inputs to routes, and its now only possible to specify exactly only 1 input to a route.

=== Crypto Component

The default signature algorithm has changed for the Crypto (JCE) Component - it
is now SHA256withRSA (before it was SHA1WithDSA).

=== Crypto DataFormat

The default encryption algorithm has changed for the Crypto (JCE) DataFormat -
it is now required to set a value for it (meaning that the default is null).
Before the default value was "DES/CBC/PKCS5Padding".

=== JSon DataFormat

The default JSon library with the JSon dataformat has changed from `XStream` to `Jackson`.

=== Shiro Component

The default encryption key for the Shiro component has been removed, so now it
is mandatory to supply the key/passphrase.

=== XML Security Component

The default signature algorithm has changed for the XML Security Component - it
is now RSA-SHA256 (before it was RSA-SHA1).

=== XML Security DataFormat

The default encryption key for the XML Security DataFormat has been removed,
so it is now mandatory to supply the key String/bytes if you are using
symmetric encryption. This means that some of the methods are removed that
used the XMLSecurityDataFormat without specifying a key.

In addition, the default symmetric encryption algorithm has changed from
Triple DES to AES-256 in GCM mode.

=== Zip and GZip DataFormat

The zip and gzip dataformat has been renamed to zipdeflater and gzipdeflater as they are for deflating using the zip/gzip compression; and not for working with zip/gzip files. Instead use camel-zipfile dataformat. Also these dataformats has been moved out of `camel-core` into `camel-zip-deflater` JAR. The XML and Java DSL has also been modified so you should migrate there too to use their new names. And if you use these data formats you need to add the `camel-zip-deflater` as dependency as they are no longer included as transitive dependency with `camel-core`.

=== Simple language

The functionality to change the simple language tokens for start/end functions has been removed. The default tokens with `+++${xxx}+++` and `+++$simple{xxx}+++` is now hardcoded (optimized). The functionality to change these tokens was never really in use and would only confuse Camel users if a new syntax are in use.

=== Moved APIs

The following API changes may affect your existing Camel applications, which needs to be migrated.

==== CamelContext

The methods on `CamelContext` that are related to catalog has been moved into a new `CatalogCamelContext` interface, which you can access by adapting:

  CatalogCamelContext ccc = context.adapt(CatalogCamelContext.class);

The `loadRouteDefinitions` and `loadRestDefinitions` on `ModelCamelContext` has been changed to `addRouteDefinitions` and `addRestDefinitions` to be aligned with the other methods. You can find `getModelToXMLDumper` and `getXMLRoutesDefinitionLoader` loader methods on the `ExtendedCamelContext` class.

==== ModelCamelContext

If you need to access the routes model (such as `addRouteDefinitions`, etc.), then you need to adapt form CamelContext as shown:

    ModelCamelContext mcc = camelContext.adapt(ModelCamelContext.class);

==== Extended CamelContext

The APIs on `CamelContext` has been reduced a bit to focus on relevant API for Camel end users. The advanced use-cases and for SPI and component developers, then some of the APIs from `CamelContext` has been moved to `ExtendedCamelContext` which you can access via adapt:

  ExtendedCamelContext ecc = context.adapt(ExtendedCamelContext.class);


=== Checked vs unchecked exceptions

Most of the Camel exception classes have been migrated to be unchecked (e.g. extends `RuntimeException`).

Also the lifecycle of the `start`, `stop` and `suspend`, `resume` methods on `Service` and `SuspendableService` has been changed to not throw checked exceptions.

==== Generic Information

The class `SimpleRegistry` is moved from `org.apache.camel.impl` to `org.apache.camel.support`. Also you should favour using the `org.apache.camel.support.DefaultRegistry` instead. Also you should use the `bind` operation instead of `put` to add entries to the `SimpleRegistry` or `DefaultRegistry`.

The class `CompositeRegistry` and `PropertyPlaceholderDelegateRegistry` has been deleted. Instead use `DefaultRegistry`.

The classes from `org.apache.camel.impl` that was intended to support Camel developers building custom components has been moved out of `camel-core` into `camel-support` into the `org.apache.camel.support` package. If you have built custom Camel components that may have used some of these APIs you would then need to migrate.  A large part of classes from the `org.apache.camel.impl` package have been moved to the `org.apache.camel.impl.engine` package in `camel-base`.

All the classes in `org.apache.camel.util.component` has been moved from the camel-core JAR to the package `org.apache.camel.support.component` in the `camel-support` JAR.

The method `xslt` has been removed from `org.apache.camel.builder.AggregationStrategies`. Instead use the `XsltAggregationStrategy` from `camel-xslt` JAR directly.

The getter/setter for `bindingMode` on `RestEndpoint` has been changed to use type `org.apache.camel.spi.RestConfiguration.RestBindingMode` from `camel-api` JAR. Instead of using this type class you can also call the setter method with string type instead.

The `activemq-camel` component has been moved from ActiveMQ into Camel and it is now called `camel-activemq`, the package has been changed accordingly to `org.apache.camel.component.activemq`

The method `includeRoutes` on `RouteBuilder` has been removed. This functionality was not fully in use and was deprecated in Camel 2.x.

The exception `PredicateValidationException` has been moved from package `org.apache.camel.processor.validation` to `org.apache.camel.support.processor.PredicateValidationException`.

The class `org.apache.camel.util.toolbox.AggregationStrategies` has been moved to `org.apache.camel.builder.AggregationStrategies`.

The class `org.apache.camel.util.toolbox.AggregationStrategies` has been moved to `org.apache.camel.builder.AggregationStrategies`.

The class `org.apache.camel.processor.RedeliveryPolicy` has been moved to `org.apache.camel.processor.errorhandler.RedeliveryPolicy`.

The class `org.apache.camel.processor.loadbalancer.SimpleLoadBalancerSupport` has been removed, instead use `org.apache.camel.processor.loadbalancer.LoadBalancerSupport`.

The class `org.apache.camel.management.JmxSystemPropertyKeys` has been moved to `org.apache.camel.api.management.JmxSystemPropertyKeys`.

The class `org.apache.camel.builder.xml.XPathBuilder` has been moved to `org.apache.camel.language.xpath.XPathBuilder` and in the `camel-xpath` JAR.

The annotation `org.apache.camel.language.XPath` has been moved to `org.apache.camel.language.xpath.XPath` and in the `camel-xpath` JAR.

The exception `org.apache.camel.builder.xml.InvalidXPathExpression` has been renamed to `org.apache.camel.language.xpath.InvalidXPathException` and in the `camel-xpath` JAR.

The annotation `org.apache.camel.language.Bean` has been moved to `org.apache.camel.language.bean.Bean` and in the `camel-bean` JAR.

The annotation `org.apache.camel.language.Simple` has been moved to `org.apache.camel.language.simple.Simple`.

The annotation `org.apache.camel.Constant` has been removed, use `@Simple` instead.

The annotation `org.apache.camel.language.SpEL` has been moved to `org.apache.camel.language.spel.SpEL` and in the `camel-spring` JAR.

The annotation `org.apache.camel.InvokeOnHeader` and `org.apache.camel.InvokeOnHeaders` has been moved to the `org.apache.camel.spi` package.

The class `OutputStreamBuilder` has been moved from package `org.apache.camel.converter.stream` to `org.apache.camel.support.builder` package.

Rename various APIs in camel-core to fix the typo `chiper` to `cipher`.

The classes `ReloadStrategySupport` and `FileWatcherReloadStrategy` has been removed.

The `MessageHistoryFactory` interface has some options to filter and copy the message and a slight change in its API.

Removed `TypeConverterAware` as you should instead use `Exchange` as parameter to the type converter method.

The `Component` and `DataFormat` interfaces now extend `Service` as components and data formats should also have service contract to manage their lifecycle. The default base classes already implements these interfaces.

The class `FactoryFinder` has changed its API to use `Optional` as return types instead of throwing checked `FactoryNotFoundException` or `ClassNotFoundException` etc.

The option `resolvePropertyPlaceholders` on all the components has been removed,
as property placeholders are already supported via Camel Main, Camel Spring Boot and other means.

=== camel-test

If you are using camel-test and override the `createRegistry` method, for example to register beans from the `JndiRegistry` class, then this is no longer necessary, and instead
you should just use the `bind` method from the `Registry` API which you can call directly from `CamelContext`, such as:

  context.getRegistry().bind("myId", myBean);

=== Controlling routes

The `startRoute`, `stopRoute`, `suspendRoute`, `resumeRoute`, `getRouteStatus`, and other related methods on `CamelContext` has been moved to the `RouteController` as shown below:

  context.getRouteController().startRoute("myRoute");

=== JMX events

All the events from package `org.apache.camel.management.event` has been moved to the class `org.apache.camel.spi.CamelEvent` as sub-classes, for example the event for CamelContext started would be `CamelEvent.CamelContextStartedEvent`.

=== AdviceWith

Testing using `adviceWith` currently needs to be changed from:

[source,java]
----
context.getRouteDefinition("start").adviceWith(camelContext, new AdviceWithRouteBuilder() {
  ...
}
----

to using style:

[source,java]
----
ModelCamelContext mcc = camelContext.adapt(ModelCamelContext.class);
RouteReifier.adviceWith(mcc.getRouteDefinition("start"), mcc, new AdviceWithRouteBuilder() {
  ...
}
----

However its even easier using lambda style with `AdviceWithRouteBuilder` directly:

[source,java]
----
AdviceWith.adviceWith(context, "myRoute", a -> {
  a.replaceFromWith("direct:start");
}
----

=== Generic Classes

The class `JNDIContext` has been moved from `org.apache.camel.util.jndi.JNDIContext` in the camel-core JAR to `org.apache.camel.support.jndi.JNDIContext` and moved to the `camel-support` JAR.

=== EIPs

The `circuitBreaker` load-balancer EIP was deprecated in Camel 2.x, and has been removed. Instead use Hystrix EIP as the load-balancer.

The class `ThreadPoolRejectedPolicy` has been moved from `org.apache.camel.ThreadPoolRejectedPolicy` to `org.apache.camel.util.concurrent.ThreadPoolRejectedPolicy`.

=== Languages

The simple language `property` function was deprecated in Camel 2.x and has been removed. Use `exchangeProperty` as function name.

The terser language has been renamed from `terser` to `hl7terser`.

=== JSSE

The classes from `org.apache.camel.util.jsse` has been moved to `org.apache.camel.support.jsse`.

=== Helpers and support

The class `AsyncProcessorHelper` has been moved from `org.apache.camel.util.AsyncProcessorHelper` in the camel-core JAR to `org.apache.camel.support.AsyncProcessorHelper` and moved to the `camel-support` JAR.

The class `AsyncProcessorConverterHelper` has been moved from `org.apache.camel.util.AsyncProcessorConverterHelper` in the camel-core JAR to `org.apache.camel.support.AsyncProcessorConverterHelper` and moved to the `camel-support` JAR.

The class `CamelContextHelper` has been moved from `org.apache.camel.util.CamelContextHelper` in the camel-core JAR to `org.apache.camel.support.CamelContextHelper` and moved to the `camel-support` JAR.

The class `EndpointHelper` has been moved from `org.apache.camel.util.EndpointHelper` in the camel-core JAR to `org.apache.camel.support.EndpointHelper` and moved to the `camel-support` JAR.

The class `EventHelper` has been moved from `org.apache.camel.util.EventHelper` in the camel-core JAR to `org.apache.camel.support.EventHelper` and moved to the `camel-support` JAR.

The class `ExchangeHelper` has been moved from `org.apache.camel.util.ExchangeHelper` in the camel-core JAR to `org.apache.camel.support.ExchangeHelper` and moved to the `camel-support` JAR.

The class `GZIPHelper` has been moved from `org.apache.camel.util.GZIPHelper` in the camel-core JAR to `org.apache.camel.support.GZIPHelper` and moved to the `camel-support` JAR.

The class `JsonSchemaHelper` has been moved from `org.apache.camel.util.JsonSchemaHelper` in the camel-core JAR to `org.apache.camel.support.JsonSchemaHelper` and moved to the `camel-support` JAR.

The class `MessageHelper` has been moved from `org.apache.camel.util.MessageHelper` in the camel-core JAR to `org.apache.camel.support.MessageHelper` and moved to the `camel-support` JAR.

The class `ObjectHelper` has been moved from `org.apache.camel.util.ObjectHelper` in the camel-core JAR and split into `org.apache.camel.support.ObjectHelper` and moved to the `camel-support` JAR and into `org.apache.camel.util.ObjectHelper` and moved to the `camel-util` JAR. This has been done to isolate the methods using `camel-api` JAR: those method are in the `camel-support` JAR, the other in the `camel-util` JAR.

The class `PlatformHelper` has been moved from `org.apache.camel.util.PlatformHelper` in the camel-core JAR to `org.apache.camel.support.PlatformHelper` and moved to the `camel-support` JAR.

The class `PredicateAssertHelper` has been moved from `org.apache.camel.util.PredicateAssertHelper` in the camel-core JAR to `org.apache.camel.support.PredicateAssertHelper` and moved to the `camel-support` JAR.

The class `ResolverHelper` has been moved from `org.apache.camel.util.ResolverHelper` in the camel-core JAR to `org.apache.camel.support.ResolverHelper` and moved to the `camel-support` JAR.

The class `ResourceHelper` has been moved from `org.apache.camel.util.ResourceHelper` in the camel-core JAR to `org.apache.camel.support.ResourceHelper` and moved to the `camel-support` JAR.

The class `RestProducerFactoryHelper` has been moved from `org.apache.camel.spi.RestProducerFactoryHelper` in the camel-core JAR to `org.apache.camel.support.RestProducerFactoryHelper` and moved to the `camel-support` JAR.

The class `ServiceHelper` has been moved from `org.apache.camel.util.ServiceHelper` in the camel-core JAR to `org.apache.camel.support.service.ServiceHelper` and moved to the `camel-api` JAR.

The class `UnitOfWorkHelper` has been moved from `org.apache.camel.util.UnitOfWorkHelper` in the camel-core JAR to `org.apache.camel.support.UnitOfWorkHelper` and moved to the `camel-support` JAR.

=== Idempotent Repositories

The class `FileIdempotentRepository` has been moved from `org.apache.camel.processor.idempotent.FileIdempotentRepository` in the camel-core JAR to `org.apache.camel.support.processor.idempotent.FileIdempotentRepository` and moved to the `camel-support` JAR.

The class `MemoryIdempotentRepository` has been moved from `org.apache.camel.processor.idempotent.MemoryIdempotentRepository` in the camel-core JAR to `org.apache.camel.support.processor.idempotent.MemoryIdempotentRepository` and moved to the `camel-support` JAR.

=== Route Policies

The class `org.apache.camel.support.RoutePolicySupport` has been moved to the `camel-support` JAR. The return type from `startConsumer` and `stopConsumer` has been changed from `boolean` to `void` as they always returned `true` before.

The class `org.apache.camel.impl.ThrottlingInflightRoutePolicy` has been moved to `org.apache.camel.throttling.ThrottlingInflightRoutePolicy`

=== Aggregation

The class `XsltAggregationStrategy` has been moved from `org.apache.camel.util.toolbox.XsltAggregationStrategy` in the camel-core JAR to `org.apache.camel.component.xslt.XsltAggregationStrategy` and moved to the `camel-xslt` JAR.

When using the option `groupedExchange` on the aggregator EIP then the output of the aggregation is now longer also stored in the exchange property `Exchange.GROUPED_EXCHANGE`. This behaviour was already deprecated from Camel 2.13 onwards.

=== Fallback type converters

The `@FallbackConverter` annotation has been removed, and you should use `@Converter(fallback = true)` instead. Also you can set `@Converter(generateLoader = true)` on the converter class to allow Camel to generate source code for loading type converters in a faster way.

=== Removed JMX APIs for explaining EIPs, components, etc.

The APIs that could find, and explain EIPs, components, endpoints etc. has been removed. These APIs have little value for production runtimes, and you can obtain this kind of information via the `camel-catalog`. Also the related Camel Karaf commands that used these APIs has been removed.

=== Other changes

The default for use breadcrumbs has been changed from `true` to `false`.

The `ProducerTemplate` and `ConsumerTemplate` now fails when being used, if `CamelContext` has not been started first.

=== XML DSL Migration

The XML DSL has been changed slightly.

The custom load balancer EIP has changed from `<custom>` to `<customLoadBalancer>`

The XMLSecurity data format has renamed the attribute `keyOrTrustStoreParametersId` to `keyOrTrustStoreParametersRef` in the `<secureXML>` tag.

The `<zipFile>` data format has been renamed to `<zipfile>`.

== Migrating Camel Maven Plugins

The `camel-maven-plugin` has been split up into two maven plugins:

- camel-maven-plugin
- camel-report-maven-plugin

The former has the `run` goal, which is intended for quickly running Camel applications standalone.

The `camel-report-maven-plugin` has the `validate` and `route-coverage` goals which is used for generating reports of your Camel projects such as validating Camel endpoint URIs and route coverage reports, etc.

== Known Issues

There is an issue with MDC logging and correctly transferring the Camel breadcrumb id's under certain situations with routing over asynchronous endpoints, due to the internal routing engine refactorings. This change also affects the `camel-zipkin` component, which may not correctly transfer the span id's when using MDC logging as well.
