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Developing Applications with Camel Quarkus

Red Hat Integration 2021.Q3

TECHNOLOGY PREVIEW - Developing applications with Camel Quarkus

Integration Documentation Team fuse-docs-support@redhat.com Integration Support Team http://access.redhat.com/support

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Abstract

This guide is for developers writing Camel applications on top of Camel Quarkus.

Preface
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Making open source more inclusive

Red Hat is committed to replacing problematic language in our code, documentation, and web properties. We are beginning with these four terms: master, slave, blacklist, and whitelist. Because of the enormity of this endeavor, these changes will be implemented gradually over several upcoming releases. For more details, see our CTO Chris Wright’s message.

Chapter 1. Introduction to developing applications with Camel Quarkus
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This guide is for developers writing Camel applications on top of Quarkus.

Camel components which are supported on Camel Quarkus have an associated Camel Quarkus extension. For more information about the Camel Quarkus extensions supported in this distribution, see the Camel Extensions for Quarkus reference guide.

Important

Camel Quarkus is a Technology Preview feature only. Technology Preview features are not supported with Red Hat production service level agreements (SLAs) and might not be functionally complete. Red Hat does not recommend using them in production.

These features provide early access to upcoming product features, enabling customers to test functionality and provide feedback during the development process. For more information about the support scope of Red Hat Technology Preview features, see https://access.redhat.com/support/offerings/techpreview.

Chapter 2. Dependency management
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A specific Camel Quarkus release is supposed to work only with a specific Quarkus release.

2.1. Quarkus BOM
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The core Quarkus dependencies are managed via com.redhat.quarkus.quarkus:quarkus-bom. This BOM does not manage the additional Quarkus extensions (for example Camel Quarkus or Kubernetes), so there are other BOMs available for you to use in your projects that contain import quarkus-bom.

Note

BOM stands for "Bill of Materials" - it is a pom.xml whose main purpose is to manage the versions of artifacts so that end users importing the BOM in their projects do not need to care which particular versions of the artifacts are supposed to work together. In other words, having a BOM imported in the <depependencyManagement> section of your pom.xml allows you to avoid specifying versions for the dependencies managed by the given BOM.

2.2. Camel Quarkus BOM
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As long as you do not plan to use any dependencies beyond those from Quarkus and Camel Quarkus, you should use org.apache.camel.quarkus:camel-quarkus-bom which manages all supported Camel artifacts and imports com.redhat.quarkus.quarkus:quarkus-bom.

Warning

For this technology preview, do not use com.redhat.quarkus:quarkus-universe-bom as it does not contain the supported Camel extensions included in this release.

2.3. Combining with other BOMs
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When combining camel-quarkus-bom with any other BOM, think carefully in which order you import them, because the order of imports defines the precedence.

For example, if my-foo-bom is imported before camel-quarkus-bom then the artifact versions defined in my-foo-bom will take the precedence. This may or may not be what you intend, depending on whether or not there are any overlapping actifacts in your my-foo-bom and camel-quarkus-bom. Additionally, you may also need to consider if those artifact versions in my-foo-bom with a higher precedence are compatible with the rest of the artifacts managed in camel-quarkus-bom.

Chapter 3. Defining Camel routes
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Camel Quarkus supports the Java DSL language to define Camel Routes.

3.1. Java DSL
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Extending org.apache.camel.builder.RouteBuilder and using the fluent builder methods available there is the most common way of defining Camel Routes. Here is a simple example of a route using the timer component:

import org.apache.camel.builder.RouteBuilder;

public class TimerRoute extends RouteBuilder {

    @Override
    public void configure() throws Exception {
        from("timer:foo?period=1000")
                .log("Hello World");
    }
}

import org.apache.camel.builder.RouteBuilder;

public class TimerRoute extends RouteBuilder {

    @Override
    public void configure() throws Exception {
        from("timer:foo?period=1000")
                .log("Hello World");
    }
}

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3.1.1. Endpoint DSL
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Since Camel 3.0, you can use fluent builders also for defining Camel endpoints. The following is equivalent with the previous example:

import org.apache.camel.builder.RouteBuilder;
import static org.apache.camel.builder.endpoint.StaticEndpointBuilders.timer;

public class TimerRoute extends RouteBuilder {

    @Override
    public void configure() throws Exception {
        from(timer("foo").period(1000))
                .log("Hello World");
    }
}

import org.apache.camel.builder.RouteBuilder;
import static org.apache.camel.builder.endpoint.StaticEndpointBuilders.timer;

public class TimerRoute extends RouteBuilder {

    @Override
    public void configure() throws Exception {
        from(timer("foo").period(1000))
                .log("Hello World");
    }
}

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Note

Builder methods for all Camel components are available via camel-quarkus-core, but you still need to add the given component’s extension as a dependency for the route to work properly. In case of the above example, it would be camel-quarkus-timer.

Chapter 4. Configuration
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Camel Quarkus automatically configures and deploys a Camel Context bean which by default is started/stopped according to the Quarkus Application lifecycle. The configuration step happens at build time during Quarkus' augmentation phase and it is driven by the Camel Quarkus extensions which can be tuned using Camel Quarkus specific quarkus.camel.* properties.

Note

quarkus.camel.* configuration properties are documented on the individual extension pages - see e.g. Camel Quarkus Core.

After the configuration is done, a minimal Camel Runtime is assembled and started in the RUNTIME_INIT phase.

4.1. Configuring Camel components
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4.1.1. application.properties
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To configure components and other aspects of Apache Camel through properties, make sure that your application depends on camel-quarkus-core directly or transitively. Because most Camel Quarkus extensions depend on camel-quarkus-core, you typically do not need to add it explicitly.

camel-quarkus-core brings functionalities from Camel Main to Camel Quarkus.

In the example below, you set a specific ExchangeFormatter configuration on the LogComponent via application.properties:

camel.component.log.exchange-formatter = #class:org.apache.camel.support.processor.DefaultExchangeFormatter
camel.component.log.exchange-formatter.show-exchange-pattern = false
camel.component.log.exchange-formatter.show-body-type = false

camel.component.log.exchange-formatter = #class:org.apache.camel.support.processor.DefaultExchangeFormatter
camel.component.log.exchange-formatter.show-exchange-pattern = false
camel.component.log.exchange-formatter.show-body-type = false

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4.1.2. CDI
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You can also configure a component programmatically using CDI.

The recommended method is to observe the ComponentAddEvent and configure the component before the routes and the CamelContext are started:

import javax.enterprise.context.ApplicationScoped;
import javax.enterprise.event.Observes;
import org.apache.camel.quarkus.core.events.ComponentAddEvent;
import org.apache.camel.component.log.LogComponent;
import org.apache.camel.support.processor.DefaultExchangeFormatter;
@ApplicationScoped
public static class EventHandler {
    public void onComponentAdd(@Observes ComponentAddEvent event) {
        if (event.getComponent() instanceof LogComponent) {
            /* Perform some custom configuration of the component */
            LogComponent logComponent = ((LogComponent) event.getComponent());
            DefaultExchangeFormatter formatter = new DefaultExchangeFormatter();
            formatter.setShowExchangePattern(false);
            formatter.setShowBodyType(false);
            logComponent.setExchangeFormatter(formatter);
        }
    }
}

import javax.enterprise.context.ApplicationScoped;
import javax.enterprise.event.Observes;
import org.apache.camel.quarkus.core.events.ComponentAddEvent;
import org.apache.camel.component.log.LogComponent;
import org.apache.camel.support.processor.DefaultExchangeFormatter;
@ApplicationScoped
public static class EventHandler {
    public void onComponentAdd(@Observes ComponentAddEvent event) {
        if (event.getComponent() instanceof LogComponent) {
            /* Perform some custom configuration of the component */
            LogComponent logComponent = ((LogComponent) event.getComponent());
            DefaultExchangeFormatter formatter = new DefaultExchangeFormatter();
            formatter.setShowExchangePattern(false);
            formatter.setShowBodyType(false);
            logComponent.setExchangeFormatter(formatter);
        }
    }
}

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4.1.2.1. Producing a @Named component instance
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Alternatively, you can create and configure the component yourself in a @Named producer method. This works as Camel uses the component URI scheme to look-up components from its registry. For example, in the case of a LogComponent Camel looks for a log named bean.

Warning

Please note that while producing a @Named component bean will usually work, it may cause subtle issues with some components.

Camel Quarkus extensions may do one or more of the following:

Pass custom subtype of the default Camel component type. See the Vert.x WebSocket extension example.
Perform some Quarkus specific customization of the component. See the JPA extension example.

These actions are not performed when you produce your own component instance, therefore, configuring components in an observer method is the recommended method.

import javax.enterprise.context.ApplicationScoped;
import javax.inject.Named;

import org.apache.camel.component.log.LogComponent;
import org.apache.camel.support.processor.DefaultExchangeFormatter;

@ApplicationScoped
public class Configurations {
    /**
     * Produces a {@link LogComponent} instance with a custom exchange formatter set-up.
     */
    @Named("log") 
    LogComponent log() {
        DefaultExchangeFormatter formatter = new DefaultExchangeFormatter();
        formatter.setShowExchangePattern(false);
        formatter.setShowBodyType(false);

        LogComponent component = new LogComponent();
        component.setExchangeFormatter(formatter);

        return component;
    }
}

import javax.enterprise.context.ApplicationScoped;
import javax.inject.Named;

import org.apache.camel.component.log.LogComponent;
import org.apache.camel.support.processor.DefaultExchangeFormatter;

@ApplicationScoped
public class Configurations {
    /**
     * Produces a {@link LogComponent} instance with a custom exchange formatter set-up.
     */
    @Named("log")


    LogComponent log() {
        DefaultExchangeFormatter formatter = new DefaultExchangeFormatter();
        formatter.setShowExchangePattern(false);
        formatter.setShowBodyType(false);

        LogComponent component = new LogComponent();
        component.setExchangeFormatter(formatter);

        return component;
    }
}

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1: The "log" argument of the @Named annotation can be omitted if the name of the method is the same.

4.2. Configuration by convention
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In addition to support configuring Camel through properties, camel-quarkus-core allows you to use conventions to configure the Camel behavior. For example, if there is a single ExchangeFormatter instance in the CDI container, then it will automatically wire that bean to the LogComponent.

Chapter 5. Contexts and Dependency Injection (CDI) in Camel Quarkus
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CDI plays a central role in Quarkus and Camel Quarkus offers a first class support for it too.

You may use @Inject, @ConfigProperty and similar annotations e.g. to inject beans and configuration values to your Camel RouteBuilder, for example:

import javax.enterprise.context.ApplicationScoped;
import javax.inject.Inject;
import org.apache.camel.builder.RouteBuilder;
import org.eclipse.microprofile.config.inject.ConfigProperty;

@ApplicationScoped 
public class TimerRoute extends RouteBuilder {

    @ConfigProperty(name = "timer.period", defaultValue = "1000") 
    String period;

    @Inject
    Counter counter;

    @Override
    public void configure() throws Exception {
        fromF("timer:foo?period=%s", period)
                .setBody(exchange -> "Incremented the counter: " + counter.increment())
                .to("log:cdi-example?showExchangePattern=false&showBodyType=false");
    }
}

import javax.enterprise.context.ApplicationScoped;
import javax.inject.Inject;
import org.apache.camel.builder.RouteBuilder;
import org.eclipse.microprofile.config.inject.ConfigProperty;

@ApplicationScoped


public class TimerRoute extends RouteBuilder {

    @ConfigProperty(name = "timer.period", defaultValue = "1000")


    String period;

    @Inject
    Counter counter;

    @Override
    public void configure() throws Exception {
        fromF("timer:foo?period=%s", period)
                .setBody(exchange -> "Incremented the counter: " + counter.increment())
                .to("log:cdi-example?showExchangePattern=false&showBodyType=false");
    }
}

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1: The @ApplicationScoped annotation is required for @Inject and @ConfigProperty to work in a RouteBuilder. Note that the @ApplicationScoped beans are managed by the CDI container and their life cycle is thus a bit more complex than the one of the plain RouteBuilder. In other words, using @ApplicationScoped in RouteBuilder comes with some boot time penalty and you should therefore only annotate your RouteBuilder with @ApplicationScoped when you really need it.
2: The value for the timer.period property is defined in src/main/resources/application.properties of the example project.

Tip

Please refer to the Quarkus Dependency Injection guide for more details.

5.1. Accessing CamelContext
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To access CamelContext just inject it into your bean:

import javax.inject.Inject;
import javax.enterprise.context.ApplicationScoped;
import java.util.stream.Collectors;
import java.util.List;
import org.apache.camel.CamelContext;

@ApplicationScoped
public class MyBean {

    @Inject
    CamelContext context;

    public List<String> listRouteIds() {
        return context.getRoutes().stream().map(Route::getId).sorted().collect(Collectors.toList());
    }
}

import javax.inject.Inject;
import javax.enterprise.context.ApplicationScoped;
import java.util.stream.Collectors;
import java.util.List;
import org.apache.camel.CamelContext;

@ApplicationScoped
public class MyBean {

    @Inject
    CamelContext context;

    public List<String> listRouteIds() {
        return context.getRoutes().stream().map(Route::getId).sorted().collect(Collectors.toList());
    }
}

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5.2. CDI and the Camel Bean component
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5.2.1. Refer to a bean by name
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To refer to a bean in a route definition by name, just annotate the bean with @Named("myNamedBean") and @ApplicationScoped. The @RegisterForReflection annotation is important for the native mode.

import javax.enterprise.context.ApplicationScoped;
import javax.inject.Named;
import io.quarkus.runtime.annotations.RegisterForReflection;

@ApplicationScoped
@Named("myNamedBean")
@RegisterForReflection
public class NamedBean {
    public String hello(String name) {
        return "Hello " + name + " from the NamedBean";
    }
}

import javax.enterprise.context.ApplicationScoped;
import javax.inject.Named;
import io.quarkus.runtime.annotations.RegisterForReflection;

@ApplicationScoped
@Named("myNamedBean")
@RegisterForReflection
public class NamedBean {
    public String hello(String name) {
        return "Hello " + name + " from the NamedBean";
    }
}

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Then you can use the myNamedBean name in a route definition:

import org.apache.camel.builder.RouteBuilder;
public class CamelRoute extends RouteBuilder {
    @Override
    public void configure() {
        from("direct:named")
                .to("bean:namedBean?method=hello");
    }
}

import org.apache.camel.builder.RouteBuilder;
public class CamelRoute extends RouteBuilder {
    @Override
    public void configure() {
        from("direct:named")
                .to("bean:namedBean?method=hello");
    }
}

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Legal Notice
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The text of and illustrations in this document are licensed by Red Hat under a Creative Commons Attribution–Share Alike 3.0 Unported license ("CC-BY-SA"). An explanation of CC-BY-SA is available at http://creativecommons.org/licenses/by-sa/3.0/. In accordance with CC-BY-SA, if you distribute this document or an adaptation of it, you must provide the URL for the original version.

Red Hat, as the licensor of this document, waives the right to enforce, and agrees not to assert, Section 4d of CC-BY-SA to the fullest extent permitted by applicable law.

Red Hat, Red Hat Enterprise Linux, the Shadowman logo, the Red Hat logo, JBoss, OpenShift, Fedora, the Infinity logo, and RHCE are trademarks of Red Hat, Inc., registered in the United States and other countries.

Linux® is the registered trademark of Linus Torvalds in the United States and other countries.

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All other trademarks are the property of their respective owners.

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Developing Applications with Camel Quarkus

TECHNOLOGY PREVIEW - Developing applications with Camel Quarkus

Preface
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Making open source more inclusive

Chapter 1. Introduction to developing applications with Camel Quarkus
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Chapter 2. Dependency management
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2.1. Quarkus BOM
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2.2. Camel Quarkus BOM
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2.3. Combining with other BOMs
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Chapter 3. Defining Camel routes
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3.1. Java DSL
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3.1.1. Endpoint DSL
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Chapter 4. Configuration
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4.1. Configuring Camel components
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4.1.1. application.properties
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4.1.2. CDI
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4.1.2.1. Producing a @Named component instance
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4.2. Configuration by convention
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Chapter 5. Contexts and Dependency Injection (CDI) in Camel Quarkus
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5.1. Accessing CamelContext
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5.2. CDI and the Camel Bean component
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5.2.1. Refer to a bean by name
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Legal Notice
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学习

尝试、购买和销售

社区

关于红帽文档

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Developing Applications with Camel Quarkus

TECHNOLOGY PREVIEW - Developing applications with Camel Quarkus

Preface复制链接链接已复制到粘贴板!

Making open source more inclusive

Chapter 1. Introduction to developing applications with Camel Quarkus复制链接链接已复制到粘贴板!

Chapter 2. Dependency management复制链接链接已复制到粘贴板!

2.1. Quarkus BOM复制链接链接已复制到粘贴板!

2.2. Camel Quarkus BOM复制链接链接已复制到粘贴板!

2.3. Combining with other BOMs复制链接链接已复制到粘贴板!

Chapter 3. Defining Camel routes复制链接链接已复制到粘贴板!

3.1. Java DSL复制链接链接已复制到粘贴板!

3.1.1. Endpoint DSL复制链接链接已复制到粘贴板!

Chapter 4. Configuration复制链接链接已复制到粘贴板!

4.1. Configuring Camel components复制链接链接已复制到粘贴板!

4.1.1. application.properties复制链接链接已复制到粘贴板!

4.1.2. CDI复制链接链接已复制到粘贴板!

4.1.2.1. Producing a @Named component instance复制链接链接已复制到粘贴板!

4.2. Configuration by convention复制链接链接已复制到粘贴板!

Chapter 5. Contexts and Dependency Injection (CDI) in Camel Quarkus复制链接链接已复制到粘贴板!

5.1. Accessing CamelContext复制链接链接已复制到粘贴板!

5.2. CDI and the Camel Bean component复制链接链接已复制到粘贴板!

5.2.1. Refer to a bean by name复制链接链接已复制到粘贴板!

Legal Notice复制链接链接已复制到粘贴板!

学习

尝试、购买和销售

社区

关于红帽文档

让开源更具包容性

關於紅帽

Theme

Red Hat legal and privacy links

Red Hat legal and privacy links

Preface
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Chapter 1. Introduction to developing applications with Camel Quarkus
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Chapter 2. Dependency management
复制链接

2.1. Quarkus BOM
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2.2. Camel Quarkus BOM
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2.3. Combining with other BOMs
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Chapter 3. Defining Camel routes
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3.1. Java DSL
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3.1.1. Endpoint DSL
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Chapter 4. Configuration
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4.1. Configuring Camel components
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4.1.1. application.properties
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4.1.2. CDI
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4.1.2.1. Producing a @Named component instance
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4.2. Configuration by convention
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Chapter 5. Contexts and Dependency Injection (CDI) in Camel Quarkus
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5.1. Accessing CamelContext
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5.2. CDI and the Camel Bean component
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5.2.1. Refer to a bean by name
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Legal Notice
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